2013

Mesoscale Discussion #0144


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 32 CONTINUES.

   

SUMMARY...A SUPERCELL TORNADO RISK WILL CONTINUE OVER SRN MS AND ADJACENT PORTIONS OF SRN LA THROUGH THE LATE EVENING.  A REPLACEMENT TORNADO WATCH WILL BE COORDINATED WITHIN THE NEXT 30 MINUTES OR SO.

   

DISCUSSION...THE SWD STALLING OF AN EWD MOVING MCS ACROSS MS AND AL HAS CONFINED BUT LEFT A MOIST/MARGINALLY UNSTABLE WARM SECTOR/250-1000 J/KG MLCAPE/ UNDISTURBED OVER SRN LA AND SRN MS. SEVERAL LOW LEVEL CONFLUENCE BANDS HAVE SERVED AS PREFERRED FOCI FOR CONTINUED STORM GENERATION THE PAST FEW HOURS AS THE BOUNDARY LAYER HAS HEATED INTO THE MID 70S NEAR THE I-10 CORRIDOR.  INPUTTING THE STORM MOTION /240 AT 40 KT/ FOR THE LAMAR COUNTY MS CONFIRMED TORNADIC STORM IS YIELDING AROUND 200 M2/S2 0-1 SRH WITHIN A FAVORABLE DEEP LAYER WIND PROFILE FOR SUPERCELLS.  ALTHOUGH THE BELT OF H85 FLOW IS EXPECTED TO SLIGHTLY WEAKEN OVER THE NEXT 6 HRS...SUFFICIENT LOW LEVEL VERTICAL SHEAR WITHIN A MOIST ENVIRONMENT /CHARACTERIZED BY MID-UPPER 60S DEWPOINTS/ SHOULD CONTINUE TO SUPPORT AN INTERMITTENT ISOLD RISK FOR SUPERCELL TORNADOES INTO THE LATE EVENING HOURS.


**This MCD was released at the exact same time that the Hattiesburg EF4 touched down.

Mesoscale Discussion #0146


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 33...34...CONTINUES.

   

SUMMARY...THE GREATEST SUPERCELL SIGNIFICANT TORNADO THREAT WILL SEEMINGLY BE PRESENT IN A WEST TO EAST CORRIDOR AS QUASI-DISCRETE POTENTIALLY TORNADIC SUPERCELLS TRAIN EWD ACROSS SERN MS INTO SRN AL.

   

DISCUSSION...LATEST RADAR IMAGERY SHOWS SEVERAL DISCRETE UPDRAFTS/SUPERCELLS/ MOVING ENEWD ACROSS SERN MS AND SRN AL.  THE 00Z/11 LIX RAOB DISPLAYED A LARGE LOOPING HODOGRAPH /EFFECTIVE SRH 400 M2/S2/WITHIN A MOISTURE RICH ENVIRONMENT /14.6 G/KG MEAN MIXING RATIO/. ALTHOUGH BUOYANCY IS LOWER WITH EWD EXTENT OVER PORTIONS OF SERN AL...SOME ADDITIONAL RECOVERY IS EXPECTED PRIOR TO THE STORMS MOVING INTO THIS REGION.  NONETHELESS...THE PRIMARY TORNADO RISK WILL BE FARTHER WEST WHERE SUPERCELLS WILL TRAIN EWD.  AS SUCH...A CONTINUATION OF AN ISOLD SIGTOR THREAT WILL PROBABLY CONTINUE OVER THE NEXT HOUR OR TWO.

Mesoscale Discussion #0647


THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 160 CONTINUES.

   

SUMMARY...DAMAGING WIND/SEVERE HAIL POTENTIAL CONTINUES ACROSS SEVERE TSTM WATCH 160...WITH THE LARGEST HAIL POTENTIAL ACROSS PARTS OF NORTHWEST INTO NORTH-CENTRAL TX. SOME TORNADO POTENTIAL EXISTS AS WELL MAINLY ACROSS NORTH-CENTRAL INTO CENTRAL TX...MONITORING FOR A PARTIAL TORNADO WATCH UPGRADE.

   

DISCUSSION...DISCUSSION PRIMARILY CONCERNS NORTH-CENTRAL TX...WHERE SOME TORNADO POTENTIAL WILL EXIST INTO THIS EVENING. SOUTH OF A CLUSTERING BAND OF STORMS ACROSS SOUTHWEST TX...CU FIELD CONTINUES TO DEEPEN WITH TSTM DEVELOPMENT IN VICINITY OF LOW-LEVEL CONFLUENT/DIFFERENTIAL HEATING AXIS THAT EXTENDS FROM EAST OF WICHITA FALLS SSW TO GRAHAM AND BROWNWOOD AREAS. STORMS MAY CONTINUE TO DEVELOP WITHIN THIS CORRIDOR AND SPREAD EAST-NORTHWARD TOWARD SOMEWHAT COOLER SIDE OF THE BOUNDARY. MODEST TEMPERATURE-DEWPOINT SPREADS AND MODERATELY STRONG LOW-LEVEL SHEAR ARE NOTED NEAR/EAST OF THE CONFLUENT AXIS...WITH A RECENT TREND OF BACKING LOW-LEVEL FLOW/SOUTHEASTERLY/ AND AS MUCH AS 150-175 M2/S2 OF 0-1 KM SRH PER MODIFIED FORT WORTH WSR-88D VWP. THIS SUPPORTS THE NOTION OF AT LEAST SOME TORNADO POTENTIAL INTO THIS EVENING...SUCH THAT A TORNADO WATCH MAY BE NEEDED SHORTLY.


**This MCD preceded the Granbury, Texas EF4

Mesoscale Discussion #0676


PROBABILITY OF WATCH ISSUANCE...95 PERCENT

   

SUMMARY...SCATTERED TSTM INITIATION IS EXPECTED ON THE DRYLINE BY 21-22Z. VERY LARGE HAIL...ISOLATED TORNADOES...AND DAMAGING WIND WILL BE POSSIBLE. WATCH ISSUANCE IS EXPECTED IN THE NEXT HOUR OR SO.

