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