Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Aug 27 2023 07:29:15

ACUS03 KWNS 270729
SWODY3
SPC AC 270728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Sun Aug 27 2023

Valid 291200Z - 301200Z

....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
FLORIDA AND THE INTERIOR NORTHWEST/NORTHERN ROCKIES...

....SUMMARY...
The potential for isolated tornadoes may gradually increase across
parts of the Florida Gulf Coast vicinity through Tuesday night as a
tropical cyclone approaches. Other strong to severe thunderstorms
may occur Tuesday over interior portions of the Northwest into the
northern Rockies.

....Florida...
A tropical cyclone is forecast by the National Hurricane Center to
strengthen over the eastern Gulf of Mexico Tuesday through Tuesday
night as it moves generally north-northeastward towards portions of
the FL Gulf Coast. Low-level flow on the eastern half of this
cyclone will likely increase through the period over the eastern
Gulf and adjacent parts of the FL Gulf Coast. Elongated and curved
low-level hodographs will conditionally support some threat for
isolated tornadoes if low-topped supercells can develop in outer
rain bands. This tornado potential over land Tuesday night through
early Wednesday morning remains somewhat unclear given continued
uncertainty in the exact track of this tropical cyclone, and how
close it will approach the coast through the end of the Day 3
period. Regardless, it appears probable that increasing low-level
shear and at least weak boundary-layer instability Tuesday night
will overlap across parts of the FL Gulf Coast, warranting low
severe probabilities.

....Northwest/Northern Rockies...
An upper trough is forecast to move eastward across the Northwest on
Tuesday. Increasing mid-level south-southwesterly flow attendant to
this trough should overspread interior portions of the Pacific
Northwest into the northern Rockies through the day, supporting
generally 30-40 kt of deep-layer shear. Even though low-level
moisture should remain fairly modest, upper 40s to low 50s surface
dewpoints and daytime heating should foster some destabilization of
the boundary layer through Tuesday afternoon. Thunderstorms are
forecast to initially develop across eastern WA/OR, and spread
east-northeastward across northern ID and western MT through Tuesday
evening. Given various NAM/GFS forecast soundings showing a very
well-mixed boundary layer and steep low/mid-level lapse rates, some
of this convection may produce severe downdraft winds. Isolated hail
may also occur with any cells that can remain somewhat discrete. The
lack of stronger forecast instability precludes greater severe
probabilities at this time.

...Gleason.. 08/27/2023

$$

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