   

DISCUSSION...LATEST SFC ANALYSIS DEPICTS THE DRYLINE EXTENDING FROM SWRN KS INTO THE FAR ERN OK/TX PANHANDLES AND NW TX. VIS IMAGERY SHOWS CU INCREASING IN THE WELL-MIXED AIRMASS IN THE VICINITY OF THE DRYLINE ACROSS SW KS INTO THE TX PANHANDLE. WHILE ONE EMBEDDED VORT MAX IS MOVING NWD OUT OF THE AREA...ANOTHER EMBEDDED VORT MAX OVER SERN CO/NERN NM SHOULD AID IN CONVECTIVE INITIATION LATER THIS AFTERNOON. 

   

THE 18Z DDC SOUNDING SHOWS VERY STEEP LAPSE RATES IN EXCESS OF 9.5 C/KM IN THE 750-500 MB LAYER...WHICH WILL SUPPORT VERY HIGH TO EXTREME MLCAPE OF 3000-4000 J/KG IN AREAS AHEAD OF THE DRYLINE THIS AFTERNOON AND EARLY EVENING. WHILE FLOW IS RELATIVELY MODEST...INCREASING SWLY MIDLEVEL FLOW IS SUPPORTING EFFECTIVE SHEAR OF 35-45 KTS AHEAD OF THE DRYLINE...WHICH WILL BE MORE THAN SUFFICIENT FOR SUPERCELL DEVELOPMENT UPON STORM INITIATION. 

   

DISCRETE SUPERCELL ACTIVITY IS EXPECTED WITHIN THE FIRST 2-3 HOURS OF INITIATION...WITH VERY LARGE HAIL IN EXCESS OF BASEBALL SIZE THE PRIMARY THREAT. LARGE T/TD SPREADS AND RELATIVELY WEAK LOW-LEVEL SHEAR WILL LIMIT THE TORNADO THREAT INITIALLY...BUT A MARKED INCREASE IN THE LOW-LEVEL JET WILL INCREASE THE TORNADO THREAT TOWARD EVENING ACROSS MAINLY NWRN OK INTO SWRN KS...WITH ISOLATED STRONG TORNADOES POSSIBLE WITH ANY STORMS THAT CAN REMAIN DISCRETE AFTER 00Z. HOWEVER...STORM CONSOLIDATION IN A WELL-MIXED ENVIRONMENT MAY RESULT IN UPSCALE GROWTH AND A TRANSITION TO MORE OF A SEVERE WIND THREAT THIS EVENING...POSSIBLY LIMITING THE WINDOW OF OPPORTUNITY FOR A MORE ROBUST TORNADO THREAT.

Mesoscale Discussion #0697


PROBABILITY OF WATCH ISSUANCE...80 PERCENT

   

SUMMARY...STORMS ARE EXPECTED TO DEVELOP BY 20Z...MOST LIKELY OVER SCNTRL KS INTO NCNTRL OK. STORMS WILL SUBSEQUENTLY CONTINUE THROUGH THE WARM SECTOR OVER ERN KS...NERN OK AND EVENTUALLY WRN MO THIS EVENING. INITIAL THREATS WILL BE SUPERCELLS WITH VERY LARGE HAIL AND TORNADOES...A FEW OF WHICH COULD BE STRONG.

   

DISCUSSION...EARLY THIS AFTERNOON A DRYLINE EXTENDS FROM WRN TX INTO FAR WRN OK THEN NWWD INTO THE OK PANHANDLE WHERE IT INTERSECTS A COLD FRONT. A WEAKENING OUTFLOW BOUNDARY EXISTS NEAR THE OK/KS BORDER AND HAS BEEN LIFTING SLOWLY NWD. SATELLITE IMAGERY ALSO INDICATES AN EWD PROPAGATING GRAVITY WAVE FROM SCNTRL KS INTO NWRN OK. UPPER 60S DEWPOINTS ARE ADVECTING NWD THROUGH THE WARM SECTOR BENEATH VERY STEEP /8-9 C/KM/ MID LEVEL LAPSE RATES. THESE FACTORS ALONG WITH DIABATIC WARMING WILL CONTRIBUTE TO STRONG INSTABILITY WITH 3000-4000 J/KG MLCAPE BY MID AFTERNOON. WARM AIR AT THE BASE OF THE EML IS SERVING TO CAP THE BOUNDARY LAYER TO SFC BASED STORMS IN THE NEAR TERM. HOWEVER...MESOSCALE FORCING FOR ASCENT ASSOCIATED WITH EWD PROPAGATING GRAVITY WAVE LOCATED WITHIN UPPER JET EXIT REGION AS WELL AS DRYLINE CONVERGENCE SHOULD CONTRIBUTE TO THUNDERSTORM INITIATION AS CONVECTIVE TEMPERATURES ARE REACHED TOWARD MID-LATE AFTERNOON. 

   

MID-UPPER JET ROTATING THROUGH BASE OF THE TROUGH IS RESULTING IN 50+ KT DEEP SHEAR SUPPORTIVE OF SUPERCELLS. 0-2 KM HODOGRAPHS WILL ALSO BE SUFFICIENT FOR LOW LEVEL MESOCYCLONES...AND THREAT FOR A FEW STRONG TORNADOES WILL EXIST GIVEN THE STEEP LAPSE RATES AND MAGNITUDE OF INSTABILITY.

Mesoscale Discussion #0698


PROBABILITY OF WATCH ISSUANCE...95 PERCENT

   

SUMMARY...TSTM INITIATION APPEARS INCREASINGLY PROBABLE OVER THE NEXT 1-2 HRS ACROSS NRN/CNTRL OK. STORMS SHOULD QUICKLY INTENSIFY AND POSE A THREAT FOR VERY LARGE HAIL...DMGG WINDS...AND A FEW TORNADOES. A TORNADO WATCH WILL LIKELY BE NEEDED IN THE NEXT HOUR OR SO.

