2010

Mesoscale Discussion #



Mesoscale Discussion #0337


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 74 CONTINUES.

   

NUMEROUS SEVERE SUPERCELL THUNDERSTORMS HAVE DEVELOPED WITHIN UPSLOPE REGION OF THE CNTRL HIGH PLAINS FROM ERN CO INTO WRN KS.  THIS ACTIVITY IS EVOLVING WITHIN STRONGLY FORCED LEFT EXIT REGION OF UPPER JET...AND CONVERGENT LOW LEVEL ELY FLOW REGIME.  ALTHOUGH INSTABILITY IS NOT PARTICULARLY IMPRESSIVE...LOW CLOUD BASES WITHIN STRONGLY SHEARED ENVIRONMENT FAVOR A CONTINUED TORNADO THREAT.  ONE PARTICULARLY LONG-LIVED TORNADIC SUPERCELL IS LIFTING NEWD ACROSS KIOWA COUNTY CO.  THIS STORM HAS EDGED INTO WRN PLUME OF GREATER BOUNDARY LAYER MOISTURE AND COULD MAINTAIN TORNADIC CHARACTERISTICS FOR SOME TIME...ESPECIALLY IF STORM MERGERS DO NOT INTERRUPT IT/S INFLOW.

Mesoscale Discussion #0371


CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   

VALID 241243Z - 241445Z

   

STORMS ARE EXPECTED TO INCREASE DURING THE MORNING ACROSS CNTRL AND NRN AL. PRIMARY INITIAL THREAT WILL BE LARGE HAIL AND DAMAGING WIND...BUT THE THREAT FOR STRONG TORNADOES WILL INCREASE LATER THIS MORNING AND ESPECIALLY THIS AFTERNOON.

   

THIS MORNING A WARM FRONT EXTENDS FROM SWRN GA THROUGH CNTRL AL INTO NRN MS AND WRN AR. THIS BOUNDARY SEPARATES WARM MOIST GULF AIR WITH LOW 70S DEWPOINTS AND MODERATE INSTABILITY IN THE WARM SECTOR FROM A MODIFIED CP BOUNDARY LAYER TO THE NORTH. THE FRONT WILL LIFT NWD AS AN INTENSE LOW-LEVEL JET DEVELOPS THROUGH THE LOWER MS VALLEY IN RESPONSE TO AN EWD EJECTING SHORTWAVE TROUGH NOW OVER TX. STORMS CURRENTLY MOVING OUT OF MS WILL INITIALLY POSE A THREAT FOR MAINLY LARGE HAIL AND DAMAGING WIND. HOWEVER...AS THE BOUNDARY LAYER CONTINUES TO MOISTEN AND DESTABILIZE...THE RISK FOR TORNADIC SUPERCELLS WILL INCREASE GIVEN THE SIZE OF HODOGRAPHS /SRH AOA 400 M2/S2 ALONG THE STRENGTHENING LOW LEVEL JET.

Mesoscale Discussion #0372


CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   

VALID 241431Z - 241530Z

   

TORNADO RISK WILL INCREASE ACROSS A LARGE PART OF THE MID-SOUTH AND LWR OH VLY THROUGH THE AFTN.  STRONG AND LONG-TRACKED TORNADOES WILL BE POSSIBLE ALONG WITH VERY LARGE HAIL AND DMGG WIND GUSTS.

   

UPR AIR ANALYSIS SHOWS UPSTREAM TROUGH GOING NEGATIVE-TILT /100 METER 12-HR HEIGHT FALLS/ WITH AN EMBEDDED JET-STREAK PUNCHING ENE INTO THE ARKLATEX REGION.  THIS FEATURE WILL TRANSLATE INTO THE MID-SOUTH/LWR OH VLY REGIONS THIS AFTN.  SFC LOW OVER NCNTRL AR WILL TRACK TO NEAR ST. LOUIS BY LATE AFTN AND UNDERGO CONSIDERABLE DEEPENING.

