2024

Mesoscale Discussion #244


Mesoscale Discussion 0244

NWS Storm Prediction Center Norman OK

0656 PM CDT Thu Mar 14 2024


Areas affected...Southeastern Indiana into portions of southwest/south-central Ohio


Concerning...Tornado Watch 44...


Valid 142356Z - 150100Z


The severe weather threat for Tornado Watch 44 continues.


SUMMARY...An area of greater tornado potential is evident from southeast Indiana into southwestern Ohio over the next 1-3 hours.


DISCUSSION...Three supercells from just east of Indianapolis to northwest of Columbus, OH have shown a rightward turn to the southeast. Surface flow remains backed in southwestern portions of Ohio. Considering the observed storm motion and regional VAD profiles, an area of greater tornado threat is evident from southeastern Indiana into southwestern Ohio. 850 mb winds are expected to increase this evening as well. Should storms remain discrete and surface wind backed, the environment would become more favorable in the next 1-3 hours.


   ..Wendt.. 03/14/2024

Mesoscale Discussion #248


Mesoscale Discussion 0248

NWS Storm Prediction Center Norman OK

0831 PM CDT Thu Mar 14 2024


Areas affected...Central Arkansas


Concerning...Tornado Watch 45...


Valid 150131Z - 150230Z


The severe weather threat for Tornado Watch 45 continues.


SUMMARY...A strong tornado will be possible in the vicinity of western Little Rock over the next hour.


DISCUSSION...Low-level flow as increased over the last hour across central Arkansas. 0-1 km storm-relative helicity on the WSR-88D VWP at Little Rock has increased from near 150 m2/s2 to about 225 m2/s2. This increase in low-level shear will continue to support a tornado threat. The storm to the west of Little Rock in the area around Hot Springs has had a history of tornadoes. As this storm moves east-northeastward, the storm-scale environment could support the development of a strong tornado in the vicinity of western Little Rock over the next 60 minutes.


..Broyles.. 03/15/2024

Mesoscale Discussion #344


Mesoscale Discussion 0344

NWS Storm Prediction Center Norman OK

0959 AM CDT Tue Apr 02 2024


Areas affected...Portions of WV


Concerning...Tornado Watch 74...


Valid 021459Z - 021630Z


The severe weather threat for Tornado Watch 74 continues.


SUMMARY...A substantial severe wind threat (70-90+ mph gusts), along with isolated tornadoes, will approach Charleston West Virginia and vicinity through noon.


DISCUSSION...KHTS recently measured a significant severe wind gust to 80 kt (92 mph) with a compact but well organized cluster currently moving quickly eastward across parts of WV. Even though the airmass across this region remains only weakly unstable, very strong low-level and deep-layer shear is helping to compensate and provide convective organization. Recent radar data from KRLX shows enhanced inbound velocities embedded within the line that suggest 70-90+ mph wind gusts will likely continue to be a threat with this line as it approaches the Charleston WV metro and vicinity over the next hour (through noon EDT). In addition to this substantial severe/damaging wind threat, isolated tornadoes embedded within the line also appear possible given the strength of the low-level flow and related shear.


..Gleason.. 04/02/2024

Mesoscale Discussion #359


Mesoscale Discussion 0359

NWS Storm Prediction Center Norman OK

0659 PM CDT Tue Apr 02 2024


Areas affected...south-central Ohio


Concerning...Tornado Watch 78...81...


Valid 022359Z - 030100Z


The severe weather threat for Tornado Watch 78, 81 continues.


SUMMARY...The greatest strong tornado threat in watch 78 and 81 will exist across south-central Ohio this evening.


DISCUSSION...A long-track supercell has become better organized in the low-levels within the last hour near the Ohio River in south-central Ohio. Recently a TDS was apparent from the ILN WSR-88D in northern Kentucky with another TDS ongoing in Adams County, Ohio as of 2355 UTC. The environment ahead of this supercell remains favorable for tornadoes with STP around 2 and no storm interference anticipated. Therefore, this supercell will pose a continued tornado threat with the potential for strong tornadoes through the evening.


..Bentley.. 04/02/2024

Mesoscale Discussion #465


Mesoscale Discussion 0465

NWS Storm Prediction Center Norman OK

0447 PM CDT Tue Apr 16 2024


Areas affected...portions of eastern/southeastern Iowa into northwestern Illinois


Concerning...Tornado Watch 117...


Valid 162147Z - 162315Z


The severe weather threat for Tornado Watch 117 continues.


SUMMARY...The ongoing convective line has evolved into semi-discrete supercells which will allow for an increase in the risk for all hazards over the next couple of hours. A favorable shear/thermodynamic environment may also support a strong (EF-2+) tornado.


DISCUSSION...As of 2140 UTC, regional radar and satellite data showed the ongoing convective line in southeastern IA has trended towards more semi-discrete elements, especially with southward extent, over the last hour. The broader environment remains favorable for severe storms with moderate buoyancy and strong deep-layer shear established. Low-level shear has also increased ahead of the storms with backed surface flow supporting 300-400 m2/s2 of effective SRH observed from area VADs and SPC mesoanalysis. With a more supercellular mode emerging, the potential for stronger mesocyclones within a strong low-level shear environment suggests an increasing potential for tornadoes, in addition to the continued risk for damaging winds and hail. STP values of 2-3 along with 0-3km CAPE of 50-100 J/kg favor strong low-level stretching of vertical vorticity. Large low-level hodographs may also support the risk for a strong (EF-2+) tornado with the longer lived supercells. This increasing risk may extended near the Quad Cities and farther east into parts of northwestern IL over the next couple of hours.


..Lyons.. 04/16/2024

Mesoscale Discussion #532


Mesoscale Discussion 0532

NWS Storm Prediction Center Norman OK

0314 PM CDT Fri Apr 26 2024


Areas affected...portions of eastern Nebraska


Concerning...Tornado Watch 140...


Valid 262014Z - 262115Z


The severe weather threat for Tornado Watch 140 continues.


SUMMARY...Well-developed supercells are moving into an environment very favorable for tornadoes. A corridor of heightened risk for significant tornadoes is emerging across eastern/southeastern NE.


DISCUSSION...Ongoing storms across southeastern NE have rapidly evolved into well-organized supercells over the past few hours. The environment ahead of these storms is becoming increasingly favorable for significant tornadoes near the modifying warm front over the NE/IA border. ESRH of 300 m2/s2 and STP values of 2-3 from SPC mesoanalysis indicate the environment could support strong (EF2-EF3) tornadoes with these organized supercells. Current radar data shows storm motions of 215-225 deg at 30-35 kt. This would place these storms near or just west of the Omaha metro in the next 60-90 minutes.


..Lyons.. 04/26/2024

Mesoscale Discussion #544


Mesoscale Discussion 0544

NWS Storm Prediction Center Norman OK

0319 PM CDT Sat Apr 27 2024


Areas affected...Western north TX and southwest OK


Concerning...Tornado Watch 146...


Valid 272019Z - 272145Z


The severe weather threat for Tornado Watch 146 continues.


SUMMARY...Pair of potentially long-lived supercells within the southern portion of WW 146 may evolve with an intense tornado and very large hail threat.


