SPC AC 231942

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0242 PM CDT Thu Jul 23 2020

   Valid 232000Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE NORTHEAST...THE NORTHERN ROCKIES AND THE NORTHERN PLAINS...

   ...SUMMARY...
   Severe thunderstorms are expected through this evening over parts of
   the Northeast and the northern Great Plains.  Damaging wind and at
   least isolated large hail will be possible in both areas.

   ...20z Update...

   The ongoing outlook remains on track. The only change with this
   update was to trim modestly from the Marginal risk from parts of
   northwest PA into NY northeastward into ME where the surface
   front/wind shift has progressed southeast. Strong to severe storms
   are underway across portions of New England to VA/NC. Better
   organized convection will remain across New England where
   shear/forcing are more favorable. Nevertheless, transient
   pulse/multi-cell clusters could produce sporadic wet microbursts as
   far south as the Carolinas. 

   Further west, thunderstorms are ongoing across southwest MT and
   adjacent portions of ID. Strong gusts and hail will continue to be
   possible with this activity through early evening. Additional severe
   storms are still expected this evening into tonight across eastern
   MT into the western Dakotas.

   ..Leitman.. 07/23/2020

   .PREV DISCUSSION... /ISSUED 1120 AM CDT Thu Jul 23 2020/

   ...Northeast States...
   A broad upper trough continues to affect the northeast states, with
   moderately strong mid level winds across parts of PA/NY/NJ into New
   England.  A weak cold front is sagging into NY/VT/NH, and should be
   the focus for scattered afternoon thunderstorm development.  Other
   more isolated clusters of storms are expected farther east in the
   moist and airmass across the remainder of New England.  Broken
   clouds are limiting heating, which should temper the overall risk of
   severe storms today.  However, more organized clusters of storms
   will pose a risk of damaging wind gusts and perhaps hail this
   afternoon and early evening.

   ...Mid Atlantic Region...
   Considerable low and mid level moisture are present today from the
   central/southern Appalachians into the Mid-Atlantic region.  Flow
   aloft is relatively weak, and considerable cloud cover both limit
   confidence in a more organized severe threat.  Nevertheless, pockets
   of heating and scattered afternoon thunderstorms will pose a risk of
   locally damaging wind gusts.

   ...Northern Plains...
   A strong upper trough is topping the upper ridge axis over the high
   Plains of WY/MT.  Forcing ahead of this system should result in
   thunderstorms by mid afternoon over parts of the western Dakotas and
   eastern MT.  These storms will track northeastward through the
   evening, posing a risk of large hail and damaging winds.

   ...ID/Southwestern MT...
   An upper low remains over central CA today, with a band of
   moderately strong winds aloft extending across NV into ID/MT.  Mid
   level drying is moving into southern ID, which may limit convective
   coverage.  But heating over the Sawtooth/Bitterroot mountains of ID
   into southwest MT should result in considerable afternoon
   thunderstorm activity.  Unusually high surface dewpoints will help
   to yield moderate CAPE values, along with weak but sufficient
   deep-layer shear for a few organized storms as they move across
   southwest MT.  Damaging winds and large hail will be possible with
   the strongest cells.

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