MESO: Mesoscale Discussion 0039

ACUS11 KWNS 140538
SWOMCD
SPC MCD 140538
INZ000-ILZ000-WIZ000-IAZ000-MOZ000-140945-

MESOSCALE DISCUSSION 0039
NWS STORM PREDICTION CENTER NORMAN OK
1138 PM CST TUE JAN 13 2009

AREAS AFFECTED...ERN IA...SWRN WI...NRN IL...NWRN INDIANA

CONCERNING...HEAVY SNOW

VALID 140538Z - 140945Z

A SWATH OF MODERATE TO HEAVY SNOWFALL WILL CONTINUE TO MOVE ESEWD
BEFORE WEAKENING OVER NWRN/CNTRL INDIANA NEAR 12Z. INCH AN HOUR
RATES WILL BE LIKELY MAINLY ACROSS ERN IA AND NWRN/CNTRL IL.

A VORT MAX ROTATING AROUND THE BACKSIDE OF A LARGER SCALE TROUGH IS
NOW PRESSING ESEWD INTO SWRN WI/IL. MODERATE TO HEAVY SNOWFALL HAS
BEEN OBSERVED OVER ERN IA...AND THE HEAVIEST SNOW BAND IS NOW
ORIENTED N-S NEAR THE IA/IL BORDER AND MOVING EWD. DESPITE VERY LOW
PWAT AND AVAILABLE MOISTURE...ISENTROPIC LIFT IN COMBINATION WITH
SUPPORT FROM THE VORT MAX IS CONTRIBUTING TO VERTICAL MOTION AND
AFOREMENTIONED SNOWFALL RATES. 05Z SURFACE ANALYSIS REFLECTS A WEAK
WARM FRONT EXTENDING EWD FROM A SURFACE LOW IN WRN IA...RUNNING
ALONG THE IA/MO BORDERS AND INTO CNTRL IL. VAD WIND PROFILE DATA
SUGGESTS THE STRONGEST LOW LEVEL WARM ADVECTION IS JUST N OF THIS
FRONT IN A SMALL AREA FROM ERN IA INTO CNTRL/NWRN IL. EXPECT THE
HIGHEST ACCUMULATIONS TO BE IN THESE AREAS OVER THE NEXT FEW HOURS.
RATES WILL GRADUALLY DECREASE AS THE LOW AND ASSOCIATED ISENTROPIC
LIFT BEGIN TO WEAKEN.

..HURLBUT.. 01/14/2009

...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...IWX...IND...LOT...ILX...MKX...LSX...DVN...ARX...
DMX...

LAT...LON 40198575 39528924 40519195 42009349 42919341 43479215
43139007 42418805 41608690 40938580 40198575

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