SPC 0700Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1200 AM CST Sat Nov 21 2020

Valid 221200Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms appear unlikely across the contiguous
United States on Sunday.

...Synopsis and Discussion...
An upper trough initially over the Plains and Upper Midwest Sunday
morning will progress eastward across the MS/OH Valleys to the
eastern states by the end of the period. At the surface, a weak low
over the mid MS Valley should develop northeastward across the OH
Valley and into the Mid-Atlantic/Northeast by late Sunday night
while slowly deepening. A cold front attendant to this surface low
is forecast to sweep east-southeastward across much of the southern
Plains, lower MS Valley/Southeast, and eastern states through early
Monday morning.

Limited low-level moisture, characterized by 50s surface dewpoints,
should be present in a narrow corridor ahead of the front across
parts of TX to the Mid-South. Isolated showers and thunderstorms may
be ongoing at the start of the period over these areas along/behind
the front, although instability should remain rather weak owing to
poor mid-level lapse rates. Thunderstorm potential should quickly
diminish by Sunday afternoon as the forcing associated with the
upper trough departs this region. Negligible instability forecast
across the OH Valley/Mid-Atlantic suggests thunderstorm potential
should remain very low as the upper trough moves over these areas.

Along much of the East Coast, surface ridging should generally
hinder the inland advance of substantial low-level moisture. One
exception may be eastern NC/SC late Sunday night into early Monday
morning. Here, upper 50s to low 60s surface dewpoints may be present
ahead of the eastward-advancing cold front. As modest mid-level
height falls associated with the approaching upper trough overspread
this region, at least isolated thunderstorms may develop. Although
deep-layer shear appears sufficient to support organized storms,
current expectations are for greater instability to remain confined
to immediate coastal areas, with any meaningful strong to severe
storm potential probably remaining offshore.

Elsewhere, isolated thunderstorms may occur Sunday across parts of
the FL Peninsula and the Keys as weak low-level easterly flow
continues, and the Four Corners vicinity into western CO as upper
troughing amplifies over the western CONUS late in the period.

..Gleason.. 11/21/2020

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