Day 1 Severe Weather Outlook

Valid 301300Z – 311200Z

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT
FROM THE NORTHERN GULF COAST TO THE TN VALLEY…

…SUMMARY…
A few strong to severe thunderstorms are possible during the day
across the northern Gulf Coast states, with a threat evolving
overnight into parts of Tennessee. Localized wind damage or a brief
tornado will be possible.

…Northern Gulf coast to TN Valley through tonight…
A pronounced midlevel shortwave trough over CO will progress
eastward toward MO tonight, while strengthening and taking on a more
neutral tilt. Surface cyclogenesis is expected downstream from the
midlevel trough, across the lower OH Valley overnight along a
pre-existing baroclinic zone. South of the developing cyclone, the
cold front will begin to surge eastward tonight across the lower MS
and TN Valleys.

Low-level moisture is spreading north-northeastward this morning
across southern MS/AL, and the warm sector should expand northward
into the TN Valley by tonight. Some surface heating will occur
today across central/southern MS/AL where cloud breaks occur in the
warm sector. However, the warm-advection pattern observed this
morning, and related low-level shear, will tend to weaken through
the afternoon. The net result will be a low-end threat for rotating
storms this morning near the coast and within the expanding warm
sector inland later today, with the possibility for isolated strong
gusts and/or a brief tornado.

Overnight, convection should begin to organize in a band along the
surging cold front from northeast MS into northern AL and middle TN.
Low-midlevel lapse rates will be poor, but weak surface-based
buoyancy will be driven largely by boundary-layer dewpoints in the
upper 60s north to lower 70s south. Strengthening deep-layer
flow/vertical shear in conjunction with the OH Valley cyclogenesis,
and the weakly unstable warm sector (MLCAPE near 500 J/kg) will
favor some threat for damaging gusts with the frontal convection,
mainly after 06z.

..Thompson/Smith.. 10/30/2019

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