Wednesday, December 23, 2009

MESO: Mesoscale Discussion 2270

ACUS11 KWNS 231821
SWOMCD
SPC MCD 231821
ILZ000-WIZ000-IAZ000-NEZ000-SDZ000-232215-

MESOSCALE DISCUSSION 2270
NWS STORM PREDICTION CENTER NORMAN OK
1221 PM CST WED DEC 23 2009

AREAS AFFECTED...ERN NEB...S/CNTRL IA...NRN IL...FAR SRN WI/MN

CONCERNING...FREEZING RAIN

VALID 231821Z - 232215Z

FREEZING RAIN WITH RATES NEAR 0.05 INCH AN HOUR WILL CONTINUE TO
SLOWLY SHIFT NWD WITH TIME...INITIALLY AFFECTING AREAS NEAR CHICAGO
WWD THROUGH DAVENPORT AND INTO OMAHA.

WV IMAGERY REFLECTS A SHORT WAVE TROUGH ROTATING THROUGH CNTRL KS
AHEAD OF A LARGER TROUGH NOW MOVING EWD THROUGH E CNTRL NM...LEADING
TO FAVORABLE VERTICAL MOTION SUPPORTING AN ONGOING BAND OF FREEZING
RAIN ACROSS PORTIONS OF IL/IA/NEB. SURFACE PRESSURE FALLS NEAR 1
MB/2 HR ARE OCCURRING AHEAD OF THIS UPPER DISTURBANCE...MAINLY
ACROSS CNTRL IA/NRN MO...INDICATING THE SURFACE LOW ANALYZED NEAR
SERN KS IS BEGINNING TO DEVELOP NWD/NEWD WITH TIME. 17Z ANALYSIS
REFLECTS THAT THE FREEZING LINE HAS BEGUN TO SHIFT NWD AS THIS
OCCURS...AND AS STRONG WARM ADVECTION SLOWLY WARMS TEMPERATURES BY A
FEW DEGREES. VAD WIND PROFILE DATA FROM CHICAGO WWD INTO DAVENPORT
AND OMAHA SHOW STRONG WARM ADVECTION/VEERING WINDS IN THE LOWEST
2000 FT. THIS WARM LAYER/ADVECTION JUST ABOVE THE SURFACE WILL
CONTINUE TO SUPPORT FREEZING RAIN WHERE SURFACE TEMPERATURES ARE
NEAR OR BELOW FREEZING...AS GROUND TEMPERATURES REMAIN COLD. 0.75
INCH PWAT OBSERVED ON GOES SATELLITE PWAT IMAGERY REFLECTS AMPLE
MOISTURE TO ASSIST IN ACCUMULATION RATES OF NEAR 0.05 INCH AN HOUR
OR GREATER.

..HURLBUT.. 12/23/2009

...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...LOT...MKX...DVN...ARX...DMX...FSD...OAX...GID...

LAT...LON 41129664 41149720 41609760 42399732 42659678 42769577
42699303 42668903 42428805 41958770 41658903 41698998
41809334 41529575 41129664

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