[MCD] SWOMCD

[Mesoscale Convective Discussions]

ACUS11 KWNS 202139
SWOMCD
SPC MCD 202139 
MIZ000-INZ000-WIZ000-ILZ000-IAZ000-210345-

MESOSCALE DISCUSSION 0074
NWS STORM PREDICTION CENTER NORMAN OK
0339 PM CST FRI JAN 20 2006

AREAS AFFECTED...NRN/ERN IA...SRN/ERN WI...NRN IL...FAR NWRN
IND...SWRN/CENTRAL AND NRN LOWER MI

CONCERNING...PRECIPITATION TRENDS...WINTER PRECIPITATION 

VALID 202139Z - 210345Z

HEAVY SNOW BANDS WITH HRLY RATES UP TO 1 INCH WILL CONTINUE TO
DEVELOP ENEWD FROM NRN/CENTRAL IA INTO SRN WI AND EVENTUALLY
WCENTRAL/NRN LOWER MI BY 03Z. SECONDARY AREA OF HEAVY SNOW WILL
CONTINUE TO DEVELOP OVER NRN IL THROUGH 00Z...WHILE MOVING INTO SWRN
AND CENTRAL LOWER MI FROM 01Z-03Z. HRLY SNOWFALL RATES AT TIMES WILL
EXCEED 1 INCH WITH ISOLATED 2 INCH/HR RATES POSSIBLE OVER THE CHI
METRO AREA NEWD INTO SWRN LOWER MI. A MIX OF SLEET WILL BE POSSIBLE
AS WELL...MAINLY AT THE ONSET OF THE PRECIP AND OVER PORTIONS OF NRN
IL/NWRN IND INTO SWRN LOWER MI.

IR IMAGERY SHOWS A WELL DEFINED MID LVL DRY SLOT THAT CONTINUES TO
WORK SLOWLY ENEWD ACROSS NRN MO AND FAR SRN IA. NORTH OF THIS DRY
SLOT...STRONG MID LEVEL FRONTOGENETIC FORCING IN A VERY FAVORABLE
THERMODYNAMIC PROFILE WAS AIDING IN BANDS OF HEAVY SNOW FROM CENTRAL
INTO NERN IA. THIS FORCING FOR HEAVY SNOW BANDS IS FORECAST TO
CONTINUE LIFTING ENEWD WITH THE UPPER SYSTEM...AND MOVE INTO SRN/ERN
WI THROUGH 00Z...AND EVENTUALLY INTO WCENTRAL AND PORTIONS OF NRN
LOWER MI BETWEEN 00Z-03Z. SOUTH OF THIS ZONE...STRONG WAA EVIDENT BY
REGIONAL VWP DATA...CONVECTIVE INSTABILITY EVIDENT BY LIGHTNING
STRIKES/VISIBLE SAT IMAGERY AND SFC PRESSURE FALLS SUGGESTS THAT
MODERATE-HVY SNOW WILL LIKELY DEVELOP....ONCE SUFFICIENT MID LEVEL
SATURATION OCCURS IN THE NEXT 1-3 HOURS OVER SCENTRAL/SERN WI AND
NRN IL. FORECAST SOUNDINGS OVER NRN IL SUGGEST SUFFICIENTLY DEEP
ELEVATED WARM LAYER CENTERED AROUND 800 MB THAT PRECIP SHOULD START
AS SLEET AND MAY AGAIN CHANGE OVER TO SLEET BRIEFLY DURING THE
HEAVIEST PRECIP FROM 00-03Z. GIVEN THE DEGREE OF LOW-MID LEVEL
FORCING AND CONVECTIVE INSTABILITY SNOWFALL RATES MAY REACH 1-2
INCHES/HR FOR BRIEF PERIODS ACROSS NRN IL/SERN WI FROM 23-02Z.
STRONGEST VERTICAL MOTION AND CONSEQUENT HEAVY SNOW POTENTIAL WILL
BEGIN TO MOVE INTO SWRN/CENTRAL MI FROM 01-03Z. IN ADDITION LOW
LEVEL COLD ADVECTION SHOULD BEGIN TO INCREASE OVER NRN IL AND SWRN
LOWER MI/NWRN IND AS THE SURFACE LOW PRESSURE CENTER APPROACHES SRN
IL. THIS SHOULD AID IN A SWD MOVEMENT OF THE SURFACE FRONT AND
SUB-FREEZING TEMPERATURES INTO THE EVENING HOURS. BEST ESTIMATE ON
THREAT FOR WINTER PRECIP SHOULD BE ALONG AND NORTH OF I-80/I-90 IN
NRN IL AND NORTH OF I-94 IN SWRN LOWER MI.

..CROSBIE.. 01/20/2006

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

ATTN...WFO...DTX...APX...IWX...GRR...GRB...LOT...ILX...MKX...DVN...ARX...DMX...

44488645 44208861 43549063 42779244 42149318 41469265
41139154 41139032 41168963 41288840 41398715 41738631
42028580 42728414 43658395 44498405 44668514 

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