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Mesoscale Discussion #90
Mesoscale Discussion #90
Date: February 12
Discussion Text:
Mesoscale Discussion 0090
NWS Storm Prediction Center Norman OK
0511 PM CST Wed Feb 12 2025
Areas affected...southeast MS and southwest AL
Concerning...Tornado Watch 5...6...
Valid 122311Z - 130045Z
The severe weather threat for Tornado Watch 5, 6 continues.
SUMMARY...Primary tornado threat will persist near the warm front, especially with discrete/semi-discrete supercells that cross/remain anchored along it. A strong tornado is possible.
DISCUSSION...Several supercells have occurred over the past hour, mainly from parts of south-central MS into southwest AL. The environment will remain quite conductive to low-level rotation, especially near/along the wavy west/east-oriented warm front that extends roughly from Simpson County, MS to Montgomery County, AL. Discrete and semi-discrete supercells that can continue to regenerate across eastern LA into southeast MS will be the most likely candidates for eventually sustaining a longer-lived tornado as they impinge on the vorticity-enriched warm front. Overall setup, with peak STP having increased to a 3 as of 22Z, should favor potential for a strong tornado.
The northern extent of the tornado threat will be limited by cooler temperatures. Per early afternoon observed and RAP forecast soundings, as storms move north of the 65-66 F isodrosotherm, the tornado threat will diminish. Surface winds deeper into the warm sector across LA are slightly veered and modulating to some extent low-level hodograph curvature.
..Grams.. 02/12/2025
Mesoscale Discussion #91
Mesoscale Discussion #91
Date: February 12
Discussion Text:
Mesoscale Discussion 0091
NWS Storm Prediction Center Norman OK
0645 PM CST Wed Feb 12 2025
Areas affected...southern AL and southeast MS
Concerning...Tornado Watch 6...
Valid 130045Z - 130215Z
The severe weather threat for Tornado Watch 6 continues.
SUMMARY...Strong tornado potential should persist along the surface warm front, expanding east of Tornado Watch 6 into an initially confined portion of southeast Alabama.
DISCUSSION...A recently intense supercell from Washington to Clarke County, AL produced a potentially strong tornado near the wavy surface warm front. This boundary arcs more east-northeast ahead of this cell through Wilcox to southern Montgomery County, then pivots southeast into Barbour County per latest surface observations. 00Z LIX sounding sampled a rather favorable supercell environment, amply buoyant with strong deep-layer shear. Enhanced vorticity along the slow-moving front will be most favorable for strong tornado potential into late evening. With neutral mid-level height change through the evening, the number of additional warm-sector supercells may be limited. The northern portion of the tornado threat will wane quickly where surface dew points hold below 65-66 F.
..Grams.. 02/13/2025
Mesoscale Discussion #180
Mesoscale Discussion #180
Date: March 14
Discussion Text:
Mesoscale Discussion 0180
NWS Storm Prediction Center Norman OK
0843 PM CDT Fri Mar 14 2025
Areas affected...Central Arkansas into far south-central Missouri
Concerning...Tornado Watch 32...
Valid 150143Z - 150345Z
The severe weather threat for Tornado Watch 32 continues.
SUMMARY...Multiple supercells across central/north-central AR will pose an increasing tornado threat as they migrate eastward through the next couple of hours, including the potential for a significant tornado.
DISCUSSION...Supercells moving out of northwest AR are becoming increasingly organized with several well-defined mid-level mesocyclones evident in KLZK and KSGF velocity imagery. These storms are moving into an environment characterized by STP values on the order of 3-5, which is largely being driven by a corridor of warm air advection between 925-850 mb over north-central AR. This diffuse warm frontal zone is supporting veering winds through the lowest 2 km with a 0-1 km SRH value of 300 m2/s2 sampled by the 00z LZK sounding and around 450 m2/s2 recently sampled by the KLZK VWP. This environment is typically supportive of robust, long-lived supercells with an attendant threat for tornadoes, including significant (EF-2+) tornadoes. The aforementioned convective trends suggest that cells are beginning to realize this environment and that the downstream tornado threat is likely increasing across central to north-central AR.
