SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1120 PM CST Fri Nov 27 2020

Valid 281200Z - 291200Z


Severe thunderstorms appear unlikely across the contiguous United
States today.

As a trough within the fast northern-stream westerlies moves quickly
across the Northeast today, an upper low south of the main belt of
polar flow will move gradually eastward out of New Mexico and across
the southern Plains.

As this low advances, weak surface cyclogenesis is expected to begin
later in the day, along a remnant baroclinic zone extending from
south Texas eastward across the northern Gulf of Mexico/Gulf Coast
region.  Elsewhere, high pressure will prevail across most of the
remainder of the country.

At the start of the period Saturday morning, two main areas of
convection will be ongoing -- one over the Southeast near the
remnant front, in conjunction with an eastward-moving disturbance,
and the second over Texas and the western Gulf.

With time, the southeastern U.S. convection is forecast to move
eastward/offshore, though a few showers and storms may linger over
northern Florida through the afternoon near the surface front. 
Meanwhile, the Texas convection is expected to increase in coverage
and spread eastward with time, eventually spreading into Louisiana
and vicinity into the overnight hours as quasi-geostrophic forcing
for ascent persists ahead of the advancing upper low.  However,
inland instability will remain weak and elevated, and post-frontal
convection acting to reinforce the cool/stable boundary layer.  

The only exception to this overall expectation could evolve along
the immediate coastal counties of the middle Texas coast.  Here,
proximity to the evolving frontal low could allow modest
surface-based instability near the coast, along with a somewhat
favorable wind profile.  However, this appears to be a very
low-probability scenario at this time, with the low expected to
remain just offshore.  Therefore, no risk areas will be added at
this time.

..Goss/Moore.. 11/28/2020

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