Monday, October 17, 2011

MESO: Mesoscale Discussion 2258

ACUS11 KWNS 172224
SWOMCD
SPC MCD 172223
ARZ000-MOZ000-OKZ000-KSZ000-TXZ000-180030-

MESOSCALE DISCUSSION 2258
NWS STORM PREDICTION CENTER NORMAN OK
0523 PM CDT MON OCT 17 2011

AREAS AFFECTED...ERN OK...N-CNTRL TX...FAR NWRN AR/SWRN MO

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 172223Z - 180030Z

SCATTERED TO NUMEROUS TSTMS WILL LIKELY INITIATE ALONG AND BEHIND
SHARP SEWD-MOVING COLD FRONT IN THE EARLY/MID-EVENING. PRIMARY
THREATS WILL BE SEVERE HAIL AND PERHAPS LOCALLY DAMAGING WINDS. THE
PROBABILITY OF A SEVERE TSTM WATCH ISSUANCE BY 00Z IS 40 PERCENT.

22Z SURFACE ANALYSIS PLACED NE-SW ORIENTED COLD FRONT FROM THE
OK/KS/MO BORDER AREA BISECTING OK TO A TRIPLE-POINT LOW JUST E OF
SPS. ALTHOUGH AIR MASS IS QUITE WARM AHEAD OF THE FRONT...SURFACE
DEW POINTS HAVE HELD IN THE 50S...WHICH HAS CONTRIBUTED TO A WEAKLY
UNSTABLE AIR MASS WITH MLCAPE AOB 1000 J/KG. SHORT WAVE TROUGH NOW
CENTERED OVER THE TX/OK PANHANDLES WILL TRACK SEWD INTO N-CNTRL TX
THIS EVENING. ASCENT ASSOCIATED WITH THIS FEATURE AND CONVERGENCE
ALONG THE FRONT WILL BE SUFFICIENT FOR TSTMS INITIATION BY 00Z AND
LIKELY INCREASING RAPIDLY IN COVERAGE TOWARDS 03Z. HOWEVER...A WARM
SECTOR CAPPING INVERSION NOTED IN ACARS DATA INVOF DFW AND
ANAFRONTAL NATURE OF THE FORCING SUGGEST TSTM UPDRAFTS WILL REMAIN
ALONG AND BEHIND THE COLD FRONT.

STRONGEST MID-LEVEL FLOW WILL STAY CONFINED SW OF THE SHORT WAVE
TROUGH. STILL...THE PRESENCE OF 40 KT W/SWLYS AT 6 KM AGL PER NORMAN
AND TULSA VWP DATA SHOULD BE SUFFICIENT FOR UPDRAFT ROTATION WITH A
THREAT FOR SEVERE HAIL. THE RAPID EVOLUTION TO A CLUSTER AND PERHAPS
LINEAR CONVECTIVE MODE INFERS THE MAGNITUDE OF THE HAIL THREAT WOULD
PEAK EARLY AND BECOME MARGINAL WITH TIME THIS EVENING.

..GRAMS.. 10/17/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...SGF...SHV...TSA...FWD...OUN...

LAT...LON 34329792 35679662 36999491 37149456 37119403 36839368
36359382 34189517 32809613 32539696 32549769 32709840
33209844 34329792

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