..Moore.. 03/15/2025
Mesoscale Discussion #181
Mesoscale Discussion #181
Date: March 14
Discussion Text:
Mesoscale Discussion 0181
NWS Storm Prediction Center Norman OK
0847 PM CDT Fri Mar 14 2025
Areas affected...east-central Missouri and into adjacent western Illinois
Concerning...Tornado Watch 32...
Valid 150147Z - 150315Z
The severe weather threat for Tornado Watch 32 continues.
SUMMARY...Tornado threat is forecast to spread into the greater St. Louis area over the next hour.
DISCUSSION...Latest surface analysis shows dewpoints now into the mid 50s west of the Mississippi River, southwest of the St. Louis Metro area. This has supported a northward expansion of the axis of greatest mixed-layer CAPE, per recent RAP-based mesoanalysis, with near 1000 J/kg now as far north as St. Louis, and 2000 J/kg to near FAM (Farmington, MO). In response, several supercell storms have organized within the main convective band, and are moving northeastward at 45 kt. At this time, one storm in particular, moving across Franklin County, is showing very strong low-level rotation, with hints of a corresponding minimum in correlation coefficient that would suggest an ongoing tornado. As such, given the background thermodynamic and kinematic environment, potential for a significant tornado appears to exist. This storm will continue to track northeastward toward the St. Louis area, potentially resulting in a particularly dangerous situation.
..Goss.. 03/15/2025
Mesoscale Discussion #184
Mesoscale Discussion #184
Date: March 14
Discussion Text:
Mesoscale Discussion 0184
NWS Storm Prediction Center Norman OK
1020 PM CDT Fri Mar 14 2025
Areas affected...Northeast Arkansas into the Missouri Bootheel
Concerning...Tornado Watch 32...36...
Valid 150320Z - 150515Z
The severe weather threat for Tornado Watch 32, 36 continues.
SUMMARY...Supercells with a history of producing tornadoes will continue to pose a tornado threat (including significant tornadoes) for the next couple of hours as they move into northeast Arkansas and southeast Missouri.
DISCUSSION...Two long-lived supercells moving across north-central AR and south-central MO have had a history of producing tornadoes per dual-pol data and spotter reports. Based on rotational velocity estimates and the magnitude of the convective environment (characterized by STP values up to 10), one or more of these tornadoes were likely significant (EF-2+). These cells will continue to reside in this exceptionally rare STP environment for the next 1-2 hours as they move into far northeast AR and southeast MO. Consequently, the potential for additional long-track and significant (possibly intense) tornadoes will continue across this region.
..Moore.. 03/15/2025
Mesoscale Discussion #188
Mesoscale Discussion #188
Date: March 14
Discussion Text:
Mesoscale Discussion 0188
NWS Storm Prediction Center Norman OK
1150 PM CDT Fri Mar 14 2025
Areas affected...southern Illinois...southwestern Indiana...southeastern Missouri...western Kentucky...western Tennessee...eastern Arkansas...and northern Mississippi
Concerning...Tornado Watch 36...
Valid 150450Z - 150645Z
The severe weather threat for Tornado Watch 36 continues.
SUMMARY...Severe/tornado risk is spreading eastward into Tornado Watch 36. A few strong tornadoes are possible.
DISCUSSION...Latest radar loop shows a broken band comprised of numerous supercell storms, extending from southern Illinois/southeastern Missouri southwestward into southwestern Arkansas. Sustained rotational signatures have persisted with several of these storms, as they move through an axis of 1500 to 2500 J/kg mixed-layer CAPE and surface dewpoints generally in the upper 50s across this area.
