SPC AC 300730

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0230 AM CDT Tue Jun 30 2020

   Valid 021200Z - 031200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE DAKOTAS AND ADJACENT NORTHERN HIGH PLAINS AREA...AND ACROSS
   PARTS OF NEW ENGLAND...

   ...SUMMARY...
   A few severe storms may affect portions of the Dakotas and into
   northeastern Wyoming/southeastern Montana, and also portions of New
   England.  Locally gusty/damaging winds will be possible in both
   areas, along with some hail risk over the Dakotas region on
   Thursday.

   ...Synopsis...
   The general western trough/central ridge/eastern trough
   configuration of the upper flow pattern will likely persist Day
   3/Thursday, though gradual deamplification is expected overall.  At
   the surface, a cold front is forecast to move across New England; a
   cold front is also forecast to advance across the northern High
   Plains region as another upper feature rotates across Montana within
   broader cyclonic flow aloft.  Finally, a weak cool front will sag
   southward across the Southeast through the period.

   ...Parts of ND to southeastern MT/northeastern WY...
   With the Montana vort max/short-wave trough -- and more substantial
   large-scale ascent -- forecast to move northward into adjacent
   Canada during the day, weaker UVV and presence of a weak cap
   suggests that storm development along the advancing cold front will
   likely remain isolated.  Still, with strong (around 50 kt)
   southwesterly mid-level flow atop the frontal zone, and a relatively
   dry/deep boundary layer promoting potential for evaporative
   enhancement of any downdrafts, potential for gusty/damaging winds
   warrants inclusion of MRGL risk across this area.  Primary risk will
   likely exist from mid afternoon through mid evening. 

   ...New England...
   Forecast models are in general agreement that a short-wave
   trough/vort max, embedded in cyclonic northwesterly flow surrounding
   an upper vortex off the southern coast of Greenland, will move
   across eastern Canada and northern New England.  With diurnal
   heating supporting ample destabilization for storm development, and
   40 to 50 kt mid-level northwesterlies progged to spread into the
   area through the afternoon and evening, fast-moving storms/storm
   clusters may be capable of producing locally gusty/damaging winds. 
   Risk will diminish later in the evening, as diurnal cooling leads to
   a decrease in storm coverage/intensity.

   ...The Southeast/Gulf Coast states...
   As a weak cool front -- in conjunction with weak upper short-wave
   troughing -- settles southward across the area, afternoon
   thunderstorms are expected.  A few stronger storms may produce
   locally gusty winds, but at this time, risk appears too low to
   warrant inclusion of even a low probability risk area.

   ..Goss.. 06/30/2020

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