MESO: Mesoscale Discussion 2136

ACUS11 KWNS 252220
SWOMCD
SPC MCD 252220
TXZ000-OKZ000-260015-

MESOSCALE DISCUSSION 2136
NWS STORM PREDICTION CENTER NORMAN OK
0520 PM CDT SUN OCT 25 2009

AREAS AFFECTED...FOR N CNTRL TX INTO S CNTRL OK

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 252220Z - 260015Z

TRENDS ARE BEING MONITORED FOR AN INCREASING SEVERE THREAT WHICH
WILL LIKELY REQUIRE A WW BY EARLY EVENING.

AS AN INITIAL SHORT WAVE TROUGH LIFTS THROUGH THE SOUTH CENTRAL
PLAINS...MODELS CONTINUE TO SUGGEST THAT THE SURFACE COLD
FRONT...NOW NOSING THROUGH WESTERN OKLAHOMA AND THE SOUTHERN TEXAS
PANHANDLE...WILL BEGIN TO SURGE MORE RAPIDLY EASTWARD AND SOUTHWARD
INTO THE LOWER SOUTHERN PLAINS. THIS WILL OCCUR AS A SOUTHERLY
LOW-LEVEL RETURN FLOW CONTINUES TO MOISTEN OFF THE WESTERN GULF OF
MEXICO...AND LARGE-SCALE ASCENT INCREASES DOWNSTREAM OF A MUCH
STRONGER SHORT WAVE IMPULSE STILL DIGGING THROUGH THE
CENTRAL/SOUTHERN ROCKIES. FORCING AND DESTABILIZATION ARE EXPECTED
TO SUPPORT INCREASINGLY WIDESPREAD CONVECTIVE DEVELOPMENT THIS
EVENING ACROSS EASTERN OKLAHOMA AND NORTHERN/CENTRAL TEXAS.

THE TENDENCY PROBABLY WILL BE FOR THIS ACTIVITY TO DEVELOP
ABOVE...OR BE UNDERCUT BY...THE SOUTHWARD ADVANCING FRONT.
HOWEVER...GUIDANCE CONTINUES TO SUGGEST THAT A WINDOW OF OPPORTUNITY
WILL EXIST LATE THIS AFTERNOON INTO THE EVENING FOR PRE-FRONTAL
BOUNDARY LAYER BASED STORM DEVELOPMENT IN THE PRESENCE OF STRONG
SHEAR BENEATH 40+ KT SOUTHWESTERLY 500 MB FLOW.

STORM INITIATION SEEMS MOST PROBABLE NEAR THE INTERSECTION OF THE
COLD FRONT AND A BROAD/DIFFUSE DRY LINE STRUCTURE...NEAR/NORTH AND
WEST OF DALLAS/FORT WORTH INTO THE ARDMORE OK AREA. NEAR SURFACE
PARCELS CHARACTERIZED BY CAPE OF 1000-1500 J/KG ARE STILL CAPPED
ACROSS THIS REGION...BUT FURTHER MOISTURE INCREASES COUPLED WITH
INCREASINGLY DIFLUENT AND DIVERGENT UPPER FLOW COULD WEAKEN
INHIBITION AS EARLY AS 00-01Z. DISCRETE SUPERCELLS ARE EXPECTED
INITIALLY...BEFORE LARGE-SCALE FORCING CONTRIBUTES TO A GROWING
CONVECTIVE LINE/CLUSTER SOUTHWARD/SOUTHEASTWARD ACROSS NORTH CENTRAL
TEXAS .

..KERR.. 10/25/2009

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

ATTN...WFO...FWD...OUN...SJT...

LAT...LON 33609870 34319828 34719783 35079736 35109677 34159627
33469583 32689578 31789717 31929857 32519913 33019907
33609870

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