2015

Mesoscale Discussion #0251


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 39...41...CONTINUES.


SUMMARY...THREAT FOR ALL SEVERE HAZARDS...INCLUDING TORNADOES...CONTINUES ACROSS THE REGION WITH THE PRIMARY THREAT CURRENTLY FOCUSED ACROSS WW 39. RISK STILL EXISTS IN WW 41 WITH ANY DISCRETE CELLS THAT DEVELOP AHEAD OF THE FRONT.


DISCUSSION...RECENT RADAR IMAGERY DEPICTS A LINE OF STRONG TO SEVERE TSTMS ALONG THE COLD FRONT EXTENDING FROM S-CNTRL IA SWWD THROUGH CNTRL MO. SUPERCELL THAT PRODUCED A TORNADO IN PEORIA COUNTY IL HAS NOW WEAKENED WITH THE MOST IMMEDIATELY APPARENT SEVERE THREAT CURRENTLY RELEGATED TO WW 39. SKIES ARE CLEARING BEHIND THE MCV /AND AHEAD OF THE COLD FRONT/ WITH THE ENVIRONMENT CURRENTLY CHARACTERIZED BY TEMPERATURES IN THE MID 70S...DEWPOINTS IN THE MID 60S...AND SWLY WINDS AROUND 20 MPH. THESE WARM AND MOIST LOW-LEVEL CONDITIONS CONTINUE TO SUPPORT MLCAPE AROUND 1500-2000 J/KG DESPITE RELATIVELY MODEST MID-LEVEL LAPSE RATES. FORCING WITHIN THE WARM SECTOR WILL BE RATHER NEBULOUS BUT A RISK FOR ALL SEVERE HAZARDS EXISTS WITH IF ANY DISCRETE DEVELOPMENT DOES OCCUR. FARTHER W ACROSS WW 39...ACTIVITY WILL LIKELY PERSIST WITH A GRADUAL INCREASE IN STORM ORGANIZATION AS LARGE SCALE ASCENT CONTINUES TO APPROACH FROM THE W.

Mesoscale Discussion #0515


PROBABILITY OF WATCH ISSUANCE...95 PERCENT


SUMMARY...THUNDERSTORMS EXPECTED TO DEVELOP RAPIDLY BETWEEN 18 AND 19Z. SEVERE HAIL AND WIND GUSTS ARE THE PRIMARY THREATS INITIALLY...BUT TURNING LOW-LEVEL HODOGRAPHS SUGGEST A TORNADO THREAT FOR ANY SUSTAINED UPDRAFTS.


DISCUSSION...STRONG HEATING HAS CONTRIBUTED TO RAPID DESTABILIZATION AHEAD OF A DIFFUSE DRYLINE WITH AN EASTERN EDGE STRETCHING FROM EAST OF LBB TO NEAR SHAMROCK.  ALTHOUGH THE MCD AREA IS UNDER NEUTRAL TO SLIGHT MID-LEVEL HEIGHT RISES IN THE WAKE OF THE EXITING WAVE...LITTLE TO NO CONVECTIVE INHIBITION IS PRESENT OVER THE AREA. MIXED-LAYER CAPE VALUES HAVE RISEN ABOVE 2000 J/KG WITH LOW-LEVEL LAPSE RATES ABOVE 8 C/KM. WITH EFFECTIVE SHEAR OF 30-40 KT...SUPERCELL STRUCTURES WILL BE THE FAVORED MODE FOR PERSISTENT UPDRAFTS...BUT LONGEVITY OF THE SUPERCELLS COULD BE NEGATIVELY IMPACTED BY STORM INTERACTIONS AS NUMEROUS STORMS ARE EXPECTED TO DEVELOP UNDER LITTLE INHIBITION AND POSSIBLY ENHANCED BY LIFT FROM A WEAK POTENTIAL VORTICITY ANOMALY PROGRESSING THROUGH THE BROAD CYCLONIC FLOW IN UPPER-LEVELS.  REGARDLESS OF STORM MODE...SEVERE HAIL IS LIKELY WITH THE STRONGER STORMS...WITH SEVERE WIND GUSTS POSSIBLE GIVEN THE STEEP LOW-LEVEL LAPSE RATES. ALTHOUGH LOW-LEVEL WIND SPEEDS REMAIN SOMEWHAT MODEST...LOW-LEVEL HODOGRAPHS SHOW CURVATURE...WITH EFFECTIVE HELICITY VALUES OF 100-150 M2/S2 FOR STORMS THAT DEVIATE TO THE RIGHT OF THE MEAN FLOW AND SHEAR.

Mesoscale Discussion #0516


PROBABILITY OF WATCH ISSUANCE...95 PERCENT


SUMMARY...STORMS WILL DEVELOP ACROSS NWRN INTO CNTRL KS WITH TORNADOES...LARGE HAIL AND DAMAGING WIND POSSIBLE.


