SPC AC 310723

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0223 AM CDT Fri Jul 31 2020

   Valid 021200Z - 031200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   THE NORTHEAST...AND FROM SOUTHEAST WY INTO EASTERN CO...

   ...SUMMARY...
   Severe thunderstorms capable of damaging wind and perhaps a couple
   of tornadoes will be possible over portions of the Northeast on
   Sunday. Thunderstorms capable of hail and locally severe wind gusts
   will also be possible from southeast Wyoming into eastern Colorado
   Sunday afternoon and evening.

   ...Synopsis...
   Little substantive change is expected to the large-scale pattern on
   Sunday, with an upper trough remaining over much of the
   central/eastern CONUS, while an upper ridge persists over most of
   the West. A surface low somewhere over the OH Valley/Lower Great
   Lakes at the start of the period is forecast to move northeastward
   into Quebec by Monday morning, as an attendant warm front moves
   northward across New England. T.C. Isaias is currently forecast by
   NHC to remain offshore through the period, though potentially
   approaching some portion of the SC/NC coast by Monday morning. 

   ...Northeast...
   Organized convection will again be possible in association with the
   northeastward-moving cyclone on Sunday, as moderate low/mid-level
   flow and rich low-level moisture overspread portions of the
   Northeast. Considerable uncertainty remains regarding how this
   scenario will evolve, but supercells and/or organized bowing
   segments will be possible, with an attendant risk of locally
   damaging wind. Some tornado potential will also be present in the
   vicinity of the retreating surface warm front as it moves northward
   through the day. Some portion of this region may require an upgrade
   once details come into better focus. 

   ...High Plains...
   Post-frontal upslope flow is forecast to advect modest low-level
   moisture into southeast WY and the CO Front Range and the adjacent
   High Plains, resulting in the development of moderate instability by
   afternoon. North-northwesterly midlevel flow on the eastern
   periphery of the ridge will support effective shear of 30-40 kt,
   sufficient to support organized convection including a few
   supercells. Large hail and locally severe wind gusts will be the
   primary hazards.  

   ...Southeast Coast...
   Refer to NHC for the latest updates/forecast for T.C. Isaias. The
   current forecast track keeps Isaias offshore through the end of the
   period, though this track would potentially result in some outer
   bands reaching the coast prior to the end of the period Monday
   morning. Uncertainty remains too high to introduce probabilities at
   this time.

   ..Dean.. 07/31/2020

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