MESO: Mesoscale Discussion 0009

ACUS11 KWNS 091251
SWOMCD
SPC MCD 091251
TXZ000-091745-

MESOSCALE DISCUSSION 0009
NWS STORM PREDICTION CENTER NORMAN OK
0651 AM CST MON JAN 09 2012

AREAS AFFECTED...PORTIONS W TX.

CONCERNING...HEAVY SNOW

VALID 091251Z - 091745Z

RAIN-SNOW TRANSITION HAS BEGUN OVER LOWER PECOS REGION GENERALLY
FROM INK-FST. PRIND RATES WILL INCREASE TO 1-2 INCHES/HOUR IN
INCREASINGLY WELL-ORGANIZED PRECIP BAND INITIALLY EXTENDING FROM WRN
PECOS COUNTY NWD OVER WINKLER COUNTY. EMBEDDED TSTMS WILL OFFER
LOCALIZED/BRIEF RATES ABOVE 2 INCHES/HOUR.

SNOW AREA SHOULD PIVOT CYCLONICALLY IN KEEPING WITH EWD SHIFT OF
MID-UPPER LOW...WHILE EXPANDING IN COVERAGE BENEATH ELEVATED MOIST
CONVEYOR. THIS WILL OCCUR AS STRONGEST DEEP-LAYER ASCENT WITHIN
OPTIMAL DENDRITIC-GROWTH LAYER MOVES ACROSS REGION. EXPECT INCREASE
IN SNOW RATES OVER MAF AREA AND NWD/NEWD TOWARD PORTIONS
GARZA/LYNN/TERRY COUNTIES...WHILE HEAVY SNOW AREA SNOW
EXPANDS/SHIFTS EWD ACROSS PORTIONS PECOS/CROCKETT/REAGAN/
GLASSCOCK/HOWARD COUNTIES THROUGH 16Z. SFC TEMPS WILL CONTINUE TO
DECREASE THROUGH MID-LOW 30S F FROM W-E...FROM COMBINATION OF
BOUNDARY-LAYER CAA...WEAK WET-BULB COOLING...AND COLUMNAR DYNAMIC
COOLING. MEANWHILE RELATIVE WARM LAYER BETWEEN 700-800 MB WILL
CONTINUE TO COOL...WHILE RH INCREASES WITHIN DENDRITIC GROWTH COLUMN
AS WELL. THESE PROCESSES WILL FOSTER RAIN-SNOW CHANGEOVER IN ERN
PARTS OF DISCUSSION AREA...AND MAINTAIN SNOW AS DOMINANT
WINTER-PRECIP PHASE. OBSERVED 12Z MAF SOUNDING AND MODIFIED RUC
FCST SOUNDINGS INDICATE THIS TREND...AS WELL AS SUFFICIENTLY STEEP
MIDLEVEL LAPSE RATES TO SUPPORT MUCAPE 100-300 J/KG ROOTED NEAR 700
MB AND EXTENDING INTO ICING LAYERS SUITABLE FOR LTG GENERATION.
THEREFORE OCNL THUNDERSNOW IS EXPECTED OVER MORE OF AREA...WITH LTG
ALREADY DETECTED BETWEEN MAF-FST.

..EDWARDS.. 01/09/2012

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

ATTN...WFO...SJT...LUB...MAF...

LAT...LON 30490278 30930310 31790306 32550272 33030231 33160177
33270107 32860077 32030119 31450130 30970160 30560229
30490278

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