[MCD] SWOMCD

[Mesoscale Convective Discussions]

ACUS11 KWNS 121850
SWOMCD
SPC MCD 121849 
OKZ000-TXZ000-122345-

MESOSCALE DISCUSSION 0043
NWS STORM PREDICTION CENTER NORMAN OK
1249 PM CST FRI JAN 12 2007

AREAS AFFECTED...NWRN TX...OK

CONCERNING...WINTER MIXED PRECIPITATION 

VALID 121849Z - 122345Z

ICE PELLETS AND FREEZING RAIN...WITH ACCUMULATION RATES OF 0.05 TO
0.10 INCH PER HOUR...SHOULD PERSIST FROM SWRN THROUGH NCNTRL OK
THROUGH THE AFTERNOON. A GRADUAL EWD SHIFT IN HEAVIER PRECIPITATION
RATES MAY BEGIN TO OCCUR ACROSS WRN PARTS OF THE MCD AREA DURING THE
AFTERNOON BASED ON SREF MEAN QPF AND LATEST RADAR TRENDS. RAIN IS
LIKELY TO CHANGE TO FREEZING RAIN IN A NARROW BAND FROM NWRN TX INTO
PARTS OF SRN AND ERN OK OVER THE NEXT 2-4 HOURS.

PRECIPITATION SHIELD COMPOSED OF FREEZING RAIN AND ICE PELLETS HAS
EXPANDED AND SPREAD NEWD ACROSS CNTRL AND NRN OK THROUGH EARLY
AFTERNOON IN THE WAKE OF STRONG ARCTIC FROPA THIS MORNING. THE
PRECIPITATION WAS INITIALLY INDUCED AS ISENTROPIC LIFT ACROSS THE 
FRONT DEVELOPED INTO A PLUME OF HIGHER THETA-E AIR EMANATING FROM
SOUTH TX AND THE GULF. IT APPEARS THAT DEEPER ASCENT...AIDED BY A
LOW AMPLITUDE SHORT WAVE TROUGH MOVING ENEWD FROM NM/WEST TX...HAS
SUSTAINED THE MIXED PRECIPITATION ACROSS MUCH OF OK OVER THE PAST
FEW HOURS. STRONGER LIFT ASSOCIATED THIS LEADING SHORT WAVE TROUGH
WILL CONTINUE TO TRANSLATE EWD/NEWD ATOP THE LOWER LEVEL FRONTAL
ZONE THIS AFTERNOON...AND A GRADUAL NEWD SHIFT IN THE HEAVIER
PRECIPITATION AREA HAS RECENTLY BEEN NOTED ON COMPOSITE RADAR.

MEANWHILE...A NEARLY STEADY-STATE WARM/MOIST CONVEYOR BELT HAS NOW
BECOME ESTABLISHED FROM TX/RIO GRANDE VALLEY NEWD ATOP THE
SURFACE-BASED COLD DOME. DEEP LAYER MOISTURE ACROSS THE REGION WAS
ALSO BEING PROVIDED BY A TROPICAL CONNECTION EVIDENT IN SATELLITE
IMAGERY. WITH THE FRONTAL ZONE NOW BECOMING INCREASINGLY ALIGNED
WITH THE DEEP-LAYER SWLY FLOW ALOFT...AND LOW-AMPLITUDE
PERTURBATIONS CONTINUING TO TRANSLATE NEWD ACROSS THE
REGION...EXPECT MIXED WINTER PRECIPITATION TO CONTINUE TO DEVELOP
AND SPREAD NEWD FROM THE RED RIVER TO CNTRL AND NERN OK THROUGH THE
REST OF THE AFTERNOON.

HIGHER PRECIPITATION RATES MAY OCCASIONALLY OCCUR ON THE MESOSCALE
AS ENHANCED ASCENT WITH THE UPPER PERTURBATIONS COINCIDE WITH LIFT
ACROSS THE LOW LEVEL FRONT. THIS APPEARS TO BE OCCURRING FROM NWRN
TX INTO SWRN OK AT THIS TIME. A GRADUAL SWD/SEWD SHIFT TO THE
SURFACE FREEZING LINE...AND CONTINUED STRONG INFLUX OF LOW LEVEL
MOISTURE...WILL RESULT IN RAIN CHANGING TO FREEZING RAIN FROM NWRN
TX INTO SCNTRL AND ERN OK THROUGH LATE THIS AFTERNOON.

..CARBIN.. 01/12/2007

...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...TSA...FWD...OUN...LUB...

35549864 36289790 36669710 36719590 36539537 36259485
35919478 35309521 34899559 34439606 34149662 33659735
33569834 33579930 33679987 34140011 34979929