DISCUSSION...A potentially long-lived, slow-moving discrete supercell is centered over Knox County, TX. This supercell appears to be anchored along the far southern portion of the broader convective plume that extends north across OK/KS. With full insolation in the warm-moist sector inflow to its southeast, its plausible that a long-lived supercell will persist for the next 2-3 hours. Amid MLCAPE of 3000 J/kg and mid 60s surface dew points to its southeast, a cyclic tornadic supercell could evolve beyond the very large hail threat with up to baseballs reported thus far. The supercell to its northeast in Wilbarger County, TX will also have potential to further intensify as it spreads towards and northwest of the Wichita Falls vicinity, given 0-1 km SRH of 100-200 m2/s2 per FDR VWP data.


..Grams.. 04/27/2024

Mesoscale Discussion #555


Mesoscale Discussion 0555

NWS Storm Prediction Center Norman OK

1133 PM CDT Sat Apr 27 2024


Areas affected...Eastern Oklahoma


Concerning...Tornado Watch 152...


Valid 280433Z - 280545Z


CORRECTED FOR AREA OUTLINE


The severe weather threat for Tornado Watch 152 continues.


SUMMARY...Tornado potential is greatest across eastern Oklahoma.


DISCUSSION...Influence of mid-level speed max appears to be affecting convection over central/southern Oklahoma. Low-level SRH has increased markedly across eastern OK this evening as LLJ is focused into this region of the southern Plains. 0-1 SRH values are currently around 600 m2/s2 at INX, and weak inhibition that was observed on 00z OUN sounding is now negligible.


Late-afternoon convection that evolved over northwest TX/southwest OK has grown upscale and progressed downstream. Leading edge of well-defined MCS now arcs from near Payne-Okfuskee-Garvin County. While embedded circulations are noted along this line, especially the northern portions, of more concern are the discrete supercells that have developed ahead of the MCS. Several notable, long-lived supercells have evolved from south-central OK into Hughes County. Tornado potential appears significant with these discrete pre-MCS updrafts. As these updrafts are overtaken by the MCS a more complex MCS will ultimately evolve within the larger warm advection corridor. A few strong tornadoes are likely with this activity.


..Darrow.. 04/28/2024

Mesoscale Discussion #609


Mesoscale Discussion 0609

NWS Storm Prediction Center Norman OK

0824 PM CDT Thu May 02 2024


Areas affected...Northwest TX into Southwest TX into the TX Hill Country


Concerning...Severe Thunderstorm Watch 177...


Valid 030124Z - 030300Z


The severe weather threat for Severe Thunderstorm Watch 177 continues.


SUMMARY...The environment from northwest Texas into southwest Texas and the Texas Hill Country remains supportive of supercells capable of all severe hazards, including very large hail up to 3" and tornadoes.


DISCUSSION...Numerous supercells continue within Severe Thunderstorm Watch 177 from northwest TX into southwest TX and the TX Hill Country. Recent KDYX VAD sampled relatively modest low-level storm-relative helicity (i.e. 0-1 km SRH of 60 to 75 m2/s2) and weak low-level shear (i.e. 0-1 km bulk shear less than 15 kt). Even so, the combination of strongly deviant motion (i.e. southeastward at around 10 kt), ample low-level vorticity in the vicinity of the dryline and more localized differential heating boundaries, and strong low-level buoyancy (i.e. 0-3 km MLCAPE over 75 J/kg) has supported several different instances of tornadogenesis, both with the northern pair of supercells near ABI and farther south in Runnels and Coleman Counties. 


Overall environment remains supportive of supercells capable of all severe hazards, including very large hail up to 3" and tornadoes. New development is possible along the outflow of ongoing storms as well as just a bit south of the watch in the TX Hill Country. The onset of nocturnal stabilization will likely lead to a gradually diminishing tornado threat over the next two hours, but the hail threat will persist through the evening. A watch may be needed farther south if convective trends merit.


..Mosier.. 05/03/2024

Mesoscale Discussion #616


Mesoscale Discussion 0616

NWS Storm Prediction Center Norman OK

0452 PM CDT Fri May 03 2024


Areas affected...west-central Texas...from the South Plains to the Concho Valley


Concerning...Tornado Watch 178...


Valid 032152Z - 032315Z


The severe weather threat for Tornado Watch 178 continues.


SUMMARY...Severe/isolated tornado risk continues across Tornado Watch 178, including a very intense/strongly rotating supercell moving southeastward across Coke County north of San Angelo.


DISCUSSION...Latest radar loop shows isolated storms extending from north of Lubbock southeastward to near San Angelo.  Given the very favorable thermodynamic environment (2500 to 3500 J/kg mixed-layer CAPE per RAP-based objective analysis) across the area, and low-level southeasterlies veering to west-southwesterly at mid levels, risk for very large hail, locally damaging winds, and isolated tornadoes continues.


One storm in particular appears strongly tornadic at this time per radar observations.  In addition to an extremely well-defined hook with an eye-like area of lesser reflectivity apparent, the latest storm-relative velocity data from the KSJT WSR-88D shows rotational velocity in excess of 90kt -- coincident with the "reflectivity eye" within the hook, would suggest the possibility of an ongoing significant tornado.  While this storm is currently moving southeastward across relatively sparsely populated areas, continued southeastward motion could allow the storm to approach areas near and east of the San Angelo area in the next hour.  With that said, a recent turn to a more east-southeastward motion has been observed in the past couple of volume scans.


..Goss.. 05/03/2024

Mesoscale Discussion #646


Mesoscale Discussion 0646

NWS Storm Prediction Center Norman OK

0712 AM CDT Mon May 06 2024


Areas affected...Central...West-central and North-central Oklahoma Into Far Southern Kansas


Concerning...Outlook upgrade 


Valid 061212Z - 061315Z


SUMMARY...An upgrade to High Risk will be done for the upcoming 13Z Day 1 Outlook. The following areas will be upgraded to High Risk.


DISCUSSION...Central Oklahoma

North-central Oklahoma

West-central Oklahoma

Far Southern Kansas


Please refer to 13Z Day 1 Outlook for detailed reasoning.


..Broyles/Edwards.. 05/06/2024

Mesoscale Discussion #649


Mesoscale Discussion 0649

NWS Storm Prediction Center Norman OK

1147 AM CDT Mon May 06 2024


Areas affected...southern KS...western/central OK...and eastern TX Panhandle


Concerning...Severe potential...Tornado Watch likely 


Valid 061647Z - 061845Z


Probability of Watch Issuance...95 percent


SUMMARY...PDS Tornado Watch issuance will be needed ahead of this portion of the dryline during the early afternoon. At least a few long-track, discrete supercells are expected, becoming capable of producing intense (EF3+) tornadoes.


DISCUSSION...16Z surface analysis placed the dryline from near Garden City, KS to Lubbock, TX, with the Pacific cold front lagging westward with southern extent in the southern High Plains. Airmass continues to destabilize ahead of the dryline, with MLCIN becoming weak into at least western OK and the TX Panhandle where boundary-layer warming has been more prominent in cloud breaks.


The expectation is for initial dryline/Pacific front development to occur in southwest KS and build south into the eastern TX Panhandle/western OK vicinity by late afternoon. Ample low to deep-layer shear will support several supercells with very large hail, tornadoes, and severe gusts probable. The impinging of an intense upper jet from NM into western OK over the next several hours, along with strengthening of low-level flow this evening, will yield an increasingly favorable kinematic environment for long-track and intense supercells capable of significant tornadoes, especially with southern extent in western/central OK.