   

MORNING STG/SVR TSTMS CLUSTERS WILL CONTINUE ENE THROUGH THE TN VLY THROUGH EARLY THIS AFTN AND PROBABLY BECOME MORE ELEVATED WITH TIME AS THEY MOVE TOWARD THE CUMBERLAND PLATEAU AND SRN APPALACHIAN MOUNTAINS.  SVR THREAT WILL SUBSEQUENTLY INCREASE UPSTREAM THIS AFTN.

   

WARM SECTOR...CHARACTERIZED BY SFC DEW POINTS IN THE MID 60S TO LWR 70S WILL SURGE N IN WAKE OF MORNING ACTIVITY INTO ERN AR...SERN MO...MIDDLE/WRN TN AND WRN KY AHEAD OF THE SFC LOW.  THIS WILL RESULT IN RAPID DESTABILIZATION AND SUBSEQUENT INCREASE IN TSTMS.  FCST LOW-LEVEL HODOGRAPHS WILL CONTINUE TO EXHIBIT TREMENDOUS 0-1KM SRH VALUES 300-500+ M2/S2.  THUS...ANY STORM WILL HAVE POTENTIAL FOR STRONG...LONG-LIVED TORNADOES ALONG WITH VERY LARGE HAIL RISKS.

   

IT APPEARS THAT THE PRIMARY SVR EVENT MAY BE BEGINNING ACROSS SCNTRL/SERN AR JUST AHEAD OF THE SFC LOW/WIND SHIFT.  ACTIVITY SHOULD GROW UPSCALE IN INTENSITY THROUGH THE AFTN ENE TOWARD THE MEMPHIS/MID-SOUTH AREA AND TOWARD THE LWR OH VLY LATER THIS AFTN.

Mesoscale Discussion #0430


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 116 CONTINUES.

   

DANGEROUS TORNADO SITUATION UNFOLDING ACROSS AR/SRN MO THIS EVENING...AND THE TORNADO THREAT WILL CONTINUE INTO THE OVERNIGHT HOURS.

   

MULTIPLE DISCRETE SUPERCELLS CONTINUE TO INTENSIFY IN A BROKEN BAND FROM N OF TXK TO NW OF LIT INTO S CENTRAL MO.  THESE STORMS ARE MOVING INTO AN ENVIRONMENT WITH STRONG LOW-LEVEL AND DEEP-LAYER SHEAR...AS WELL AS RICH LOW-LEVEL MOISTURE AND MODERATE INSTABILITY/PER THE 00Z LZK SOUNDING/.  GIVEN THE OBSERVED STORM STRUCTURES AND ENVIRONMENT...A FEW STRONG/LONG-TRACK TORNADOES NOW APPEAR LIKELY. THE CONVECTIVE MODE AND STORM ENVIRONMENT ARE NOT EXPECTED TO CHANGE SUBSTANTIALLY INTO THE EARLY OVERNIGHT HOURS...THUS THE SIGNIFICANT TORNADO THREAT WILL PERSIST WELL AFTER DARK.

Mesoscale Discussion #0435


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 118 CONTINUES.

   

DANGEROUS TORNADO SITUATION CONTINUES ACROSS SWRN-SRN INTO CENTRAL AND ERN AR...WITH LONG-TRACK...STRONG TORNADOES EXPECTED TO CONTINUE AND REMAIN LIKELY THROUGH THE LATE EVENING TO THE EARLY OVERNIGHT HOURS.

   

IN ADDITION TO TORNADIC SUPERCELLS LOCATED ALONG THE COLD FRONT OVER SWRN AND NERN AR...REGIONAL RADARS SHOWED SEVERAL /4-5/ DISCRETE TORNADIC SUPERCELLS TRACKING NEWD FROM DALLAS COUNTY AR TO JACKSON COUNTY AR.  THESE LATTER STORMS ARE LOCATED ALONG A PRE-FRONTAL CONFLUENCE ZONE.  ENVIRONMENT ACROSS PDS TORNADO WATCH 118 REMAINS VERY CONDUCIVE FOR TORNADOES GIVEN MODERATE INSTABILITY...STRONG LOW LEVEL /SFC-1 KM 30-40 KT/ AND EFFECTIVE BULK SHEAR /40-60 KT/...AND LOW LCLS /500-800 M/.

