NWS Storm Prediction Center - Day 3 Convective Outlook

Jul 31, 2021 0730 UTC Day 3 Severe Thunderstorm Outlook
Updated: Sat Jul 31 07:05:01 UTC 2021
SPC Day 3 0830Z Categorical Outlook SPC Day 3 0830Z Categorical Outlook Legend

 Forecast Discussion - Day 3 Convective Outlook

   SPC AC 310705

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0205 AM CDT Sat Jul 31 2021

   Valid 021200Z - 031200Z


   The probability of severe storms appears low across the USA on

   A deep upper low will move from Hudson Bay into western Quebec, with
   an expansive area of cyclonic flow aloft over eastern North America.
   Cool temperatures aloft with -10 C at 500 mb will extend as far
   south as northern AL/GA, though midlevel winds will be modest across
   the South. To the west, an upper high will shift a bit westward
   toward the Mojave Desert.

   At the surface, high pressure will stretch from the Rockies eastward
   across the Plains and into the Appalachians, with an east-west
   oriented front sagging south across TX and the Deep South. This
   front will provide a focus for nearly continuous thunderstorms
   throughout the period with 70s F dewpoints and ample instability
   ahead of the boundary.

   Elsewhere, cool midlevel temperatures will also exist west of the
   upper ridge across western WA and OR, aiding destabilization near a
   weak surface trough.

   ..TX into the Deep South...
   Storms are likely to be ongoing Monday morning from NM across
   northern and central TX and into the lower MS Valley. These storms
   are not expected to be severe as deep-layer shear remains below 30
   kt and midlevel lapse rates will be poor. Pockets of heating are
   expected in between storm clusters, with increasing diurnal activity
   as the front/outflows progress slowly south. While localized,
   marginally severe gusts cannot be ruled out, predictability is
   currently low, and best addressed in later outlooks.

   Destabilization is forecast near a surface trough during the
   afternoon over central OR, beneath weak upper ridging. Forecast
   soundings indicate an uncapped airmass by late afternoon, with steep
   lapse rates supporting at least 500 J/kg MUCAPE. Southerly midlevel
   winds around 30 kt combined with light (but veering with height)
   low-level winds may support a few cells capable of strong wind gusts
   or small hail, but the severe threat appears low at this time.

   ..Jewell.. 07/31/2021



Data courtesy the Storm Prediction Center
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