DISCUSSION...VISIBLE SATELLITE SHOWS CU INCREASING IN DEPTH ACROSS MUCH OF CNTRL KS INTO SWRN NEB DUE TO HEATING AND A RAPID NWD ADVECTION OF LOW-LEVEL MOISTURE WITH DEWPOINTS RISING INTO THE 60S F. MEANWHILE...AN UPPER TROUGH AXIS EXTENDS FROM NERN CO INTO WRN KS...WITH ENHANCED VORTICITY ON THE N SIDE OF THE MIDLEVEL JET. 


NEARBY VWPS SHOW SUBSTANTIAL LOW-LEVEL TURNING OF THE WINDS WITH HEIGHT...FAVORABLE FOR SUPERCELLS. THE LACK OF A CAPPING INVERSION COMBINED WITH THE RELATIVELY HIGH-RH BOUNDARY LAYER AND AMPLE LOW-LEVEL SRH SUGGEST TORNADOES MAY OCCUR. LARGE HAIL IS ALSO LIKELY BUT MID TO UPPER LEVEL FLOW IS WEAK...SUGGESTING HP SUPERCELLS WITH LARGE PROPAGATIONAL COMPONENT. SOME HIGH RESOLUTION MODELS SUGGEST A LINEAR MODE AND DAMAGING WIND THREAT AS WELL...MAINLY OVER NRN KS INTO SRN NEB.

Mesoscale Discussion #0520


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 133 CONTINUES.


SUMMARY...TORNADO THREAT CONTINUES FOR WATCH 0133.


DISCUSSION...A WEAKLY-TORNADIC SUPERCELL THUNDERSTORM CONTINUES TO ORGANIZE OVER SOUTHEAST CADDO COUNTY WITH ADDITIONAL STORMS DEVELOPING ALONG A CONFLUENCE LINE ACROSS WESTERN OK.  VISIBLE SATELLITE TRENDS SHOW CONVECTION STRUGGLING TO DEVELOP OVER THE SOUTHERN PORTION OF THE WATCH AREA...BUT STORMS DEVELOPING BETWEEN MAF AND ABI WILL AFFECT THE SOUTHWEST PORTION OF THE WATCH SOON. KTLX VWPS AND 19Z OUN SOUNDING INDICATE THE NORTHERN HALF OF THE WATCH REMAINS UNDER THE INFLUENCE OF THE ENHANCED 900-700 MB FLOW ASSOCIATED WITH THE STRONG EXITING WAVE TO THE NORTH WHICH HAS ENLARGED THE LOW-LEVEL HODOGRAPH AND PRODUCED OVER 200 M2/S2 OF 0-3 KM STORM-RELATIVE HELICITY OVER THE WATCH AREA.  RELATIVELY WEAK WINDS IN THE 700-400 MB LAYER MAY BE PREVENTING A STRONGER ORGANIZATION TO THE SUPERCELL CURRENTLY.  HOWEVER...THE KTLX VWP INDICATES THE LOW-PRESSURE ASSOCIATED WITH THE SUPERCELL OVER WEST-CENTRAL OKLAHOMA MAY BE LOCALLY-ENHANCING THE SREH THROUGH BACKING OF THE LOW-LEVEL WINDS...IN ADDITION TO A LARGER-SCALE BACKING OF THE LOW-LEVEL WINDS CURRENTLY UNDERWAY. THIS WILL ALLOW FOR CONTINUED STRONG LOW- TO MID-LEVEL ROTATION.  ADDITIONALLY...THE EASTERN EDGE OF THE HIGHER MLCAPE OVER 1500-3000 J/KG NOW EXTENDS TO EASTERN OKLAHOMA WITH LITTLE INHIBITION REMAINING.  THEREFORE THE TORNADO THREAT IS EXPECTED TO CONTINUE IN THE NEXT FEW HOURS WILL THIS STORM AS IT APPROACHED THE OKC METRO AREA.

Mesoscale Discussion #0522


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 134 CONTINUES.


SUMMARY...A TORNADO THREAT WILL CONTINUE ACROSS WW 134 THROUGH EARLY THIS EVENING. LARGE HAIL AND WIND DAMAGE WILL ALSO BE LIKELY WITH THE STRONGER THUNDERSTORMS. A STRONG TORNADO WILL BE POSSIBLE EARLY THIS EVENING. WW EXTENSIONS COULD BECOME NECESSARY IMMEDIATELY TO THE EAST OF WW 134 AS CELLS APPROACH THE ERN EDGE OF THE WATCH.


