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Mesoscale Discussion
2570

MESOSCALE DISCUSSION 2570
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CST THU DEC 23 2004

AREAS AFFECTED...MUCH OF KY/IND...MIDDLE TN....SERN MI...OH AND FAR
NWRN PA/SWRN NY

CONCERNING...PRECIPITATION TRENDS...WINTER PRECIPITATION

VALID 230657Z - 231200Z

SIGNIFICANT WINTER STORM WILL CONTINUE TO DEVELOP NEWD FROM THE OHIO
VALLEY INTO THE ERN GREAT LAKES REGION THROUGH 12Z. MOD-HVY SNOW
WITH HRLY RATES AT TIMES ABOVE 1 INCH WILL OCCUR OVER MUCH OF
IND/WRN OH AND SERN LOWER MI...WITH A NARROWING TRANSITION ZONE OF
SLEET FROM CENTRAL KY NWD INTO NCENTRAL OH...AND A ZONE OF FREEZING
RAIN FROM PORTIONS OF MIDDLE TN NEWD INTO SWRN NY/NWRN PA. GIVEN THE
RAPID PROGRESSIVE NATURE OF THIS SYSTEM HVY SNOW WILL DIMINISH OVER
MOST OF IND BY 10Z AND SERN OH BY 12Z. MODERATE FREEZING RAIN OVER
MIDDLE TN/CENTRAL KY WILL TRANSITION TO LIGHT SNOW AND BEFORE ENDING
BY 12Z.

MID LEVEL FRONTOGENESIS IN THE 650-550 MB LAYER AIDED BY STRONG
LOW-MID LEVEL WAA PROFILE BENEATH AN AMPLIFYING NEGATIVELY TILTED
UPPER TROUGH WILL CONTINUE TO FOCUS BANDS OF HVY SNOW OVER
CENTRAL/SRN IND...WCENTRAL OH THROUGH 10Z...WHILE DEVELOPING NEWD
INTO FAR SERN MI AND NWRN OH. AS A STRONG MID LEVEL DRY SLOT CLEARLY
EVIDENT ON IR/WV SAT IMAGERY MOVES IN BEHIND UPPER TROUGH ...EXPECT
A RAPID DEMISE OF MOD-HVY SNOW FROM SW-NE THROUGH 12Z.

SOUTH OF THIS AREA OF MOD-HVY SNOW...A MIX OF SLEET AND FREEZING
RAIN WILL CONTINUE ALONG A 40-60 MILE WIDE CORRIDOR FROM MIDDLE TN
NEWD INTO FAR SWRN NY/NWRN PA THROUGH 09Z. RECENT 06Z SOUNDING FROM
BNA INDICATES A SUBSTANTIAL ELEVATED WARM LAYER ABOVE THE SHALLOW
SUBFREEZING LAYER IN THE POST SFC COLD FRONTAL ENVIRONMENT. AXIS OF
THIS MIX PRECIP ZONE WILL BECOME MORE NORTH-SOUTH ORIENTED THROUGH
12Z...AS UPPER TROUGH CONTINUES TO EJECT NEGATIVELY TILTED AND
STRENGTHENS LOW LEVEL CAA/FRONTAL INVERSION AND THE SFC LOW LIFTS
NWD TOWARDS CNTRL LAKE ERIE. IN ADDITION THE ELEVATED FREEZING LAYER
AND MIX PTYPE ZONE NORTH OF SFC COLD/STATIONARY FRONT WILL NARROW
THROUGH 12Z. AS A RESULT OF THE RAPID MOTION OF THE UPPER
TROUGH...AND LOW LEVEL CAA..FREEZING RAIN SHOULD CHANGE OVER TO
SLEET AND EVENTUALLY LIGHT TO MOD SNOW FROM MIDDLE TN NWD ACROSS
NCENTRAL KY. FURTHER NEWD...MOVEMENT OF SFC LOW FROM SCENTRAL KY
INTO NWRN PA...EVIDENT BY AXIS OF STRONGEST PRESSURE FALLS AT
06Z...WILL RESULT IN PORTIONS OF NCENTRAL/NERN OH SEEING A CHANGE
FROM LIGHT-MOD SNOW TO FREEZING RAIN/SLEET. NERN/ECENTRAL OH...FAR
NWRN PA AND SWRN NY SHOULD SEE A GRADUAL WWD MVMNT OF THE SFC
FREEZING LINE/WARM FRONT AND A TRANSITION FROM FREEZING RAIN TO RAIN
THROUGH 12Z

..CROSBIE.. 12/23/2004

...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
SCHEDULED BASIS...FOUR TIMES A DAY...BETWEEN 00-01 UTC...
06-07 UTC...12-13 UTC...AND 18-19 UTC AS SIGNIFICANT SHORT
RANGE WINTER WEATHER EVENTS UNFOLD. THIS SCHEDULE WILL BE
USED FROM DECEMBER 1 THROUGH FEBRUARY 28.

ATTN...WFO...BUF...CTP...PBZ...RLX...CLE...MRX...JKL...ILN...DTX...LMK...IWX...OHX...IND...PAH...ILX...

43327796 42007955 40488092 38658304 36438446 36208528
36148613 36488724 37708805 38758797 40568580 42128400
43098239

41508297 39158517 36988739 36408702 36158587 36258509
41838182

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