MESOSCALE DISCUSSION 2211
   NWS STORM PREDICTION CENTER NORMAN OK
   1147 AM CST TUE DEC 11 2007
   
   AREAS AFFECTED...FAR NRN MO...SERN IA...FAR NWRN IL...FAR SERN WI
   
   CONCERNING...WINTER MIXED PRECIPITATION 
   
   VALID 111747Z - 112115Z
   
   A LARGE REGION OF FREEZING RAIN AND SLEET FROM THE LOWER MO RIVER
   VALLEY TO THE LOWER GREAT LAKES SHOULD BECOME BETTER DEFINED WITHIN
   A MORE NARROW CORRIDOR THIS AFTERNOON. SIGNIFICANT ICE ACCUMULATIONS
   WILL REMAIN POSSIBLE WITHIN THIS AXIS...WITH LIQUID EQUIVALENT
   PRECIPITATION RATES OF 0.05 TO 0.15 IN/HR LIKELY.
   
   A SERIES OF MID-LEVEL IMPULSES EJECTING OUT AHEAD OF PRIMARY
   LARGE-SCALE TROUGH IN THE SWRN CONUS COUPLED WITH STRONG UPPER-LEVEL
   DIVERGENCE IN THE RIGHT REAR OF A 175 KT JET AXIS OVER THE UPPER
   GREAT LAKES HAS HELPED PRODUCE SEVERAL AREAS OF MIXED PRECIPITATION
   THIS MORNING. ONE IMPULSE NOW TRACKING THROUGH IA WILL LIKELY
   CONTINUE AIDING IN MODERATE PRECIPITATION DOWNSTREAM ACROSS SRN WI
   INTO CNTRL LOWER MI THROUGH 21Z. ADDITIONAL MODERATE TO STRONG UVV
   EMANATING AHEAD OF ANOTHER IMPULSE IN THE SRN PLAINS SHOULD SUPPORT
   CONTINUED PRECIPITATION THROUGH THE LOWER MO AND MID-MS RIVER
   VALLEYS.
   
   AS OF 17Z...THE SURFACE FREEZING LINE EXTENDED ROUGHLY FROM FNB TO
   JUST N OF MKE. WITH WEAK LOW-LEVEL FLOW INVOF THIS LINE...IT SHOULD
   REMAIN QUASI-STATIONARY THROUGH THE AFTERNOON. STILL...MODEST NLY
   NEAR-SURFACE FLOW HAS EXPANDED IN DEPTH /PER RECENT SLATER IA
   PROFILER TIME-SERIES TRENDS/. THIS HAS AIDED IN SUFFICIENT COLD
   ADVECTION FOR A TRANSITION FROM FREEZING RAIN TO SLEET AND SNOW /REF
   RECENT DSM AND MSN SURFACE OBS/. THIS TREND WILL LIKELY
   CONTINUE...FURTHER SHRINKING THE OVERALL WIDTH OF THE CORRIDOR FOR
   POTENTIAL FREEZING RAIN. ALTHOUGH MORNING MODEL GUIDANCE DIFFERS ON
   EXACT PTYPE...LIKELY DUE TO THE SHARP TRANSITION IN
   PTYPES...CONSENSUS IS THAT ROUGHLY A 80 MILE WIDE CORRIDOR ARCING
   FROM NRN MO INTO SERN WI WILL EXPERIENCE THE LONGEST
   DURATION/HEAVIEST RATES OF EITHER FREEZING RAIN OR SLEET THROUGH
   00Z.
   
   ..GRAMS.. 12/11/2007
   
   
   ...NOTICE...
   SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
   SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
   TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
   FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.
   
   ATTN...WFO...LOT...MKX...DVN...ARX...DMX...EAX...
   
   43398770 42298855 41379068 40369277 39679473 39829514
   40259484 41159310 42179137 43188893