DISCUSSION...THE LATEST SFC ANALYSIS SHOWS A DUAL-CENTERED LOW FROM SE CO INTO SW NEB WITH SOUTH TO SOUTHEASTERLY WINDS LOCATED ACROSS MUCH OF THE CNTRL PLAINS. AN AXIS OF INSTABILITY IS ANALYZED FROM SCNTRL KS NWD INTO SE NEB WHERE MLCAPE IS ESTIMATED IN THE 1000 TO 2000 J/KG RANGE. THE LATEST WATER VAPOR IMAGERY SHOWS A UPPER-LEVEL TROUGH OVER WRN NEB AND WRN KS WITH A BELT OF STRONGER MID-LEVEL FLOW EXTENDING NEWD FROM THE TX PANHANDLE NEWD INTO THE MID MO VALLEY. THIS IS CREATING MODERATE DEEP-LAYER SHEAR PROFILES WHICH COMBINED WITH THE INSTABILITY...WILL BE FAVORABLE FOR SUPERCELLS EARLY THIS EVENING. IN ADDITION...THE HASTINGS WSR-88D VWP SHOWS SELY FLOW AT THE SFC...STRONG DIRECTIONAL SHEAR IN THE BOUNDARY LAYER AND SPEED SHEAR IN THE LOW TO MID-LEVELS. THIS SHOULD BE FAVORABLE FOR TORNADOES WITH THE MORE DOMINANT SUPERCELLS THAT MOVE ACROSS NRN KS AND SE NEB EARLY THIS EVENING. A STRONG TORNADO COULD OCCUR WITH THE MOST DOMINANT SUPERCELL.


FURTHER TO THE SOUTH...THE WICHITA WSR-88D VWP ALSO SHOWS STRONG LOW-LEVEL SHEAR WITH 0-3 KM STORM RELATIVE HELICITY BETWEEN 450 AND 500 M2/S2. THIS ENVIRONMENT SHOULD ALSO BE FAVORABLE FOR SUPERCELLS AND TORNADOES. A STRONG TORNADO CAN NOT BE RULED OUT IN SCNTRL KS OVER THE NEXT HOUR OR TWO.

Mesoscale Discussion #0566


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 150 CONTINUES.


SUMMARY...LARGE HAIL AND TORNADO POTENTIAL IS EXPECTED TO STEADILY INCREASE ACROSS NORTH-CENTRAL TX THROUGH EARLY EVENING...INITIALLY IN AREAS JUST TO THE WEST OF THE DFW METROPLEX VICINITY. LOCALLY DAMAGING WINDS/MARGINALLY SEVERE HAIL AND POSSIBLY SOME TORNADO RISK WILL OTHERWISE CONTINUE ACROSS SOUTH-CENTRAL OK/FAR NORTHEAST TX. TORNADO WATCH 150 CONTINUES UNTIL 02Z.


DISCUSSION...AN OUTFLOW BOUNDARY-RELATED EFFECTIVE WARM FRONT EXTENDS ROUGHLY WEST-EAST ACROSS FAR NORTH TX ROUGHLY ALONG THE NORTHERN EDGE OF THE METROPLEX AND THE ADJACENT NORTHERN TWO-TIERS OF COUNTIES OF NORTH TX. STORMS SHOULD CONTINUE TO DEVELOP ALONG THE I-20 CORRIDOR IN VICINITY OF BRECKENRIDGE/BROWNWOOD/STEPHENVILLE VICINITIES NEAR A SURFACE LOW/DRYLINE THROUGH LATE AFTERNOON. AS AT LEAST ISOLATED STORMS CONTINUE TO DEVELOP/MATURE AND SPREAD NORTHEASTWARD...LARGE HAIL WILL BE POSSIBLE...AND TORNADOES/INCLUDING A STRONG TORNADO RISK/ WOULD ESPECIALLY BE A CONCERN AS STORMS ENCOUNTER A STRONGER CORRIDOR OF LOW-LEVEL SOUTHERLY WINDS TO THE EAST AND/OR INTERACT WITH THE AFOREMENTIONED OUTFLOW BOUNDARY. A SPECIAL 19Z OBSERVED SOUNDING FROM DALLAS-FORT WORTH SAMPLED A VERY MOIST BOUNDARY LAYER /LOWER 70S F SURFACE DEWPOINTS/ WITH 300+ M2/S2 EFFECTIVE SRH.


FARTHER NORTH...THE PRIMARY SCENARIO WILL BE FOR CONTINUED STORM MERGERS AHEAD OF SOUTHEASTWARD-PROPAGATING OUTFLOW CURRENTLY ACROSS PORTIONS OF SOUTHWEST/SOUTH-CENTRAL OK. LOCALLY DAMAGING WINDS/SOME HAIL WILL BE THE PRIMARY HAZARDS ACROSS SOUTH-CENTRAL OK.

Mesoscale Discussion #0599


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 155...157...CONTINUES.


SUMMARY...A NEW TORNADO WATCH WILL LIKELY BE ISSUED ENE OF WW/S 155/157 WITH PORTIONS OF THOSE WATCHES POTENTIALLY BEING REPLACED WITH A TORNADO THREAT PERSISTING BEYOND 02Z.


