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| Mesoscale Discussion 321 |
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MESOSCALE DISCUSSION 0321
NWS STORM PREDICTION CENTER NORMAN OK
0912 AM CDT SUN MAR 24 2013
AREAS AFFECTED...CNTRL IL
CONCERNING...HEAVY SNOW
VALID 241412Z - 241715Z
SUMMARY...SNOW WITH RATES OF 1-2 IN/HR WILL OVERSPREAD CNTRL IL
THROUGH LATE MORNING...WITH SIMILAR SNOW RATES FORECAST TO PERSIST
INTO THE AFTERNOON.
DISCUSSION...SHORT-RANGE DETERMINISTIC GUIDANCE...INCLUDING
HIGH-RESOLUTION WRF ENSEMBLE OUTPUT...APPEAR TOO AGGRESSIVE WITH
DAMPENING THE HEAVY SNOW POTENTIAL ACCOMPANYING THE BAND OF
ISENTROPIC ASCENT ATTENDANT TO THE WARM CONVEYOR BELT CURRENTLY
CROSSING THE MS RIVER. SFC OBSERVATIONS AND RADAR DATA INDICATE
HEAVY SNOW ALREADY APPROACHING THE MS RIVER AS OF AROUND 14Z WITH
THE N/S-ORIENTED WARM-CONVEYOR-RELATED PRECIPITATION BAND...WITH
OCCASIONAL INSTANCES OF SLEET.
WITH THE DOWNSTREAM ILX 12Z RAOB INDICATING AN ANTECEDENT DEEP AND
NEARLY SATURATED PROFILE BELOW THE 600-MB LEVEL...IT WILL TAKE VERY
LITTLE ADDITIONAL ASCENT/MOISTENING FOR THE PRECIPITATION TO BE
MAINTAINED INTO CNTRL IL. ACCORDINGLY...HEAVY SNOW WILL BECOME
INCREASINGLY LIKELY IN CNTRL IL BETWEEN 1430Z AND 1530Z. TRENDS IN
WATER VAPOR IMAGERY REGARDING THE TRACK OF THE ATTENDANT MID-LEVEL
CYCLONE SUGGEST THAT SIMILAR PRECIPITATION RATES WILL BE MAINTAINED
INTO THE AFTERNOON...AS THE DRY SLOT REMAINS TO THE S...AND HEAVY
SNOW WITHIN THE DEFORMATION ZONE/COLD CONVEYOR BELT EVENTUALLY
OVERSPREADS THE AREA LATER IN THE DAY. AN ISOLATED LIGHTNING STRIKE
OR TWO WILL BE POSSIBLE WITH THE MOST INTENSE SNOWFALL RATES OWING
TO WEAK ELEVATED BUOYANCY.
..COHEN.. 03/24/2013
ATTN...WFO...ILX...LSX...DVN...
LAT...LON 39508829 38958849 38888931 39849070 40399042 40538931
40188857 39508829
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