ACUS02 KWNS 210554
SWODY2
SPC AC 210553

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1253 AM CDT Tue Apr 21 2026

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE HIGH PLAINS...

...SUMMARY...
Severe thunderstorms capable of hail and gusty winds may develop
during the late afternoon and evening on Wednesday across portions
of the High Plains.

... Synopsis ...

A closed upper low across the western US will devolve into an open
wave as it lifts northeast toward the northern Plains. At the same
time, a surface low will gradually deepen as it moves across
northern Montana east into North Dakota by Thursday morning.

Lee troughing will strengthen during the day with the approach of
the western trough. The surface wind field within this lee trough
will function to sharpen a dryline from the surface low south across
much of the High Plains. To the east of the dryline, strengthening
southerly winds will draw Gulf moisture northward into the
strengthening cyclone. The quality of this moisture return remains a significant source of uncertainty regarding thunderstorm chances
with northward extent.

... Northern High Plains including areas of eastern Montana...

By late afternoon increasing large-scale ascent, driven by modest
height falls, will overspread northern portions of the dryline.
Despite moisture concerns, isolated to scattered thunderstorms
should develop across portions of the dryline during the afternoon.
Large temperature/dewpoint spreads may support strong wind gusts
with the strongest storms.

The best synoptic scale forcing for ascent will move across portions
of eastern Montana during the late afternoon and evening. Should
boundary layer moisture be richer than currently anticipated (e.g.,
closer to 40F than 25F), a threat for marginally severe wind gusts
may materialize. This area will continued to be assessed in
subsequent outlooks for an upgrade to Level 1/Marginal.

... Southern High Plains ...

Midlevel height falls will not be as great here as compared to areas
farther north. However, richer boundary layer moisture and strong
dryline circulations aided by temperatures approaching 90F to the
west of the dryline should support at least isolated thunderstorm
development. Around 40 knots of cloud-layer shear should support at
least a marginal hail risk with any storm that develops.

..Marsh.. 04/21/2026

$$

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