DISCUSSION...A PAIR OF POSSIBLE TORNADIC SUPERCELLS OVER SERN OK ARE EVOLVING WITHIN THE STRONGEST LOW-LEVEL SHEAR IN THE WARM SECTOR CHARACTERIZED BY 0-1 KM VALUES OF 25-30 KT PER KINX/KSRX VWP DATA. WITH THIS BELT OF STRONG SWLYS SHIFTING GRADUALLY EWD THIS EVENING...THE RISK FOR TORNADOES WILL PERSIST FOR SEVERAL HOURS ESPECIALLY WHERE NEAR-SURFACE SRH IS ENHANCED ALONG REMNANT OUTFLOW BOUNDARIES FROM EARLIER AFTERNOON CONVECTION. ADDITIONAL SEVERE STORMS OVER E-CNTRL TX SHOULD EVENTUALLY EVOLVE INTO NERN TX LATER THIS EVENING.


**This MCD preceded the Van Zandt County EF3

Mesoscale Discussion #0666


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 175 CONTINUES.


SUMMARY...A BROKEN LINE OF INTENSE TSTMS IS PROGRESSING NEWD ACROSS THE ERN TX PANHANDLE AND NW TX. THE DOWNSHEAR ENVIRONMENT ACROSS OK IS BECOMING INCREASINGLY FAVORABLE FOR TORNADO POTENTIAL /POSSIBLY STRONG/. A NEW TORNADO WILL BE ISSUED SOON FOR WRN/CNTRL OK AND POSSIBLY PARTS OF NORTH TX.


DISCUSSION...A BROKEN LINE OF INTENSE TSTMS WITH A FEW EMBEDDED SUPERCELLS CONTINUES TO MOVE NEWD ACROSS THE ERN TX PANHANDLE AND THE ROLLING PLAINS OF NWRN TX...WITH REPORTS RECEIVED RECENTLY OF LARGE HAIL AND A COUPLE TORNADOES. ADDITIONAL TSTMS ARE DEVELOPING FARTHER W WITHIN TORNADO WATCH 175...BUT WITH VEERED LOW-LEVEL WINDS AND A DRIER BOUNDARY-LAYER...LARGE HAIL AND DMGG WINDS WILL BE THE PRIMARY THREATS. 


THE ENVIRONMENT ACROSS WRN/CNTRL OK IS ONLY MARGINALLY TO MODERATELY UNSTABLE /PER 18Z OUN AND LMN SOUNDINGS/...AND STILL CAPPED WITH A WARM LAYER NOTED NEAR 1.5 KM AGL. EXTENSIVE CLOUD COVER HAS ALSO LIMITED DIABATIC HEATING ACROSS CNTRL OK...WITH TEMPERATURES REMAINING IN THE LOW-MID 70S. DESPITE THESE POTENTIAL LIMITING FACTORS...LOW-LEVEL SHEAR WILL CONTINUE TO INCREASE INTO THE EVENING...AND WILL FAVOR THE RISK FOR TORNADOES /SOME POTENTIALLY STRONG/ ACCOMPANYING DISCRETE SUPERCELLS ACROSS WRN/CNTRL OK AND POSSIBLY INTO PORTIONS OF N TX. AS A RESULT...A NEW TORNADO WATCH WILL BE ISSUED SOON.

Mesoscale Discussion #0673


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 175...177...179...CONTINUES.


SUMMARY...SEVERE/TORNADO POTENTIAL -- INCLUDING RISK FOR A FEW SIGNIFICANT EVENTS -- CONTINUES.


DISCUSSION...LATEST RADAR LOOP SHOWS SEVERAL SUPERCELLS ONGOING ATTM FROM SWRN OK SWD INTO WRN N TX...EXTENDING ROUGHLY FROM THE WICHITA MOUNTAINS VICINITY IN OK TO ROUGHLY ABILENE TX. WHILE THE LARGEST SUPERCELL -- NOW CROSSING WRN COMANCHE CO OK -- HAS SHOWN SOME/POSSIBLY TEMPORARY/ WEAKENING OF THE LOW-LEVEL MESOCYCLONE...BUT REMAINS A WELL-ORGANIZED STORM CAPABLE OF PRODUCING A STRONG TORNADO.


FARTHER S..SUPERCELLS ACROSS WRN N TX CONTINUE TO GRADUALLY INTENSIFY...INCLUDING A CELL IN NERN BAYLOR COUNTY SHOWING AN INCREASING LOW-LEVEL MESOCYCLONE.  THIS STORM COULD AFFECT THE WICHITA FALLS TX AREA IN THE NEXT HOUR OR SO.


OVERALL...A VERY MOIST BOUNDARY LAYER REMAINS IN PLACE...ALONG WITH UNUSUALLY STRONG/FAVORABLE LOW-LEVEL SHEAR /PER EVENING RAOB AND SURFACE DATA/.  THIS ENVIRONMENT REMAINS FAVORABLE FOR SIGNIFICANT/POTENTIALLY LONG-TRACK TORNADOES...ALONG WITH DAMAGING WINDS AND VERY LARGE HAIL.

Mesoscale Discussion #0752


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 206 CONTINUES.


SUMMARY...THE THREAT FOR LARGE HAIL AND A FEW DAMAGING WIND GUSTS...AS WELL AS A TORNADO OR TWO...CONTINUES PRIMARILY ACROSS FAR SRN PORTIONS OF WW 206.


