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Mesoscale Discussion 1209
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MD 1209 graphic

   Mesoscale Discussion 1209
   NWS Storm Prediction Center Norman OK
   1132 AM CDT Sat Jul 01 2017

   Areas affected...portions of central/eastern New York...much of
   Vermont/New Hampshire...southwest Maine...western Massachusetts

   Concerning...Severe potential...Watch likely 

   Valid 011632Z - 011830Z

   Probability of Watch Issuance...80 percent

   SUMMARY...An increase in thunderstorm coverage and intensity is
   anticipated through early/mid afternoon. Damaging winds will be the
   primary threat with a tornado or two possible.  Isolated instances
   of large hail can also be expected.  Short-term trends are being
   monitored and a watch is likely prior to 18Z.

   DISCUSSION...A expansive area of rain and thunderstorms extended
   from central New York northeast through the North Country region and
   northern Vermont at 16Z, with most of the thunderstorms confined to
   the southern periphery of the precipitation area.  Along and
   south/east of this precipitation area, diurnal heating through
   layered clouds has allowed temperatures to warm into the 80s.
   Continued heating of this very moist air mass (PW values in excess
   of 1.75 inches) will contribute to weak/pockets of moderate
   surface-based instability this afternoon.  

   Modest large-scale ascent will develop over the discussion area this
   afternoon associated with a mid-level impulse moving northeast
   across the lower Great Lakes/Ohio Valley.  This will contribute to
   an increase in thunderstorm coverage over the next few hours along
   the southwest-northeast oriented zone of differential heating, and
   along a surface trough/confluence zone over central New York. 
   Short-term guidance continues to suggest that strengthening 850-mb
   flow beneath 40-50 kt mid-level flow will result in a risk for
   damaging winds, isolated large hail and perhaps a tornado or two
   given some low-level hodograph curvature noted on forecast
   soundings.  With time, a more linear storm mode should become
   established with a continued risk for damaging winds.

   Observational and short-term model trends will be monitored and a
   watch is likely prior to 18z.

   ..Bunting/Grams.. 07/01/2017

   ...Please see for graphic product...


   LAT...LON   43317476 43267481 43737416 44227320 44667226 44887124
               44727094 44137078 43197145 42507225 42117300 42057386
               42127437 42377490 42667501 42957500 43317476 

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