MESOSCALE DISCUSSION 2015
   NWS STORM PREDICTION CENTER NORMAN OK
   0737 PM CDT MON SEP 24 2007
   
   AREAS AFFECTED...NRN WI INTO THE UPPER PENINSULA OF MICHIGAN
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 687...
   
   VALID 250037Z - 250200Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 687
   CONTINUES.
   
   POTENTIAL FOR AT LEAST SPORADIC WIND DAMAGE COULD INCREASE THROUGH
   03-06Z ACROSS CENTRAL WISCONSIN INTO THE UPPER PENINSULA OF
   MICHIGAN...BUT IT IS UNCERTAIN WHETHER AN ADDITIONAL WW WILL BE
   NEEDED.  TRENDS WILL CONTINUE TO BE MONITORED.
   
   DIVERGENT UPPER FLOW FIELD EAST OF UPPER TROUGH SHIFTING INTO THE
   NORTHERN/CENTRAL PLAINS IS SUPPORTING ONGOING SQUALL LINE WITHIN
   PRE-FRONTAL CONFLUENCE ACROSS THE UPPER MISSISSIPPI VALLEY. 
   ACTIVITY IS EMBEDDED WITHIN A DEEP LOW/MID-LEVEL PLUME OF MOISTURE
   EMANATING FROM THE LOWER LATITUDE EASTERN PACIFIC...WHICH WILL SHIFT
   EAST OF THE UPPER MISSISSIPPI VALLEY INTO THE UPPER GREAT LAKES THIS
   EVENING.  GIVEN FAVORABLE LARGE-SCALE FORCING...WEAK TO MODERATE
   CONDITIONAL INSTABILITY WITHIN THIS PLUME...BASED NEAR THE
   SURFACE...PROBABLY WILL MAINTAIN A NARROW BAND OF STORMS THROUGH THE
   EVENING HOURS.
   
   LATEST RUC GUIDANCE SUGGESTS THAT THE SOUTHERLY LOW-LEVEL JET NEAR
   OR JUST AHEAD OF THE SQUALL LINE WILL INTENSIFY IN EXCESS OF 50 KTS
   THIS EVENING...FROM CENTRAL WISCONSIN THROUGH THE WESTERN UPPER
   PENINSULA OF MICHIGAN.  AND...AS THIS OCCURS...THE CONTINUING
   PRESENCE OF CONVECTIVE ACTIVITY COULD AID THE DOWNWARD TRANSFER OF
   HIGHER MOMENTUM AIR TO THE SURFACE.  LOW-LEVEL LAPSE RATES WILL NOT
   BE PARTICULARLY STEEP...BUT RUC FORECAST SOUNDINGS SUGGEST THAT ANY
   NEAR SURFACE RADIATIONAL INVERSION WILL BE SLOW TO DEVELOP THIS
   EVENING IN THE MOIST BOUNDARY LAYER...WITH 40-50 KT FLOW WITHIN THE
   LOWEST KILOMETER ABOVE GROUND LEVEL.
   
   ..KERR.. 09/25/2007
   
   
   ATTN...WFO...MQT...GRB...DLH...ARX...
   
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