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Mesoscale Discussion 1769
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   MESOSCALE DISCUSSION 1769
   NWS STORM PREDICTION CENTER NORMAN OK
   0912 AM CDT SAT SEP 27 2014

   AREAS AFFECTED...NV...AZ...UT

   CONCERNING...SEVERE THUNDERSTORM WATCH 507...

   VALID 271412Z - 271615Z

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 507
   CONTINUES.

   SUMMARY...STRONG TO ISOLATED SEVERE STORMS REMAIN POSSIBLE FROM
   NORTHWEST AZ INTO SOUTHWEST UT EARLY THIS MORNING.

   DISCUSSION...CYCLONICALLY-CURVED JET WITH MID-LEVEL SPEED MAX AROUND
   75KT WAS ROUNDING THE BASE OF A SUBSTANTIAL MID/UPPER TROUGH OVER CA
   THIS MORNING. ABUNDANTLY MOIST AIRMASS /PW VALUES 1-1.5 INCHES/
   STREAMING NORTH AHEAD OF THIS SYSTEM WAS CONTRIBUTING TO A
   PERSISTENT BAND OF VIGOROUS CONVECTION FOCUSED ALONG A LOW-LEVEL
   CONFLUENCE ZONE OVER WESTERN AZ WHERE DEEP-LAYER ASCENT WAS
   MAXIMIZED AHEAD OF THE UPPER TROUGH. DOWNSLOPE FLOW OFF THE SOUTHERN
   SIERRA CREST HAS LIKELY CONTRIBUTED TO A DRYLINE ON THE WESTERN EDGE
   OF THE STRONGER CONVECTION AND EXPECT SEVERE THREAT HAS ENDED FOR
   NOW ACROSS SOUTHERN NV.

   EFFECTIVE DEEP-LAYER SHEAR OF 35-40KT WILL CONTINUE TO SUPPORT
   TRANSIENT SUPERCELL STRUCTURES AND LINE SEGMENTS TRACKING
   NORTH-NORTHEAST AROUND 30KT AS STRONG LIFT ACTS ON MOIST AND
   SUFFICIENTLY UNSTABLE AIRMASS FROM WESTERN AZ NORTHWARD INTO UT. A
   FEW OF THESE STORMS COULD PRODUCE DAMAGING WINDS...MARGINALLY SEVERE
   HAIL AROUND 1 INCH...AND PERHAPS A BRIEF TORNADO. TRAINING NATURE OF
   THE CONVECTION WILL ALSO RESULT IN LOCALIZED FLASH FLOODING.

   ..CARBIN/MEAD.. 09/27/2014


   ATTN...WFO...FGZ...SLC...PSR...VEF...LKN...

   LAT...LON   34131241 34131416 36131512 38131608 38151423 38131240
               36131154 34131066 34131241 

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Page last modified: September 27, 2014
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