[MCD] SWOMCD

[Mesoscale Convective Discussions]

ACUS11 KWNS 071125
SWOMCD
SPC MCD 071124 
TXZ000-071630-

MESOSCALE DISCUSSION 2542
NWS STORM PREDICTION CENTER NORMAN OK
0524 AM CST WED DEC 07 2005

AREAS AFFECTED...N CNTRL TX

CONCERNING...WINTER MIXED PRECIPITATION 

VALID 071124Z - 071630Z

PRECIPITATION IS EXPECTED TO GRADUALLY INCREASE ACROSS N CNTRL TX
THROUGH THE MORNING. LIGHT FREEZING RAIN WILL BE POSSIBLE OVER THE
WRN HALF OF N CNTRL TX BY MID MORNING. THE FREEZING RAIN MAY BEGIN
TO MIX WITH SLEET OR SNOW BY LATE MORNING OR AFTERNOON. 

A COLD FRONT EXTENDS FROM SRN AR INTO N CNTRL TX NEAR FORT WORTH
THEN SWWD INTO THE BIG BEND AREA. THIS FRONT WILL MOVE SEWD
TODAY...ALLOWING COLD ARCTIC HIGH PRESSURE TO CONTINUE BUILDING INTO
TX. POST FRONTAL WET BULB TEMPERATURES ARE WELL BELOW FREEZING OVER
THE WRN PARTS OF N CNTRL TX. A 20-30 KT LOW LEVEL JET WILL PERSIST
OVER CNTRL TX INTO THE AFTERNOON. THIS WILL MAINTAIN ISENTROPIC
ASCENT AND WARM ADVECTION WITHIN THE 1-3 KM LAYER. THIS ASCENT IS
ALREADY CONTRIBUTING TO AN INCREASE IN STRATUS AND PRECIPITATION
OVER THE SRN HALF OF N CNTRL TX. OWING TO THE RELATIVE DRY BOUNDARY
LAYER...MUCH OF THIS ACTIVITY IS NOT LIKELY REACHING THE GROUND IN
POST FRONTAL REGION. EVAPORATIVE COOLING WILL EVENTUALLY SATURATE
THE LAYER BELOW 3 KM AND MAINTAIN SURFACE TEMPERATURES BELOW
FREEZING OVER THE WRN HALF OF N CNTRL TX. RUC SOUNDINGS VALID FOR
EARLY THIS MORNING SHOW A WARM LAYER AROUND 2 KM...AND THIS PROFILE
WILL LIKELY SUPPORT FREEZING RAIN AS SURFACE TEMPERATURES WET BULB
BELOW ZERO. THIS WARM LAYER IS FORECAST TO GRADUALLY ERODE AS THE
SUBZERO LAYER DEEPENS WITHIN THE POST FRONTAL ZONE. A CHANGEOVER OR
MIX WITH SLEET AND SNOW WILL THEREFORE BE POSSIBLE. THE CHANGEOVER
TO SNOW WILL BE MOST LIKELY OVER NWRN PARTS OF N CNTRL TX BY LATE
MORNING...ESPECIALLY IF VERTICAL MOTION IS DEEP ENOUGH TO SATURATE
THE LAYERS BELOW -10C WHERE DENDRITIC GROWTH IS FAVORED. BOTH ETA
AND RUC FORECAST SOUNDINGS SHOW A SHALLOW UNSTABLE LAYER DEVELOPING
BETWEEN 3 AND 5 KM BY MID-DAY...WHICH MAY CONTRIBUTE TO SOME
CONVECTIVE ENHANCEMENT TO THE PRECIPITATION.

..DIAL.. 12/07/2005

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

ATTN...WFO...SHV...FWD...SJT...

33689593 32529547 32059669 31509814 31139904 31819913
33309755 

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