..Grams/Smith.. 05/06/2024

Mesoscale Discussion #655


Mesoscale Discussion 0655

NWS Storm Prediction Center Norman OK

0335 PM CDT Mon May 06 2024


Areas affected...Northwest OK


Concerning...Tornado Watch 189...


Valid 062035Z - 062130Z


The severe weather threat for Tornado Watch 189 continues.


SUMMARY...Initial supercell development across northwest Oklahoma will pose a primary near-term risk for large to very large hail. Tornado threat should increase rapidly towards 5 to 6 pm.


DISCUSSION...Most prominent convective development on the dryline south of KS has been in the Ellis county vicinity of northwest OK. Additional cells should form farther south towards I-40 based on the agitated CU field noted in the southeast TX Panhandle. These cells will likely evolve into long-track supercells as they mature with a primary initial threat of large to very large hail. OK-Mesonet surface observations confirm the leading edge of upper 60s dew points are along a line from roughly Tipton to Lahoma. As these cells impinge on the greater low-level buoyancy and stronger low-level shear over central OK (per comparison of FDR/TLX/VNX VWP data), potential for tornadoes will increase substantially during the early evening. This scenario is supported by recent WoFS guidance.


..Grams.. 05/06/2024

Mesoscale Discussion #659


Mesoscale Discussion 0659

NWS Storm Prediction Center Norman OK

0542 PM CDT Mon May 06 2024


Areas affected...West-central into northwest/north-central OK...extreme south-central KS


Concerning...Tornado Watch 189...


Valid 062242Z - 070015Z


The severe weather threat for Tornado Watch 189 continues.


SUMMARY...The threat for strong and potentially long-tracked tornadoes is expected to increase into this evening. Very large hail will also be possible with any supercell.


DISCUSSION...Three mature supercells are ongoing across northwest OK as of 5:30 PM CDT. Initial development occurred in an environment characterized by warm temperatures (well into the 80s F) and dewpoints generally in the mid 60s F. However, dewpoints downstream of the ongoing cells into north-central OK are in the upper 60s to near 70F, supporting even greater buoyancy (MLCAPE of 3000-4000 J/kg) and a more favorable thermodynamic environment for tornadoes. In addition, VWP data from KOUN and KVNX depict a notable increase in low-level flow over the last hour, with some modest backing of surface winds noted in recent Oklahoma Mesonet data. 0-1 km SRH of around 200 m2/s2 was noted in the 21Z OUN sounding, with values expected to increase above 300 m2/s2 into this evening. The combination of strengthening low-level shear and strong to extreme instability will support a rapid increase in potential for strong and possibly long-tracked tornadoes as storms spread east-northeastward this evening. 


In addition to the tornado threat, very large hail and localized severe gusts will also remain possible. Additional development southwest of the ongoing supercells remains possible with time this evening, as the low-level jet continues to increase.


..Dean.. 05/06/2024

Mesoscale Discussion #663


Mesoscale Discussion 0663

NWS Storm Prediction Center Norman OK

0743 PM CDT Mon May 06 2024


Areas affected...Northwest into central OK


Concerning...Tornado Watch 189...


Valid 070043Z - 070215Z


The severe weather threat for Tornado Watch 189 continues.


SUMMARY...An uptick in strong tornado potential is expected through and beyond 9 PM CDT.


DISCUSSION...A southwest to northeast corridor of supercells has become established from west-central into north-central OK. Midlevel mesocyclones with the cells across Blaine and Kingfisher County have intensified this evening as they have moved into an environment characterized by increasing low-level moisture (with dewpoints near 70 F), strong to extreme instability, and strengthening low-level flow/shear as noted on the KTLX and KVNX VWPs. The cell over Garfield County earlier produced a tornado, and tornado potential with the other storms along this corridor will increase as they move eastward this evening. 


The 00Z OUN sounding depicts a volatile environment, with MLCAPE in excess of 3500 J/kg, effective shear of around 60 kt, and 0-1 km SRH in excess of 300 m2/s2. Low-level flow/shear will continue to increase through the evening, becoming even more favorable for strong to intense tornadoes. The primary uncertainty this evening is the cluster storm mode that has developed, but the ongoing cell south of Enid and the trailing cell over Custer County will both have an opportunity to move through a very favorable environment through 9 PM CDT.


..Dean.. 05/07/2024

Mesoscale Discussion #668


Mesoscale Discussion 0668

NWS Storm Prediction Center Norman OK

0935 PM CDT Mon May 06 2024


Areas affected...Northeast OK into southeast KS


Concerning...Tornado Watch 189...


Valid 070235Z - 070330Z


The severe weather threat for Tornado Watch 189 continues.


SUMMARY...A discrete supercell will pose a strong/intense tornado threat, while a growing QLCS to the west may pose an increasing threat for severe wind gusts and line-embedded tornadoes with time.


DISCUSSION...A discrete supercell has recently intensified across northeast OK, and may be producing a strong to intense tornado, based on rotational velocity, environment, and TDS characteristics. Strong instability and intense low-level shear/SRH (with 0-1 km SRH increasing above 400 m2/s2 on the KINX VWP) will continue to support intense tornado potential with this cell as it moves northeastward. 


Farther north and west, a growing QLCS will pose an increasing threat of severe wind gusts and line-embedded tornadoes as it moves eastward. This QLCS will eventually tend to absorb the ongoing tornadic cell and other discrete cells that may develop ahead of the line, which would potentially increase the tornado threat in the area of the QLCS where these mergers occur.


..Dean.. 05/07/2024

Mesoscale Discussion #698


Mesoscale Discussion 0698

NWS Storm Prediction Center Norman OK

1135 AM CDT Wed May 08 2024


Areas affected...Southeast MO...southern IL...and far western KY


Concerning...Tornado Watch 204...


Valid 081635Z - 081800Z


CORRECTED FOR WATCH NUMBER


The severe weather threat for Tornado Watch 204 continues.


SUMMARY...Tornado threat is increasing across southeast Missouri, into southern Illinois, and far western Kentucky. This will include potential for cyclical tornadogenesis and a strong (EF2-EF3) tornado.


DISCUSSION...Long-lived/tracked supercell centered on northern Crawford/southern Franklin counties in MO as of 1620Z has fully transitioned from earlier elevated character to surface-based. Measured severe gusts up to 58 kt have been reported in the past hour at the Vichy ASOS. It will likely persist along the composite outflow that extends southeastward, where additional supercells are maturing in far southern IL. The strongest low-level flow across the region remains in southern MO per SGF VWP data, with somewhat weaker but more veering with height over the MS/OH Valley confluence per the PAH VWP data. This will yield an STP environment of 1-3 across the region, supportive of a strong tornado. Overall convective mode will probably become increasingly complex with time as considerable storm-scale consolidation occurs through the afternoon, but occasional attempts at tornadogenesis should occur with multiple embedded supercells.


..Grams.. 05/08/2024

Mesoscale Discussion #701


Mesoscale Discussion 0701

NWS Storm Prediction Center Norman OK

0116 PM CDT Wed May 08 2024


Areas affected...much of eastern Oklahoma...western Arkansas...and far northeast Texas


Concerning...Severe potential...Tornado Watch likely 


Valid 081816Z - 082045Z


Probability of Watch Issuance...80 percent


SUMMARY...Scattered severe storms with very large hail and a few tornadoes (possibly strong) are expected by late afternoon from eastern Oklahoma into western Arkansas, and into parts of northern Texas.


