SPC AC 010604

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0104 AM CDT Wed Jul 01 2020

   Valid 021200Z - 031200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE DAKOTAS AND ADJACENT SOUTHEASTERN MONTANA/NORTHEASTERN
   WYOMING...AND ALSO OVER LARGE PORTION OF THE NORTHEAST...

   ...SUMMARY...
   A few severe storms may affect portions of the northern High
   Plains/northern Plains, and also portions of the Northeast.  Locally
   gusty/damaging winds will be possible in both areas, along with some
   hail risk over the Dakotas region on Thursday.

   ...Synopsis...
   Very gradual deamplification of the upper flow field over the U.S.
   is expected Thursday, though the western trough/central
   ridge/eastern trough configuration will generally be maintained
   through the period.  Within the broader flow field, a short-wave
   trough over the Northeast and eastern Canada will continue to shift
   off the Atlantic Coast, while a second/more subtle feature crosses
   New England and the Canadian Maritimes in its wake.  In the West, a
   short-wave trough -- also embedded in broader cyclonic flow -- will
   shift across Montana and the Canadian Prairie Provinces.  Finally,
   weak short-wave troughing will drift southward across the
   Southeast/Gulf Coast States through the period.

   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 while weakening with time.  Finally, a weak cool front will
   linger in a west-to-east orientation across the Southeast through
   the period.

   ...Parts of ND to southeastern MT/northeastern WY, and southward
   across the central High Plains...
   With a majority of the large-scale forcing for ascent associated
   with the aforementioned short-wave trough crossing Montana and the
   Canadian Prairie to remain north of the international border, weaker
   UVV and presence of a weak cap suggests that storm development along
   the advancing cold front across eastern Montana/the Dakotas and
   vicinity 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. 

   Farther south across the central High Plains, a much weaker/subtle
   short-wave trough is progged to shift eastward across the region,
   accompanied by 25 to 35 kt westerly mid-level flow.  Atop low-level
   southeasterlies, shear will support organized updraft evolution. 
   This, combined with ample CAPE development, suggests that a few
   stronger storms will become capable of producing large hail, and
   damaging wind gusts.  At this time, will expand MRGL risk southward
   across portions of the central High Plains, with SLGT risk possibly
   becoming necessary in later outlooks.

   ...New England...
   Mid-level short-wave troughing, embedded in cyclonic northwesterly
   flow surrounding an upper vortex off the southern coast of Greenland
   will move across eastern Canada and northern New England through the
   day.  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.

   ..Goss.. 07/01/2020

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