[MCD] SWOMCD

Sat Jan 21 05:53:28 UTC 2006

ACUS11 KWNS 210553
SWOMCD
SPC MCD 210552 
MIZ000-INZ000-ILZ000-WIZ000-211145-

MESOSCALE DISCUSSION 0076
NWS STORM PREDICTION CENTER NORMAN OK
1152 PM CST FRI JAN 20 2006

AREAS AFFECTED...LOWER MI

CONCERNING...HEAVY SNOW 

VALID 210552Z - 211145Z

BAND OF HEAVY SNOW WITH HOURLY RATES APPROACHING 1-2 INCHES IS
EXPECTED TO DEVELOP NEWD ACROSS CNTRL AND SRN PORTIONS OF LOWER MI
OVERNIGHT. A NARROW ZONE OF FREEZING RAIN CURRENTLY OBSERVED FROM
FNT TO AZO MAY PERSIST FOR THE NEXT COUPLE OF HOURS ALONG THE I-94
CORRIDOR...BUT SHOULD GRADUALLY CHANGEOVER TO SNOW FROM W TO E WITH
TIME.

CURRENT WATER VAPOR LOOP SHOWS MID AND UPPER-LEVEL SHORTWAVE TROUGH
DE-AMPLIFYING AS IT ACCELERATES NEWD ACROSS THE UPPER MIDWEST
TONIGHT WITH ASSOCIATED SURFACE LOW OVER NERN IND AS OF 05Z. 
ATTENDANT WARM FRONT EXTENDED ENEWD FROM THIS LOW ACROSS ERN LOWER
MI INTO SWRN ONTARIO WHILE TRAILING COLD FRONT STRETCHED SWWD INTO
E-CNTRL IL.  AS MENTIONED ABOVE...RADAR AND SURFACE OBSERVATIONAL
DATA SHOW MAIN BAND OF HEAVY SNOW FROM W-CNTRL LOWER MI SWWD TO THE
CHICAGO METRO AREA WHERE HOURLY SNOW RATES OF 2 INCHES HAVE BEEN
REPORTED WITHIN THE PAST COUPLE OF HOURS.

LATEST SHORT-TERM MODEL GUIDANCE SUGGESTS THAT AGEOSTROPHIC RESPONSE
TO STRONG FRONTOGENETICAL FORCING IN THE 850-700 MB LAYER WITHIN
SYNOPTIC SYSTEM DEFORMATION ZONE IS LIKELY CONTRIBUTING TO THIS BAND
OF HEAVY SNOW. CORRESPONDING FORECAST SOUNDINGS INDICATE
DEEP...SATURATED THERMODYNAMIC PROFILES...SUPPORTIVE OF DENDRITE
GROWTH VIA AGGREGATION.  MOREOVER...CONVECTIVE CHARACTER ALONG SRN
EDGE OF PRIMARY PRECIPITATION SHIELD INDICATES THE LIKELIHOOD OF
MARGINAL CONVECTIVE INSTABILITY WHICH WILL EFFECTIVELY ENHANCE
PRECIPITATION RATES.

THROUGH 21/12Z...IT APPEARS THAT THE HEAVIEST SNOW WILL FALL FROM
MKG AND BEH NEWD THROUGH LAN TO NEAR OR S OF BAX. HOURLY RATES WILL
LIKELY PEAK AT 1-1.5 INCHES THOUGH SOME LOCAL RATES MAY EXCEED 2
INCHES IN ASSOCIATION WITH ANY EMBEDDED CONVECTIVE ELEMENTS.

..MEAD.. 01/21/2006

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

ATTN...WFO...DTX...APX...IWX...GRR...LOT...MKX...

42048483 41488742 42578806 44018673 44918372 44888216
43778180 42258380 

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