DISCUSSION...Visible satellite imagery as well as surface observations show a cold front extending from far southeast KS and northeast OK southward toward the Red River. Additionally, a dryline extends roughly from just west of the Metroplex southwestward towards Del Rio TX.


A very moist and unstable air mass exists across the region, with MLCAPE of 3500-4000 J/kg common. Low-level convergence continues to increase along the boundaries, with winds gusting to 15-20 kt out of the west behind them.


Effective deep-layer shear of 45-50 kt across the entire length of the boundaries, combined with the very strong instability will favor the development of scattered supercells, potentially producing 3-4" diameter hail by early evening. Tornadoes, a few of which may be strong, will also be possible given the tremendous thermodynamic energy, favorable storm mode, and sufficient 0-1 SRH over 100 m2/s2.


..Jewell/Smith.. 05/08/2024

Mesoscale Discussion #707


Mesoscale Discussion 0707

NWS Storm Prediction Center Norman OK

0341 PM CDT Wed May 08 2024


Areas affected...Mid-MS/Lower OH and TN Valleys


Concerning...Tornado Watch 204...206...209...


Valid 082041Z - 082215Z


The severe weather threat for Tornado Watch 204, 206, 209 continues.


SUMMARY...Numerous supercells are ongoing and will continue to pose threats for significant severe weather during the next several hours. Additional/expansion of tornado watches with south-southeast extent and replacement/extension of parts of WW 206 (which is scheduled to expire at 22Z) should be expected through early evening.


DISCUSSION...An outbreak of supercells is underway from the Ozark Plateau across the Mid-MS and Lower OH into the TN Valleys. These storms will remain capable of producing tornadoes, large to very large hail, and damaging winds for the next several hours. Greatest tornado threat in the next few hours should be focused within three regimes. One along, the residual outflow that extends in a west/east-orientation across southern MO. The second with the long-lived supercell cluster along the tight buoyancy gradient over far southern IL into western KY. And the third area across middle TN into south-central KY, where the strongest low-level shear exists near/north of the modified convective outflow from earlier today. The southern/eastern extent of the supercell development in the TN Valley will likely necessitate additional tornado watches this evening.


..Grams.. 05/08/2024

Mesoscale Discussion #712


Mesoscale Discussion 0712

NWS Storm Prediction Center Norman OK

0551 PM CDT Wed May 08 2024


Areas affected...Middle Tennessee...south-central Kentucky


Concerning...Tornado Watch 206...


Valid 082251Z - 090045Z


The severe weather threat for Tornado Watch 206 continues.


SUMMARY...Several supercells are ongoing across parts of the Mid-South region (south-central Kentucky and Middle Tennessee). Storms will continue over the next couple of hours, with large hail and damaging winds expected, along with a few tornadoes.


DISCUSSION...Scattered severe/supercell storms continue across portions of the southern half of Kentucky at this time, and southward into Middle Tennessee.  Several of these storms are exhibiting sustained rotation, and large hail signatures as they move eastward across WW 206.  One storm in particular, moving across Maury County at this time, appears to be potentially tornadic, per KOHX WSR-88D storm-relative velocity (roughly 65 kt VROT) and correlation coefficient data from the most recent volume scan.


Instability diminishes with eastward extent into eastern portions of Kentucky, but expect some severe risk to spill east of the existing WW.  Farther south, into eastern Tennessee, greater instability suggests greater risk for eventual eastward expansion of severe potential.  At this time, expectations are that risk into eastern Kentucky may remain sufficiently muted to preclude a downstream WW in the short term.  Later, with WW 206 set to expire at 09/03Z, a new WW may be needed, and could include eastern Tennessee counties east of the current watch, and potentially a few counties into southern portions of eastern Kentucky.


..Goss.. 05/08/2024


**This MCD was issued as the deadly Columbia, Tennessee, EF3 was ongoing.

Mesoscale Discussion #717


Mesoscale Discussion 0717

NWS Storm Prediction Center Norman OK

0742 PM CDT Wed May 08 2024


Areas affected...northern Alabama...southern Middle and into eastern Tennessee...northwestern Georgia...and far western North Carolina


Concerning...Tornado Watch 211...


Valid 090042Z - 090245Z


The severe weather threat for Tornado Watch 211 continues.


SUMMARY...Severe/tornado threat is increasing across Tornado Watch 211 -- from the Tennessee Valley into the southern Appalachians.


DISCUSSION...Latest radar loop across the region shows storms increasing rapidly in coverage and intensity from northern Alabama and southern Middle Tennessee, eastward to southeastern Tennessee and northwestern Georgia.  This appears to be occurring in response to an increase in low-level warm advection, associated with a gradually veering low-level jet.  Meanwhile, strong storms -- including a long-lived supercell now moving into the Warren County Tennessee vicinity -- are expected to continue moving eastward out of WW 206 into Tornado Watch 211 in the next hour or so.


With this area on the eastern edge of a very moist/unstable airmass across the lower Mississippi and Tennessee Valleys, and shear favoring organized/rotating storms, severe/isolated tornado risk should continue to increase in the short term, across this area.


..Goss.. 05/09/2024


**This MCD preceded the Tennessee River Valley outbreak.

Mesoscale Discussion #844


Mesoscale Discussion 0844

NWS Storm Prediction Center Norman OK

0748 PM CDT Sun May 19 2024


Areas affected...parts  of west central into north central Oklahoma


Concerning...Severe Thunderstorm Watch 260...


Valid 200048Z - 200245Z


The severe weather threat for Severe Thunderstorm Watch 260 continues.


SUMMARY...A long-lived isolated supercell storm may be maintained at least another couple of hours, possibly impacting at least northern portions of the Greater Oklahoma City area by 10-11 PM CDT, with a risk for large hail in excess of 2 inches, strong, damaging wind gusts and perhaps a continuing risk for a tornado.


DISCUSSION...Embedded within southwesterly deep-layer mean flow on the order of 30-35 kt, an isolated intense supercell has been slowly propagating eastward, away from the initiating dryline, to the north of the Clinton-Sherman vicinity.  Low-level hodographs have been enlarging some, and a more notable increase in low-level shear is forecast through 04-06Z, along a strengthening southerly 850 mb jet (in excess of 50 kt) from northwest Texas toward the Medicine Loge KS area.  However, with the onset of diurnal boundary-layer cooling, inhibition across and east of the dryline is already in the process of increasing, and lower/mid-tropospheric warming forecast across much of Oklahoma this evening will contribute further to this.  Even so, given the favorable shear beneath a seasonably strong westerly mid/upper jet nosing into the south central Great Plains, and the strong potential instability eastward into the I-35 corridor, it is possible that the ongoing supercell may be maintained another couple of hours, eastward through northern portions of the Greater Oklahoma City area.