DISCUSSION...THE 02Z WSR-88D MOSAIC EXHIBITS A PAIR OF SUPERCELLS OVER SEWARD CO KS. MEANWHILE...A BAND OF CONVECTION FROM WICHITA CO TO STANTON CO /WITH AN EMBEDDED MESOVORTEX ON THE NRN END/ CONTINUES TO PROGRESS EWD. ADDITIONALLY...AN EMBEDDED SUPERCELL APPEARS TO HAVE EVOLVED WITHIN THE SRN END OF THIS LINE. NRN PORTIONS OF THIS LINEAR SYSTEM HAVE WEAKENED OVER THE LAST HOUR...BUT THE AFOREMENTIONED CELLS TO THE SOUTHEAST /AS WELL AS THE TAIL-END SUPERCELL/ ARE CONTINUING TO SUPPORT A THREAT FOR LARGE HAIL...DAMAGING WINDS...AND A COUPLE OF TORNADOES. WHILE NOCTURNAL COOLING HAS COMMENCED AND THE 00Z DDC RAOB SAMPLED SOME MLCIN AROUND 750-700 MB /INDICATIVE OF A MORE HOSTILE THERMODYNAMIC ENVIRONMENT TO THE EAST/...UPDRAFT ORGANIZATION/ROTATION AIDED BY STEEP MID-LEVEL LAPSE RATES AND A VEERING 0-3-KM WIND PROFILE MAY MAINTAIN CONVECTIVE INTENSITY VIA DYNAMIC PRESSURE PERTURBATION PROCESSES. INDEED...SEVERAL REPORTS OF LARGE HAIL /INCLUDING A 3-INCH REPORT/IN SEWARD CO HAVE BEEN RECEIVED. AS SUCH...THE SEVERE THREAT CONTINUES ACROSS SRN PORTIONS OF WW 206. WHILE CELLS WILL LIKELYY WEAKEN AS THEY PROGRESS EAST...A LOCAL AREAL EXTENSION BY A TIER OF COUNTIES EWD MAY BE NECESSARY IF CELLS MAINTAIN THEIR CURRENT INTENSITY.


**This MCD preceded the likely intense Plains, KS wedge and a strong EF2 near Dodge City

Mesoscale Discussion #0754


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 206 CONTINUES.


SUMMARY...A TORNADO THREAT /POTENTIALLY STRONG/ MAY CONTINUE THROUGH AT LEAST 05Z/MIDNIGHT CDT ACROSS SOUTHWEST KS INCLUDING AREAS NEAR/WEST OF DODGE CITY. SEVERE HAIL/WIND WILL OTHERWISE REMAIN POSSIBLE.


DISCUSSION...AHEAD OF AN EASTWARD-MOVING CONVECTIVE LINE...A PERSISTENT DISCRETE SUPERCELL WITH HISTORY OF PRODUCING TORNADOES CONTINUES TO SLOWLY MOVE NORTHEASTWARD ACROSS FAR SOUTHERN GRAY COUNTY AS OF 1115 PM CDT/0415Z. WHILE OVERALL SUPERCELL INTENSITY MAY BE POST-PEAK AND ENVIRONMENTAL CINH HAS INCREASED OVER THE PAST 1-2 HOURS...SUPERCELL INTERNAL DYNAMICAL PROCESSES AND RELATIVELY STRONG LOW-LEVEL SHEAR PER DODGE CITY WSR-88D VWP DATA COULD MAINTAIN A SUPERCELL TORNADO THREAT TOWARD THE DODGE CITY AREA THROUGH AT LEAST THE 05Z/MIDNIGHT CDT TIME FRAME...IF NOT BEYOND. OTHERWISE...SOME SEVERE WIND/HAIL MAY REMAIN A CONCERN WITH THE EASTWARD-MOVING CONVECTIVE LINE...WITH IT LIKELY TO EVENTUALLY OVERTAKE THE AFOREMENTIONED SUPERCELL.

Mesoscale Discussion #1950


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 537 CONTINUES.


SUMMARY...THE SEVERE THREAT IS EXPECTED TO GRADUALLY INCREASE OVER THE NEXT FEW HOURS. TORNADOES...LARGE HAIL AND WIND DAMAGE WILL BE POSSIBLE WITH STRONGER THUNDERSTORMS IN AND NEAR TORNADO WATCH 537.