Mesoscale Discussion #0443


CONCERNING...OUTLOOK UPGRADE 


VALID 011248Z - 011345Z

   

VALID THIS AFTERNOON AND TONIGHT...FCST JUXTAPOSITION OF VERY RICH LOW-LEVEL MOISTURE...VERTICAL SHEAR...BUOYANCY AND SUFFICIENT LIFT...IS BOOSTING PROBABILITIES FOR BOTH MULTIPLE SUPERCELLS WITH TORNADOES.  SOME OF THOSE TORNADOES CAN REACH STG-VIOLENT LEVELS. ACCORDINGLY...CATEGORICAL HIGH RISK IS BEING INTRODUCED ACROSS THESE AREAS WITH 13Z SPC DAY-1 OUTLOOK.  FOR MORE DETAILS REFER TO OUTLOOK DISCUSSION.

Mesoscale Discussion #0445


CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   

VALID 011837Z - 011930Z

   

...PDS TORNADO WATCH WILL BE ISSUED BY 20Z ACROSS MUCH OF AR/NRN LA AND NERN TX...

   

BOUNDARY LAYER AIRMASS IS HEATING CONSIDERABLY SOUTH-EAST OF PRIMARY WIND SHIFT FROM ERN TX INTO SRN AR WHERE SFC TEMPERATURES HAVE WARMED WELL INTO THE 80S.  BOUNDARY LAYER CU FIELD HAS GRADUALLY CHANGED CHARACTER OVER THE LAST HOUR WITH APPARENT DEEPENING OF THERMALS AS CONVECTIVE TEMPERATURES HAVE BEEN BREACHED. MODIFIED 18Z SOUNDING FROM LZK...WITH WARM SECTOR CONDITIONS...SUPPORTS AN UNCAPPED ENVIRONMENT WITH SBCAPE VALUES ON THE ORDER OF 2000 J/KG.  LATEST SHORT RANGE MODEL GUIDANCE STRONGLY SUPPORTS A RAPID STRENGTHENING OF THE LLJ ACROSS LA AND SRN AR BY LATE AFTERNOON. THIS SHOULD ENHANCE CONVERGENCE ALONG AFOREMENTIONED BOUNDARY AND CONVECTIVE UPDRAFTS SHOULD EASILY MATURE AND ORGANIZE INTO SUPERCELL STRUCTURES WITHIN STRONGLY SHEARED AIRMASS.  LATEST THINKING IS TORNADIC SUPERCELLS MAY INITIATE ACROSS THE SRN HALF OF AR...SUBSEQUENTLY EXPANDING INTO REGIONS OF NERN TX AND NRN LA BY 21-22Z.  ACTIVITY WILL THEN SPREAD NEWD TOWARD THE BOOT HEEL OF MO THIS EVENING.  ENVIRONMENTAL CONDITIONS STRONGLY FAVOR LONG-TRACK STRONG TORNADOES.

Mesoscale Discussion #0449


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 125 CONTINUES.

   

CONVECTION/UPDRAFTS ARE BECOMING MORE PERSISTENT FROM WEST CENTRAL AR /HOT SPRING TO GARLAND COUNTIES AR/ ENEWD TO CROSS COUNTY AR IN THE VICINITY OF A SURFACE BOUNDARY EXTENDING WSW-ENE THROUGH THIS REGION.  REGIONAL RADARS/LIGHTNING DATA SHOWED STORMS DEVELOPING IN THIS CORRIDOR.  OBJECTIVE ANALYSES INDICATED THIS 40 MILE WIDE ZONE EXTENDING FROM 30 WSW HOT TO 25 NW MEM IS A FAVORABLE ZONE FOR SUSTAINED ROTATING UPDRAFTS.  THIS WILL BE ESPECIALLY SUBSTANTIAL WITH ANY STORM THAT TRACKS ENEWD ALONG THE BOUNDARY WHERE ENELY WINDS ON THE N SIDE OF THE BOUNDARY ARE ENHANCING LOW LEVEL SHEAR/LIT WSR-88D VWP SFC-1 KM SHEAR 30 KT/.  AN ENEWD STORM MOTION ALONG THE BOUNDARY WILL ALSO PROVIDE A LONGER RESIDENCE TIME FOR THE UPDRAFTS/SUPERCELLS TO INGEST STREAM-WISE VORTICITY...INCREASING THE TORNADO POTENTIAL.

