Thursday, February 21, 2008

MESO: Mesoscale Discussion 0276

ACUS11 KWNS 211216
SWOMCD
SPC MCD 211215
KYZ000-TNZ000-INZ000-ILZ000-MOZ000-ARZ000-OKZ000-KSZ000-211815-

MESOSCALE DISCUSSION 0276
NWS STORM PREDICTION CENTER NORMAN OK
0615 AM CST THU FEB 21 2008

AREAS AFFECTED...CENTRAL/NERN OK...SERN KS...SRN MO/NRN AR...SRN
IL/SRN IN...MUCH OF KY AND NWRN TN

CONCERNING...WINTER MIXED PRECIPITATION

VALID 211215Z - 211815Z

FREEZING RAIN AND SLEET WILL DEVELOP EWD FROM NERN OK/SERN KS INTO
THE LOWER OHIO VALLEY THROUGH 18Z. HRLY ACCUMULATION RATES UP TO
0.25 WILL BE POSSIBLE WITHIN CONVECTIVE SHOWERS...WITH AVERAGE HRLY
RATES LESS THAN 0.05 INCHES.

A LARGE AREA OF PRECIPITATION HAS DEVELOPED FROM CENTRAL/NRN
OK...SERN KS EWD INTO THE MID MS VALLEY IN RESPONSE TO MODERATE WAA
AHEAD OF A SHORTWAVE TROUGH MOVING THROUGH THE SRN PLAINS. A SHALLOW
SUB-FREEZING AIRMASS BENEATH A LARGE ELEVATED WARM LAYER WILL
CONTINUE TO SUPPORT FREEZING RAIN AND SLEET ACROSS THE AREA THROUGH
THE PERIOD...WITH SLEET THE PRIMARY P-TYPE DEVELOPING OVER CENTRAL
KY/SRN IND AND FREEZING RAIN THE MOST COMMON P-TYPE ELSEWHERE. STEEP
MID LEVEL LAPSE RATES ABOVE THE ELEVATED WARM LAYER WERE SUPPORTING
ELEVATED INSTABILITY /PER THE 12Z SGF SOUNDING/ AND A CONVECTIVE
NATURE OF THE PRECIPITATION OVER MUCH OF MO/SERN KS AND NRN/ERN OK.
THE CONVECTIVE NATURE WILL CONTINUE TO SUPPORT HRLY RATES UP TO
0.25 INCHES...LEADING TO ISOLATED AREAS OF SIGNIFICANT ICING THROUGH
18Z. THE GREATEST PROBABILITY FOR THE ISOLATED AREAS OF SIGNIFICANT
ICING WILL BE FROM SERN KS/FAR NERN OK ACROSS SRN MO/FAR NRN AR AND
INTO SWRN KY THROUGH 18Z AHEAD OF A LARGE SWATH OF ELEVATED
CONVECTION. THE BACK EDGE OF THE CONVECTIVE FREEZING RAIN POTENTIAL
WILL SLOWLY MOVE EWD ACROSS CENTRAL/ERN OK AND SERN KS THROUGH THE
MORNING HOURS ASSOCIATED WITH VEERING FLOW IN THE 1-2 KM LAYER
/NOTED RECENTLY BY THE VCI PROFILER AND FDR VWP/ AIDING IN
DRYING/SUBSIDENCE IN THIS LAYER. HOWEVER...FREEZING DRIZZLE OR LIGHT
FREEZING RAIN WILL STILL BE POSSIBLE OVER THESE AREAS.

.CROSBIE.. 02/21/2008

..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...MRX...JKL...ILN...LMK...OHX...IND...PAH...ILX...MEG...LSX...LZK...SGF...EAX...TSA...TOP...ICT...OUN...

38279584 37279771 36419767 35239745 34999693 35709370
35839142 36018975 36258768 36578474 38098361 38678495
38628689 38279202

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