Day 1 Severe Weather Outlook

Valid 312000Z – 011200Z

…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTH FL AND THE KEYS…

…SUMMARY…
A few severe storms may occur across parts of south Florida and the
Florida Keys this evening into tonight, with isolated damaging wind
gusts and perhaps a tornado or two.

…20Z Update…
No changes have been made to the Marginal and Slight Risk areas
across parts of south FL. An extensive band of thunderstorms is
ongoing this afternoon over the central Gulf of Mexico. This
activity is expected to track slowly eastward over the next several
hours, eventually approaching the Keys and south FL later this
evening and overnight. Additional storm development may occur this
evening in a modest low-level warm advection regime over the Keys
along a northward-advancing warm front. Surface dewpoints south of
this boundary have risen into the low 70s, with gradual
destabilization forecast to continue through the evening and
overnight.

An 18Z sounding from Key West FL shows around 1000 J/kg of MLCAPE
has already developed, along with strong effective bulk shear.
However, low-level winds remain weak. Isolated damaging winds remain
the primary threat, especially if the line of storms can maintain
its intensity and organization with eastward extent across south FL
and the Keys. A tornado or two still appears possible. This threat
should focus along/near the warm front across the Keys and far
southern FL Peninsula where greater low-level moisture will
contribute to a more unstable airmass and low-level winds will be
locally backed to southeasterly, locally enhancing effective SRH.

..Gleason.. 01/31/2020

.PREV DISCUSSION… /ISSUED 1006 AM CST Fri Jan 31 2020/

…South FL…
No changes have been made to the ongoing forecast. Morning water
vapor loop shows a low-amplitude shortwave trough moving into the
western Gulf of Mexico. Scattered thunderstorms have developed
ahead of this feature along a surface boundary that extends across
the central Gulf. 12z guidance is very consistent in this
convection building eastward into south FL and the Keys this
evening. Low-level moisture and instability will slowly increase
this afternoon prior to the arrival of storms, with sufficient
SBCAPE to pose a risk of surface-based storms across the SLGT risk
area. Deep layer shear values will promote the risk of
rotating/bowing storm structures capable of gusty/damaging winds or
perhaps a tornado or two. The period of greatest threat appears to
be from 03-09z tonight.

$$

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