MESOSCALE DISCUSSION 0178
NWS STORM PREDICTION CENTER NORMAN OK
1240 PM CST SUN FEB 20 2005
AREAS AFFECTED...CNTRL/SRN LOWER MI INTO EXTREME NW OH
CONCERNING...PRECIPITATION TRENDS...WINTER PRECIPITATION
VALID 201840Z - 202245Z
SNOW EXPECTED TO INCREASE ACROSS PORTIONS OF CNTRL/SRN LOWER MI THIS
AFTERNOON...ESPECIALLY ALONG/NORTH OF INTERSTATE 69/96
CORRIDORS...WHERE SNOW RATES MAY REACH 1-1.5 IN/HR BETWEEN 21Z-03Z.
SLEET/FZRA EXPECTED TO BECOME MORE LIKELY THIS AFTERNOON ACROSS SRN
LOWER MI INVOF I-94.
WARM CONVEYOR/MOISTURE TRANSPORT REGIME CONTINUES TO OVERSPREAD
LOWER MI AHEAD OF SHORTWAVE TROUGH EVIDENT IN WATER VAPOR IMAGERY
OVER IA. LIGHT/MDT SNOW ALREADY OCCURRING ACROSS CNTRL/SRN LOWER
MI...AND INTENSITY EXPECTED TO INCREASE THIS AFTERNOON OWING TO
INFLUENCE OF UPPER JET DIV/MID LEVEL FRONTOGENETICAL FORCING.
IN ADDITION TO INCREASING SYNOPTIC SCALE UVVS...STEEP MID LEVEL
LAPSE RATES OBSERVED IN 12Z DVN/ILX RAOBS WILL CONTINUE TO ADVECT
DOWNSTREAM TOWARD LOWER MI. INCREASING POTENTIAL INSTABILITY THIS
AFTERNOON -- FURTHER CONFIRMED BY RECENT CG LIGHTNING OVER NRN IN/SW
LOWER MI -- COINCIDENT WITH STRONG 600 MB-750 MB FRONTOGENESIS
SUGGESTS MARKED POTENTIAL FOR W/NW-E/SE BANDING AND ENHANCED SNOW
RATES ON THE MESOSCALE.
ACROSS SRN LOWER MI INVOF I-94/SRN IRISH HILLS...FZRA AND/OR SLEET
EXPECTED TO BECOME INCREASINGLY LIKELY AFTER 21Z. 12Z NAM/15Z RUC
SOUNDINGS AND PRECIP TYPE ALGORITHMS SUGGEST FZRA/SLEET CORRIDOR
WILL MATERIALIZE AS ENCROACHING 850-700 MB WARM LAYER OVERSPREADS
SHALLOW SUB-FREEZING LAYER.
..GUYER.. 02/20/2005
...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...CLE...DTX...APX...IWX...GRR...
43968499 43938376 43808276 43078244 42078276 41728298
41568337 41598393 41858508 42278584 42478604 42998610
43638599 43838556
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