SPC AC 010546

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1246 AM CDT Tue Sep 01 2020

   Valid 021200Z - 031200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   THE OHIO VALLEY EASTWARD INTO PORTIONS OF THE MID-ATLANTIC STATES
   AND NORTHERN NEW YORK...

   ...SUMMARY...
   Strong to severe thunderstorms are forecast for parts of the Ohio
   Valley into the Mid-Atlantic states and northern New York on
   Wednesday.

   ...Synopsis...
   The primary belt of stronger mid-level flow will remain across the
   northern tier of states as a slow-moving, positive-tilt mid-level
   trough slowly moves eastward across the southern High Plains.  A
   mid-level shortwave trough will move across Quebec during the day. 
   Farther upstream, a stronger disturbance will move from the southern
   Canadian Rockies into the Upper Midwest.  

   In the low levels, an effective front will extend from the southern
   Plains northeast through the OH Valley and lower Great Lakes.  The
   front will push southeast across the Northeast whereas the southern
   portion of the front will become modulated by convective outflow
   across the TX-AR vicinity.

   ...OH Valley into the Mid-Atlantic states...
   The southern fringe of moderate westerly mid-level flow will extend
   from the OH Valley eastward to the Delmarva.  A residual pool of
   rich low-level moisture will encompass much of this region with
   upper 60s to lower 70s surface dewpoints.  Strong heating over the
   higher terrain of the central Appalachians will favor
   isolated-scattered thunderstorms developing during the afternoon. 
   The stronger thunderstorms may yield a localized risk for wind
   damage.  In the upper OH Valley, the front may be a focus for strong
   thunderstorm development during the afternoon, but uncertainty
   regarding the magnitude of destabilization is signaled in the model
   output.  Will refrain from including a larger portion of eastern
   OH/western PA in low-severe probabilities this outlook update.

   ...Northern NY/VT...
   A narrow corridor of richer low-level moisture is forecast over
   parts of the lower Great Lakes into the St. Lawrence Valley ahead of
   the cold front.  Despite limited mid-level lapse rates, sufficient
   heating during the day may lead to a zone of weak to moderate
   destabilization across eastern parts of Ontario and perhaps into the
   Adirondacks and northern VT.  Model guidance differs regarding the
   magnitude of destabilization, but strong wind profiles will aid in
   storm organization.  A few stronger storms may move across the
   Canadian border into parts of NY/VT before weakening during the
   early evening.  

   ...TX...
   The aforementioned larger-scale trough over the southern High Plains
   will meander east across western parts of the state.  Mid- to
   high-level flow associated with this feature will be modest, thereby
   limiting the potential for storm organization.  Several areas of
   convective episodes are forecast prior to Wednesday and this will
   contribute to uncertainty for where stronger heating/destabilization
   will occur.  At this time, models indicate several thunderstorm
   clusters will likely develop from parts of west TX eastward into
   central and north-central TX during the afternoon/early evening. 
   Forecast soundings show weak to moderate buoyancy due in part to
   marginal mid-level lapse rates, and general thunderstorms are
   forecast.

   ..Smith.. 09/01/2020

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