DISCUSSION...THE LATEST WATER VAPOR IMAGERY SHOWS A VERY WELL-ORGANIZED UPPER-LEVEL LOW IN THE FOUR CORNERS REGION. AN IMPRESSIVE 90 TO 110 KT MID-LEVEL JET IS ROUNDING THE BASE OF THE TROUGH WITH THE EXIT REGION OF THE JET SPREADING OVER THE SRN AND CNTRL HIGH PLAINS ATTM. THIS ALONG WITH STRONG LARGE-SCALE ASCENT ASSOCIATED WITH THE SYSTEM IS AIDING A STEADY EXPANSION OF CONVECTIVE COVERAGE ACROSS THE TORNADO WATCH. AS THIS OCCURS OVER THE NEXT FEW HOURS...LOW-LEVEL MOISTURE...INSTABILITY AND LOW-LEVEL SHEAR WILL INCREASE. THIS WILL MAINTAIN AN ENVIRONMENT FAVORABLE FOR SUPERCELLS. SFC DEWPOINTS ARE CURRENTLY IN THE LOWER 60S F ACROSS THE LOW ROLLING PLAINS OF NW TX. THIS LOW-LEVEL MOISTURE EXPAND NWD INTO THE ERN TX PANHANDLE...WRN OK AND SW KS LATE THIS AFTERNOON INTO EARLY THIS EVENING. AS DISCRETE CELLS MOVE EWD INTO THIS MOIST AIRMASS AND AS THE LOW-LEVEL JET STRENGTHENS DUE TO THE APPROACH OF THE UPPER-LEVEL SYSTEM...THE TORNADO THREAT WILL LIKELY INCREASE. A POTENTIAL WILL EXIST FOR A STRONG TORNADO OR TWO. LARGE HAIL AND WIND DAMAGE WILL BE LIKELY WITH THE STRONGER STORMS.

Mesoscale Discussion #1953


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 537 CONTINUES.


SUMMARY...THE RISK FOR TORNADOES STILL APPEARS LIKELY TO INCREASE THROUGH THE 01-03Z TIME FRAME.  EVENTUALLY...ADDITIONAL WATCHES WILL LIKELY BE NEEDED TO THE EAST OF WW 537...BUT IT MAY STILL BE ANOTHER SEVERAL HOURS.


DISCUSSION...DISCRETE STORM DEVELOPMENT IS NOW WELL UNDERWAY NEAR/EAST OF A PRE-COLD FRONTAL DRY-LINE TYPE STRUCTURE.  THE SURFACE COLD FRONT STILL APPEARS TO EXTEND ACROSS FAR WESTERN PORTIONS OF THE OKLAHOMA AND NORTHWEST TEXAS PANHANDLES INTO EASTERN NEW MEXICO...AND IS FORECAST TO EVENTUALLY SURGE EASTWARD ACROSS THE HIGH PLAINS TONIGHT.  IT REMAINS A BIT UNCERTAIN HOW QUICKLY THIS WILL OCCUR...BUT IT PROBABLY WILL NOT BE UNTIL AN ASSOCIATED UPSTREAM MID-LEVEL CLOSED LOW FINALLY PROGRESSES EAST NORTHEAST OF THE SOUTHERN ROCKIES.  THIS MAY NOT BE UNTIL AT LEAST THE 03-06Z TIME FRAME.


UNTIL THE FRONT BEGINS ITS EASTWARD SURGE...THE STORM MODE WILL PROBABLY REMAIN MOSTLY DISCRETE/SUPERCELLULAR...WITH ACTIVITY TENDING TO MOVE FASTER TO THE NORTH NORTHEAST...THAN EAST...IN THE PRESENCE OF 40-50+ KT SOUTHERLY LOWER/MID-TROPOSPHERIC FLOW.  THROUGH 01-03Z...MODELS CONTINUE TO INDICATE FURTHER STRENGTHENING OF SOUTHERLY 850 MB FLOW TO 50-60+ KT ACROSS PARTS OF NORTHWEST TEXAS INTO WESTERN OKLAHOMA.  ACCOMPANIED BY A CONTINUED GRADUAL MOISTENING IN LOWER LEVELS...WHICH MAY OFFSET STABILIZATION TRENDS ASSOCIATED WITH RADIATIONAL COOLING...INCREASING LOW-LEVEL SHEAR PROBABLY WILL BE ACCOMPANIED BY IN INCREASING RISK FOR TORNADOES IN STRONGEST STORMS.

Mesoscale Discussion #2036


PROBABILITY OF WATCH ISSUANCE...95 PERCENT


SUMMARY...TRENDS CONTINUE TO SUGGEST THE POTENTIAL FOR A SIGNIFICANT RISK OF SEVERE STORMS AND TORNADOES THIS AFTERNOON.  A TORNADO WATCH WILL BE ISSUED IN THE NEXT HOUR OR SO.


DISCUSSION...VISIBLE SATELLITE LOOPS SHOW A FEW BREAKS IN THE CLOUDS SLOWLY DEVELOPING OVER EASTERN AR AND ADJACENT PARTS OF TN/MS/LA...WITH STRONG SOUTHERLY LOW LEVEL WINDS ARE TRANSPORTING MID/UPPER 60S DEWPOINTS NORTHWARD INTO THE REGION.  SO FAR...DEEP CONVECTIVE DEVELOPMENT HAS BEEN SUPPRESSED ALONG A SURFACE CONVERGENCE AXIS OVER NORTHERN LA.  MULTIPLE CAM SOLUTIONS SUGGEST THIS WILL BE THE GENERATION ZONE FOR SUPERCELL DEVELOPMENT IN THE NEXT FEW HOURS.  FORECAST SOUNDINGS AND REGIONAL VAD PROFILES SHOW SUBSTANTIAL LOW LEVEL VERTICAL SHEAR THAT WILL ONLY STRENGTHEN WITH TIME. STRONG TORNADOES WILL BE A CONCERN IF DISCRETE STORMS CAN MAINTAIN INTENSITY.  CURRENT INDICATIONS ARE THAT A TORNADO WATCH WILL BE NEEDED ACROSS PARTS OF THIS REGION IN THE NEXT HOUR OR SO.

