Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Oct 27 2024 19:22:25

ACUS03 KWNS 271922
SWODY3
SPC AC 271921

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0221 PM CDT Sun Oct 27 2024

Valid 291200Z - 301200Z

....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE CENTRAL PLAINS INTO THE UPPER MISSISSIPPI VALLEY...

....SUMMARY...
Isolated severe thunderstorms, with hail and strong wind gusts,
remain possible Tuesday night into early Wednesday morning, from the
central Plains north-northeastward into the upper Mississippi
Valley.

....Synopsis...
A pronounced mid-level trough will traverse the Four Corners region
Tuesday and eject into the Plains states Tuesday night into early
Wednesday morning. Through the day Tuesday, surface lee troughing
will encourage appreciable low-level moisture return ahead of a
surface front that is expected to be draped across the Plains states
through the period. Substantial mid-level inhibition should limit
robust thunderstorm development through much of Tuesday. However,
mid-level cooling should gradually overspread the moist axis ahead
of the surface cold front overnight, supporting at least scattered
thunderstorm development across the Plains states into the Upper MS
Valley into early Wednesday morning. Substantial low-level warm-air
advection associated with a strong low-level jet, overspread by
strong southwesterly 500 mb flow and accompanying cooler
temperatures, will yield destabilization amid increasing vertical
shear across the Plains states. Here, at least isolated severe
storms will be possible, mainly within the 06-12Z Wednesday morning
time frame.

....Central Plains into the Upper MS Valley...
Guidance consensus shows a 75+ kt southwesterly 500 mb speed max
ejecting into the central Plains from the central/southern Rockies
in the 06-12Z Wednesday time frame. At the same time, low to mid 60s
F surface dewpoints are expected to advect north-northwestward up to
the cold front. Forecast soundings depict an erosion of the capping
layer along the surface cold front, driven by 800-600 mb cooling, as
the aforementioned mid-level speed max overspreads the central High
Plains. 7-8 C/km mid-level lapse rates atop low to mid 60s F surface
dewpoints may yield over 1500 J/kg MLCAPE along the cold front over
the central Plains, with 500 J/kg MLCAPE over the Upper MS Valley. A
50-60 kt south-southwesterly low-level jet beneath the southwesterly
500 mb speed max will contribute to 50+ kts of effective bulk shear.
As such, transient supercells and small bowing line segments capable
of isolated severe hail/gusts could develop if adequate buoyancy can
develop ahead of the cold front before sunrise.

...Squitieri.. 10/27/2024

$$

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