ACUS01 KWNS 231254
SWODY1
SPC AC 231252

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0752 AM CDT Sun Aug 23 2026

Valid 231300Z - 241200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN ROCKIES/PLAINS AND GREAT BASIN...

...SUMMARY...
Thunderstorms capable of producing large hail and severe/damaging
winds are forecast across parts of the northern Rockies/Plains this
afternoon and evening. Other thunderstorms with mainly a severe wind
threat may occur over portions of the northern Great Basin.

...Great Basin into the Northern Rockies/High Plains...
A mid-level shortwave trough evident on water vapor satellite
imagery this morning across the Pacific Northwest will move
east-northeastward today across the northern Rockies and western
Canada. 40-50 kt of west-southwesterly mid-level winds will
overspread the northern Rockies and adjacent High Plains of
central/eastern MT by this afternoon. As large-scale ascent
preceding the mid-level trough spreads eastward, thunderstorms
should initially form over the higher terrain of western MT.
Downstream destabilization of a sufficiently moist low-level airmass
will support the development of weak instability (MLCAPE generally
500-1000 J/kg) into central/eastern MT and vicinity. 30-40 kt of
effective bulk shear will support a mix of multicells and supercells
initially moving off the higher terrain, with both severe hail and
wind gusts possible. With time, upscale growth into bowing clusters
seems probable with eastward extent in MT, and an increasing risk
for severe/damaging winds. Given the very well-mixed boundary layer
and enhanced mid-level flow expected, some of these gusts could
exceed 75 mph on an isolated basis.

A somewhat separate area of convection should develop this afternoon
across parts of the northern Great Basin. While mid-level flow will
be somewhat weaker across this region compared to locations farther
north, the presence of generally 50s surface dewpoints across
northern UT and vicinity suggests that sufficient low-level moisture
exists to support robust updrafts. As daytime heating occurs and
low-level lapse rates steepen, loosely organized cells/clusters
should form and subsequently spread northeastward while posing a
threat for scattered severe gusts.

...Northern/Central Plains...
A band of elevated thunderstorms is ongoing this morning from
southern SD into NE, aided by modest low-level warm/moist advection.
This activity should gradually weaken through the morning as the
low-level jet subsides, but an isolated threat for severe hail may
continue in the short term given sufficient MUCAPE and deep-layer
shear to support supercells. A narrow corridor of moderate to
locally strong instability is forecast to develop this afternoon
across the western Dakotas/NE along/east of a lee surface trough
where greater low-level moisture will reside. At least isolated
thunderstorms should develop by peak afternoon heating across these
areas, with west-northwesterly flow strengthening with height
through mid/upper levels. Around 35-45 kt of deep-layer shear will
support supercells and associated threat for large hail with any
sustained surface-based convection.

Overall coverage remains uncertain given weak/nebulous large-scale
ascent, but some guidance shows these cells growing upscale into a
cluster or two this evening with some severe wind risk. Regardless,
severe hail should be the main concern with supercells initially,
and the Slight Risk has been nudged westward a little to account for
the probable zone of initiation. Weaker mid-level flow is expected
with southward extent into the central High Plains, but occasional
hail and gusty winds could still occur with any high-based
convection that develops and spreads eastward through the early
evening.

...Northeast Oklahoma/Southeast Kansas into the Ozarks...
A weak mid-level disturbance aiding convection this morning over
SD/NE will move southeastward today on the eastern periphery of
upper ridging centered over the southern High Plains/Southwest. This
feature, in tandem with increasing isentropic ascent associated with
a modest south-southwesterly low-level jet, may aid thunderstorm
development late tonight into early Monday morning across parts of
northeast OK/southeast KS into the Ozarks. Instability is forecast
to remain fairly weak (MUCAPE generally less than 1000 J/kg), but
some clustering may occur with a low chance for gusty/locally
damaging winds. No changes have been made to the Marginal Risk
across this area, as confidence remains limited in both overall
convective intensity and evolution.

...Northeast...
An upper trough/low centered over Ontario and the Great Lakes this
morning will translate slowly eastward across the Mid-Atlantic and
Northeast through the period. A corresponding weak/occluding surface
low will make only modest eastward progress into Quebec through the
day, with a cold front forecast to move eastward across parts of the
Mid-Atlantic/Northeast by this evening. Cloud cover is prevalent
across these regions per latest visible satellite imagery. This,
coupled with poor lapse rates aloft (reference 12Z observed
soundings from ALB/OKX), will limit the amount of destabilization
that can occur through this afternoon with filtered daytime heating.
Still, enhanced south-southwesterly mid-level flow will be present
today across parts of NY into New England, with around 30-35 kt of
deep-layer shear supporting some updraft organization. Current
expectations are for cells and clusters that develop along/ahead of
this front this afternoon to pose a threat for mainly isolated
damaging winds as they spread east-northeastward through this
evening before eventually weakening. Marginally severe hail may also
occur with the strongest cores. But, the weak instability and poor
lapse rates aloft should generally limit the overall severe threat.

...Southeast...
Isolated to scattered thunderstorms should develop later today
along/south of a weak front draped across the lower MS Valley into
the Gulf Coast states, and continuing northeastward into the
Carolinas. With the exception of the Carolinas, low/mid-level flow
will remain quite weak for much of the Southeast. Still, any cells
which can develop may pose an isolated threat for damaging winds, as
moderate to strong MLCAPE coupled with steep low-level lapse rates
through daytime heating support the potential for wet microbursts.
On the southern periphery of mid/upper troughing over the Great
Lakes/Mid-Atlantic and Northeast, stronger flow aloft will exist
across the Carolinas. This may foster some updraft organization
given sufficient deep-layer shear. But, most guidance continues to
show any convection that forms this afternoon across the eastern
Carolinas will move quickly offshore.

...Arizona...
To the west of a mid/upper-level anticyclone centered over the
southern Rockies/High Plains, weak southeasterly mid-level flow will
exist today across southern/central AZ. Instability across this
region is forecast to remain rather muted/weak owing to shallow
low-level moisture. A deeply mixed boundary layer is forecast to
develop with robust daytime heating, but confidence in thunderstorms
developing over the higher terrain of southeast AZ and subsequent
clustering into the lower deserts remains low. Even so, have
maintained the Marginal Risk for severe gusts with no changes.

..Gleason/Broyles.. 08/23/2026

$$