With very strong flow present across the region, that veers with height, these kinematically favorable conditions suggest continuation of the tornado risk as storms move through the instability axis ahead of the surface front. A few of the tornadoes could be strong/potentially significant over the next few hours, as they spread eastward toward/across the Mississippi River.
..Goss.. 03/15/2025
Mesoscale Discussion #190
Mesoscale Discussion #190
Date: March 14
Discussion Text:
Mesoscale Discussion 0190
NWS Storm Prediction Center Norman OK
1249 AM CDT Sat Mar 15 2025
Areas affected...Northeast and east central Mississippi
Concerning...Tornado Watch 36...38...
Valid 150549Z - 150715Z
The severe weather threat for Tornado Watch 36, 38 continues.
SUMMARY...Potential for strong-intense (EF2-EF3+) tornadoes will persist with a supercell cluster moving into northeast Mississippi, while new supercell development is possible into east central Mississippi.
DISCUSSION...An intense supercell is approaching the southern tier of counties in PDS tornado watch #36 across northeast MS. This storm is located in the open warm sector in a zone of low-level moisture advection and strong low-level shear with large, curved hodographs per regional VWP time series. The potential for strong-intense tornadoes will persist with this cluster for the next 1-2 hours. Farther south, thunderstorms are developing in the warm advection zone along the east edge of the richer moisture into east central MS. One or two supercells could emerge from this developing convection and pose a tornado threat in the next few hours. For this reason, a local eastward extension of tornado watch #38 will need to be considered by 06-07z.
..Thompson.. 03/15/2025
Mesoscale Discussion #197
Mesoscale Discussion #197
Date: March 15
Discussion Text:
Mesoscale Discussion 0197
NWS Storm Prediction Center Norman OK
0804 AM CDT Sat Mar 15 2025
Areas affected...portions of central Louisiana into northern Mississippi and extreme southwestern Tennessee
Concerning...Tornado Watch 44...
Valid 151304Z - 151430Z
The severe weather threat for Tornado Watch 44 continues.
SUMMARY...The severe threat continues across Tornado Watch 44. The potential for tornadoes (some strong) will only increase into the morning hours. Severe wind and hail will also be possible.
DISCUSSION...Deep-moist convection continues to increase in coverage and intensity along a baroclinic zone characterizing the northwestern bounds of the free warm sector. Recently, storms along the southern extent of this convective band have developed supercell characteristics, with pronounced low-level mesocyclones noted via KSHV radar data. 12Z JAN and LCH soundings show mid-level lapse rates above 8.5 C/km, along with rich low-level moisture and large, curved/elongated hodographs already in place, which is highly supportive of tornadic supercells. Through the morning hours, increased boundary-layer heating and ascent from the approaching upper trough should only boost shear/buoyancy further, resulting in a continued increasing severe threat. All severe hazards will be possible, including strong tornadoes, particularly with the more sustained supercells with unimpeded inflow.
..Squitieri.. 03/15/2025
Mesoscale Discussion #199
Mesoscale Discussion #199
Date: March 15
Discussion Text:
Mesoscale Discussion 0199
NWS Storm Prediction Center Norman OK
1007 AM CDT Sat Mar 15 2025
Areas affected...Eastern Louisiana and much of Mississippi
Concerning...Severe potential...Tornado Watch likely
Valid 151507Z - 151700Z
Probability of Watch Issuance...95 percent
SUMMARY...A Particularly Dangerous Situation Tornado Watch will be issued soon. A tornado outbreak with multiple intense to violent long-track tornadoes is likely.