..Kerr.. 05/20/2024


**This MCD was issued as the massive Custer City, Oklahoma, EF2 was ongoing.

Mesoscale Discussion #871


Mesoscale Discussion 0871

NWS Storm Prediction Center Norman OK

1232 PM CDT Tue May 21 2024


Areas affected...Central/Eastern IA...South-Central/Southeast MN...Far Southwest WI...Far Northwest IL


Concerning...Severe potential...Tornado Watch likely 


Valid 211732Z - 211930Z


Probability of Watch Issuance...95 percent


SUMMARY...Environmental conditions are expected to becoming increasingly supportive of a significant severe thunderstorms capable of all severe hazards, including very large hail up to 3" inches, strong gusts to 75 mph, and long-track tornadoes. A Tornado Watch will likely be needed around 18-19Z, and a PDS designation is being considered.


DISCUSSION...Recent surface analysis places a low over southeast NE, with an outflow-modified warm front extending east-northeast across southern IA through the IA/IL/WI border vicinity. This warm front is expected to rapidly move northward in response to strong mass response ahead of the approaching shortwave trough, with upper 60s dewpoints likely in place across much of IA and mid 60s possibly reaching southern MN. As this occurs, steep mid-level lapse rates will also advect into the region, resulting strong buoyancy (i.e. MLCAPE 2500-3000 J/kg) by the early afternoon. Wind fields are expected to strengthen during this time frame as well, result in in very long hodographs and fast storm motion. Bunkers right motion for much of the region will be around 50 kt by the early afternoon. The result will be an environment very supportive of significant severe thunderstorms. 


An initially discrete mode is anticipated, with the fast storm motions allowing storms to stay ahead of the cold front impinging on the region from the west. Any discrete storms will likely obtain supercellular characteristics quickly, with very large hail up to 3" inches, strong gusts to 75 mph, and tornadoes all possible. This includes the possibility of long-lived, long-track supercells capable of strong tornadoes and intense wind damage. Storm interactions with the warm front, as well as the presence of the deepening surface low, suggest the significant severe potential will likely extend into south-central/southeast MI and southwest MN, despite being displaced just north of the better mid-level flow and low-level moisture. 


Some upscale growth is anticipated as storms continue eastward, with the resulting convective line capable of significant wind gusts around 75 mph. Given the continued strengthening of the low-level flow anticipated, some embedded QLCS circulations are likely as well. 


All of these factors suggests a significant severe weather event is probable, and a Tornado Watch will likely be needed around 18-19Z. A PDS designation is being considered for this watch.


..Mosier/Guyer.. 05/21/2024

Mesoscale Discussion #875


Mesoscale Discussion 0875

NWS Storm Prediction Center Norman OK

0320 PM CDT Tue May 21 2024


Areas affected...Southwest/South-Central IA


Concerning...Tornado Watch 277...


Valid 212020Z - 212145Z


The severe weather threat for Tornado Watch 277 continues.


SUMMARY...A localized corridor favorable for strong tornadoes exists across southwest/south-central Iowa, including Des Moines vicinity.


DISCUSSION...Pair of supercells on the southern end of the line of storms extending across western IA have recently shown notable intensification, with rotational velocity recently estimated around 50 to 55 kt within the southernmost cell. Strong southerly flow exists ahead of this storm, contributing to strong low-level shear, evidenced by recent 0-500m storm relative-helicity around 200 m2/s2 from DMX VAD. Robust deep-layer shear exists as well, with DMX VAD sampling 0-6 km bulk shear was over 60 kt. Recent mesoanalysis estimates effective-layer STP from 3 to 4 downstream. All of these factors suggest the downstream environment will remain conducive for supercell persistence. Storm motion for this southernmost storm is estimated to be northeasterly at around 45 kt, bring it into the Des Moines vicinity around 2130Z.


..Mosier.. 05/21/2024


**This MCD was issued as the violent Greenfield, Iowa, EF4 was ongoing.

Mesoscale Discussion #878


Mesoscale Discussion 0878

NWS Storm Prediction Center Norman OK

0503 PM CDT Tue May 21 2024


Areas affected...Central Iowa and far southeastern Minnesota


Concerning...Tornado Watch 277...


Valid 212203Z - 212330Z


The severe weather threat for Tornado Watch 277 continues.


SUMMARY...Long tracked supercells within a line extending north to south across central IA will continue to move eastward into an even more favorable tornadic environment.


DISCUSSION...Ongoing tornadic supercells continue from Cambridge, to just east of Des Moines. The latest DMX VAD profile data indicates 0-1 km SRH around 100 m2/s2. However, just upstream the DVN VAD shows SRH is double to triple that. In addition, a corridor of higher boundary layer moisture and backed surface flow east of the current line of deep moist convection from around Olmsted County south-southeastward to Linn County suggests localized SRH should be maximized there, juxtaposed with maximum buoyancy. Therefore, the potential for long tracked, damaging tornadoes appears most likely over the next 1-2 hours as far north as extreme southeastern MN.


   ..Barnes.. 05/21/2024

Mesoscale Discussion #879


Mesoscale Discussion 0879

NWS Storm Prediction Center Norman OK

0509 PM CDT Tue May 21 2024


Areas affected...Central Iowa into northeast Iowa and far southwest Wisconsin.


Concerning...Tornado Watch 277...


Valid 212209Z - 212345Z


The severe weather threat for Tornado Watch 277 continues.


SUMMARY...Intense to potentially violent tornado threat across northeast Iowa and into southwest Wisconsin over the next 2 hours


DISCUSSION...The supercell which formed the intense to potentially violent tornado which impacted Greenfield and other portions of southwest Iowa this afternoon has re-intensified after storm mergers. This storm and another strong supercell to its south are moving into an increasingly favorable tornadic environment with a STP of 5 to 6 (per SPC mesoanalysis). The backed surface winds and vorticity rich environment in the wake of the morning convection will provide ample low-level vorticity for a sustained tornado threat into the early evening. One or more long-track, potentially violent tornadoes are possible in this corridor over the next 90 to 120 minutes.


..Bentley/Thompson.. 05/21/2024

Mesoscale Discussion #918


Mesoscale Discussion 0918

NWS Storm Prediction Center Norman OK

0733 PM CDT Thu May 23 2024


Areas affected...Southwestern Oklahoma


Concerning...Tornado Watch 295...


Valid 240033Z - 240130Z


The severe weather threat for Tornado Watch 295 continues.


SUMMARY...A dangerous, tornadic supercell is expected to continue slowly moving ESE across Jackson County, and as far south as the Red River over the next hour.


DISCUSSION...Recent radar imagery from KFDR indicates VROT has increased to 90-105 kt within an ongoing, confirmed tornado located just west of Olustee, OK (southwest of Altus). The extremely unstable environment downstream of this strong to violent tornado will continue to favor tornadogensis, where SSE sustained surface winds around 20 to 25 kt will enhance localized surface vorticity.


   ..Barnes.. 05/24/2024

Mesoscale Discussion #954


Mesoscale Discussion 0954

NWS Storm Prediction Center Norman OK

0256 PM CDT Sat May 25 2024


Areas affected...much of western into central Oklahoma...northwest Texas...and south-central Kansas


Concerning...Severe potential...Tornado Watch likely 


Valid 251956Z - 252330Z


Probability of Watch Issuance...95 percent


SUMMARY...Tornadic supercells capable of dangerous tornadoes and extreme hail are expected to develop from northwest Texas into much of southwest and southern Oklahoma through evening. A similar threat is expected to develop with rapidly changing conditions this evening from northern Oklahoma into southern Kansas.


