Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Mon Sep 28 2026
Valid 281630Z - 291200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS...
...SUMMARY...
Isolated strong to severe thunderstorms may occur this afternoon and
evening across parts of western/northern South Dakota and vicinity.
...Northern Plains...
Clouds and elevated thunderstorms remain prevalent late this morning
across parts of the Dakotas. A narrow window for strong to locally
severe thunderstorms may exist this afternoon/evening across parts
of western/northern SD and vicinity as convection develops
along/east of a weak surface trough. While lapse rates aloft should
remain modest, filtered daytime heating with surface temperatures
reaching the mid/upper 70s will probably be sufficient for robust
thunderstorm development. A belt of modestly enhanced southwesterly
mid-level flow will extend across the northern Rockies/Plains today,
and 30-40 kt of deep-layer shear should support updraft
organization. Current expectations are for thunderstorms to
initially form near the Black Hills by 20-22Z, and then spread
east-northeastward along/near a surface front through the evening.
The stronger cells may be capable of producing isolated hail and
gusty winds, before convection tends to become elevated with
eastward extent across northern SD/southern ND by late evening.
...Lower Colorado River Valley...
Showers and thunderstorms should develop this afternoon as an
anomalously moist low-level airmass spreads northward ahead of a
mid-level shortwave trough forecast to move from CA/NV to the lower
CO River Valley through the period. Cloudiness and weak mid-level
lapse rates should limit instability through early afternoon, before
cloud cover gradually diminishes through early evening. A stronger
thunderstorm or two may occur parts of interior southern
CA/northwest AZ/southern NV, but the overall risk for severe
hail/wind appears too limited to include any probabilities for this
region at this time.
..Gleason/Chalmers.. 09/28/2026
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