SPC 0730Z Day 3 Outlook

Day 3 Outlook Image

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

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