DISCUSSION...Moisture continues to rapidly increase from northwest TX into southern OK, with 70s F dewpoints and increasing shear. Extreme instability will favor particularly large supercells, with right-moving cells possibly traveling for over 100 miles, producing periodic tornadoes and giant hail. 


The initial threat is from activity now developing over northwest TX, and this should spread north of the Red River and move into south-central OK by evening. 


Farther north, destabilization and a rapidly increasing low-level jet will result in a developing tornadic supercell threat into the evening. Storms may initialize near the TX Panhandle/OK border ot even toward the KS border over the next few hours.


   ..Jewell/Bunting.. 05/25/2024

Mesoscale Discussion #957


Mesoscale Discussion 0957

NWS Storm Prediction Center Norman OK

0540 PM CDT Sat May 25 2024


Areas affected...Southwest/Central/South-Central OK...Far Northwest/North-Central TX


Concerning...Tornado Watch 308...


Valid 252240Z - 260015Z


The severe weather threat for Tornado Watch 308 continues.


SUMMARY...All severe hazards, including very large hail up to 4" and strong tornadoes, remain possible into central/south-central OK and north-central TX.


DISCUSSION...Regional radar imagery has shown a messy convective evolution across northwest TX and southwest OK over the past two hours, with the initially close-proximity initiation and numerous left-splits contributing to numerous interactions. Some trend back to a more discrete mode may be evolving, with 2 right-moving supercells now apparent over Cotton County OK, and Archer and Clay Counties in northwest TX. The southernmost supercell appears to be the strongest currently, with strong low-level rotation and 60 kft echo tops both noted in recent radar imagery.  


Despite some boundary-layer cooling due to anvil shading, the airmass ahead of these cells is still extremely buoyant. Mesoanalysis estimates a large area of 3500-4000 J/kg of MLCAPE remains from northwest TX/southwest OK into central/south-central OK and north-central TX. Strong vertical shear exists as well, with over 60 kt of 0-6 km bulk shear sampled with the VAD profiles at both KFDR and KTLX. Some modest convective inhibition is likely in place downstream, particularly given the now cooler surface temperatures. However, the organized character to the ongoing storms coupled with increasing large-scale ascent, should help these storms persist in spite of this inhibition. The overall environment remains supportive of very large hail up to 4" in diameter, strong damaging gusts, and tornadoes. 


Some additional development is possible in the wake of this main cluster across southwest OK where the airmass remains unstable. There may be some influence from storm outflow, but the large-scale ascent is just now beginning to arrive in this area, with additional convective initiation still possible.


   ..Mosier.. 05/25/2024

Mesoscale Discussion #963


Mesoscale Discussion 0963

NWS Storm Prediction Center Norman OK

1016 PM CDT Sat May 25 2024


Areas affected...Far North-Central TX


Concerning...Tornado Watch 308...


Valid 260316Z - 260415Z


The severe weather threat for Tornado Watch 308 continues.


SUMMARY...An intense supercell capable of producing a strong tornado is expected to continue for at least the next hour over far north-central Texas.


DISCUSSION...Recent radar imagery has shown an notable increase in intensity of the supercell over Montague and Cooke County in far north-central Texas. Echo tops now over 60 kft, with a very strong low-level circulation observed as well. Recent mesoanalysis estimates that effective helicity is over 800 m2/s2 and effective shear is over 70 kt near this supercell. This intense shear coupled with very strong buoyancy (i.e. 4500 J/kg) is resulting in STP values from 16 to 18. Given the supercellular mode, a strong tornado is possible within this environment. An extension in time for Tornado Watch 308 may be needed.


   ..Mosier.. 05/26/2024

Mesoscale Discussion #980


Mesoscale Discussion 0980

NWS Storm Prediction Center Norman OK

0238 PM CDT Sun May 26 2024


Areas affected...from parts of southern and southeast Missouri into far northeast Arkansas...southern Illinois...and across the Missouri Bootheel and surrounding areas


Concerning...Severe potential...Tornado Watch likely 


Valid 261938Z - 262215Z


Probability of Watch Issuance...95 percent


SUMMARY...A strong tornado situation appears to be developing for later this afternoon and into the early evening. In addition, very large hail and eventual significant damaging winds may develop across the region.


DISCUSSION...Satellite imagery shows heating and rapid air mass recovery across southeast MO, where boundary layer clouds are developing, and, satellite derived PWAT indicates ample moisture. This is ahead of a cold front which is currently northwest of St. Louis and extends into southeast KS near a weak low. Surface observations show a very moist air mass with mid 70s F dewpoints spreading north out of AR, MS, and western TN as well, just south of the old/dissipating outflow boundary. 


A special 18Z LZK sounding shows strong shear, steep midlevel lapse rates and ample moisture. A capping inversion exits just above 850 mb, however, much less capping exists farther north into MO where lift will be increasing ahead of the surface trough. Forecast soundings across this region strong favor tornadic supercells as well, along with very large hail. Depending on storm mode later this evening, widespread damaging winds could also materialize.


As such, the 20Z outlook will be upgraded to MODERATE RISK for the developing situation.


   ..Jewell/Bunting.. 05/26/2024

Mesoscale Discussion #981


Mesoscale Discussion 0981

NWS Storm Prediction Center Norman OK

0246 PM CDT Sun May 26 2024


Areas affected...portions of the Ozarks...mid Mississippi River Valley and western Tennessee Valley


Concerning...Outlook upgrade 


Valid 261946Z - 262045Z


SUMMARY...Confidence has increased that severe storms capable of strong tornadoes, very large hail, and intense damaging winds are likely this afternoon and continuing into the evening. An upgrade to a Tornado/Wind driven Moderate Risk is forthcoming at 20z.


DISCUSSION...Rapid air mass recovery is ongoing along a remnant outflow boundary over portions of central and eastern MO, northeast AR, southern IL/IN and western KY/TN. Confidence has increased in a significant severe risk such that an upgrade to a categorical Moderate Risk (15% Sig Tornado and 45% Sig Wind) will be forthcoming at 20z. Please see MCD #980 for the relevant environmental information and the upcoming 20z Convective Outlook for more information.


   ..Lyons/Bentley.. 05/26/2024

Mesoscale Discussion #990


Mesoscale Discussion 0990

NWS Storm Prediction Center Norman OK

0547 PM CDT Sun May 26 2024


Areas affected...Southern MO...Northwest/North-Central AR


Concerning...Tornado Watch 319...320...


Valid 262247Z - 270015Z


The severe weather threat for Tornado Watch 319, 320 continues.


SUMMARY...Discrete supercells capable of all severe hazards, including tornadoes, very large hail up to 3" in diameter, and strong gusts up to 70 mph, will persist from central Missouri into northwest/north-central AR.


DISCUSSION...Several supercells have developed within the open warm sector across southern MO and northwest AR, ahead of the line of storms along the cold front approaching for the northwest. The triplet of supercells in south-central MO (i.e. Texas, Shannon, and Howell Counties) have all shown a notable increase in updraft intensity over the past half hour, with echo tops now over 50 kft in each storm. Another supercell has developed quickly just ahead of the primary line of storms across Pulaski and Phelps Counties.


