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Mesoscale Discussion 1415
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   MESOSCALE DISCUSSION 1415
   NWS STORM PREDICTION CENTER NORMAN OK
   1116 AM CDT THU JUL 28 2016

   AREAS AFFECTED...PORTIONS OF NRN IL AND FAR SRN WI

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 281616Z - 281845Z

   PROBABILITY OF WATCH ISSUANCE...5 PERCENT

   SUMMARY...PORTIONS OF NRN IL AND FAR SRN WI ARE BEING MONITORED FOR
   A WEAK/BRIEF TORNADO POTENTIAL THROUGH THE AFTERNOON. SUCH RISK
   SHOULD REMAIN MARGINAL...AND WW ISSUANCE IS NOT EXPECTED.

   DISCUSSION...SFC MESOANALYSIS PLACES A QUASI-STATIONARY BOUNDARY
   FROM THE CHICAGO AREA THROUGH ROCKFORD AND THEN WWD TO SFC LOW
   PRESSURE ANALYZED NEAR DUBUQUE. A WEAK COLD FRONT ARCHES SWWD FROM
   THE SFC LOW NEAR THE MS RIVER AND SWWD INTO N-CNTRL MO...WHILE A SFC
   TROUGH/OUTFLOW BOUNDARY INTERSECTS THE QUASI-STATIONARY BOUNDARY
   NEAR CHICAGO AND EXTENDS SWD INTO CNTRL IL. THE AIR MASS IN
   PROXIMITY TO THE SFC TROUGH/OUTFLOW BOUNDARY AND QUASI-STATIONARY
   BOUNDARY...AND WITHIN THE WARM SECTOR...CONTINUES TO DESTABILIZE AS
   INSOLATION CONTRIBUTES TO DIABATIC HEATING OF A MOIST BOUNDARY
   LAYER. WITH SFC DEWPOINTS GENERALLY IN THE LOWER TO LOCALLY MIDDLE
   70S...MLCAPE HAS INCREASED TO AROUND 1000-2000 J/KG.

   WITH ADDITIONAL DIURNAL HEATING...AN INCREASE IN CONVECTIVE
   COVERAGE/INTENSITY IS EXPECTED ACROSS THE REGION THROUGH THE
   AFTERNOON. THIS IS ANTICIPATED GIVEN THE LARGELY UNCAPPED/MOIST
   ENVIRONMENT...AND MODEST ASCENT AROUND THE SFC LOW AND
   AFOREMENTIONED BOUNDARIES.

   POOR MID-LEVEL LAPSE RATES WILL CONTINUE LIMITING THE DEGREE OF
   NORMALIZED CAPE AND STORM-SCALE UPWARD ACCELERATIONS. HOWEVER...THE
   MOIST BOUNDARY LAYER IS CONTRIBUTING TO DIURNALLY INCREASING
   LOW-LEVEL BUOYANCY...WITH AROUND 100-150 J/KG OF 0-3-KM MLCAPE
   ACROSS THE WARM SECTOR.

   THE COMBINATION OF THIS LOW-LEVEL BUOYANCY IN THE MOIST
   ENVIRONMENT...AND AMBIENT SFC VERTICAL VORTICITY IN PROXIMITY TO THE
   RELATIVELY COMPACT SFC LOW...QUASI-STATIONARY BOUNDARY...AND SFC
   TROUGH/OUTFLOW BOUNDARY...WILL SUPPORT THE POTENTIAL FOR A FEW
   STORM-SCALE CIRCULATIONS WITH TSTM CELLS THROUGH THE AFTERNOON
   HOURS. LOCALLY BACKED SFC WINDS N OF THE QUASI-STATIONARY BOUNDARY
   AND RELATED STREAMWISE VORTICITY MAY ALSO ENCOURAGE SUCH POTENTIAL.
   A WEAK/BRIEF TORNADO CANNOT BE RULED OUT WITH THIS ACTIVITY.

   HOWEVER...GIVEN THE RELATIVELY WEAK LOW-LEVEL FLOW...LACK OF ANY
   SALIENT MID-LEVEL WAVE/PERTURBATION ENHANCING LARGE-SCALE UPWARD
   MOTION...AND POOR MID-LEVEL LAPSE RATES...A MORE SUBSTANTIAL SVR
   RISK IS NOT ANTICIPATED.

   ..COHEN/DIAL.. 07/28/2016


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

   LAT...LON   41848772 41208816 40818895 40988973 41389008 41729014
               42559009 42708933 42608821 42408780 41848772 

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Page last modified: July 28, 2016
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