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Mesoscale Discussion 1564
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   MESOSCALE DISCUSSION 1564
   NWS STORM PREDICTION CENTER NORMAN OK
   0340 PM CDT TUE JUL 28 2015

   AREAS AFFECTED...SOUTHEAST NEB/PARTS OF WESTERN...CENTRAL AND
   SOUTHERN IA/EXTREME NORTHERN MO

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 282040Z - 282245Z

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...THE POTENTIAL FOR NEW TSTM DEVELOPMENT IS EXPECTED TO
   INCREASE THROUGH THE AFTERNOON ACROSS SOUTHEAST NEB INTO PORTIONS OF
   WESTERN...CENTRAL AND SOUTHERN IA...WITH ACTIVITY EVENTUALLY
   SPREADING INTO FAR NORTHERN MO.  WW ISSUANCE IS BEING CONSIDERED.

   DISCUSSION...TRENDS IN MOSAIC RADAR IMAGERY AND SURFACE OBSERVATIONS
   SHOWED A COLD FRONT ADVANCING EASTWARD INTO NORTHWEST IA AND EASTERN
   NEBRASKA...AND AT 20Z THIS BOUNDARY EXTENDED FROM WRN MN SSWWD
   THROUGH NORTHWEST IA /30 W SPW/ TO 30 ESE OLU TO 15 WNW CNK. 
   MEANWHILE...AS INDICATED IN THE RECENT SWODY1...AN OUTFLOW BOUNDARY
   HAS RETURNED NWD THIS AFTERNOON FROM THE LATE MORNING POSITION ALONG
   THE MO/IA BORDER.  THIS BOUNDARY CURRENTLY EXTENDS FROM THE
   INTERSECTION WITH THE COLD FRONT IN DODGE COUNTY NEB EWD THROUGH
   WESTERN IA /ALONG AND NORTH OF I-80/ TO NEAR DSM...AND THEN INTO
   SOUTHEAST IA.

   STRONG SURFACE HEATING ACROSS THE WARM SECTOR HAS BOOSTED AFTERNOON
   TEMPERATURES TO AROUND 90 F...WHILE SLY WINDS AND EVAPOTRANSPIRATION
   HAVE RESULTED IN SURFACE DEW POINTS RISING INTO THE MID-UPPER
   70S...RESULTING IN RECENT REDUCTION IN SURFACE-BASED INHIBITION. 
   THIS COMBINED WITH A PLUME OF STEEP MIDLEVEL LAPSE RATES /7-7.5 C
   PER KM/ IS CONTRIBUTING TO VERY STRONG INSTABILITY /MLCAPE 2000-3500
   J PER KG/.  VERTICALLY VEERING WIND PROFILES WITH SWLY 500-MB FLOW
   OF 35 KT HAS ALLOWED FOR BULK SHEAR TO BECOME SUPPORTIVE FOR
   ORGANIZED STORMS.  DESPITE FAVORABLE THERMODYNAMICS/KINEMATICS...
   RECENT TRENDS IN THE CU FIELD ACROSS ERN NEB AND WEST-CENTRAL/SWRN
   IA DO NOT INDICATE STRONG VERTICAL DEVELOPMENT PER VISIBLE SATELLITE
   IMAGERY.  THIS MAY BE DUE TO SUBSIDENCE IN THE WAKE OF THE EARLIER
   MCS AND APPARENT SHORTWAVE RIDGING PRESENT ACROSS ERN NEB/WRN IA PER
   WATER VAPOR IMAGERY.  MEANWHILE...SOME INCREASE IN CONVECTIVE
   DEVELOPMENT ACROSS CENTRAL NEB MAY BE INDICATING AN INCREASE IN
   LARGE SCALE ASCENT AHEAD OF A WEAK MIDLEVEL IMPULSE ADVANCING NEWD
   FROM NERN CO.  ALTHOUGH MOST SHORT-TERM MODELS LACK ROBUST
   CONVECTIVE DEVELOPMENT IN THE SHORT-TERM...THE APPROACHING
   DEEP-LAYER ASCENT MAY PROVE SUFFICIENT FOR NEW STORM DEVELOPMENT
   ACROSS SOUTHEAST NEB INTO SWRN IA BY 22-23Z.

   ..PETERS/GOSS.. 07/28/2015


   ATTN...WFO...DVN...DMX...EAX...OAX...

   LAT...LON   40909663 41559618 41829528 41859380 41569246 41009175
               40659179 40349301 40239443 40089522 40049591 40099655
               40309697 40909663 

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Page last modified: July 28, 2015
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