The easternmost two storms also are likely undergoing the splitting process, suggesting some additional strengthening and maturation is possible once this process completes. The downstream airmass is very unstable, with recent mesoanalysis estimating over 3500 J/kg of MLCAPE. Vertical shear is strong as well, with mesoanalysis estimating effective bulk shear around 50 kt. Low-level flow is somewhat veered, but strong low-level buoyancy (i.e. 0-3 km MLCAPE over 150 J/kg) should still be more than sufficient for stretching and potential tornadogenesis. Very large hail up to 3" in diameter and strong gusts up to 70 mph are possible in addition to tornadoes.


The lone supercell along the far western MO/AR border continues to maintain its intensity, although it may now be trending towards a more outflow-dominant structure. However, given the strong buoyancy and robust vertical shear, some additional reorganizing is possible, with an attendant threat for tornadoes once this reorganization occurs. Very large hail up to 3" in diameter and strong gusts up to 70 mph remain possible with this storm as well.


   ..Mosier.. 05/26/2024

Mesoscale Discussion #992


Mesoscale Discussion 0992

NWS Storm Prediction Center Norman OK

0618 PM CDT Sun May 26 2024


Areas affected...Far Southeast MO...Far Southern IL...Western/Central KY...Far Southwest IN


Concerning...Tornado Watch 320...


Valid 262318Z - 270045Z


The severe weather threat for Tornado Watch 320 continues.


SUMMARY...Open warm sector initiation appears to be underway from far southeast Missouri across far southern Illinois into western/central Kentucky and southern Indiana. Supercells capable of all severe hazards, including strong tornadoes, are possible. Southern IN and western/central KY will likely need an additional Tornado Watch soon.


DISCUSSION...Recent visible satellite  has shown increasingly deep cumulus within the warm sector well ahead of the main cold front from far southwest MO across southern IL into southwest KY and far southwest IN. Some radar returns have been recently noted with this activity as well, giving increasing confidence that at least isolated convective initiation may be realized shortly. 


A belt of stronger mid-level flow extends across much of this region, resulting in notable low-level veering within the VAD profiles at PAH and HPX. Ample low-level moisture and strong buoyancy exists across the region as well. Mesoanalysis estimates STP is currently from 3 to 5, with this high values expected to persist and expand northeastward with time. The result is an environment that is favorable for supercells capable of all severe hazards, including strong tornadoes. Very large hail up to 2.5" in diameter is possible as well. Some of this area is within the Tornado Watch 230, but those areas to its east including far southern IN and western KY will likely need an additional Tornado Watch soon.


   ..Mosier/Smith.. 05/26/2024

Mesoscale Discussion #994


Mesoscale Discussion 0994

NWS Storm Prediction Center Norman OK

0657 PM CDT Sun May 26 2024


Areas affected...portions of southeastern MO...and northeast AR.


Concerning...Tornado Watch 320...


Valid 262357Z - 270100Z


The severe weather threat for Tornado Watch 320 continues.


SUMMARY...Ongoing cluster of supercells with a history of producing tornadoes will continue eastward with a risk for strong to intense tornadoes.


DISCUSSION...As of 2350 UTC regional radar analysis showed a cluster of supercells ongoing across southeastern MO within PDS Tornado Watch #320. Several of these storms have produced tornadoes over the past couple of hours. The environment ahead of these storms is strongly unstable with MLCAPE greater than 4000 J/kg which is very favorable for intense updrafts. Large ambient vorticity and enhanced low-level shear (ESRH >200 m2/s2) is present along a modified outflow boundary from southeast MO into northern AR and western TN/KY, supporting the potential for strong low-level mesocyclones. With STP values greater than 4, these storms will likely remain capable of strong to potentially intense tornadoes this evening. Eventual upscale growth is possible, but a significant tornado risk, along with very large hail and damaging winds remains likely for the next couple of hours.


   ..Lyons/Mosier.. 05/26/2024

Mesoscale Discussion #998


Mesoscale Discussion 0998

NWS Storm Prediction Center Norman OK

0836 PM CDT Sun May 26 2024


Areas affected...portions of western KY and far southern IN


Concerning...Tornado Watch 324...


Valid 270136Z - 270300Z


The severe weather threat for Tornado Watch 324 continues.


SUMMARY...Isolated supercells are in a favorable environment for strong to intense tornadoes.


DISCUSSION...As of 0130 UTC, regional radar analysis showed mature supercells ongoing over Caldwell and Davies county KY. These storms have exhibited strong low-level rotation and have a history of producing tornadoes. The environment ahead of these storms remains very favorable for strong to intense tornadoes with large buoyancy, ESRH greater than 400 m2/s2 and STP values of 5. Strong to intense tornado potential will remain high as these storms approach a modified baroclinic boundary left over from previous convection. Large to very large hail and damaging winds are also possible with these intense storms.


..Lyons.. 05/27/2024

Mesoscale Discussion #1558


Mesoscale Discussion 1558

NWS Storm Prediction Center Norman OK

1119 AM CDT Mon Jul 08 2024


Areas affected...parts of southeastern Texas and southwestern/west central Louisiana


Concerning...Tornado Watch 514...


Valid 081619Z - 081815Z


The severe weather threat for Tornado Watch 514 continues.


SUMMARY...Within and ahead of outer bands of Beryl, the risk for supercells with potential to produce tornadoes may undergo a substantive increase through 1-3 PM CDT.


DISCUSSION...The low-level circulation center of Beryl is progressing slowly northward, near/west through north of the Houston Intercontinental vicinity.  VWP data from KGHX indicates that low-level wind fields have veered to a south-southwesterly component with hodographs becoming more linear, and downward mixing of drier air is lowering surface dew points into the lower 70s F across much of the Greater Houston area.


On the eastern to northeastern periphery of Beryl, surface dew points continue to rise through the upper 70s F, in the presence of enlarging clockwise-curved low-level hodographs closer to the Sabine River and into southwestern and west central Louisiana.  Coupled with further boundary-layer destabilization, aided by daytime heating beneath the eastern periphery of the mid-level warm core, the potential for tornadoes may begin to substantively increase through 18-20Z.  This may include with evolving supercells within the north-northeastward pivoting outer bands, and perhaps discretely to their north and east.


..Kerr.. 07/08/2024

Mesoscale Discussion #1570


Mesoscale Discussion 1570

NWS Storm Prediction Center Norman OK

1215 PM CDT Wed Jul 10 2024


Areas affected...Parts of central/northern New York


Concerning...Tornado Watch 517...


Valid 101715Z - 101845Z


The severe weather threat for Tornado Watch 517 continues.


SUMMARY...Discrete storms in central New York will encounter increasingly favorable environment for tornadoes as the move northeast the next 1-2 hours.


DISCUSSION...A few discrete storms have formed north-northeast of Binghamton. With the more dense cloud cover shifting northward, temperatures are beginning to rise into the low to mid 80s F ahead of these storms. Given the favorable storm mode and low-level shear near the warm front (effective SRH around 200 m2/s2 per objective mesoanalysis), the tornado risk with these storms will likely increase over the next 1-2 hours.


   ..Wendt.. 07/10/2024

Mesoscale Discussion #1641


Mesoscale Discussion 1641

NWS Storm Prediction Center Norman OK

0655 PM CDT Mon Jul 15 2024


Areas affected...East-central Iowa into northwest Illinois


Concerning...Severe Thunderstorm Watch 539...