   

DISCUSSION...SFC ANALYSIS FROM 18Z SHOWS A DRYLINE RAPIDLY MIXING EWD ACROSS WRN OK...ATTENDANT TO A DEEPENING SFC LOW OVER NWRN OK...WITH UPPER 60S TO LOWER 70S F DEWPOINTS WIDESPREAD ACROSS CNTRL OK. A REMNANT OUTFLOW BOUNDARY FROM OVERNIGHT CONVECTION REMAINS DRAPED ACROSS FAR NRN OK...BUT UNIFORM SLY WINDS WERE NOTED ON BOTH SIDES OF THIS BOUNDARY. MEANWHILE...AN INCREASINGLY AGITATED LINE OF CU WAS NOTED PRECEDING THE DRYLINE...ORIENTED SW-NE FROM NEAR A 30 E CSM TO 15 NW END LINE...WITHIN A ZONE OF WEAK LOW-LEVEL CONVERGENCE. THIS AREA APPEARS TO BE THE MOST LIKELY FOCUS FOR INITIAL CONVECTIVE DEVELOPMENT THIS AFTERNOON...AS A PROGRESSIVE UPPER IMPULSE CURRENTLY POSITIONED OVER THE OK AND NRN TX PANHANDLES SHOULD CONTINUE EWD NEAR THE OK/KS BORDER.

   

STRONG SFC HEATING IS UNDERWAY ACROSS MOST OF OK...WITH BOUNDARY LAYER CU FORMING MORE RECENTLY BUT STILL EXHIBITING CAPPED/FLAT CHARACTER. PERSISTENT CONVERGENCE ALONG THE DRYLINE...ALONG WITH FURTHER BOUNDARY LAYER HEATING WITH TEMPERATURES REACHING THE UPPER 80S/LOWER 90S F WITHIN THE MOIST AIR...SHOULD RESULT IN EROSION OF THE SIGNIFICANT CAPPING INVERSION NOTED IN THE 18Z OUN SOUNDING. AS THIS OCCURS...DISCRETE TSTM DEVELOPMENT ALONG THE DRYLINE APPEARS LIKELY...WITH AN ACCOMPANYING THREAT FOR LARGE HAIL AND DMGG WINDS. TORNADO POTENTIAL SHOULD STEADILY INCREASE THROUGH THE LATE AFTERNOON/EVENING ACCOMPANYING SUSTAINED SUPERCELLS...AS WIND PROFILES CONTINUE TO STRENGTHEN. 

   

RECENT SUITE OF HIGH-RESOLUTION MODEL GUIDANCE INDICATES CONVECTION SHOULD INITIATE ACROSS THE NRN HALF OF THE HIGHLIGHTED AREA BETWEEN 20-21Z...AND PERHAPS AFTER 21Z ACROSS SWRN/S-CNTRL OK. A TORNADO WATCH WILL LIKELY BE ISSUED WITHIN THE NEXT HOUR.

Mesoscale Discussion #0703


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 182 CONTINUES.

   

SUMMARY...SUPERCELL TORNADO POTENTIAL WILL CONTINUE TO MARKEDLY INCREASE ACROSS CNTRL OK OVER THE NEXT HOUR AS THE LOW LEVEL WIND PROFILE HAS INTENSIFIED SOME DURING THE PAST 1-2 HRS.

   

DISCUSSION...RECENT KTLX RADAR IMAGERY SHOWS A WELL DEVELOPED AND POTENTIALLY TORNADIC SUPERCELL OVER NRN OKLAHOMA COUNTY WITH SEVERAL OTHER INTENSE UPDRAFTS SW OF THE OKC METRO TRYING TO ACQUIRE ROBUST SUPERCELL ROTATION.  SURFACE OBS SHOW A THIN CORRIDOR FROM CNTRL OK THROUGH OSAGE COUNTY OK WHERE PRESSURE FALLS ARE MAXIMIZED AHEAD OF THE APPROACHING STORMS/DRYLINE.  A NOTED INCREASE IN LOW LEVEL FLOW HAS BEEN NOTED IN THE PAST HOUR FROM KTLX VWP SHOWING 1 KM FLOW INCREASING TO AROUND 40 KT.  THIS IS RESULTING IN AROUND 200-250 M2/S2 0-1 KM SRH WHEN INPUTTING THE NRN OKLAHOMA COUNTY STORM/S STORM MOTION --THUS INCREASING THIS VALUE FROM AROUND 100 M2/S2 1-2 HRS EARLIER.  AS THESE STORMS MATURE AND INTENSIFY...THESE DISCRETE SUPERCELLS WILL POSSESS CYCLIC VERY STRONG LOW LEVEL MESOCYCLONES. THE MAIN THREAT WILL BE SEVERAL TORNADOES DOWNSTREAM OF THESE SUPERCELLS /POTENTIALLY LONG LIVED AND DAMAGING/ IN ADDITION TO LARGE TO VERY LARGE HAIL AND DMGG WINDS.

Mesoscale Discussion #1048


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 182 CONTINUES.

   

SUMMARY...HIGH-END LONG TRACK TORNADO WILL LIKELY CONTINUE NEWD ALONG THE I-44 CORRIDOR FROM LINCOLN COUNTY AND EVENTUALLY THREATEN CREEK COUNTY.

