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



$$