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Mesoscale Discussion 1825
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   Mesoscale Discussion 1825
   NWS Storm Prediction Center Norman OK
   1031 AM CDT Wed Aug 21 2019

   Areas affected...Northern Mid Atlantic Coast region through southern
   New England

   Concerning...Severe potential...Watch possible 

   Valid 211531Z - 211730Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Intensifying thunderstorms posing a risk for potentially
   damaging wind gusts and, perhaps, an isolated tornado or two, appear
   increasingly possible by 2-4 PM EDT.  This could require the
   issuance of one or two severe weather watches.

   DISCUSSION...Convective development appears to be undergoing at
   least some gradual intensification, within a narrow band now
   overspreading the Champlain and Hudson Valleys, and as far south as
   northern New Jersey.  This appears to be occurring on the leading
   edge of mid-level forcing for ascent associated with a remnant
   convectively generated or enhanced perturbation, which is forecast
   to progress into and through western and northern New England by mid
   to late afternoon.  This may be trailed to the southwest by another
   area of mid-level forcing for ascent spreading northeastward across
   the northern Mid Atlantic Coast region into southern New England.

   Based on latest observational data, seasonably moist boundary layer
   air may mostly remain confined to the south of a weak surface front,
   reinforced by rain-cooled air associated with weakening convection
   preceding the main ongoing band.  This extends roughly from the
   leading edge of the convective band across northern Massachusetts,
   though this boundary could shift northward some into and through the
   afternoon.

   To the south of the front, insolation during the next few hours is
   expected to contribute to moderate mixed-layer CAPE of 1000-2000
   J/kg, coincident with strengthening of west-southwesterly flow in
   the 700-500 mb layer.  This may contribute to an environment
   increasingly conducive to organized convection by 18-20Z, which
   could include further intensification of the ongoing line and
   perhaps additional discrete storms, with supercell structures
   possible.  Although low-level hodographs may be somewhat modest in
   size, a tornado or two might not be out of the question, mainly near
   the surface boundary across southern New England.  Otherwise,
   strongest storms probably will pose a risk for potentially damaging
   wind gusts.

   ..Kerr/Guyer.. 08/21/2019

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...GYX...BOX...BTV...OKX...ALY...PHI...BGM...CTP...
   LWX...

   LAT...LON   43597276 43207186 43187060 42567029 41777017 40667291
               39807417 39187526 39897661 40957572 41367524 41547425
               41877353 42307324 43597276 

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Page last modified: August 21, 2019
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