DISCUSSION...Morning observational data continues to support a likely tornado outbreak today across parts of eastern Louisiana and Mississippi. 12Z RAOBS from LCH and LIX indicate rich low-level moisture featuring a mean mixing ratio of 14 to 15 beneath a steep EML with mid-level lapse rates of 8 to nearly 9 C/km. This thermodynamic profile, combined with broken cloud cover across Louisiana and southern Mississippi suggest substantial heating will occur and strong instability will be present for much of the day today. The EML will play a critical role in the storm mode today. Discrete supercells are anticipated given the EML which will suppress more widespread convection and also provide enough mid-level dry air for potentially multiple well-organized supercells in close proximity through the day. In addition, 12Z RAOB data along the Gulf Coast is consistent with the data observed the morning of historical tornado outbreaks across Mississippi and Alabama.
Strong shear is already present across Louisiana and Mississippi this morning with effective shear 40 to 60 knots at the LIX/LCH/JAN 12Z RAOBs. However, shear will increase further through the morning as mid-level flow strengthens with the mid-level jet streak overspreading more of the warm sector and with secondary surface cyclogenesis in the mid-Mississippi Valley. Early evidence of this secondary low-pressure center has already been observed with a sub-995mb surface low analyzed northwest of Little Rock, Arkansas at 15Z. This surface low will continue to deepen and consolidate through the day which will keep flow backed across the warm sector and result in further strengthening of the already strong low-level jet. By mid-afternoon, a low-level jet of 65 to 70 knots is forecast with corresponding 0-1km SRH of 300 to 500 m2/s2. The presence of nearly pure streamwise vorticity in the lowest 1km will create an environment extremely conducive to the stretching of the ambient low-level vorticity.
Confluence bands across Louisiana this morning likely represent the initial supercell initiation zone for the storms of greatest concern this afternoon. Multiple bands of supercells are possible. Once mature supercells develop in the environment south of the messier convection, there should be very little to interrupt their longevity through the afternoon.
Given the aforementioned factors, many discrete supercells are expected in an environment which is extremely conducive to tornadic activity. Therefore, a tornado outbreak appears imminent with the potential for multiple, intense to violent long track tornadoes from mid-day through this evening across eastern Louisiana and much of Mississippi. A Particularly Dangerous Situation Tornado Watch will be issued soon to address this threat.
..Bentley/Gleason.. 03/15/2025
Mesoscale Discussion #200
Mesoscale Discussion #200
Date: March 15
Discussion Text:
Mesoscale Discussion 0200
NWS Storm Prediction Center Norman OK
1119 AM CDT Sat Mar 15 2025
Areas affected... Extreme southeast Mississippi into much of western and central Alabama
Concerning... Severe potential...Tornado Watch likely
Valid 151619Z - 151745Z
Probability of Watch Issuance... 95 percent
SUMMARY... The severe threat will increase through the afternoon, including the potential for multiple intense, destructive tornadoes. A Particularly Dangerous Situation Tornado Watch will be issued in the next hour.
DISCUSSION... Thunderstorms, including supercells, continue to increase in coverage and intensity over MS with the rapid approach of a potent mid-level trough. A pronounced 500 mb speed max will glance the region to the west, promoting the maintenance of ongoing storms, while also contributing to adequate deep-layer ascent for the development of new supercells in warm-sector confluence bands.
As this occurs, these supercells will mature in a moistening low-level airmass, with dewpoints in the mid-60s °F, overspread by 8°C/km mid-level lapse rates. MLCAPE should reach around 2000 J/kg amid 400+ m²/s² effective SRH (driven by large, elongated/curved hodographs that are already evident via regional VADs). The anticipated parameter space will be highly supportive of tornadic supercells.
The more discrete, dominant supercell structures will be capable of intense, destructive tornadoes, and violent tornadoes cannot be ruled out. A severe hail/wind threat should also accompany any robust, sustained thunderstorms. A Particularly Dangerous Situation Tornado Watch will be needed in the next hour to address the impending severe threat.
..Squitieri/Gleason.. 03/15/2025
Mesoscale Discussion #201
Mesoscale Discussion #201
Date: March 15
Discussion Text:
Mesoscale Discussion 0201
NWS Storm Prediction Center Norman OK
1120 AM CDT Sat Mar 15 2025
Areas affected... Northern Mississippi
Concerning... Tornado Watch 45...
