Valid 042000Z – 051200Z
…NO SEVERE THUNDERSTORM AREAS FORECAST…
Severe thunderstorms appear unlikely across the contiguous United
States through the remainder of the afternoon and tonight.
The only appreciable change to the outlook has been to shift the
general thunderstorm line southward over the FL Peninsula in tandem
with a southward-moving cold front. Organized severe thunderstorms
continue to appear unlikely across the central/southern FL Peninsula
owing to poor mid-level lapse rates limiting instability. Still,
locally strong/gusty winds up to 40-45 mph that have been observed
at a few locations may continue through the remainder of the
afternoon as storms move generally east-southeastward.
.PREV DISCUSSION… /ISSUED 1023 AM CST Sat Jan 04 2020/
A sharp upper trough will continue moving across the eastern U.S.
today, as an associated cold frontal advance — comprised of two
successive wind shift/airmass changes — continues across the East
Coast states. These two wind shifts — one now off the middle and
southern Atlantic Coast and the second shifting east of the
Appalachian Crest — will gradually congeal into one, more cohesive
front, as it shifts eastward across Florida and eastward across the
western Atlantic through this evening.
Aloft, a lower-amplitude pattern will continue to spread across the
U.S. in the wake of the eastern trough as it continues progressing
off the middle and southern Atlantic Coasts tonight. Two
smaller-scale upstream short-wave troughs will shift through the
more westerly upstream flow regime — one crossing the Rockies and
reaching the Plains overnight, while the second reaches the Pacific
Northwest/northern and central California Coasts late.
Aside from a few lightning flashes which may occur near the end of
the period over the Pacific Northwest Coast area, showers and a
few/embedded thunderstorms will also continue to affect Florida
today. The convection is occurring primarily within a band that
extends from near Daytona to the Tampa area, along the initial
front/wind shift. This band will continue shifting southward in
conjunction with the frontal advance through this afternoon, before
moving offshore/south of the Keys this evening. With very weak
lapse rates across the area, yielding minimal CAPE, severe risk will