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Mesoscale Discussion 1658
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   MESOSCALE DISCUSSION 1658
   NWS STORM PREDICTION CENTER NORMAN OK
   0336 PM CDT WED SEP 07 2016

   AREAS AFFECTED...PORTIONS OF NRN IL...SRN WI...FAR NWRN INDIANA

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 072036Z - 072300Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...THE AREA IS BEING MONITORED FOR AN INCREASING POTENTIAL
   FOR DMGG WIND GUSTS AND POSSIBLE ISSUANCE OF A WW.

   DISCUSSION...TSTMS HAVE ORGANIZED FROM SRN WI TO THE ERN IA/NWRN IL
   BORDER IN ASSOCIATION WITH ASCENT PRECEDING A LONG-LIVED MCV.
   EMBEDDED BOWING STRUCTURES HAVE OCCASIONALLY BECOME EVIDENT WITHIN A
   QUASI-LINEAR CONVECTIVE SEGMENT CROSSING THE MS RIVER...AND THIS
   LINE WILL CONTINUE ADVANCING EWD/ENEWD THROUGH THE LATE
   AFTERNOON/EARLY EVENING -- PERHAPS EVENTUALLY AFFECTING THE CHICAGO
   METROPOLITAN AREA AND VICINITY. STRONG SFC HEATING AMIDST DEWPOINTS
   IN THE LOWER/MIDDLE 70S HAS BOOSTED MLCAPE TO AROUND 1500-2500 J/KG
   WITH NEGLIGIBLE MLCINH IN ADVANCE OF THIS ACTIVITY. THIS SHOULD
   SUPPORT CONVECTIVE MAINTENANCE FOR THE NEXT SEVERAL HOURS...GIVEN
   25-40 KT OF EFFECTIVE SHEAR IN PLACE. POOR MID-LEVEL LAPSE RATES AND
   ONLY MODEST LOW-LEVEL FLOW SAMPLED BY THE LOT VWP MAY LIMIT THE
   OVERALL SVR RISK. HOWEVER...THE UPSTREAM DVN VWP IS SAMPLING AROUND
   30-40 KT OF FLOW IN THE 1-2-KM-AGL LAYER...AND LOW-LEVEL FLOW COULD
   INCREASE ACROSS THE REGION RELATED TO THE PASSAGE OF A SUBTLE
   MID-LEVEL SPEED MAX. THIS COULD LOCALLY ENHANCE THE SVR-WIND RISK
   VIA CONVECTIVE MOMENTUM TRANSPORT...ESPECIALLY AS CONVECTION
   ENCOUNTERS STEEPER LOW-LEVEL LAPSE RATES ACROSS N-CNTRL/NERN IL AND
   VICINITY.

   ..COHEN/HART.. 09/07/2016


   ATTN...WFO...LOT...ILX...MKX...DVN...

   LAT...LON   40629055 41629036 42428976 42838879 42758777 42298736
               41388718 40398830 40198991 40629055 

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Page last modified: September 07, 2016
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