Day 1 Severe Weather Outlook

Valid 251300Z – 261200Z

…NO SEVERE THUNDERSTORM AREAS FORECAST…

…SUMMARY…
Thundersorms are possible through tonight over parts of the
Southeast. Strong gusts may occur over parts of northern Florida.

…Synopsis…
In mid/upper levels, a sharply defined ridge is present over the
West Coast, while broadly cyclonic flow covers most of the CONUS
downstream. Moisture-channel imagery indicates a primary vorticity
max/circulation center over the central High Plains. This will
phase with a speed max/vorticity banner over the Four Corners region
and accelerate eastward, resulting in a strong, positively tilted
trough by 12Z tomorrow from the upper Mississippi Valley across the
Ozarks and Arklatex to southwest TX. To its southeast, a broad
fetch of west-southwesterly to southwesterly flow, with very gradual
cyclonic curvature, will extend from central/northern MX across the
western/northern Gulf, across southern GA and northern/central FL.

At the surface, 11Z analysis showed a low near SDF with an
occluded/cold front across eastern TN, southeastern AL, and the
north-central/northwest Gulf to south of BRO. A secondary/
reinforcing cold front was drawn from the low across central MS and
south-central TX. The first front will move slowly southeastward
prior to being overtaken by the second. By the end of the period,
the combined cold front should extend from a triple-point low near
southeastern VA or the Delmarva Peninsula southwestward across the
central Carolinas, eastern Fl Panhandle and central/southwestern
Gulf.

…FL…southern GA…
A west-southwest/east-northeast belt of widely scattered to
scattered thunderstorms has formed across parts of the northeastern
Gulf, as evident in satellite and composited radar imagery. The
associated zone of prefrontal low-level lift should continue through
much of the period, with some baroclinic reinforcement possible
along its own outflow edge, further reinforcing lift. Thunderstorms
should continue to form over the Gulf, then train along this
corridor, moving over a relatively low-theta-e, incompletely
modified inland air mass for most of the day. Additional convection
may develop across southern GA in a regime of weak capping and
favorable diurnal heating for MLCAPE around 500-1000 J/kg. While
flow aloft will be strong, weak and mostly veered low-level winds
will keep hodographs small and lift subtle, amidst messy storm
modes. In both regimes, while isolated strong gusts cannot be ruled
out, severe potential appears minimal for most of the day.

Late this afternoon into evening, veering of low-level flow is
forecast across western parts of central/northern FL, which will
offer offsetting effects in terms of severe potential:
1. Increase in boundary-layer moisture through more-direct
advection from the Gulf, which will boost theta-e and buoyancy, but
2. Reduced low-level hodograph size, though favorable deep shear
should remain with effective-shear magnitudes around 45-55 kt.
Weak mid/upper-level lapse rates should keep MLCAPE generally below
500 J/kg, with the possible exception of near-coastal areas closest
to the best-modified Gulf boundary layer.

While the most intense convection should remain well out across Gulf
waters, some possibility exists for short-lived organization of
convection into bow/LEWP formations, which would increase localized
gust potential. At this time, the risk appears too uncertain and
low for an unconditional/categorical severe area, though later progs
and mesoscale trends will be monitored in the event the parameter
space and potential storm mode may become more favorable over land.

..Edwards/Dial.. 02/25/2020

$$

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