SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1138 PM CST Mon Jan 18 2021

Valid 191200Z - 201200Z


A few thunderstorms may occur today across parts of Texas as well as
near the coast of southern California into the lower Colorado River
Valley. Severe thunderstorms are not expected.

Shortwave ridging should build over the southern Plains today as a
surface cold front slowly moves southward over parts of central/east
TX. Partially modified low-level moisture, with surface dewpoints
generally in the low 60s, will reside to the south of the cold
front. Scattered, low-topped showers should be ongoing at the start
of the period along/near the front across parts of central/east TX.
Some of this convection may become deep enough through the day to
support isolated lightning flashes, even though the presence of an
inversion centered around 700 mb should generally limit
boundary-layer instability. A minor mid-level perturbation
approaching the southern Plains from northern Mexico may also
encourage continued convective development along the front through
the evening and overnight hours. Weak forecast instability and poor
lapse rates are expected to preclude an organized severe threat.

...Channel Islands/Southern California into the Lower Colorado River
A closed upper low over the western CONUS will develop southward off
the coast of southern CA and the northern Baja Peninsula by tonight.
Cool mid-level temperatures will promote steepened mid-level lapse
rates beneath the upper low. Lift associated with multiple vorticity
maxima should support shallow convection. The deepest cores could
reach sufficient height to induce charge separation and isolated
lightning flashes. The best potential for thunderstorms will likely
remain just off the CA Coast and over the Channel Islands. Other
isolated thunderstorms may also occur in the mid-level moisture
plume over parts of the lower CO River Valley, but instability
should remain rather weak across this region.

..Gleason/Moore.. 01/19/2021

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