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Mesoscale Discussion 1733
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   MESOSCALE DISCUSSION 1733
   NWS STORM PREDICTION CENTER NORMAN OK
   0255 PM CDT SAT AUG 22 2015

   AREAS AFFECTED...ERN NEB...SWRN IA...NWRN MO...NERN KS

   CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   VALID 221955Z - 222100Z

   PROBABILITY OF WATCH ISSUANCE...95 PERCENT

   SUMMARY...TSTM INITIATION IS EXPECTED BY 21Z...WITH AN INITIAL
   THREAT OF SUPERCELLS CAPABLE OF LARGE HAIL...DAMAGING WINDS...AND A
   COUPLE OF TORNADOES. TORNADO WATCH ISSUANCE IS LIKELY BY 20Z.

   DISCUSSION...A POWERFUL UPPER TROUGH IS NOW MOVING INTO THE WRN
   DAKOTAS...WITH AN ASSOCIATED 998 MB SFC LOW LOCATED OVER SRN SASK
   AND A TRAILING COLD FRONT MOVING THROUGH THE DAKOTAS INTO CNTRL NEB.
   VERY STEEP LAPSE RATES /AS INDICATED BY THE 18Z OAX RAOB/ COMBINED
   WITH A WARM/MOIST BOUNDARY LAYER IS RESULTING IN STRONG
   BUOYANCY...WITH MLCAPE RISING INTO THE 2000-3000 J/KG RANGE. WHILE
   MIDLEVEL FLOW IS SOMEWHAT MODEST...VEERING WIND PROFILES ARE
   SUPPORTING EFFECTIVE SHEAR OF 30-35 KTS AND EFFECTIVE SRH OF 150-200
   M2/S2...SUFFICIENT FOR ORGANIZED STORM STRUCTURES GIVEN STRONG
   INSTABILITY. 

   SOME UNCERTAINTY REMAINS REGARDING THE TIMING AND COVERAGE OF
   INITIATION WITH SWRN EXTENT...BUT STRONG ASCENT ALONG THE COLD FRONT
   SHOULD QUICKLY ERODE THE CAP AND ALLOW FOR INITIATION ACROSS
   E-CNTRL/SERN NEB INTO WRN IA BY 21Z. A FEW SUPERCELLS WILL BE
   POSSIBLE WITHIN 1-2 HRS OF INITIATION...WITH A THREAT OF VERY LARGE
   HAIL AND A COUPLE OF TORNADOES. UPSCALE GROWTH IS EXPECTED WITH
   TIME...GIVEN STRENGTH OF ASCENT SPREADING OVER THE REGION...WITH A
   MORE FOCUSED DAMAGING WIND THREAT BECOMING POSSIBLE ACROSS PARTS OF
   SERN NEB/SWRN IA INTO NERN KS/NWRN MO THIS EVENING. 

   GIVEN THE ABOVE CONCERNS...TORNADO WATCH ISSUANCE IS LIKELY BY 21Z
   ACROSS THE AREA.

   ..DEAN/CORFIDI.. 08/22/2015


   ATTN...WFO...DMX...EAX...OAX...TOP...ICT...GID...

   LAT...LON   40219895 41019780 41679702 42119665 42159613 42159548
               42159492 42139424 42169318 40849384 40139416 39689448
               39439507 38999813 40219895 

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Page last modified: August 22, 2015
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