   

DISCUSSION...KTLX RADAR STORM VELOCITY DATA SHOWS A HIGH CONFIDENCE INTENSE TORNADO MOVING INTO LINCOLN COUNTY OKLAHOMA WITH 0.5 DEG ROTATIONAL VELOCITIES 80-90 KTS.  THE PURCELL WIND PROFILE AND KTLX SHOW A SICKLE-SHAPE HODOGRAPH.  GIVEN THE VERY BUOYANT AND MOIST BOUNDARY LAYER...STRONG TO POTENTIALLY VIOLENT TORNADOES MAY CONTINUE TO AFFECT CNTRL OK OVER THE NEXT FEW HOURS.  AS THE STORMS FARTHER SOUTH MATURE...POTENTIALLY STRONG TORNADOES MAY EVENTUALLY EVOLVE FROM THOSE DISCRETE SUPERCELLS.

Mesoscale Discussion #0709


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 181...182...CONTINUES.

   

SUMMARY...INTENSE TORNADO THREAT WILL CONTINUE OVER CNTRL OK EXTENDING NEWD INTO NERN OK AND SERN KS.

   

DISCUSSION...RADAR MOSAIC SHOWS SEVERAL DISCRETE SUPERCELLS FROM SERN KS ON THE SRN END OF A SQUALL LINE WITH ANOTHER CLUSTER OF DISCRETE SUPERCELLS FROM 35 MI W OF TUL...5 NNW CQB...AND 25 ESE OF OKC.  KTLX VWP SHOWED A PRONOUNCED SICKLE SHAPED HODOGRAPH /350 M2/S2 0-1 KM SRH/ WITH A MARKED INCREASE IN LOW LEVEL SHEAR PRIOR TO THE PASSAGE OF THE NOW CONFIRMED TORNADIC SUPERCELL.  VERY INTENSE ROTATIONAL VELOCITIES WITH THE CLEVELAND COUNTY/POTTAWATOMIE COUNTY STORM...COMBINED WITH A FAVORABLE CONVECTIVE MODE AND NEAR-STORM ENVIRONMENT...WILL LIKELY YIELD A HIGH PROBABILITY FOR CONTINUED CYCLING OF INTENSE TORNADOES DOWNSTREAM OF THIS STORM.  THE 105 KT ROTATIONAL VELOCITY AT 0.5 DEG AS OF 2320Z...IS HIGHLY INDICATIVE OF A VERY INTENSE/POTENTIALLY VIOLENT TORNADO WITH THIS STORM.  

   

FARTHER NE OVER NERN OK...KINX VWP SHOWS 50 KT SLY FLOW AT 1 KM AGL. ALTHOUGH THE HODOGRAPH STRUCTURE IS NOT AS IMPRESSIVE AS KTLX...300 M2/S2 0-1 KM SRH WILL MORE THAN SUPPORT THE THREAT FOR LONG-LIVED SUPERCELLS CAPABLE OF DAMAGING TORNADOES.

Mesoscale Discussion #0726


PROBABILITY OF WATCH ISSUANCE...95 PERCENT

   

SUMMARY...SEVERE STORMS ARE LIKELY TO FORM THIS AFTERNOON WITH A FEW SIGNIFICANT TORNADOES...EXTREMELY LARGE HAIL...AND DAMAGING WINDS ALL POSSIBLE. TWO WATCHES WILL BE NEEDED SOON FROM KS INTO N TX.

   

DISCUSSION...SURFACE MAP SHOWS A QUASI-STATIONARY BOUNDARY FROM SERN KS INTO NRN OK AND BENDING SWWD W OF THE I-44 CORRIDOR. FARTHER SW...A WEAK AREA OF LOW PRESSURE WAS NOTED OVER NWRN TX...ON THE NOSE OF A LOW LEVEL LAPSE RATE PLUME WITH DRYLINE EXTENDING SW ACROSS W TX.

   

VISIBLE IMAGERY SHOWS DEEPENING CU ALONG THE BOUNDARY FROM NRN OK INTO SERN KS WHERE A DEEP MOIST LAYER EXISTS. GIVEN A GRADUAL INCREASE IN THETA-E AND BREAKS IN THE CLOUDS...THIS AREA COULD BE WHERE INITIAL DEVELOPMENT OCCURS. LONG HODOGRAPHS AND STEEP MIDLEVEL LAPSE RATES WILL FAVOR VERY LARGE HAIL...AND LOW LEVEL VEERING WIND PROFILES WILL BE SUFFICIENT FOR TORNADOES GIVEN AFOREMENTIONED THERMODYNAMIC FACTORS.

   

TO THE S...AN EXTREMELY VOLATILE AIR MASS EXISTS WITH AN INCREASING CU FIELD FROM NWRN TX INTO SWRN OK WHERE STRONG HEATING PERSISTS. WIND FIELDS ALOFT ARE MORE THAN FAVORABLE FOR SUPERCELLS...WITH VERY LARGE HAIL LIKELY. ALTHOUGH SHEAR IN THE LOWEST 1-2 KM IS NOT PARTICULARLY STRONG...VERY LARGE VERTICAL ACCELERATIONS...AS WELL AS HODOGRAPH AUGMENTATION NEAR THE SFC FRONT WILL AID IN TORNADO POTENTIAL. HP SUPERCELLS ARE EXPECTED WITH STRONG MESOCYCLONES AND POSSIBLE RAIN-WRAPPED TORNADOES.

   

ACTIVITY MAY EVENTUALLY MERGE INTO ONE OR MORE BOWS...AND RAPIDLY EXPAND NEWD ACROSS ERN OK LATER THIS EVENING PER MULTIPLE CONVECTION ALLOWING MODELS.

Mesoscale Discussion #0728


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 190...191...CONTINUES.

   

SUMMARY...THE THREAT FOR TORNADOES MAY BE INCREASING OVER THE NEXT FEW HOURS...ESPECIALLY ACROSS NERN OK.

   

DISCUSSION...STORMS ARE GRADUALLY FORMING ALONG THE FRONT FROM NWRN TX ACROSS OK AND INTO SERN KS. SPECIAL SOUNDINGS ACROSS THE AREA...AS WELL AS PROFILER DATA INDICATE A VEER-BACK PATTERN BETWEEN 850 AND 700 MB ESPECIALLY FROM NRN TX INTO SRN OK. THIS WEAKNESS IN THE HODOGRAPH MAY INHIBIT THE DEVELOPMENT OF ROBUST ROTATION UNTIL LATER IN THE AFTERNOON.