Valid 151620Z - 151745Z
The severe weather threat for Tornado Watch 45 continues.
SUMMARY... Strong to intense tornadoes are likely through mid-afternoon across northern Mississippi.
DISCUSSION... Several mature, embedded supercells are starting to emerge out of the larger area of precipitation across northwest Mississippi, with additional development possible from showers evident on radar across northeast Mississippi.
One of these supercells, in Humphreys County, has had a persistent very strong mid-level mesocyclone and tops over 50,000 feet. In addition, structural damage has been reported from this storm, indicating the potential for a tornado. This supercell and any other mature supercells that develop are expected to persist east across the state through the early-to-mid afternoon.
0-1 km SRH from the GWX VWP is around 350 m²/s² and increasing. Instability is not as great across northern Mississippi, where extensive cloud cover has muted daytime heating somewhat. However, there is still ample instability for the maintenance of ongoing supercells. The combination of instability and shear has yielded STP values of 2 to 3, which should increase through the early afternoon as both shear and instability increase.
The 15Z WoFs shows several moderate low-level rotation tracks across the northern part of the state over the next several hours, which supports expectations based on the aforementioned observational data. Therefore, several strong to intense tornadoes are likely over the next 2 to 3 hours across northern Mississippi within PDS Tornado Watch 45.
..Bentley.. 03/15/2025
Mesoscale Discussion #202
Mesoscale Discussion #202
Date: March 15
Discussion Text:
Mesoscale Discussion 0202
NWS Storm Prediction Center Norman OK
1153 AM CDT Sat Mar 15 2025
Areas affected... Parts of southern Louisiana into south and east-central Mississippi
Concerning... Tornado Watch 45...
Valid 151653Z - 151830Z
The severe weather threat for Tornado Watch 45 continues.
SUMMARY... The greatest threat for long-track intense to violent tornadoes through mid-afternoon is across portions of southern into east-central Mississippi.
DISCUSSION... A line of supercells is developing within a confluence band across eastern Louisiana and south-central Mississippi. Temperatures are expected to warm into the 80s ahead of these supercells within the next 1 to 2 hours, which should aid the maturity of multiple supercells out of this confluence band.
SPC Mesoanalysis shows STP values across the area are already 4 to 6, and these values are expected to increase through the afternoon as shear and instability increase further. As these supercells mature into peak heating, they will pose a threat for long-track intense to violent tornadoes.
Of particular interest are two consolidating supercells entering St. Helena Parish in eastern Louisiana and Lincoln County in Mississippi. These storms already have echo tops over 50,000 feet and are near the greatest instability. The 16Z LIX RAOB acts as a proximity sounding to these storms, with MLCAPE over 2200 J/kg and an STP of 6. In addition, temperatures have warmed a few degrees since it was launched.
These storms, with broken cloud cover and instability downstream in a volatile kinematic environment, have the greatest potential to realize this environment over the next 1 to 3 hours.
..Bentley.. 03/15/2025
Mesoscale Discussion #204
Mesoscale Discussion #204
Date: March 15
Discussion Text:
Mesoscale Discussion 0204
NWS Storm Prediction Center Norman OK
1251 PM CDT Sat Mar 15 2025
Areas affected... South-central Mississippi
Concerning... Tornado Watch 45...
Valid 151751Z - 151845Z
The severe weather threat for Tornado Watch 45 continues.
SUMMARY... An intense to potentially violent tornado is ongoing across Waltha County, MS, and is expected to continue northeast.
DISCUSSION... WSR-88D data from KHDC shows a rapidly intensifying tornadic circulation with radar-derived rotation of 60+ knots (briefly over 90 knots) and a tornado debris signature over 25,000 feet. This suggests an intense to violent tornado is ongoing.
