SWOMCD
SPC MCD 231238
TXZ000-231815-
MESOSCALE DISCUSSION 0140
NWS STORM PREDICTION CENTER NORMAN OK
0638 AM CST TUE FEB 23 2010
AREAS AFFECTED...PORTIONS CENTRAL/N-CENTRAL/SW TX.
CONCERNING...HEAVY SNOW
VALID 231238Z - 231815Z
ALTHOUGH HEAVIEST PRECIP WILL REMAIN AS RAIN IN AREAS OF
SUPERFREEZING SFC AIR...SNOW IS EXPECTED ACROSS PORTIONS
CENTRAL/N-CENTRAL TX THROUGH 18Z. WITHIN BROADER AREA OF MDT
SNOW...EPISODIC/CONVECTIVELY DERIVED BURSTS OF HEAVY SNOW ARE
LIKELY...THE LATTER OFFERING SNOWFALL RATES 1-2 INCH/HOUR.
MOISTURE CHANNEL IMAGERY AND AVAILABLE RAOB DATA INDICATE
POSITIVELY-TILTED SHORTWAVE TROUGH OVER PORTIONS SRN NM...FAR W TX
AND NRN CHIHUAHUA. THIS PERTURBATION...AND FOREGOING FIELD OF
MID-UPPER LEVEL DPVA/ASCENT...WILL SHIFT ESEWD THROUGH REMAINDER
MORNING...ERN EDGE OF MID-UPPER LIFT BEING JUXTAPOSED WITH WRN PART
OF PLUME OF LOW LEVEL WAA. RELATED STEEPENING OF LOW-MIDLEVEL LAPSE
RATES...ATOP ROUGHLY 3 KM DEEP STABLE LAYER...WILL RESULT IN WEAK
ELEVATED BUOYANCY IN SOME LOCALES...UP TO ABOUT 100 /KG. THIS WILL
SUPPORT EMBEDDED CONVECTIVE ENHANCEMENT TO PRECIP...AND ISOLATED
THUNDER. STRONGEST LIFT IS EXPECTED ALONG AND N OF QUASISTATIONARY
850 MB FRONTAL/CONFLUENCE ZONE...EVIDENT IN 12Z RAOB/VWP/PROFILER
DATA FROM BIG BEND AREA ENEWD TOWARD CLL.
12Z SFC ANALYSIS INDICATES WAVY FREEZING LINE...GENERALLY FROM SWRN
AR NWWD TO S-CENTRAL OK THEN SWWD ACROSS WRN PORTIONS N-CENTRAL TX
TO EDWARDS PLATEAU AND BIG BEND. FREEZING LINE IS EXPECTED TO
UNDERGO NET SEWD MOTION ACROSS THIS REGION AS LOW LEVEL CAA AND
EVAPORATIONAL/SUBLIMATIONAL COOLING OFFSET SECOND-ORDER EFFECT OF
VERY WEAK DIABATIC HEATING. SNOW IS LIKELY BEHIND AND WITHIN ABOUT
50-75 NM AHEAD OF FREEZING LINE...GIVEN MODIFIED RAOBS AND RUC
SOUNDINGS INDICATING COMBINATION OF MOSTLY BELOW-FREEZING THERMAL
PROFILES ALOFT AND HIGH RH/UVV WITHIN DENDRITIC GROWTH ZONE.
HOWEVER...NARROW AND SHORT-LIVED CORRIDOR OF FREEZING RAIN...LOCALLY
MIXED WITH SLEET...ALSO IS POSSIBLE ALONG AND WITHIN 20-30 NM N OF
SFC FREEZING LINE. THIS ZONE WILL MIGRATE SEWD WITH FREEZING LINE
DURING REMAINDER MORNING.
..EDWARDS.. 02/23/2010
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.
ATTN...WFO...FWD...EWX...SJT...MAF...
LAT...LON 31530075 32589856 32949730 32939611 31589634 30699771
29839936 29260076 29470104 29500124 29640123 29530131
29660132 29770143 29790175 29830214 30890148 31530075
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