   

HOWEVER...IN THE SHORT TERM...WIND PROFILES CURRENTLY APPEAR TO BE MORE FAVORABLE FOR ROTATION FROM CNTRL/NERN OK INTO SERN KS...WITH 0-1 SRH OF 100-150 M2/S2. IN ADDITION...CLEARING HAS ALLOWED FOR A ROBUST CU FIELD GENERALLY E OF I-35 AND N OF I-40...WHERE THICK STRATUS PREVIOUSLY EXISTED. DEEP LAYER SHEAR AND EXTREME INSTABILITY PROFILES WILL FAVOR RAPID INTENSIFICATION AND STORMS MAY CHANGE CHARACTER QUICKLY AS THEY TRAVEL NEWD ACROSS A VERY MOIST WARM SECTOR WITH LOCALLY BACKED SFC WINDS.

Mesoscale Discussion #0732


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 191...192...CONTINUES.

   

SUMMARY...THE ENVIRONMENT FOR LONG-LIVED SUPERCELLS CAPABLE OF A STRONG TORNADO OR TWO APPEAR TO BE MAXIMIZING NEAR THE RED RIVER OVER THE NEXT 1-2 HRS.

   

DISCUSSION...22Z SURFACE ANALYSIS SHOWS PRESSURE FALLS MAXIMIZING OVER N-CNTRL TX TO THE E OF THE DRYLINE AND TEMP/DEWPOINT SPREADS ARE BEGINNING TO LOWER IN THE 10-15 DEG RANGE...SIGNIFYING HIGHER BOUNDARY LAYER RH AND LOWER LCLS.  ADDITIONALLY...SURFACE WINDS ARE BEGINNING TO BACK SLIGHTLY FROM THE S TO SSE.  ALTHOUGH THE 18Z FWD RAOB SHOWED AN INVERSION LAYER AROUND H85...THE INFLUENCE OF THIS FEATURE WILL PROBABLY BE LESSENED THROUGH FORCED STORM-SCALE ASCENT. BECAUSE OF THE VERY UNSTABLE AIRMASS IN PLACE AND THE FORECAST INCREASE IN H85 FLOW /INCREASING LOW LEVEL SHEAR/...THE TORNADO THREAT APPEARS TO BE INCREASING.  IF THE KFWS VWP OBSERVATIONS SHOW A SIMILAR INCREASE IN LOW LEVEL SHEAR OVER THE NEXT HOUR OR SO AS THE VARIOUS RAP FORECAST SOUNDINGS...A STRONG TORNADO OR TWO IS POSSIBLE IN ADDITION TO LARGE HAIL AND DMGG WINDS.

Mesoscale Discussion #0905


PROBABILITY OF WATCH ISSUANCE...95 PERCENT


SUMMARY...TSTM COVERAGE SHOULD INCREASE RAPIDLY IN THE NEXT FEW HOURS. HIGHLY FAVORABLE COMBINATION OF CAPE/SHEAR WILL YIELD SUPERCELLS WITH RISKS OF LARGE HAIL /SOME SIGNIFICANT/...TORNADOES/POSSIBLY STRONG/ AND ISOLATED DAMAGING WINDS.


DISCUSSION...TCU/SMALL CBS HAVE BECOME INCREASINGLY AGITATED ALONG A COUPLE OF SW/NE-ORIENTED CLOUD STREETS ACROSS FAR SERN KS. LARGE-SCALE ASCENT ASSOCIATED WITH PERSISTENT LOW-LEVEL WAA AND APPROACH OF A SHORT WAVE IMPULSE OVER THE CNTRL HIGH PLAINS SHOULD FOSTER DEEPENING CONVECTION THROUGH THE AFTERNOON. MODIFIED 18Z SGF RAOB SUGGESTS MLCIN HAS BECOME MINIMAL WITH PRESENCE OF A STRONGLY UNSTABLE AIR MASS. ALTHOUGH LOW-LEVEL SHEAR MAY DIMINISH SLIGHTLY OVER THE NEXT FEW HOURS...IT WILL REMAIN MORE THAN ADEQUATE FOR SUPERCELLS AND AN ASSOCIATED TORNADO RISK. THIS THREAT MAY BE MAXIMIZED INVOF REMNANT OUTFLOW BOUNDARY ARCING ACROSS PARTS OF CNTRL MO.

Mesoscale Discussion #0907


PROBABILITY OF WATCH ISSUANCE...95 PERCENT


SUMMARY...PDS TORNADO WATCH WILL BE ISSUED BY 21Z. ISOLATED TO SCATTERED DISCRETE SUPERCELLS SHOULD FORM ALONG DRYLINE BETWEEN 21-23Z WITH PRIMARY INITIAL THREAT OF VERY LARGE HAIL AND ISOLATED SEVERE WINDS. TORNADO RISK WILL INCREASE TOWARDS 00Z WITH AN EXPECTATION OF A FEW SIGNIFICANT TORNADOES.


DISCUSSION...19Z SURFACE ANALYSIS PLACED A QUASI-STATIONARY FRONT FROM GRANT TO CUSTER COUNTIES WITH A DRYLINE DRAPED S/SWWD INTO THE LOW ROLLING PLAINS OF NWRN TX. SURFACE TEMPERATURES HAVE NOW BREACHED 100 DEG F ALONG THE RED RIVER IN SWRN OK/NWRN TX...RESULTING IN MINIMAL MLCIN PER MODIFIED 18Z OUN RAOB. CU JUST AHEAD OF THE DRYLINE HAS BECOME MORE AGITATED IN LATEST VISIBLE SATELLITE IMAGERY AND SHOULD CONTINUE TO GROW WITH GLANCING INFLUENCE OF A SHORTWAVE IMPULSE OVER THE CNTRL HIGH PLAINS. THIS SHOULD RESULT IN TSTM INITIATION  BY 21Z. 


