MESOSCALE DISCUSSION 0016
   NWS STORM PREDICTION CENTER NORMAN OK
   0138 PM CST FRI JAN 16 2004
   
   AREAS AFFECTED...NERN IA/FAR NRN IL AND SWRN WI
   
   CONCERNING...FREEZING RAIN AND SLEET 
   
   VALID 161938Z - 170145Z
   
   A BROAD AREA OF PRECIPITATION WILL OVERSPREAD THE AREA FROM SW TO NE
   THROUGH THE EARLY EVENING. A MIX OF FREEZING RAIN/SLEET WILL OCCUR
   IN AREAS WHERE TEMPERATURES REMAIN AT OR COOL TO BELOW FREEZING OVER
   NERN IA/FAR NRN IL AND SWRN WI. THE FREEZING RAIN SHOULD BEGIN OVER
   PORTIONS OF NERN IA BY 16/21Z.
   
   RECENT IR IMAGES AND RADAR DATA SUGGEST INCREASING VERTICAL MOTION
   OVERSPREADING SWRN/SCENTRAL IA. THIS INCREASING LIFT WAS AHEAD OF A
   WEAKENING SHORTWAVE TROUGH EVIDENT OVER NEB...AND IN A REGION WHERE
   LOW LEVEL WARM ADVECTION WAS INCREASING DRIVEN BY THIS SHORTWAVE
   TROUGH AND ANOTHER SHORTWAVE TROUGH MOVING SEWD OUT OF SRN CANADA.
   THE INCREASING VERTICAL MOTION OVER THE AREA IS ALSO EVIDENT BY THE
   PRESENCE OF MODERATE RAIN RECENTLY BEING REPORTED AT SEVERAL SITES
   IN SWRN IA AND INCLUDING DSM. TO THE NE OF A LINE FROM MCW TO CID TO
   SQI THE PREDOMINANT PRECIP TYPE WILL BE FREEZING RAIN. SOME
   LOCATIONS MAY SEE PRECIPITATION START OUT AS COLD RAIN...AS
   TEMPERATURES THAT MAY BE SLIGHTLY ABOVE FREEZING INITIALLY COOL DUE
   TO EVAPORATION...DESPITE MODEST LOW LEVEL WARM ADVECTION. FARTHER
   NORTH OVER SWRN/FAR NCENTRAL IL...PRECIPITATION SHOULD DEVELOP
   AROUND 00Z. HERE THE WARM NOSE CENTERED AROUND 850 MB WILL BE
   SMALLER...REMAINING JUST ABOVE 0 DEG C THROUGH A INCREASINGLY SMALL
   LAYER. THIS WILL ALLOW FOR SLEET TO MIX WITH THE FREEZING RAIN...OR
   BECOME THE MAIN PRECIP TYPE ACROSS THIS AREA. HOURLY LIQUID PRECIP
   RATES FROM 0.05 TO 0.10 IN. CAN BE EXPECTED FOR A SEVERAL HOUR
   PERIOD...ESPECIALLY IN AN AREA BOUNDED FROM CID TO DBQ TO RFD TO
   SQI...WHERE THE DEEPEST COLUMN OF VERTICAL MOTION WILL EXIST. IN
   THESE AREAS..TOTAL LIQUID ACCUMULATIONS SHOULD APPROACH/OR EXCEED
   0.25 INCHES.
   
   ..CROSBIE.. 01/16/2004
   
   
   ATTN...WFO...LOT...MKX...DVN...ARX...DMX...
   
   42259261 42619325 43389259 43359175 42858973 42028891
   41498975