Subj : DAY1SVR: Day 1 Convective Outlook
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Dec 18 2022 12:49:48

ACUS01 KWNS 181249
SWODY1
SPC AC 181248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0648 AM CST Sun Dec 18 2022

Valid 181300Z - 191200Z

....NO SEVERE THUNDERSTORM AREAS FORECAST...

....SUMMARY...
A few thunderstorms are possible over south Florida and the Keys
today, and across parts of south Texas and southwestern Louisiana
overnight.

....Synopsis/Discussion...
The CONUS mid/upper-level pattern will be characterized largely by
decreasing amplitude and progressive shortwaves.  A
long-lived/occluded cyclone -- its center apparent in
moisture-channel imagery over ON north of Lake Huron -- will
continue to weaken as it moves eastward to southwestern QC through
the period.  A basal shortwave trough -- initially located over
parts of the mid/upper Ohio Valley -- will move offshore from the
Mid-Atlantic Coast this evening.  As this occurs, heights will rise
across FL through the period, and a currently quasistationary front
over south FL will drift southward again as a cold front.  Isolated
to widely scattered thunderstorms are possible along and ahead of
the front, in an air mass characterized by 70s F surface dewpoints,
modest midlevel lapse rates, weak low-level winds/shear, and
500-1500 J/kg MLCAPE (slightly higher values possible in the Keys,
per 12Z KEY sounding). The boundary should move out of southernmost
mainland FL and the Keys this afternoon, taking deep-convective
potential with it.

Elsewhere, a well-defined/southern-stream shortwave trough was
evident over southern CA and northern Baja.  This feature is
forecast to assume more-positive tilt through the period, as its
northern part ejects eastward faster than the southern portions.  By
12Z tomorrow, the trough should extend from central KS across the TX
Panhandle, the ELP area, and northern Sonora.  A broad plume of
low-level warm advection will precede this trough, well north of the
central/western Gulf segment of the aforementioned surface front.
Isolated, elevated thunderstorms may develop tonight and especially
after 06Z over south TX and southwestern LA, as increasingly moist
parcels are lifted isentropically to an LFC located mainly between
700-800 mb, with MUCAPE reaching 300-800 J/kg.

...Edwards/Kerr.. 12/18/2022

$$

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