STRONG EFFECTIVE SHEAR WILL PROMOTE SUPERCELLS WITH AN INITIAL PRIMARY RISK OF VERY LARGE HAIL. WITH A PLUME OF 73-74 DEG F SURFACE DEW POINTS REMAINING ACROSS CNTRL OK BENEATH THE CAPPING INVERSION NOTED IN 18Z OUN RAOB...AND AS THE LLJ INTENSIFIES BY 00Z...TORNADO THREAT WILL INCREASE SUBSTANTIALLY. SOME OF THESE WILL LIKELY BE SIGNIFICANT...ESPECIALLY ALONG THE I-35 CORRIDOR.

Mesoscale Discussion #0908


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 262 CONTINUES.


SUMMARY...STORMS WILL UNDERGO A RAPID INCREASE IN ORGANIZATION AND INTENSITY OVER WCNTRL AND SWRN OK. THE STORMS ARE EXPECTED TO MATURE INTO SUPERCELLS AND BECOME CAPABLE OF PRODUCING VERY LARGE HAIL AND STRONG TORNADOES AS THEY MOVE EWD AND ENEWD TOWARD CNTRL OK THIS EVENING.


DISCUSSION...EARLY THIS EVENING A COLD FRONT EXTENDS FROM ERN KS SWWD THROUGH NWRN OK THEN WWD INTO THE NRN TX PANHANDLE. A DRYLINE EXTENDS FROM WRN TX NWD INTO WRN OK WHERE IT INTERSECTS THE DRYLINE. TRENDS IN SATELLITE IMAGERY SHOW CUMULUS CONGESTUS INCREASING WITHIN THE MORE DEEPLY MIXED REGIME NEAR THE DRYLINE ACROSS SWRN OK AND THE FIRST STORMS ARE INITIATING ALONG THE DRYLINE/FRONT INTERSECTION NEAR WATONGA. THE ATMOSPHERE DOWNSTREAM IS VERY UNSTABLE WITH 4000+ J/KG MLCAPE WITH DEWPOINTS IN THE LOW 70S AND VERY STEEP LAPSE RATES ALONG WITH EFFECTIVE SHEAR IS AROUND 50 KT. LOW LEVEL HODOGRAPHS ARE NOT PARTICULARLY LARGE...BUT WINDS NEAR THE SFC ARE BACKED TO SSELY ACROSS CNTRL-WCNTRL OK...AND HODOGRAPHS WILL GRADUALLY INCREASE IN SIZE AS THE LLJ STRENGTHENS. THIS ENVIRONMENT WILL SUPPORT EXPLOSIVE THUNDERSTORM DEVELOPMENT WITH STORMS RAPIDLY ORGANIZING INTO SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL AND STRONG TORNADOES AS THEY MOVE ENEWD THROUGH THE VERY MOIST AND UNSTABLE WARM SECTOR NEXT FEW HOURS.

Mesoscale Discussion #0913


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 262 CONTINUES.


SUMMARY...TORNADIC SUPERCELL MOVING TOWARD THE OKLAHOMA CITY METRO AREA. OTHER STORMS CONTINUE FROM NCNTRL THROUGH NERN OK AND REMAIN CAPABLE OF PRODUCING VERY LARGE HAIL AND STRONG TORNADOES.


DISCUSSION...SUPERCELL WITH A HISTORY OF PRODUCING TORNADOES CURRENTLY LOCATED OVER CANADIAN COUNTY CONTINUES EWD AT AROUND 20 KT AND IS BEGINNING TO MOVE INTO THE OKLAHOMA CITY METRO AREA. THIS STORM IS ALONG THE SRN END OF A BROKEN LINE WHERE STORM RELATIVE INFLOW WILL REMAIN UNIMPEDED...SUGGESTING IT WILL CAPABLE OF PRODUCING STRONG TORNADOES AND VERY LARGE HAIL AS WELL AS DAMAGING WIND NEXT COUPLE HOURS.


OTHER STORMS INCLUDING A FEW SUPERCELLS CONTINUE ALONG THE NE-SW ORIENTED COLD FRONT. THIS ACTIVITY WILL ALSO LIKELY PRODUCE VERY LARGE HAIL...STRONG TORNADOES AND DAMAGING WIND.

Mesoscale Discussion #0915


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 262 CONTINUES.


SUMMARY...THREAT FOR TORNADOES...DAMAGING WIND AND VERY LARGE HAIL WILL PERSIST THIS EVENING WITH STORMS DEVELOPING FROM CNTRL THROUGH NERN OK.


DISCUSSION...HP SUPERCELLS HAVE BEEN BACKBUILDING ACROSS CNTRL OK WHERE THE SWD MOVING FRONT INTERSECTS THE DRYLINE...AND STORMS ARE SUBSEQUENTLY TRAINING ESEWD. STORMS MAY TREND TOWARD OUTFLOW DOMINANCE LATER THIS EVENING. IN THE MEANTIME...VWP DATA SHOW LOW LEVEL HODOGRAPHS HAVE BECOME LARGER AS THE LLJ STRENGTHENS...AND STORMS ARE MOVING THROUGH A VERY UNSTABLE ENVIRONMENT WITH 4000+ J/KG MLCAPE. VERY LARGE HAIL...WIND IN EXCESS OF 70 MPH AND TORNADOES REMAIN POSSIBLE.