This storm is located in the centroid of the maximum STP of 6-8 from SPC Mesoanalysis. This storm will likely be unimpeded as it moves northeast through the afternoon. Therefore, this tornado may persist for quite a while at intense to violent intensity.
..Bentley.. 03/15/2025
Mesoscale Discussion #205
Mesoscale Discussion #205
Date: March 15
Discussion Text:
Mesoscale Discussion 0205
NWS Storm Prediction Center Norman OK
0116 PM CDT Sat Mar 15 2025
Areas affected... Portions of northern Mississippi into northwestern Alabama
Concerning... Tornado Watch 45, 46...
Valid 151816Z - 151945Z
The severe weather threat for Tornado Watch 45, 46 continues.
SUMMARY... The risk for tornadoes continues across northern MS into northwestern AL, particularly with a supercell in Montgomery County. Intense tornadoes (EF3+) are possible.
DISCUSSION... A QLCS has evolved into more discrete supercells, some of which have become dominant relative to other convective elements in the area. Some of these storms have a history of tornadoes, and a supercell in Montgomery County, MS, has a persistent mesocyclone that continues to intensify per KDGX and KGWX NEXRAD data.
The GWX VAD shows an impressively large and curved hodograph, with nearly 500 m²/s² effective SRH in just the surface-500 m layer, with about 1000 m²/s² SRH in the surface-3 km layer. As such, the ambient environment supports intense tornadoes (EF3+).
However, this is contingent on storms benefiting from minimal interference by other nearby storms, including the absorption of smaller storms. If one of the more dominant storms (especially the Montgomery County storm) can obtain a pristine inflow environment, the chance for intense tornado development is high.
Damaging gusts are possible, especially with any linear segments that materialize.
..Squitieri.. 03/15/2025
Mesoscale Discussion #206
Mesoscale Discussion #206
Date: March 15
Discussion Text:
Mesoscale Discussion 0206
NWS Storm Prediction Center Norman OK
0131 PM CDT Sat Mar 15 2025
Areas affected... Southern Mississippi to central Alabama
Concerning... Tornado Watch 45, 46...
Valid 151831Z - 152030Z
The severe weather threat for Tornado Watch 45, 46 continues.
SUMMARY... Ongoing supercells are likely to persist through the afternoon with intense to violent tornadoes.
DISCUSSION... Multiple mature supercells have developed from central to south-central Mississippi. One of these supercells has already produced a likely violent tornado across Walthall County. The environment downstream of these supercells continues to destabilize, which will maintain the threat through the afternoon and likely into the evening.
Eventually, these storms will likely move east of the upper 60s dewpoints. However, mid-60s dewpoints, which are expected to be prevalent across Alabama, should be sufficient for a continued intense to violent tornado threat given the continued favorable kinematics and the presence of already strong supercells. This is supported by the 17Z WoFS, with more than half of the ensemble members showing one or more long-track UH swaths from south-central Mississippi to central Alabama through the afternoon.
Increased forcing with the ejecting mid-level jet max has led to a large amount of additional showers and small thunderstorms in the vicinity of these storms. This may lead to occasional disruptions of tornadic circulations, but the strongly dynamic pressure perturbations associated with the ongoing supercells are expected to persist through the entire afternoon.
..Bentley.. 03/15/2025
Mesoscale Discussion #207
Mesoscale Discussion #207
Date: March 15
Discussion Text:
Mesoscale Discussion 0207
NWS Storm Prediction Center Norman OK
0207 PM CDT Sat Mar 15 2025
Areas affected... Parts of far eastern Louisiana into eastern Mississippi and far western Alabama
Concerning... Tornado Watch 45, 46...
Valid 151907Z - 152030Z
The severe weather threat for Tornado Watch 45, 46 continues.
SUMMARY... The most concerning tornado threat for the next 1 to 2 hours extends from south-central Mississippi into far west-central Alabama.
