Day 1 Severe Weather Outlook

Valid 041300Z – 051200Z


Isolated thunderstorms may occur across portions of the southeastern
US and the Big Bend of Texas.

A high-amplitude, blocky pattern will persist in mid/upper levels,
featuring a mean ridge over the northeast Pacific, just offshore
from CA to the Gulf of Alaska, and longwave troughing over
east-central North America. Associated cyclonic flow will cover
most of the CONUS from the Rockies to the East Coast. A small,
cut-off 500-mb cyclone will remain offshore from southern CA and
northern Baja, with slight southward drift progged. A difluent
southern-stream pattern will persist downstream over southern AZ and
Sonora, becoming confluent in a merger with the cyclonic longwave
pattern across southern NM and west TX.

At the surface, 11Z analysis showed a wavy, quasistationary front
across southern FL and west-southwestward over the adjoining eastern
Gulf. This boundary is weakening — a trend that will continue
through the period, with surface moisture-theta-e axes already
becoming prominent to its north, offshore from both the east and
west coasts of the FL Peninsula.

…TX Big Bend region…
Beneath the aforementioned upper difluence, weak, residual
low/middle-level moisture, diurnal heating, orographic forcing, and
low-level warm advection will support thunderstorm development again
today over the high terrain of northwestern MX, some of which may
affect the Big Bend region before dissipating. Forecast soundings
suggest a well-mixed subcloud layer may support strong gusts with
any strong cells that can affect the area prior to substantial
nocturnal near-surface cooling, but severe potential appears too low
and conditional for an outlook area.

Isolated thunderstorms are possible mainly this afternoon through
tonight over outlined land areas. Northward spread of favorable
boundary-layer theta-e is expected through the FL Peninsula as the
frontal zone becomes more diffuse, with convection focused best
along sea-breeze and outflow boundaries. A secondary coverage
maximum is expected the latter half of the period across the Gulf
south of the FL Panhandle, and over Gulf Stream waters of the
Atlantic, each in a regime of relative maxima in:
1. Supportive sea-air thermodynamic fluxes, already contributing to
the moist axes noted above, and
2. Low-level lift in confluence/convergence zones developing south
to southeast of weak surface waves over the northeast Gulf and
offshore from JAX.

..Edwards.. 11/04/2019


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