Mesoscale Discussion #2040


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 559 CONTINUES.


SUMMARY...SATELLITE AND RADAR TRENDS SUGGEST THAT DISCRETE SUPERCELL DEVELOPMENT MAY BEGIN IN THE NEXT 1-2 HOURS.


DISCUSSION...VISIBLE SATELLITE IMAGERY CONTINUES TO SHOW LOW CLOUDS BREAKING UP ACROSS THIS REGION...LEADING TO SURFACE TEMPERATURES RISING INTO THE LOWER/MID 70S.  DEWPOINTS ALSO CONTINUE TO INCREASE...WITH MLCAPE VALUES NOW OVER 1000 J/KG AS FAR NORTH AS SOUTHEAST AR AND NORTHERN MS.  LOCAL VAD PROFILES AND MESOANALYSIS DATA SHOW SUBSTANTIAL LOW LEVEL VERTICAL SHEAR IN PLACE...WITH EFFECTIVE SRH VALUES AS HIGH AS 500 M2/S2 ON MEG VAD.


IT APPEARS LIKELY THAT CONTINUED LOW LEVEL DESTABILIZATION WILL BREAK THE MINIMAL CAP AND RESULT IN ISOLATED DISCRETE SUPERCELLS IN THE WARM SECTOR DURING THE NEXT COUPLE OF HOURS.  A FEW CELLS EMBEDDED IN THE SQUALL LINE OVER CENTRAL/EASTERN AR HAVE ALSO SHOWN INCREASING SUPERCELLULAR TENDENCIES.  PARAMETERS REMAIN FAVORABLE FOR STRONG TORNADOES WHERE PERSISTENT LOW LEVEL MESOCYCLONES CAN BE MAINTAINED.

Mesoscale Discussion #2045


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 559 CONTINUES.


SUMMARY...CONDITIONS REMAIN FAVORABLE FOR TORNADIC SUPERCELLS CAPABLE OF STRONG TORNADOES AND DAMAGING WINDS.


DISCUSSION...THUNDERSTORMS ARE SLOWLY INCREASING IN COVERAGE AND INTENSITY OVER EASTERN AR...ALONG A LINE FROM WEST OF PAH - BYH - WEST OF MEM.  SEVERAL STORMS ALONG THE LINE HAVE DEVELOPED PERSISTENT MID-LEVEL ROTATION AND HAVE PRODUCED LARGE HAIL /UP TO BASEBALL SIZE/.  LOCAL RADARS INDICATE THAT STRONG LOW LEVEL ROTATION HAS YET TO DEVELOP IN THESE STORMS...AND SO FAR THE TORNADO RISK HAS BEEN LIMITED.  THE VAD PROFILE AT MEM SHOWS INTENSE LOW LEVEL VERTICAL SHEAR IS PRESENT AHEAD OF THE STORMS...WITH 0-3KM SRH VALUES NOW OVER 700 M2/S2.  SURFACE DEWPOINTS NOW IN THE MID 60S INTO WEST TN IS YIELDING SUFFICIENT MLCAPE VALUES TO MAINTAIN A RISK OF STRONG TORNADOES THROUGH THE EARLY EVENING.


A FEW ISOLATED THUNDERSTORMS HAVE ALSO FORMED OVER WEST TN AHEAD OF THE MAIN CONVECTIVE LINE.  THIS TRENDS SUGGESTS THAT A NEW WW MAY BE NEEDED TO THE EAST OF WW 559 WITHIN THE NEXT COUPLE OF HOURS...INCLUDING MORE OF MIDDLE TN AND NORTHWEST AL.

Mesoscale Discussion #2066


PROBABILITY OF WATCH ISSUANCE...80 PERCENT


SUMMARY...TORNADO WATCH ISSUANCE IS LIKELY ACROSS PARTS OF NORTH TX AND SOUTH TO SOUTHEAST OK INTO WESTERN AR.  CONCERN IS INCREASING FOR SEVERE WEATHER TO DEVELOP ACROSS THIS REGION THIS AFTERNOON WITH ALL SEVERE HAZARDS POSSIBLE INCLUDING A FEW TORNADOES.