DISCUSSION... Several supercells across southern Mississippi have already produced intense to violent tornadoes, including two paths within very close proximity from Walthall to Marion Counties from consecutive supercells.
These supercells, along with a few others that have recently developed across St. Helena and Tangipahoa Parishes, are the storms of greatest tornadic concern over the next 1 to 2 hours. These supercells are in the centroid of the greatest STP (6+) and in the closest proximity to upper 70s to low 80s temperatures, where surface winds remain backed.
Expect this environment to persist through the afternoon as a meso-low (~994 mb) currently over central Mississippi translates northeast at a similar speed to the mean storm motion.
..Bentley.. 03/15/2025
Mesoscale Discussion #210
Mesoscale Discussion #210
Date: March 15
Discussion Text:
Mesoscale Discussion 0210
NWS Storm Prediction Center Norman OK
0329 PM CDT Sat Mar 15 2025
Areas affected... Southeast Mississippi into central Alabama
Concerning... Tornado Watch 45, 46...
Valid 152029Z - 152230Z
The severe weather threat for Tornado Watch 45, 46 continues.
SUMMARY... Multiple supercells capable of intense to potentially violent tornadoes will persist into the evening.
DISCUSSION... A line of supercells continues from east-central Alabama to south-central Mississippi. Most of these supercells have a history of tornadoes, including a few intense to potentially violent tornadoes.
The environment ahead of these supercells remains very favorable for tornadoes, with 1500 to 2000 J/kg MLCAPE per SPC mesoanalysis and 0-1 km SRH in excess of 300 m²/s² per GWX VWP. This yields an STP value around 5, which is forecast to shift east with these storms through the evening.
Convective trends have shown rapid strong to intense tornado development in supercells with unimpeded inflow, while circulation disruption occurs when surrounding showers/thunderstorms impede this inflow. Expect this pattern to continue into the early evening, with the greatest concern being supercells that have clear inflow of at least mid-60s dewpoints.
The threat for intense to potentially violent tornadoes will persist as long as these supercells remain ahead of the developing line of storms across central Mississippi. Based on current storm motions, they should remain ahead of this line into the early evening.
..Bentley.. 03/15/2025
Mesoscale Discussion #213
Mesoscale Discussion #213
Date: March 15
Discussion Text:
Mesoscale Discussion 0213
NWS Storm Prediction Center Norman OK
0618 PM CDT Sat Mar 15 2025
Areas affected... Southern Mississippi into central and southern Alabama
Concerning... Tornado Watch 46...
Valid 152318Z - 160215Z
The severe weather threat for Tornado Watch 46 continues.
SUMMARY... The environment remains quite favorable for strong tornadoes, but the threat will depend on storm mode going into the evening and early morning hours.
DISCUSSION... Supercells moving out of eastern Mississippi have transitioned into more of a small MCS this evening, extending from west-central Alabama into parts of eastern Mississippi. Farther south, a more discrete cell mode was noted across far southern Mississippi near the Louisiana border.
While storm mode is currently somewhat disorganized, shear, moisture, and instability all remain favorable for strong tornadoes at any point this evening and into the early morning hours. In addition, dewpoints and instability are expected to increase across eastern Alabama and into Georgia late tonight as the low-level jet persists.
It is possible that storm reorganization may take place later this evening as we transition out of the daytime/diurnal regime. Any robust, discrete cells will have a high conditional risk of producing strong tornadoes. Meanwhile, any linear structures may still produce tornadoes and swaths of damaging wind, as effective SRH remains at or above 500 m²/s².
..Jewell.. 03/15/2025
Mesoscale Discussion #217
Mesoscale Discussion #217
Date: March 15
Discussion Text:
Mesoscale Discussion 0217
NWS Storm Prediction Center Norman OK
0900 PM CDT Sat Mar 15 2025
Areas affected... Much of central Alabama
Concerning... Tornado Watch 49...
Valid 160200Z - 160400Z
The severe weather threat for Tornado Watch 49 continues.
