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Mesoscale Discussion 173

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SPC MESOSCALE DISCUSSION 0173 FOR CNTRL LOWER MI
CONCERNING...FREEZING RAIN AND SLEET...

VALID 241643Z - 242300Z

FREEZING RAIN...SLEET...AND SNOW...CHANGING TO PRIMARIARLY FREEZING
RAIN IS EXPECTED ACROSS MUCH OF CNTRL LOWER MI WITH ICE
ACCUMULATIONS OF 0.1 IN/HR POSSIBLE THROUGH 24/21Z.

RADAR AND SATELLITE TRENDS INDICATE AXIS OF DEEP LAYER MOISTURE AND
PRECIPITATION ADVANCING NEWD INTO NRN IN AT 24/16Z.  THIS ACTIVITY
IS ASSOCIATED WITH INCREASING WARM ADVECTION AS PER KIWX VAD AND
UPPER LEVEL DIVERGENCE ASSOCIATED WITH ENTRANCE REGION OF UPPER JET
ACROSS SRN CANADA.  AS SECONDARY JET MAX AND SHORT WAVE TROUGH
APPROACH AREA FROM THE WEST...RAPID DEEPING OF 850 MB LOW IS
FORECAST OVER NE/IA BORDER WITH STRONG 850 MB FRONTOGENESIS
EXPECTED TO DEVELOP ACROSS CNTRL LOWER MI BY 24/21Z RESULTING IN
INCREASING DEEP LAYER VERTICAL MOTION.  50-60 KT LLJ IS EXPECTED TO
TRANSPORT CONSIDERABLE MOISTURE INTO REGION OF STRONG LIFT OVER
NEXT FEW HOURS RESULTING IN AN INCREASE IN COVERAGE AND INTENSITY
OF PRECIPITATION.  GIVEN THE MAGNITUDE OF WARM ADVECTION... SNOW...
SLEET AND FREEZING RAIN OVER CNTRL LOWER MI SHOULD CHANGE OVER TO
PRIMARIARLY FREEZING RAIN WITH SOME SLEET AFTER 24/18Z.  SURFACE
TEMPERATURES ARE ONLY EXPECTED TO RISE TO NEAR 30 OR LOWER 30S
THROUGH 24/21Z WITH ICE ACCUMULATIONS UP TO 0.1 IN/HR ARE POSSIBLE.

PRECIPITATION ACROSS SRN LOWER MI SHOULD CHANGE TO RAIN AFTER
24/18Z AS VEERING WINDS AND MARGINAL INSOLATION WARM SURFACE
TEMPERATURES ABOVE FREEZING.

..JANISH.. 02/24/01

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