Valid 152355Z - 160130Z


The severe weather threat for Severe Thunderstorm Watch 539 continues.


SUMMARY...A corridor of higher wind potential appears to be emerging across east-central Iowa into northwestern Illinois. High-res experimental guidance suggests wind gusts upwards of 80-90 mph and embedded circulations will be possible over the next 1-2 hours.


DISCUSSION...Reflectivity and velocity data from KDVN shows a broad circulation developing across the IA/WI/IL tri-state region, which is believed a deepening MCV that is typically associated with a mature MCS. To the southwest, a bowing segment is becoming established across eastern IA. A diffuse baroclinic zone (denoted by temperature/dewpoints in the 90s and upper 70s respectively lies immediately downstream to the southeast of this emerging bow. This should provide a focus for propagation over the next few hours. Latest WoFS guidance and HRRR solutions have picked up on this trend and suggest significant severe wind gusts (including gusts upwards of 80-90 mph) are probable. Additionally, adequately strong (around 30 knots) low-level shear is in place and should support embedded circulations - especially within any portions of the line that can become more north-south oriented. Portions of WW 539 have been added to tornado watch 541 to address this potential.


   ..Moore.. 07/15/2024

Mesoscale Discussion #1642


Mesoscale Discussion 1642

NWS Storm Prediction Center Norman OK

0826 PM CDT Mon Jul 15 2024


Areas affected...Northern Illinois


Concerning...Tornado Watch 541...


Valid 160126Z - 160330Z


The severe weather threat for Tornado Watch 541 continues.


SUMMARY...The potential for significant wind gusts upwards of 80-95 mph and embedded QLCS tornadoes will continue as a severe MCS pushes east across northern Illinois.


DISCUSSION...The evolution of a severe MCS is progressing as expected with two primary bowing segments evident in regional radar across north-central IL and to the east of the Davenport, IA area. Several embedded circulations have been noted as well as multiple reports of wind gusts over 75 mph (including one gust of 93 mph in Stephenson county, IL) across eastern IA and northwest IL. Latest WoFS guidance continues to capture recent convective trends well and depicts the potential for similar wind speeds within the two bowing segments over the next couple of hours. Given aforementioned reports and favorable environmental conditions downstream, these forecasts appear to be reasonable. Observed storm motion tracks and WoFS timing guidance both suggest the MCS will be approaching the lower Lake Michigan shore between 02 to 03 UTC with a slightly later arrival time for eastern IL/far western IN.


..Moore.. 07/16/2024

Mesoscale Discussion #2122


Mesoscale Discussion 2122

NWS Storm Prediction Center Norman OK

1146 PM CDT Thu Sep 26 2024


Areas affected...northern Florida into the Carolinas


Concerning...Tornado Watch 686...687...


Valid 270446Z - 270645Z


The severe weather threat for Tornado Watch 686, 687 continues.


SUMMARY...The environment remains conditionally favorable for supercells producing tornadoes, primary over southeast Georgia into South Carolina.


DISCUSSION...Unstable air continues to wrap northwestward ahead of Helene, with the high theta-e air mass now inland across eastern SC and GA. Very strong gusts continue into the Jacksonville FL area within the well-mixed boundary layer where temperatures are in the 80s F. Dewpoints are also averaging 78- 80 F along the coast farther north.


While severe cell coverage has decreased compared to a few hours ago, conditions remain quite favorable for tornadoes should additional bands of storms form. This is quite possible through tonight as low-level flow remains confluent. In addition, the high dewpoints will easily favor development with relatively minimal lift. As such, the tornado watch will continue from GA into southern NC for some time.  Areas to the south into central FL should eventually see a waning threat as convergence weakens due to the system pulling rapidly north.


..Jewell.. 09/27/2024

Mesoscale Discussion #2138


Mesoscale Discussion 2138

NWS Storm Prediction Center Norman OK

1050 AM CDT Wed Oct 09 2024


Areas affected...Parts of central Florida


Concerning...Tornado Watch 690...


Valid 091550Z - 091745Z


The severe weather threat for Tornado Watch 690 continues.


SUMMARY...The tornado threat north of Lake Okeechobee is increasing as a cluster of discrete supercells move generally northward. A strong tornado or two will be possible this afternoon.


DISCUSSION...A cluster of discrete supercells continue to move north/north-northwest near Lake Okeechobee. Surface temperatures have risen into the low 80s F, with the most heating occurring in east-central Florida. The area where temperatures in the 80s and dewpoints in the upper 70s F will be where the tornado threat will be maximized this afternoon. The storm just west of Lake Okeechobee (Glades County) is currently producing a tornado per TDS evident on KMLB radar dual-pol data. Given the easterly flow and the expected strengthening of the low-level wind field with time (KMLB VAD data has shown slow improvement in low-level shear), the tornado threat north of Lake Okeechobee will continue to increase this afternoon. The environment will support a strong tornado or two with these storms.


   ..Wendt.. 10/09/2024

Mesoscale Discussion #2142


Mesoscale Discussion 2142

NWS Storm Prediction Center Norman OK

0149 PM CDT Wed Oct 09 2024


Areas affected...East-Central and Southeastern Florida


Concerning...Tornado Watch 690...


Valid 091849Z - 092015Z


The severe weather threat for Tornado Watch 690 continues.


SUMMARY...Threat for tornadoes, a few of which may be strong, to continue over the next 1-2 hours.


DISCUSSION...Supercells are tracking northward in a highly favorable environment across southeastern Florida, with confirmed tornadoes ongoing. Along the eastern Florida Peninsula, temperatures have warmed into the 80s with dew points in the mid 75 to 80s. This moisture rich environment is further enhanced by favorable wind profiles, with back easterly surface winds and effective SRH around 300-400 m2/s2 analyzed by the VAD profile at MLB (Melbourne, FL) and in surface objective analysis. This volatile environment will support continued potential for strong tornadoes.


   ..Thornton/Smith.. 10/09/2024

Mesoscale Discussion #2187


Mesoscale Discussion 2187

NWS Storm Prediction Center Norman OK

0154 AM CST Sun Nov 03 2024


Areas affected...Central and Eastern OK


Concerning...Tornado Watch 700...


Valid 030754Z - 030930Z


The severe weather threat for Tornado Watch 700 continues.


SUMMARY...The threat for tornadoes, both within cells ahead of the convective line and within the convective line itself, will persist for at least the next few hours. Tornado Watch 700 was recently issued across central and eastern Oklahoma to address this threat.


DISCUSSION...Several discrete supercells have matured within the open warm sector across central OK. This includes the supercell over Stephens County, which had a rotational velocity over 65 kt for several scans within the last 25 minutes. The maturing of these cells corresponded with the strengthening of the surface winds by 5 to 10 kt within the warm sector, with southeasterly winds now gusting 20 to 25 kt. The longevity of these discrete cells will be limited by the approaching convective line, but the persistence of strong low-level flow suggests the tornado threat will likely persist within the line itself as it continues eastward. Given this continued threat for tornadoes in both discrete cells ahead of the line and QLCS circulations within the line, a Tornado Watch was recently issued for central and eastern OK. The airmass ahead of the line is expected to remain at least modestly unstable into eastern OK, justifying its inclusion in the recent watch.


..Mosier.. 11/03/2024