   

AT 22Z...WATER VAPOR IMAGERY SHOWED SHORTWAVE RIDGING MOVING NEWD ACROSS AR WHICH MAY HAVE BEEN INHIBITING MORE ROBUST UPDRAFT DEVELOPMENT THUS FAR THIS AFTERNOON.  HOWEVER...THE RICH MOIST BOUNDARY LAYER /SURFACE DEWPOINTS IN THE LOWER 70S/ IS LIKELY BEGINNING TO SENSE THE EFFECTS OF LARGE SCALE ASCENT/STEEPER MID LEVEL LAPSE RATES SPREADING NEWD WITH THE APPROACH OF AN UPSTREAM TROUGH...NOW LOCATED ALONG THE TX RIO GRANDE VALLEY.  STRENGTHENING SWLY MID LEVEL WINDS AND SSWLY LLJ WITH THE APPROACH OF THE RIO GRANDE TROUGH WILL FURTHER ENHANCE THE LIKELIHOOD FOR STRONG TORNADIC SUPERCELLS THROUGH THE EVENING.

Mesoscale Discussion #0508


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 147 CONTINUES.

   

THE RISK FOR STRONG TORNADOES APPEARS LIKELY TO INCREASE DURING THE NEXT FEW HOURS.

   

THE SURFACE WARM FRONT APPEARS TO BE STRENGTHENING NEAR THE KANSAS/OKLAHOMA BORDER AREA...AND THE DRY LINE/WARM FRONT INTERSECTION NOW APPROACHING MEDICINE LODGE IS BECOMING THE FOCUS FOR STRONGEST FORCING FOR UPWARD VERTICAL MOTION AND DESTABILIZATION...AS THE EXIT REGION OF THE STRONG 500 MB JET STREAK OVERSPREADS IT.  MODELS ARE SUGGESTIVE THAT THIS BOUNDARY INTERSECTION WILL DEVELOP EASTWARD NEAR THE STATE BORDER AREA...SOUTH OF WICHITA/NORTH OF STILLWATER...BETWEEN NOW AND 23-00Z.  AS SURFACE DEW POINTS INCREASE THROUGH THE MID/UPPER 60S AND LOW-LEVEL LAPSE RATES CONTINUE TO STEEPENING...IN THE PRESENCE OF LARGE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS ACROSS THIS REGION...POTENTIAL FOR SUPERCELLS TO PRODUCE STRONG TORNADOES APPEARS LIKELY TO INCREASE LATE THIS AFTERNOON.

Mesoscale Discussion #0512


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 147...148...CONTINUES.

   

...NEW TORNADO WATCH WILL BE ISSUED SOON FOR PORTIONS OF SERN KS...SWRN MO...NERN OK...NWRN AR...

   

RAPID BOUNDARY LAYER RECOVERY IS UNDERWAY ACROSS SCNTRL KS INTO NERN OK AHEAD OF SFC LOW ALONG THE KS/OK BORDER WEST OF PNC.  FOCUSED PRESSURE FALLS ARE NOTED JUST AHEAD OF THIS FEATURE WITH 2 HOUR FALLS ON THE ORDER OF 4-7MB.  NEEDLESS TO SAY SHEAR AND THERMODYNAMIC PARAMETERS ARE UNUSUALLY STRONG AND VERY SUPPORTIVE OF VIOLENT TORNADIC SUPERCELLS.  LATEST RADAR TRENDS SUGGEST EARLIER ISOLATED ACTIVITY IS NOW MORE CONCENTRATED AND FOCUSED ALONG SURGING DRYLINE WITH AT LEAST HALF A DOZEN STRONG TO RAPIDLY INTENSIFYING SUPERCELLS...A FEW WITH POTENTIALLY SIGNIFICANT TORNADOES...FROM KINGMAN COUNTY KS...ARCING TO THE WEST AND SOUTHWEST OF OKC IN SWRN OKLAHOMA.