Mesoscale Discussion #1040


CONCERNING...OUTLOOK UPGRADE 


VALID 121526Z - 121630Z


SUMMARY...THE 1630Z CONVECTIVE OUTLOOK WILL INCLUDE A CATEGORICAL UPGRADE TO HIGH RISK FOR DAMAGING WIND POTENTIAL FROM EXTREME EASTERN IOWA INTO NORTHERN PORTIONS OF ILLINOIS AND INDIANA...AND NORTHWEST PORTIONS OF OHIO. IN ADDITION...TORNADO PROBABILITIES WILL BE INCREASED TO 15 PERCENT OVER PORTIONS OF EXTREME EASTERN IOWA INTO NORTHWEST ILLINOIS.


DISCUSSION...SVR TSTMS ARE EXPECTED TO DEVELOP THIS AFTERNOON IN THE VICINITY OF EASTERN IOWA/NORTHWEST ILLINOIS AND QUICKLY BECOME SEVERE SUPERCELLS WITH A RISK FOR TORNADOES...POSSIBLY SIGNIFICANT...WITH UPSCALE GROWTH INTO A FAST-MOVING AND FORWARD-PROPAGATING MESOSCALE CONVECTIVE SYSTEM. WIDESPREAD DAMAGING WINDS ARE LIKELY ACROSS THE HIGH RISK AREA...WITH SOME SIGNIFICANT SEVERE GUSTS POSSIBLE.


DETAILS WILL BE FORTHCOMING IN THE 1630Z CONVECTIVE OUTLOOK.

Mesoscale Discussion #1934


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 539 CONTINUES.


SUMMARY...THE TORNADO THREAT APPEARS LIKELY TO CONTINUE ACROSS NE NEB INTO THE EARLY EVENING AND MAY SPREAD NWD INTO SE SD AND POSSIBLY EWD INTO NW IA. ISOLATED LARGE HAIL AND WIND DAMAGE WILL ALSO BE POSSIBLE WITH THE MORE INTENSE STORMS. A LOCAL EXTENSION HAS BEEN DONE ACROSS SERN SD FROM WEST OF YANKTON SD EWD INTO NW IA.


DISCUSSION...THE LATEST SFC ANALYSIS SHOWS A 1001 MB LOW IN NERN NEB WITH A MOIST AXIS EXTENDING FROM NEAR THE SFC LOW SEWD ACROSS THE OMAHA AREA WHERE SFC DEWPOINTS ARE IN THE MID 60S TO LOWER 70S F. THIS IS CONTRIBUTING TO MLCAPE IN THE 2000 TO 2500 J/KG RANGE AS ESTIMATED BY MESOSCALE ANALYSIS. IN ADDITION...THE OMAHA AND SIOUX FALLS WSR-88D VWPS SHOW DEEP LAYER SHEAR AROUND 60 KT WITH 0-1 KM SHEAR OF 25 TO 30 KT. THIS MAGNITUDE OF INSTABILITY AND SHEAR SHOULD CONTINUE TO SUPPORT SUPERCELL DEVELOPMENT AND TORNADOES WILL BE POSSIBLE WITH THE MORE DOMINANT ROTATING STORMS. THE CELLS IN NERN NEB JUST TO THE SOUTH OF THE SD BORDER ARE SFC-BASED AND SHOULD REMAIN SO FOR SEVERAL MORE HOURS BEFORE MOVING INTO THE COOLER AIR IN THE SIOUX FALLS AREA. FOR THIS REASON...THE STORMS SHOULD CONTINUE TO HAVE A TORNADO THREAT INTO EARLY THIS EVENING. IN ADDITION TO THE TORNADO THREAT...ISOLATED LARGE HAIL WILL BE POSSIBLE DUE TO THE COLD TEMPS ALOFT AND MODERATE INSTABILITY IN PLACE. AS THE STORMS CONTINUE TO EXPAND IN COVERAGE...LINEAR DEVELOPMENT WILL BE POSSIBLE ALONG THE FRONT SUGGESTING THE WIND DAMAGE THREAT COULD INCREASE EARLY THIS EVENING.

Mesoscale Discussion #2013


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 561 CONTINUES.


SUMMARY...RISK FOR SIGNIFICANT AND POTENTIALLY LONG-TRACK TORNADOES APPEARS TO BE INCREASING...ESPECIALLY ACROSS PARTS OF CNTRL/ERN IL.


DISCUSSION...NUMEROUS PRE-FRONTAL STORMS HAVE FORMED FROM NEAR MILWAUKEE S/SWWD TOWARDS ST LOUIS. 16Z ILX RAOB WELL-SAMPLED THE AMBIENT WARM SECTOR...DEPICTING MODERATE BUOYANCY DESPITE A SLIGHT INVERSION NOTED NEAR 600 MB. LOW-LEVEL HODOGRAPHS HAVE BECOME EVEN LARGER IN LATEST VWP DATA FROM ILX WITH A CLASSIC SICKLE-SHAPE AND 0-1 KM SRH AROUND 500 M2/S2. POTENTIAL IS HIGH FOR SEVERAL SUPERCELLS AND GIVEN RAPID STORM MOTIONS...A FEW SHOULD BE LONG-TRACKED ACROSS THE HEART OF IL WITH SIGNIFICANT TORNADOES.

Mesoscale Discussion #2015


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 561...562...CONTINUES.


SUMMARY...GREATEST NEAR-TERM SIGNIFICANT TORNADO RISK IS APPROACHING THE I-55 AND I-57 CORRIDORS BETWEEN JOLIET AND KANKAKEE AND PERHAPS THE SRN PORTIONS OF THE CHICAGOLAND METRO AREA.


DISCUSSION...AN INTENSE SUPERCELL OVER NWRN LIVINGSTON COUNTY IL HAS HAD A TORNADO CYCLONE EVIDENT IN RADAR IMAGERY FOR NEARLY 50 MILES. DOWNSTREAM ENVIRONMENT REMAINS SUPPORTIVE FOR A LONG-TRACK SIGNIFICANT TORNADO GIVEN A SICKLE-CELL ENLARGED HODOGRAPH STRUCTURE SAMPLED IN ILX VWP DATA AND SURFACE TEMPERATURES WARMING INTO THE LOWER 70S IMMEDIATELY AHEAD OF THE BROKEN BAND OF SUPERCELLS. ADDITIONAL LONG-TRACK/SIGNIFICANT TORNADOES MAY EVOLVE E/NEWD OUT OF PERSISTENT SUPERCELLS CURRENTLY IN MCLEAN AND CHRISTIAN COUNTIES IN CNTRL IL.

