Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0146 AM CDT Fri Aug 21 2026

Valid 211200Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL PLAINS...THE MIDWEST AND THE CAROLINAS...

CORRECTED FOR TEXT

...SUMMARY...
Scattered damaging hail (some greater than 2 inch diameter) and
severe wind gusts may occur over parts of the central Plains this
afternoon and evening. Scattered storms, some with severe wind gusts
and hail, also are possible across parts of the Midwest. Scattered
to numerous storms with damaging wind gusts are possible over the
Carolinas and Southeast.

...Central Plains...
Mid-level ridging over the western US is forecast to intensify,
strengthening northwesterly flow aloft over much of the central US.
Several embedded disturbances will pass overhead with the enhanced
northwesterlies through the day. A surface low will move
southeastward through the Great Lakes as a weak trailing cold front
moves southward through the central Plains and Midwest.

Ahead of the front, a plume of steep mid-level lapse rates will
shift eastward across the central Plains toward the Mid-MO Valley
atop a corridor of rich low-level moisture. Diurnal destabilization
should result in 3000-4000 J/kg of MLCAPE from SD to NE. Isolated to
widely scattered thunderstorm development is expected from the Black
Hills southeastward along the cold front. Elongated/straight
hodographs and 45+ kt effective shear will favor initial supercells.
Large to very large hail (some greater than 2 inches diameter) will
be possible. With time, a forward propagating cluster or two may
develop and move southeast across parts of NE and KS with the
potential for severe gusts (a few near 70-80 mph). It is unclear
exactly how far southeast any storms will persist overnight, but any
more substantial clustering could allow at least an isolated severe
threat to continue into early Saturday.

A much drier and hotter environment over the High Plains to the west
could also support isolated to widely scattered high-based storms
from eastern CO into western KS. Very steep lapse rates in the
lowest 2-3 km with modest buoyancy aloft could allow a few severe
gusts.

...Midwest...
Beneath the upper trough over the western Great Lakes, cool
mid-level temperatures and robust surface moisture should result in
moderate destabilization from WI into eastern IA and northwest IL.
Scattered thunderstorms by mid afternoon ahead of the cold front
spreading southeastward. Enhanced northwesterly flow with deep-layer
shear of 30-40 kt will promote a mix of organized clusters and
supercells. The large buoyancy will support a risk for damaging
gusts and some hail.

...Southeast and Gulf Coast...
A broad upper trough will move across the central US into parts of
the southern Appalachians while a weak cold front moves southward
from the mid Atlantic today and tonight. Weak ascent from the upper
trough and near the front should focus diurnal thunderstorm activity
across the Carolinas and southern Appalachians. Warm surface
temperatures and plentiful boundary-layer moisture will support
large buoyancy (3000+ J/kg MLCAPE) through the afternoon and evening
despite modest mid-level lapse rates. With scattered to numerous
storms expected, a few organized clusters may emerge with a risk
primarily for damaging wind gusts. Slight enhancement of the
westerly flow aloft could also support some isolated hail with the
stronger updrafts.

Farther south and west, a very humid and warm air mass is forecast
to become strongly unstable by early afternoon across the lower MS
Valley and Gulf Coast. Scattered to numerous thunderstorms are
expected along prior outflows and a weak, southward moving cold
front from East TX into LA/MS. The very strong buoyancy and high
PWAT content will support clustering and strong downdrafts with
sporadic damaging gust potential. Otherwise, weak vertical shear
will limit overall organization.

..Lyons/Weinman.. 08/21/2026

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1248 AM CDT Fri Aug 21 2026

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR NORTHERN
IDAHO AND WESTERN MONTANA...THE CENTRAL HIGH PLAINS...ARKANSAS AND
VICINITY...AND THE OHIO VALLEY...

...SUMMARY...
Strong to severe thunderstorms capable of wind gusts and isolated
large hail will be possible in the Ohio Valley and Arkansas
vicinity. Severe gusts are possible across the central High Plains
and northern Idaho into western Montana.

...Northern Idaho and western Montana...
A strong mid-level shortwave trough will move into the Northwest on
Saturday with modest diffluence ahead of it during the day. Strong
heating should result in steep lapse rates and weak instability
across the region. Storms should develop over the mountains by
midday and advance northeast. As 6km flow strengthens to ~40 knots
by mid-afternoon, adequate shear should be in place for a few
organized storms. The steep lapse rates and inverted-v thermodynamic
profile will support severe wind gusts as the primary threat. 

...Central High Plains...
Diurnal, terrain driven thunderstorms will develop by early
afternoon and eventually move into the adjacent Plains by late
afternoon/evening. Forecast soundings show moderate to potentially
strong instability across the Plains with moderately steep lapse
rates and dewpoints perhaps into the low 60s. The primary limiting
factor will be shear with less than 30 knots of flow below 300mb.
However, enough flow should be present, when combined with the
moderate to strong instability, to support some storms capable of
severe wind gusts. 

...Arkansas and Vicinity...
The most favorable environment across the CONUS on Saturday appears
to be from eastern Kansas to Arkansas beneath a belt of stronger
mid-level flow where moderate to strong instability may also be in
place. This environment would even support supercells. However,
storm coverage remains uncertain. Added a small 5% in the Arkansas
vicinity where at least isolated storms appear most likely. However,
with relatively nebulous forcing, perhaps related to remaining
convection from Friday, confidence is low where the strongest storms
may occur. 

...Ohio Valley...
A mid-level shortwave trough will amplify across the Great Lakes on
Saturday and become negatively tilted toward the end of the period.
As this occurs, a surface low will deepen somewhat across southern
Ontario with a cold front sweeping across Ohio and northern Kentucky
through the day. Despite relatively weak heating across the region
due to extensive cloud cover, moderate instability is forecast to
develop amid upper 60s dewpoints and cooling temperatures aloft.
This, combined with 25 to 30 knots of shear, should be sufficient
for multicells and occasional supercells capable of primarily
damaging wind gusts.

..Bentley.. 08/21/2026