   

LATEST THINKING IS SPEED/MOVEMENT OF CURRENT ACTIVITY WILL REQUIRE AN ADDITIONAL TORNADO WATCH TO BE ISSUED OVER SERN KS/SWRN MO/NERN OK/NWRN AR SHORTLY.

Mesoscale Discussion #0513


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 147...150...CONTINUES.

   

SEVERAL LONG-TRACK SUPERCELLS WITH DAMAGING TORNADOES CONTINUE ACROSS WW147...ESPECIALLY OVER OK.  ONE INTENSE TORNADIC SUPERCELL IS TRACKING ACROSS SEMINOLE COUNTY INTO SRN OKFUSKEE/NRN HUGHES COUNTY.  OTHER INTENSE STORMS HAVE DEVELOPED AND ARE TRACKING ENEWD ACROSS SRN OK OVER CARTER AND LOVE COUNTIES.  ENVIRONMENTAL CONDITIONS REMAIN VERY FAVORABLE FOR STRONG TORNADIC SUPERCELLS...ESPECIALLY ALONG AND JUST SOUTH OF RETREATING WARM FRONT THAT IS CURRENTLY DRAPED FROM SERN OK INTO SFC LOW NEAR PNC. ADDITIONALLY...NEW SUPERCELLS ARE INTENSIFYING ALONG IMMEDIATE DRYLINE IN THE WAKE OF THE PRE-DRYLINE ACTIVITY FROM LINCOLN COUNTY...SWWD INTO MCLAIN COUNTY OK.  THESE STORMS MAY VERY WELL BECOME TORNADIC SHORTLY.

Mesoscale Discussion #0623


CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   

VALID 191822Z - 192015Z

   

MID-LVL SHORTWAVE RIDGING IN WAKE OF THE MORNING MCS WAS BEGINNING TO MIGRATE INTO ERN OK AND ACCELERATED COOLING ALOFT IS EXPECTED TO SPREAD EWD THROUGH THE NEXT FEW HOURS.  18Z VSBL SATL ALREADY SHOWS EVIDENCE OF TCU INVOF THE TRIPLE POINT OVER ERN HEMPHILL/WHEELER COUNTIES IN THE TX PNHDL AND MAY MARK THE BEGINNING OF AN ACTIVE MID-LATE AFTN/EVENING DOWNSTREAM.  

   

18Z MESOANALYSIS DEPICTS AN OUTFLOW BOUNDARY VERY NEAR I-40 WITH A WRMFNT EXTENDING ESE FROM THE TRIPLE POINT ACROSS NORMAN TO SERN OK. A PRE-FRONTAL TROUGH SEEMINGLY HAS EVOLVED AND WAS LOCATED A COUPLE ROWS OF COUNTIES W OF I-44...WELL-AHEAD OF THE DRYLINE. TO THE W OF THIS FEATURE...CU FIELD WAS INCREASING AND STRATUS WAS ERODING TO THE N OF THE OUTFLOW BOUNDARY FROM ABOUT EL RENO WWD TO THE STATE LINE.

   

AS THE SFC LOW BEGINS TO DEEPEN THIS AFTN...EXPECT THAT THE SFC-H85 FLOW WILL BACK SOMEWHAT AND MAINTAIN SUFFICIENT CONVERGENCE ALONG THE DRYLINE TO SUPPORT TSTM INITIATION IN THE 19-21Z TIME FRAME...PERHAPS EVOLVING FROM CURRENT BUILD-UPS ENTERING WCNTRL OK.  OTHER STORMS MAY ALSO INITIATE EWD ALONG THE OUTFLOW OR EVEN PERHAPS THE PRE-FRONTAL TROUGH FROM OKC METRO WWD ALONG/JUST N OF I-40 AFTER 21Z.  MATURE STORMS WILL TRACK ROUGHLY 250/30 KTS.

