Wednesday, November 9, 2011

Mesoscale Discussion #2310- Heavy Snow- Wisconsin/NE Iowa

MESOSCALE DISCUSSION 2310
   NWS STORM PREDICTION CENTER NORMAN OK
   0441 AM CST WED NOV 09 2011
   
   AREAS AFFECTED...PARTS OF NERN IA/SERN MN NORTHEASTWARD THRU MUCH OF
   CNTRL WI
   
   CONCERNING...HEAVY SNOW 
   
   VALID 091041Z - 091415Z
   
   HEAVY WET SNOW AND GUSTY STRENGTHENING WINDS ARE EXPECTED TO DEVELOP
   ACROSS THE REGION THROUGH MID MORNING.
   
   AS A VIGOROUS SHORT WAVE IMPULSE AND ASSOCIATED MID/UPPER JET STREAK
   LIFT NORTHEASTWARD ACROSS THE MIDDLE MISSISSIPPI VALLEY TOWARD THE
   UPPER GREAT LAKES...RAPID DEEPENING OF AN ASSOCIATED SURFACE CYCLONE
   IS NOW UNDERWAY.  LATEST SURFACE DATA SUGGEST THAT THIS IS OCCURRING
   FASTER THAN PERHAPS MOST MODEL GUIDANCE HAS INDICATED...AND FURTHER
   INTENSIFICATION IS EXPECTED AS THE LOW TRACKS FROM WEST CENTRAL
   ILLINOIS INTO THE VICINITY OF SOUTHERN LAKE MICHIGAN BY 18Z.  
   
   LATEST RUC GUIDANCE SUGGESTS THE DEVELOPMENT OF A NEW DEFORMATION
   ZONE...WITH SUBSTANTIAL STRENGTHENING OF MID-LEVEL FRONTOGENETIC
   FORCING EXPECTED DURING THE 12-16Z TIME FRAME ALONG AN AXIS NEAR OR
   JUST NORTH OF NORTHEASTERN IOWA TOWARD CENTRAL UPPER MICHIGAN.
   THERMODYNAMIC PROFILES ACROSS THIS REGION ARE ALREADY MOSTLY BELOW
   FREEZING...AND MELTING OF SNOW IS EXPECTED TO CONTRIBUTE TO COOLING
   OF THE BOUNDARY LAYER CLOSER TO FREEZING.  COUPLED WITH INCREASING
   LIFT IN THE FAVORABLE MIXED PHASE LAYER FOR DENDRITIC ICE CRYSTAL
   GROWTH...HEAVY SNOW RATES IN EXCESS OF 1 INCH PER HOUR APPEAR
   POSSIBLE IN THE PRESENCE OF RELATIVELY HIGH PRECIPITABLE WATER
   VALUES AROUND OR ABOVE .5 INCHES.

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