ACUS01 KWNS 191944
SPC AC 191943
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0243 PM CDT Mon Apr 19 2021
Valid 192000Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE CENTRAL FLORIDA PENINSULA...
Isolated severe thunderstorms remain possible through early tomorrow
morning across parts of the central and southern Florida Peninsula.
Minor changes have been made to the Day 1 Outlook. The northeast
extent of the Marginal across the central FL Peninsula was trimmed,
and severe probabilities across the Mid Atlantic were removed given
convective overturning of earlier storms. Thunder probabilities were
also removed from the Hudson Valley into New England as relatively
shallower convection, driven by boundary-layer mixing, has struggled
to support lightning flashes during peak heating. Otherwise, the
rest of the forecast remains on track, with a gradual increase in
thunderstorms and corresponding risk of severe hail, a damaging
gust, or brief tornado expected across the west-central FL peninsula
.PREV DISCUSSION... /ISSUED 1133 AM CDT Mon Apr 19 2021/
...Central/southern Florida Peninsula...
A corridor of convection continues to focus along a convectively
reinforced boundary across the south-central Peninsula/Lake
Okeechobee vicinity at midday. Destabilization through the afternoon
will likely be maximized to the south of the lingering midday
convection (where low/mid-level winds trend weaker), although some
measure of air mass recovery could occur a bit north into more of
the central Peninsula in closer proximity to the synoptic front.
Additional cloud breaks/heating may allow for some renewed
development/reinvigoration of storms this afternoon with a couple of
downbursts and/or marginally severe hail a possibility.
A lull in deep convection is expected this evening into the
overnight as low-level winds become quite weak and convergence
wanes. However, in response to the upstream shortwave trough
approaching the northwest Gulf of Mexico, extensive convection is
anticipated to form late tonight across the eastern Gulf. Some of
this convection may reach the west-central/southwest Florida
Peninsula early Tuesday with some increase in severe risk.
...Eastern North Carolina/far southeast Virginia...
Ahead of a low-amplitude shortwave trough crossing the Appalachians,
a modestly moist (around 60F surface dewpoints) and weakly unstable
warm sector resides across the region at midday in advance of a weak
front/surface trough. Thunderstorms will continue to develop across
the region through early afternoon before the warm sector shifts
offshore by late afternoon (likely by 21Z/5pm EDT). As low-level
lapse rates further steepen early this afternoon, instability may be
sufficient in the presence of long/semi-straight hodographs (atop a
near-surface easterly component) to allow for some strong/locally
severe thunderstorms capable of hail and/or wind gusts.