MESO: Mesoscale Discussion 0326

ACUS11 KWNS 241938
SWOMCD
SPC MCD 241937
INZ000-242330-

MESOSCALE DISCUSSION 0326
NWS STORM PREDICTION CENTER NORMAN OK
0237 PM CDT SUN MAR 24 2013

AREAS AFFECTED...CNTRL INDIANA

CONCERNING...HEAVY SNOW

VALID 241937Z - 242330Z

SUMMARY...HEAVY SNOW WILL OVERSPREAD CNTRL INDIANA DURING THE
MID/LATE AFTERNOON HOURS -- PRIMARILY AFTER 2030Z -- WITH RATES OF 1
TO LOCALLY 2 IN/HR LIKELY.

DISCUSSION...BANDS OF HEAVY SNOW WILL DEVELOP EWD/ENEWD FROM CNTRL
IL AND OVERSPREAD CNTRL INDIANA AFTER 2030Z. THIS SNOW IS IN
ASSOCIATION WITH STRONG DEEP ASCENT TO THE N OF A MID-LEVEL JET
MAX/DRY SLOT THAT IS SURGING EWD THROUGH THE LOWER OH VALLEY AND MID
SOUTH. N OF THIS FEATURE...ASCENT ACCOMPANYING MODEST FRONTOGENETIC
CIRCULATIONS WILL AUGMENT STRONG DCVA AT THE ENTRANCE REGION OF THE
JET MAX TO MAINTAIN EFFICIENT PRECIP GENERATION. THIS WILL
ESPECIALLY BE THE CASE AS GPS DATA INDICATE 0.5-0.7-INCH PW VALUES
EXTENDING INTO THE REGION WITHIN A WARM CONVEYOR BELT THAT LEADS THE
JET MAX/DRY SLOT. WHILE LOW-LEVEL THERMAL PROFILES ARE INITIALLY
WARM FOR SNOW...ESPECIALLY ALONG AND SOUTH OF THE INTERSTATE 70
CORRIDOR...ADIABATIC COOLING ASSOCIATED WITH THE FORCED ASCENT
COMBINED WITH LOW-LEVEL EVAPORATIVE COOLING WILL ALLOW WET-BULB ZERO
HEIGHTS TO QUICKLY DESCEND SUFFICIENTLY TO SUPPORT HEAVY SNOW
SUCCEEDING THE ONSET OF PRECIP.

FORECAST SOUNDINGS SUGGEST THAT THE STRONG ASCENT WILL BE
SUPERIMPOSED WITH SATURATED DENDRITIC GROWTH ZONES WITHIN THE
600-500-MB LAYER TO SUPPORT EFFICIENT SNOW GROWTH. SNOW RATES OF 1
TO LOCALLY 2 IN/HR WILL BE LIKELY...AND AN ISOLATED LIGHTNING STRIKE
OR TWO CANNOT BE RULED OUT IN ASSOCIATION WITH THE
HIGHEST...CONVECTIVELY ENHANCED SNOW RATES. SUCH RATES ARE ALSO
SUPPORTED BY THE MULTI-MODEL CONSENSUS AMONGST THE LATEST
HIGH-RESOLUTION WRF GUIDANCE. THE HEAVY SNOW...WITH SIMILAR
RATES...WILL LIKELY CONTINUE INTO THE EVENING HOURS AS ASCENT
ACCOMPANYING THE DEFORMATION ZONE N/NW OF THE MID-LEVEL CYCLONE
TRACKS ACROSS THE REGION.

..COHEN.. 03/24/2013

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

ATTN...WFO...ILN...IWX...IND...LOT...

LAT...LON 39268595 39198689 39438746 39788711 40148700 40488718
40878685 40838616 40568531 40198511 39658526 39268595

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