   

INGREDIENTS ARE BEGINNING TO CONGEAL FOR THE POSSIBILITY OF STRONG TORNADOES FROM N OF KCSM ESE THROUGH KOKC METRO IN THE 21Z-02Z AND POSSIBLY FARTHER ESE INTO ECNTRL OK BY MID-EVENING.  HERE...0-1KM SRH WILL GENERALLY BE 250-300 M2/S2 AMIDST LOW LCL/S AND A HIGH PROBABILITY FOR DISCRETE STORMS.  OTHERWISE...VERY LARGE HAIL AND DMGG WIND GUSTS CAN ALSO BE EXPECTED.

Mesoscale Discussion #0624


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 190 CONTINUES.

   

20Z MESOANALYSIS PLACES A LOW JUST S OF KGAG WITH A WRMFNT ESE ACROSS DEWEY...BLAINE...KINGFISHER...OKLAHOMA COUNTIES...THEN SEWD TO CHOCTAW COUNTY.  A DRYLINE EXTENDED S FROM THE LOW INTO THE ALTUS AREA.  

   

TSTMS WERE INCREASING OVER WCNTRL OK NEAR THE TRIPLE POINT AND WILL LIKELY BUILD SWD ALONG THE DRYLINE THROUGH LATE AFTN.  OTHER STORMS WILL CONTINUE TO GROW ALONG THE WRMFNT FROM JUST W OF KOKC WNW INTO BLAINE/MAJOR COUNTIES.  YET A THIRD REGION OF INITIATION...PER LATEST RAPID REFRESH AND RECENT TCU DEVELOPMENT...WILL BE ACROSS SERN OK TO THE SW THROUGH NW OF KMLC ALONG A POSSIBLE GRAVITY WAVE.

   

AS STORMS MATURE INTO SUPERCELLS THEY WILL MOVE 250/30 KTS WITH THE TORNADO THREAT MAXIMIZED INVOF THE WRMFNT...PARTICULARLY FROM KINGFISHER ESE THROUGH OKC METRO AND INTO SE OK NEAR KMLC.  THIS ZONE WILL MAINTAIN ESELY LLVL FLOW VEERING QUICKLY TO SW ABOVE 2-3 KM AMIDST LOW LCLS.  VERY LARGE HAIL CAN ALSO BE EXPECTED.

Mesoscale Discussion #0666


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 202 CONTINUES.

   

SEVERE/TORNADO THREAT CONTINUES -- MOST IMMEDIATELY ACROSS PARTS OF N CENTRAL/NERN SD.

   

LATEST RADAR LOOP SHOWS A LARGE/INTENSE/SLOW-MOVING SUPERCELL CROSSING NRN EDMUNDS AND MCPHERSON COUNTIES...WHICH HAS PRODUCED MULTIPLE -- AND POSSIBLY SIGNIFICANT -- TORNADOES OVER THE PAST HOUR OR SO.  OTHER STORMS CONTINUE TO INCREASE S OF THIS STORM INVOF THE SURGING COLD FRONT...AND NWD INTO SD ALONG THE SURFACE TROUGH EXTENDING NWWD INTO WRN ND.

   

THE ENVIRONMENT REMAINS QUITE FAVORABLE FOR STRONG/LONG-LIVED SUPERCELLS...PARTICULARLY OVER NERN SD WHERE THE WARM FRONT -- EXTENDING EWD FROM THE N CENTRAL SD SURFACE LOW -- REMAINS IN PLACE. STRONG SHEAR -- BOTH LOW-LEVEL AND DEEP-LAYER -- AND A VERY MOIST/UNSTABLE ENVIRONMENT SHOULD SUPPORT A CONTINUED SEVERE/ISOLATED TORNADO THREAT OVER THE NEXT FEW HOURS.

Mesoscale Discussion #0686


CONCERNING...OUTLOOK UPGRADE 

   

VALID 241106Z - 241300Z

   

BASED ON OVERNIGHT NUMERICAL GUIDANCE/OBSERVATIONAL TRENDS...THE 13Z DAY 1 CONVECTIVE OUTLOOK WILL UPGRADE TO A CATEGORICAL MODERATE RISK ACROSS PORTIONS OF WESTERN NEB...WESTERN AND CENTRAL SD...AND SOUTHERN ND. THIS INCLUDES THE POTENTIAL FOR LARGE HAIL...TORNADOES...AND DAMAGING WINDS. FOR ADDITIONAL METEOROLOGICAL DISCUSSION...PLEASE CONSULT THE FORTHCOMING 13Z DAY 1 OUTLOOK. A PUBLIC SEVERE WEATHER OUTLOOK /PWO/ WILL BE ISSUED SHORTLY.

