256
ACUS03 KWNS 200728
SWODY3
SPC AC 200727

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 AM CDT Wed Aug 20 2025

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE CENTRAL/NORTHERN HIGH PLAINS INTO THE UPPER MIDWEST...

...SUMMARY...
Strong to locally severe thunderstorms are possible Friday from
parts of the central and northern High Plains into the Upper
Midwest.

...Northern Great Lakes to the Central High Plains...
A seasonably deep mid/upper-level trough is forecast to dig
southeastward across parts of the central/northern Plains into the
Upper Midwest/Great Lakes on Friday. A surface low is forecast to
move across northwest Ontario, as a trailing cold front continues
southeastward across parts of the central Plains and Upper Midwest.
A secondary cold front is forecast to move across the northern
Plains and northern MN, with a much drier airmass expected behind
this secondary front.

As the mid/upper-level trough digs into the region during the
afternoon and evening, isolated to widely scattered storm
development will be possible from Upper MI into parts of
WI/IA/southeast MN and eastern NE. Relatively weak midlevel lapse
rates may tend to limit updraft intensity to some extent, but
moderate MLCAPE and 25-35 kt of effective shear within the
west-northwesterly flow regime may support some storm organization,
with a threat of isolated hail and damaging gusts.

Farther west, strong to locally severe storms may develop within a
post-frontal regime across parts of eastern WY/CO and the NE
Panhandle. Relatively steep midlevel lapse rates could support
isolated hail with the strongest storms, with localized strong gusts
also possible.

...Arizona...
Scattered thunderstorms will again be possible across parts of AZ on
Friday, within a similar regime to D2/Thursday. Locally gusty winds
will be possible with the strongest storms, along with some
potential for outflows to spread into the lower elevations. Trends
will be monitored regarding the potential for a greater coverage of
damaging gusts.

..Dean.. 08/20/2025

$$