DISCUSSION...TRENDS IN MESONET OBSERVATIONS SHOWED A COLD FRONT HAS ADVANCED THROUGH MUCH OF THE WESTERN THIRD OF OK...THE WESTERN HALF OF THE TX BIG COUNTRY TO SOUTHWEST TX.  CURRENTLY...THE NORTHERN EXTENT FOR SURFACE-BASED STORMS IS LIKELY IN VICINITY OF A WARM FRONT THAT EXTENDS FROM JUST SOUTH OF THE OKC METRO /SOUTHERN MCCLAIN AND CLEVELAND COUNTIES/ EAST INTO WEST CENTRAL AR...WITH SURFACE DEW POINTS IN THE UPPER 60S TO AROUND 70 F SOUTH OF THIS BOUNDARY. THE WARM SECTOR ENVIRONMENT ACROSS CENTRAL AND NORTH TX INTO PORTIONS OF SOUTHERN AND EASTERN OK AND WESTERN AR IS ALREADY CONDUCIVE TO SUPPORT STRONG TO SEVERE STORMS.  THE SPECIAL 18Z FWD SOUNDING SAMPLED THIS ENVIRONMENT VERY WELL /MODERATE INSTABILITY/MLCAPE EXCEEDING 1500 J PER KG/...EFFECTIVE BULK SHEAR EXCEEDING 50 KT...AND SFC-3 KM SRH EXCEEDING 300 M2 PER S2/...SUPPORTING THE LIKELIHOOD FOR ORGANIZED ROTATING STORMS.  ALTHOUGH STRONGER DEEP-LAYER FORCING FOR ASCENT WILL TEND TO REMAIN WEST OF THE WARM SECTOR THIS AFTERNOON...EVEN WEAK UPWARD VERTICAL MOTION WITHIN THIS ANOMALOUSLY MOIST AND FAVORABLY SHEARED ENVIRONMENT POSES CONCERN FOR A TORNADO THREAT.  


STORMS THAT FORM NEAR OR ALONG THE COLD FRONT SHOULD QUICKLY BECOME UNDERCUT BY THIS BOUNDARY AND TEND TO POSE A THREAT FOR PRIMARILY HAIL. REFER TO MCD 2065 FOR THIS ELEVATED HAIL THREAT.  THE TORNADO THREAT WILL BE ATTENDANT TO NEW UPDRAFTS/STORM DEVELOPMENT FARTHER EAST ACROSS THE WARM SECTOR IN NORTH-CENTRAL TX TO SOUTHEAST OK AND WESTERN AR.  ACTIVITY IN THIS REGIME WILL TEND TO TRACK PARALLEL TO AXES OF LOW-LEVEL CONFLUENCE AHEAD OF THE COLD FRONT...RESULTING IN A LONGER GESTATION PERIOD OF THE STRONGER INSTABILITY AND STRONGLY SHEARED ENVIRONMENT.

Mesoscale Discussion #2070


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 569 CONTINUES.


SUMMARY...A TORNADO THREAT WILL CONTINUE THROUGH THE EARLY EVENING HOURS PARTICULARLY ACROSS NORTH-CENTRAL TX /INCLUDING NEAR THE DFW METRO AREA/ INTO EAST-CENTRAL/FAR SOUTH-CENTRAL OK. TORNADO WATCH 569 CONTINUES UNTIL 02Z/8PM CST.


DISCUSSION...RELATED TO A PERSISTENT CORRIDOR OF MOIST/CONFLUENCE LOW-LEVEL FLOW AHEAD OF A SOUTHEASTWARD-ADVANCING COLD FRONT...THE PRIMARY TORNADO THREAT WILL CONTINUE THROUGH EARLY EVENING /THROUGH 7PM-8PM CST/ ESPECIALLY IN AREAS NEAR/EAST OF I-35 ACROSS NORTH-CENTRAL TX...AND TO A LESSER EXTENT INTO SOUTHERN/EASTERN OK AS FAR NORTH-NORTHEAST AS THE I-40 VICINITY. SIMILAR TO THE RECENT 00Z DFW OBSERVED SOUNDING...THE FORT WORTH 88D VWP CONTINUES TO SAMPLE VERY STRONG/LARGELY UNIDIRECTIONAL SOUTH-SOUTHWESTERLY WINDS ATOP SOUTH-SOUTHEASTERLY NEAR-SURFACE-WINDS...WITH 0-1 KM SRH ESTIMATED TO BE AROUND 200-250 M2/S2. WITHIN A MOIST ENVIRONMENT...THIS SCENARIO WILL CONTINUE THE POTENTIAL FOR SCATTERED SUPERCELLS THROUGH THE EARLY EVENING WITH AT LEAST TRANSIENT/MODERATE LOW-LEVEL ROTATION AND THE RELATED RISK FOR AN ADDITIONAL TORNADO OR TWO. WITH ANY TORNADO THREAT LIKELY CURRENTLY AT ITS PEAK AS OF 530 PM CST...CURRENT THINKING IS THE DISCRETE SUPERCELL-RELATED TORNADO RISK SHOULD GRADUALLY DIMINISH WITH INCREASINGLY EFFECTIVE-FRONT-DOMINANT CONVECTION INTO MID/LATE EVENING.


**This MCD preceded the Garland-Rowlett EF4