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Mesoscale Discussion 815
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   Mesoscale Discussion 0815
   NWS Storm Prediction Center Norman OK
   1122 AM CDT Tue May 23 2017

   Areas affected...Portions of northern Florida and southern Georgia

   Concerning...Tornado Watch 257...

   Valid 231622Z - 231745Z

   The severe weather threat for Tornado Watch 257 continues.

   SUMMARY...Strong to occasionally severe thunderstorms will continue
   east/northeastward across Watch 257 through the early afternoon,
   with an attendant threat for a couple tornadoes and damaging wind

   DISCUSSION...Along and ahead of a line of thunderstorms (near the
   AL/GA border as of 16 UTC/12 EDT), pockets of heating have brought
   surface temperatures into the mid/upper 70s and low 80s. In turn,
   with rich boundary-layer moisture present, mixed-layer CAPE values
   have risen to upwards of 1000 J/kg, based on forecast and modified
   observed sounding data. Radar/lightning observations have indicated
   a gradual upward trend in intensity over the last hour, and storms
   should persist in this relatively favorable thermodynamic
   environment for several hours.

   Deep-layer shear profiles remain favorable for occasional
   low/mid-level rotation, as a southwesterly low-level jet crosses the
   region and winds veer with height from the surface to mid levels.
   Recent KVAX and KTLH VWP data depict the presence of approximately
   150-200 m2/s2 of 0-1km storm-relative helicity, suggesting
   occasional low-level mesocyclogenesis potential (either
   line-embedded or in semi-discrete cells). Indeed, a dual-pol
   tornadic debris signature was observed in southern Randolph County,
   Georgia around 1545-1555 UTC, confirming this environmental
   potential. As such, a threat for damaging winds and a couple
   tornadoes will persist as storms spread east across Watch 257 this

   ..Picca.. 05/23/2017

   ...Please see for graphic product...


   LAT...LON   31868481 32368339 32638263 32518217 31918228 30918273
               30458304 30148410 30118510 30388573 31418521 31868481 

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