SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0651 AM CST Fri Dec 11 2020

Valid 111300Z - 121200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EAST TX...FAR
SOUTHEAST OK...SOUTHWEST TO CENTRAL AR...WESTERN LA...

...SUMMARY...
Very isolated damaging winds are possible across a portion of the
South-Central States mainly this evening, with a brief tornado also
possible in southeast Texas.

...South-Central States...
Primary changes this outlook are to reduce the spatial extent of the
Marginal Risk, as well as add low tornado probabilities over
southeast TX.

Overall severe weather setup will be constrained by weak to moderate
mid-level lapse rates and marginal boundary-layer moisture. Modified
boundary-layer moisture return from the western Gulf should yield
mid 50s dew points as far north as eastern OK to central AR with mid
60s dew points remaining confined close to the coast. Ongoing belt
of elevated showers supported by 700-mb warm theta-e advection from
the Ozark to the Edwards Plateau should shift east through the day.
In the wake of this swath during the late afternoon to early
evening, renewed convective development may occur along the surface
front near the southeast OK/northeast TX border and farther south in
southeast TX within pre-frontal confluence. These corridors will be
supported by more favorable mid-level lapse rates which should yield
a plume of weak MLCAPE around 250-750 J/kg across east TX.

Deep-layer shear will be sufficient for organized convection which
may include the development of one or more clusters/line segments
that would likely become rooted atop near-neutral boundary-layer
lapse rates with eastern extent in AR/LA. Enlarged low-level
hodographs may have narrow spatial overlap with weak surface-based
buoyancy across southeast TX and yield a couple transient supercell
structures with low probability of a brief tornado. Otherwise, a few
strong gusts capable of very isolated damaging winds appear
possible.

..Grams/Goss.. 12/11/2020

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