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Mesoscale Discussion 1378
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   Mesoscale Discussion 1378
   NWS Storm Prediction Center Norman OK
   1100 AM CDT Fri Jul 21 2017

   Areas affected...Portions of Maine

   Concerning...Severe potential...Watch unlikely 

   Valid 211600Z - 211830Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Some risk for isolated severe thunderstorms will develop
   through the mid-day hours and continue into the late afternoon.
   Watch issuance is unlikely.

   DISCUSSION...Beneath broadly cyclonic flow aloft -- embedded with
   low-amplitude impulses -- isolated thunderstorm development is
   expected during the next few hours. This activity will likely
   initiate along subtle, fragmented baroclinic troughs along which
   initially swelling cumulus fields are noted over southern Quebec,
   along a differential-heating zone peripheral to persistent mid-level
   clouds over northern Maine, and amid diurnally deepening
   boundary-layer circulations augmented by orographic effects. A
   modestly moist boundary layer characterized by lower 60s dewpoints
   will offer sufficient -- albeit marginal -- buoyancy (MLCAPE around
   500-1000 J/kg) amid minimal convective inhibition for convection to
   be sustained throughout the afternoon. Long mid/high-level
   hodographs supporting around 35-40 kt of effective shear may support
   sustained cells and small convective clusters capable of isolated
   severe hail and wind. However, without stronger buoyancy, and given
   the lack of stronger ascent, greater severe coverage is not

   ..Cohen/Coniglio/Dial.. 07/21/2017

   ...Please see for graphic product...


   LAT...LON   45377074 46247023 47086942 47056817 46416778 45356759
               44666821 44456961 44847064 45377074 

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