Mesoscale Discussion #2017


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 563 CONTINUES.


SUMMARY...THE POTENTIAL FOR SIGNIFICANT TORNADOES WILL EXIST IN THE SHORT-TERM WITH CONVECTION APPROACHING THE OHIO RIVER.


DISCUSSION...AN ARC OF DISCRETE TO SEMI-DISCRETE SUPERCELLS HAS ADVANCED OFF THE INITIATING BOUNDARY /PRE-FRONTAL TROUGH/ INTO A MODEST-WIDTH WARM SECTOR FEATURING MLCAPE AROUND 1000 J/KG. INTENSE PRESSURE FALLS AROUND 6 MB PER 2 HOURS IN CNTRL IL ARE DRIVING AN ISALLOBARIC RESPONSE THAT ENCOURAGES ADDITIONAL NORTHWARD TRANSPORT OF RICH LOW-LEVEL MOISTURE N OF THE OHIO RIVER -- DEWPOINTS AROUND 64-67F -- SUPPORTING LOW LCL/S AMIDST THE MODERATE INSTABILITY. SUBSIDING BRANCHES OF WAVE-LIKE STRUCTURES EMBEDDED IN THE LOW-LEVEL STRATUS FIELD IMMEDIATELY PRECEDING THE CONVECTION ARE SUPPORTING AREAS OF PARTIAL SUNSHINE TO BOLSTER BUOYANCY WHILE ALSO REFLECTING THE PARTICULARLY INTENSE LOW-LEVEL SHEAR IN PLACE. PAH VWP DATA INDICATE A FAVORABLE HODOGRAPH FOR TORNADOGENESIS WITH 0-1-KM SRH AOA 500 M2/S2 AND AROUND 80 KT OF 0-6-KM BULK SHEAR LARGELY ORTHOGONAL TO THE AFOREMENTIONED BOUNDARY. SUSTAINED SUPERCELL STRUCTURES WITH AT LEAST MODEST SPATIAL DISPLACEMENTS FROM OTHER STORMS WILL BE CAPABLE OF PRODUCING SIGNIFICANT TORNADOES IN THE SHORT TERM AS THEY APPROACH THE OHIO RIVER.

Mesoscale Discussion #2018


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 561...562...564...CONTINUES.


SUMMARY...WIDESPREAD DAMAGING WINDS AND SEVERAL TORNADOES...SOME OF WHICH SHOULD BE SIGNIFICANT...WILL EVOLVE FROM IL INTO IND AND LOWER MI THROUGH MID-AFTERNOON.


DISCUSSION...THE NRN TWO-THIRDS OF AN EXTENSIVE CONVECTIVE BAND HAS CONSOLIDATED INTO A QLCS FROM SRN LK MI INTO E-CNTRL IL. WITH AN IMPRESSIVELY LARGE SURFACE PRESSURE RISE/FALL COUPLET NOTED ACROSS THE MID-MS VALLEY TO MIDWEST...TENDENCY FOR FAST-MOVING LINEAR ORGANIZATION SHOULD CONTINUE ACROSS NRN IND AND LOWER MI. EMBEDDED MESOVORTICES WILL REMAIN CAPABLE OF DAMAGING TORNADOES WHILE EXTENSIVE SWATHS OF STRONG TO SEVERE WIND GUSTS SHOULD REMAIN ATTENDANT TO THE QLCS AS AN 986 MB SURFACE CYCLONE OVER SERN WI CONTINUES TO DEEPEN.


FARTHER S...TENDENCY FOR MORE DISCRETE SUPERCELL STRUCTURES APPEAR PROBABLE FOR CONVECTION EMANATING NEWD OUT OF SRN IL. ALTHOUGH DOWNSTREAM SURFACE TEMPERATURES ARE COOLER...VERY STRONG LOW-LEVEL SHEAR NOTED IN KVWX VWP DATA WILL SUPPORT A CONSIDERABLE RISK OF SIGNIFICANT TORNADOES AS CONVECTION REMAINS COINCIDENT WITHIN A

   PLUME OF LOWER TO MIDDLE 60S SURFACE DEW POINTS.

Mesoscale Discussion #2020


PROBABILITY OF WATCH ISSUANCE...95 PERCENT


SUMMARY...TORNADO WATCH ISSUANCE DOWNSTREAM OF WW 562 IS EXPECTED BY 2130Z AS A QLCS RACES EWD FROM IND. WIDESPREAD DAMAGING WINDS ALONG WITH A FEW TORNADOES APPEAR LIKELY...SOME OF WHICH MAY BE SIGNIFICANT.


DISCUSSION...CURRENT 55-60 KT MOVEMENT OF A QLCS AND SEMI-DISCRETE SUPERCELLS ACROSS WRN IND EXTRAPOLATES TO A 2230-2300Z TIMING AT THE ERN EDGE OF WW 562. WHILE WIDESPREAD CLOUDINESS AND A BAND OF LOW-LEVEL WAA DRIVEN RAINFALL HAVE YIELDED NEGLIGIBLE BUOYANCY PER 19Z ILN RAOB...A LARGE ISALLOBARIC RESPONSE ACCOMPANYING A POWERFUL CYCLONE OVER LK MI SHOULD RESULT IN A NARROW CORRIDOR OF MARGINAL BUOYANCY INTO OH BY EARLY EVENING. ALREADY STRONG WIND PROFILES WILL STRENGTHEN FURTHER...SUPPORTING THE POTENTIAL FOR DAMAGING WINDS AND A FEW TORNADOES.