Mesoscale Discussion 2326
NWS Storm Prediction Center Norman OK
0348 PM CDT Wed Sep 23 2026

Areas affected...parts of southwestern North Dakota and adjacent
portions of southeastern Montana and northwestern South Dakota

Concerning...Severe potential...Watch unlikely 

Valid 232048Z - 232245Z

Probability of Watch Issuance...5 percent

SUMMARY...Isolated strong thunderstorm development posing at least a
risk for severe hail appears increasingly probable by 4-6 PM MDT. 
This may be maintained for a couple of hours late this afternoon
into evening.  Although this is still not anticipated to require a
severe weather watch, trends will be monitored.

DISCUSSION...Stronger boundary-layer warming and deeper mixing has
become focused near a weak surface low across the southeastern
Montana/western Dakotas border vicinity, with some
north-northeastward development still possible through late
afternoon.  Near the interface of this environment, and a narrow
corridor of better low-level moisture return to the north/east, it
appears that boundary-layer destabilization may maximize around the
Dickinson, ND vicinity by 22-00Z.   

Aided by lift associated with a corresponding focused area of
stronger low-level warm advection, as low-amplitude mid-level
troughing continues to overspread the region, it appears that
thunderstorms will initiate as remaining inhibition erodes.  Near
and just to the northwest of a strong southwesterly mid/upper jet
(including speeds on the order of 40-70 kt in the 500-700 mb layer),
updraft inflow of boundary-layer air characterized by CAPE up to
1000+ J/kg may support an evolving supercell structure.  As this
tends to propagate eastward, or east-southeastward, it may pose
primarily a risk for severe hail, with perhaps some potential for
locally damaging surface gusts and/or a brief tornado, for at least
a couple of hours late this afternoon into evening.

..Kerr/Mosier.. 09/23/2026

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...ABR...BIS...UNR...GGW...

LAT...LON   47460273 46080146 45570280 46370359 47070444 47460273 

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0258 PM CDT Wed Sep 23 2026

Valid 232000Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PATS OF
THE WESTERN DAKOTAS...

...SUMMARY...
Isolated severe thunderstorms are possible this afternoon across
parts of the western Dakotas.

...20Z Update...

The forecast for this afternoon remains largely on track. Isolated
damaging wind gusts and severe hail are possible late this afternoon
across portions of the Western Dakotas, where moisture pooling has
resulted in upper-50s to low-60s F dewpoints coincident with
clearing on visible satellite. Moderate deep-layer shear and modest
buoyancy will support organized storms and potentially transient
supercells. Given the potential for supercells, adequate buoyancy
and shear combinations, and cooler temperatures aloft, a CIG 1 area
was introduced to highlight the potential for isolated occurrences
of 2" hail, particularly with any stronger/more organized supercell
structures. See the previous discussion for more details.

..Halbert/Lyons.. 09/23/2026

.PREV DISCUSSION... /ISSUED 1122 AM CDT Wed Sep 23 2026/

...Western Dakotas...
Recent surface analysis placed a low over far southeast MT, with a
lee trough extending southward from this low across the High Plains
into far West TX. A plume of moderate low-level moisture exists just
east of this troughing, with upper 50s dewpoints currently reaching
into southwest SD and mid 50s into western ND. This lee trough will
help facilitate the maintenance of this moisture plume as the
shortwave trough currently moving through WY and eastern MT
continues northeastward into the region today and tonight. 

Widely scattered thunderstorms are forecast to develop as convective
inhibition erodes in the vicinity of the lee trough and the Black
Hills this afternoon.  Strengthening southwesterly flow aloft will
result in moderate deep-layer vertical shear (i.e. 30 to 40 kt from
0-6 km) amid 500 to 1000 J/kg of MLCAPE. This shear may aid in some
storm organization potential, with the stronger thunderstorms
perhaps yielding an isolated risk for marginally severe hail/gusts
through early evening.  

...Southern Appalachians...
Recent visible satellite imagery shows widespread low stratus across
both the Mid-Atlantic/Carolinas and farther east over much of the TN
Valley. There is corridor between these regions from roughly
northwest GA across far eastern TN/far western NC into far western
VA where less low-level cloud cover is in place, replaced by more
vertically developed structures. Temperatures in this region range
from the upper 70s across northwest GA to the upper 60s/low 70s
across far western VA. There is also slightly greater low-level
moisture in this region (i.e. low 70s dewpoints), and these
thermodynamic conditions are supporting modest buoyancy. This
buoyancy explains the deeper clouds and recent lightning that has
been observed in eastern TN. Thunderstorm activity will likely
persist in this region throughout the day, supported by large-scale
ascent attendant to an approaching shortwave trough and mesoscale
convergence on an inverted surface trough that extends from southern
AL into the southern KY/VA border vicinity. Some increase in the
mid-level flow is anticipated as the shortwave moves through, but
modest buoyancy and a mostly cluster multicellular mode should keep
severe potential low. As such, removed the 5% wind probabilities
across the region.

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0228 PM CDT Wed Sep 23 2026

Valid 251200Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected on Friday.

...Synopsis...
The Northwest upper trough will progress into the northern Rockies
on Friday. The upper ridge in the Plains will flatten as small-scale
mid-level shortwave troughs move through the central Rockies into
the Plains. The moisture plume within the Southwest will continue to
stream into the central Rockies and adjacent Plains. This should
lead to continued areas of cloud cover and precipitation that will
shift eastward with time. Weak mid-level lapse rates and generally
limited destabilization should limit the potential for organized
severe storms.

..Wendt.. 09/23/2026

Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0154 PM CDT Wed Sep 23 2026

Valid 241200Z - 251200Z

Only minor adjustments were made to the Day 2/Thursday Elevated fire
weather risk area across the Northwest; otherwise, the forecast
remains on track. Please see the previous discussion for details.

..Elizalde-Garcia.. 09/23/2026

.PREV DISCUSSION... /ISSUED 1200 AM CDT Wed Sep 23 2026/

...Synopsis...
An upper-level trough approaching the Pacific Northwest will promote
an increasing fire weather threat across northwestern portions of
the Great Basin Thursday. Upper-level ridging will persist across
the south-central U.S. while a surface low strengthens in the
adjacent Mid-Atlantic waters.

...Northwestern Great Basin...
The next mid/upper trough will approach the Pacific Northwest on
D2/Thursday. A surface lee trough emerges across eastern OR/WA as
strengthening mid-level southwesterly flow pushes into the Pacific
Northwest. Resultant southwest winds of 15-20 mph and afternoon RH
reductions in the 15-25% range within a dry and well-mixed boundary
layer will bring Elevated fire weather conditions to portions of
northeastern CA, northwestern NV and southeastern OR late Thursday
morning into the afternoon. Although fuels are not expected to be
critically dry, annual ERC values remain above normal nearing the
80th percentile in some areas which could support fire spread within
the dry and breezy environment.

...Please see www.spc.noaa.gov/fire for graphic product...