SUMMARY... The risk of strong tornadoes persists over the watch area, especially over central Alabama.
DISCUSSION... In the wake of tornadic storms that passed over the BMX radar, a residual region of outflow remains across parts of Shelby, Talladega, Chilton, and Coosa counties. Meanwhile, a very large complex of storms is moving up from the southwest. Very strong inflow winds exist ahead of this complex, which will continue to feed these storms and possibly enhance lift along the residual outflow from the earlier storms. Given over 400 m²/s² 0-1 km SRH, it is possible that any interaction with the boundary could result in a strong tornado.
The environment remains favorable farther south as well, where a north-south confluence line is noted ahead of the primary cold front, including the Wilcox County cell.
..Jewell.. 03/16/2025
Mesoscale Discussion #218
Mesoscale Discussion #218
Date: March 15
Discussion Text:
Mesoscale Discussion 0218
NWS Storm Prediction Center Norman OK
1119 PM CDT Sat Mar 15 2025
Areas affected... Southeast Alabama
Concerning... Tornado Watch 49
Valid 160419Z - 160615Z
The severe weather threat for Tornado Watch 49 continues.
SUMMARY... Two long-track supercells across eastern/southeastern AL will pose a risk for significant tornadoes downstream into far western GA over the next 1-2 hours.
DISCUSSION... Two leading supercells across eastern and southeastern AL have both recently produced tornadoes based on KEOX and KMXX velocity and dual-pol data. Surface observations just ahead of these cells show 30-40 mph low-level winds are advecting high-quality moisture (mid 60s dewpoints) ahead of the storms. This suggests that although these cells are approaching the eastern edge of the effective warm sector, they will likely remain in a favorable thermodynamic environment for the next 1-2 hours. Additionally, regional VWPs continue to sample 0-1 km SRH on the order of 500 m²/s², which is supporting STP values on the order of 2-4 in proximity to the storms/within the inflow region. Based on this environment and observed rotational velocities (50-60 knots at times), these cells will continue to be capable of producing significant (EF-2+) tornadoes in the short term.
..Moore.. 03/16/2025
Mesoscale Discussion #246
Mesoscale Discussion #246
Date: March 19
Discussion Text:
Mesoscale Discussion 0246
NWS Storm Prediction Center Norman OK
0337 PM CDT Wed Mar 19 2025
Areas affected... Eastern Illinois into far western Indiana
Concerning... Tornado Watch 57
Valid 192037Z - 192230Z
The severe weather threat for Tornado Watch 57 continues.
SUMMARY... Strong to severe thunderstorm development is likely to continue to increase during the next few hours, including the potential for supercells with tornadoes across much of east-central Illinois into the Indiana state border vicinity through 5-7 PM CDT.
DISCUSSION... Aided by stronger mid-level forcing for ascent and cooling, within the exit region of the intense mid-level jet nosing through the middle Mississippi Valley, an intensifying and evolving broken line of thunderstorms appears likely to spread across and east of the Interstate 55 corridor of central Illinois through 21-22Z. This is where 20Z surface observations indicate that rapid (2-hourly in excess of 4 mb) surface pressure falls are maximized, and lower 50s surface dewpoints are being maintained with perhaps some further increase ongoing farther east, into the vicinity of the Indiana state border.
More discrete thunderstorms are now initiating farther south, between Taylorville and Salem, which are likely to continue rapidly moving north-northeastward within 50-60 kt south-southwesterly deep-layer mean flow. Rapid Refresh forecast soundings continue to suggest that this will coincide with enlarging clockwise-curved low-level hodographs near/east of Kankakee, Champaign, Decatur vicinities, where south to southwesterly flow is forecast to intensify within the 850-700 mb layer through 22-00Z. And it still appears the low-level thermodynamic profiles may become conducive to supercell tornadoes, perhaps including a strong tornado or two.
..Kerr.. 03/19/2025
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