LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1234 AM CDT Mon Sep 25 2023
Valid 251200Z - 261200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PORTIONS OF
SOUTHERN TEXAS AND CENTRAL FLORIDA...
...SUMMARY...
Isolated strong to severe thunderstorms will be possible across
parts of Texas and Florida today.
...Synopsis...
Strong to severe thunderstorm potential is expected to remain
confined to southern portions of Texas and the Florida Peninsula for
today. An occluding low over the upper MS River Valley will continue
to weaken as an attendant mid-level impulse shifts east through the
day. In its wake, upper-level ridging will become established across
the Intermountain West. This synoptic regime will favor a gradually
building surface high over the Plains (as evidenced by steady
pressure rises over the past 12 hours). As a result, the diffuse
cold front draped across the southern Plains will continue to
migrate south through the day, and will be a focus for thunderstorm
development later this afternoon and evening.
...Texas...
Latest forecast guidance shows reasonably good agreement in the
southward progression of the cold front across southern TX today.
This boundary may be convectively reinforced by ongoing thunderstorm
clusters across eastern TX at the start of the period. This
early-morning convection may re-intensify and pose a severe wind
threat for the TX coastal plain during the afternoon hours amid
diurnal warming of a moist air mass downstream. To the west, closer
to the Edwards Plateau and the Big Bend region, thunderstorm develop
along the cold front is expected by mid/late afternoon. MLCAPE
values are forecast to reach near 2000 J/kg as temperatures warm
into the low to mid 90s. Although mid-level winds will be somewhat
modest (20-30 knots), southeasterly low-level flow will support
elongated hodographs with effective bulk shear values near 30-40
knots. Such wind profiles and weak ascent along the front may
support initially discrete modes, including the potential for a
supercell or two with an attendant large-hail threat. However,
deep-layer shear and storm-motion vectors largely along the frontal
boundary may favor a tendency for storm clustering through the late
afternoon/evening. Thunderstorm development off the higher terrain
of the Davis and Serranias del Burro mountains may also support
discrete supercells, but confidence in storm coverage via orographic
ascent is limited.
...Florida...
A weak tropical low north of the Yucatan Peninsula is establishing a
plume of rich moisture into FL (as sampled by 00z soundings).
Moderate heating of this air mass through the day should support a
modestly buoyant, but uncapped environment (MLCAPE upwards of 1000
J/kg) by mid afternoon over central FL. Glancing ascent from the
passing mid-level trough to the north will support scattered to
widespread thunderstorms, and may sufficiently strengthen mid-level
flow to support effective bulk shear values between 20-25 knots.
Although the kinematic environment will be meager, a few instances
of hail approaching severe criteria are possible. Additionally,
steepening low-level lapse rates and PWAT values approaching 2
inches will be conducive for wet downbursts capable of strong to
severe winds.
..Moore/Leitman.. 09/25/2023
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