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Mesoscale Discussion 766
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   MESOSCALE DISCUSSION 0766
   NWS STORM PREDICTION CENTER NORMAN OK
   0543 PM CDT SAT MAY 31 2014

   AREAS AFFECTED...EASTERN MONTANA

   CONCERNING...SEVERE THUNDERSTORM WATCH 199...

   VALID 312243Z - 312330Z

   CORRECTED FOR IMAGE

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 199
   CONTINUES.

   SUMMARY...THE RISK FOR SEVERE THUNDERSTORMS WITH LARGE HAIL AND
   DAMAGING WINDS CONTINUES ACROSS WW 199.

   DISCUSSION...EARLIER CONVECTION ASSOCIATED WITH AN MCV -- CURRENTLY
   DRIFTING NEWD WITH A CENTER WNW OF GLASGOW PER WSR-88D DATA -- HAS
   DEPOSITED AN OUTFLOW BOUNDARY DRAWN N/S FROM NEAR GLASGOW MT TO NEAR
   SHERIDAN WY. VIS SATELLITE IMAGERY INDICATE SE/NW-ORIENTED
   HORIZONTAL CONVECTIVE ROLLS ON THE WARM SIDE OF THE BOUNDARY --
   WHICH SERVES AS THE TERMINUS FOR THESE ROLLS. THESE ROLLS HIGHLIGHT
   THE RELATIVELY RICH MOISTURE ANALYZED E OF THE BOUNDARY -- E.G. SFC
   DEWPOINTS IN THE UPPER 50S TO LOWER 60S.

   POCKETS OF ENHANCED SFC CONVERGENCE NEAR THE INTERSECTION POINTS
   BETWEEN THE ROLLS AND THE BOUNDARY WILL CONTINUE TO FAVOR DISCRETE
   CONVECTIVE DEVELOPMENT FROM ERN GARFIELD COUNTY TO ERN SHERIDAN
   COUNTY. THE GGW VWP SAMPLES MODESTLY STRENGTHENING MID-LEVEL FLOW --
   PERHAPS AUGMENTED BY THE CIRCULATION AROUND THE MCV -- WITH AROUND
   35-40 KT OF 4-6-KM-AGL SWLYS GENERATING MODERATE DEEP SHEAR CAPABLE
   OF SUPERCELL STRUCTURES. MEANWHILE...MODIFICATIONS TO THE 19Z GGW
   RAOB TO ACCOUNT FOR THE AIR MASS ON THE WARM SIDE OF THE BOUNDARY
   SUGGESTS AROUND 2000 J/KG OF MLCAPE...YIELDING A POTENTIAL FOR LARGE
   HAIL -- POSSIBLY SIGNIFICANT. A TORNADO CANNOT BE RULED OUT OWING TO
   DIRECTIONAL SHEAR IN THE LOW LEVELS -- ALBEIT WITH WEAK FLOW
   MAGNITUDE.

   BEHIND THE OUTFLOW BOUNDARY...A STABILIZED BOUNDARY LAYER SHOULD
   LIMIT THE POTENTIAL FOR STRONG-THUNDERSTORM DEVELOPMENT.
   HOWEVER...WITH AROUND 25-35 OF DEEP SHEAR AND MODEST DEEP FORCING
   FOR ASCENT STILL CROSSING THE AREA...ISOLATED SVR TSTMS CANNOT BE
   RULED OUT THROUGH THE EVENING HOURS.

   ..COHEN.. 05/31/2014


   ATTN...WFO...BYZ...GGW...TFX...

   LAT...LON   45010857 48850816 48840425 45030487 45010857 

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Page last modified: May 31, 2014
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