Mesoscale Discussion #0822


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 266...267...CONTINUES.

   

HIGHEST PROBABILITY FOR TORNADOES THROUGH LATE EVENING WILL BE IN CNTRL IL NEAR/E OF KPIA-JOLIET EWD INTO NEWLY ISSUED TORNADO WATCH 268 IN CNTRL/NRN IND.  ILX VWP EXHIBITED AROUND 500 M2/S2 0-1KM STORM RELATIVE HELICITY AND THE DISCRETE STORMS THAT MOVE ACROSS ECNTRL/NERN IL INTO IND WILL CONTINUE TO HAVE THE RISK OF TORNADOES. EVENTUALLY... NUMBER OF STORMS WILL INCREASE SUFFICIENTLY FOR ACTIVITY TO TRANSITION INTO BOWING LINE SEGMENTS AS UPSTREAM 50+ KT FLOW ABOVE 3 KM PUNCHES EWD. AT THAT TIME...DAMAGING WINDS WILL BECOME MORE OF A THREAT.

   

FARTHER SW...TRAILING BAND OF STORMS CONTINUES TO BACKBUILD SWWD INTO THE STRONGER CAP NOTED ON THE 00Z SGF SOUNDING.  PROPAGATION VECTORS SUGGEST STORMS WILL TRACK ESE TOWARD THE I-70 CORRIDOR. OBJECTIVE ANALYSIS AND LATEST HRRR SUGGEST THAT ACTIVITY WILL BEGIN TO WEAKEN AS THE CONVECTION MOVES INTO LESS UNSTABLE AIR AT THAT LATITUDE AND SWD AWAY FROM THE STRONGER LARGE-SCALE FORCING.

Mesoscale Discussion #0824


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 267...268...269...CONTINUES.

   

HIGHEST PROBABILITIES FOR TORNADOES WITHIN THE TORNADO WATCHES THROUGH 06Z WILL EXIST ACROSS SCNTRL/SERN LOWER MI...EXTREME NWRN OH AND NRN IND.  

   

WARM FRONT HAS JUMPED N INTO THE FIRST ROW OR TWO OF COUNTIES IN LOWER MI AS OF 04Z.  WARM SECTOR TO THE S REMAINS VERY UNSTABLE WITH AN E-W CORRIDOR OF MLCAPES TO 2000 J/KG.  LONG-LIVED DISCRETE SUPERCELLS THAT DEVELOPED OVER IL EARLIER HAVE GROWN INTO LARGER CLUSTERS AND MAY BEGIN A TRANSITION INTO SEVERAL BOWING/EMBEDDED SUPERCELL TYPE MCS/S WITH TIME.  JOLIET VWP SHOWS 50 KT WLY FLOW DOWN TO ABOUT 3 KM AND INCREASING ASCENT/UNIDIRECTIONAL NATURE TO THE FLOW REGIME MAY BEGIN A TRANSITION TO VERY STRONG WIND GUSTS. HOWEVER...HIGH-LEVEL FLOW REMAINS VERY STRONG AND GIVEN 0-1KM SHEAR IN EXCESS OF 35 KTS PER WOLCOTT PROFILER...TORNADO THREAT WILL CONTINUE...ESPECIALLY IN THE HIGHLIGHTED AREA ABOVE.  EXTRAPOLATION HAS THE STORMS REACHING HILLSDALE MI-KSBN-KGUS 05-0530Z...ADRIAN MI-DEFIANCE OH/KFWA REGIONS 06-0630Z.  TO THE SW...SUPERCELL CLUSTER NEAR LINCOLN IL AT 04Z WILL CONTINUE ESE TOWARD THE WABASH RIVER NEAR/N OF KHUF AFTER 0515Z.