[MCD] SWOMCD

Wed Dec 14 12:44:37 UTC 2005

ACUS11 KWNS 141241
SWOMCD
SPC MCD 141241 
INZ000-KYZ000-MIZ000-ILZ000-WIZ000-141645-

MESOSCALE DISCUSSION 2555
NWS STORM PREDICTION CENTER NORMAN OK
0641 AM CST WED DEC 14 2005

AREAS AFFECTED...PORTIONS ERN/NRN IL...SERN WI...SRN LM...SWRN LOWER
MI...MOST OF INDIANA...SMALL PORTION N-CENTRAL KY.

CONCERNING...HEAVY SNOW 

VALID 141241Z - 141645Z

WITHIN BROAD NNW-SSE PLUME OF LIGHT-MDT SNOW...POCKETS OF HEAVIER
RATES OF 1-1.5 INCHES/HOUR ARE EXPECTED THROUGH MID-LATE
MORNING...AS BAND SHIFTS EWD ACROSS DISCUSSION AREA.  SNOW SHOULD
TRANSITION QUICKLY TO RAIN AT...OR SHORTLY AFTER...PASSAGE OF SFC
FREEZING LINE...ALSO FROM SW-NE.

MOISTURE CHANNEL IMAGERY AND VWP/PROFILER DATA AT 12Z INDICATED
SHORTWAVE TROUGH FROM MSP AREA SEWD ACROSS SWRN IL.  EXPECT THIS
FEATURE TO DEAMPLIFY GRADUALLY AND EJECT ENEWD ACROSS WI/IL THROUGH
REMAINDER MORNING...SUPPORTING PRECURSORY CORRIDOR OF MIDLEVEL DPVA
AND STRONG/ELEVATED WAA PLUME IN LOW LEVELS.  RELATED ASCENT OF
DEEPLY SATURATED AND SUBFREEZING AIR MASS...WITH PW AROUND .5-.75
INCH BASED ON 12Z RAOBS AND INTERMEDIARY RUC SOUNDINGS...SHOULD
SUPPORT EWD EXTENSION OF INTERMITTENT HEAVY SNOW NOW OBSERVED IN
THIS REGIME.  STRONGER DYNAMIC FORCING FARTHER N ACROSS NRN WI AND
NWRN LOWER MI SHOULD BE OFFSET BY WEAKER MOISTURE TO LIMIT HEAVY
SNOW THREAT...WHILE WARMING WITH TIME WILL RESTRICT SNOW POTENTIAL
FARTHER S IN KY.

OBSERVATIONAL DATA INDICATES QUICK TRANSITION FROM SNOW TO RAIN W OF
SFC FREEZING LINE...A TREND EXPECTED TO CONTINUE THROUGH REMAINDER
MORNING.  HOWEVER...TIME SERIES OF RUC FCST SOUNDINGS SUGGESTS VERY
BRIEF/LOCALIZED EPISODE OF FREEZING RAIN IS POSSIBLE INVOF 32 F
ISOTHERM...AS WARMING ALOFT IN DENDRITIC CRYSTAL GROWTH LAYERS KEEPS
PRECIP PARTICLES SUPERCOOLED.  ANY FREEZING RAIN SHOULD BE
SHORT-LIVED WITH RATES GENERALLY AROUND .10 INCH/HOUR OR LESS...AND
REPLACED BY RAIN AT ANY GIVEN LOCATION WITHIN AN HOUR OR LESS.

..EDWARDS.. 12/14/2005

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

ATTN...WFO...ILN...LMK...IWX...GRR...IND...PAH...LOT...ILX...MKX...

38568734 39648867 41598911 42968777 42908661 41998603
39028519 37838594 

WWWW