Day 1 Severe Weather Outlook

Valid 211300Z – 221200Z


Thunderstorms are not expected today and tonight.

…Synopsis and Discussion…
The upper-air pattern through the period will feature a synoptic-
scale ridge moving slowly eastward across the central Rockies and
from the southern Rockies across the southern High Plains. To its
east, a strong, positively tilted trough — now located from New
England across the southern Appalachians to the Mid-South region —
will move offshore from the Atlantic Coast. An associated strong
cold front was crossing the southern FL Peninsula at 11Z, and will
clear all of FL by early afternoon. The cold, stable post-frontal
air mass and lack of substantial mid/upper forcing will preclude
thunderstorm potential east of the Rockies, while ridging and lack
of lift have the same effect over much of the Rockies and
Intermountain region.

West of the ridge aloft, a closed mid/upper-level cyclone was
apparent in moisture-channel imagery west of southern CA and
northern Baja, centered near 33N129W. The 500-mb low will approach
the southern CA coastline near the end of the period, and may be
preceded by a band or arc of low-topped/cold-core convection taking
advantage of steep low/midlevel lapse rates atop a weakly capped
marine layer. Though thunder may occur in such convection, based on
time series of forecast soundings and the presence of sporadic
lightning in the regime the last 8-10 hours, current indications are
for the thunder potential to remain west of the coast until shortly
after the end of the period.

..Edwards.. 02/21/2020


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