258
ACUS01 KWNS 232001
SWODY1
SPC AC 231959

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Sun Aug 23 2026

Valid 232000Z - 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 wind gusts
are forecast across parts of the northern Rockies/Plains this
afternoon and evening.  Other thunderstorms with mainly a severe
wind threat are probable over portions of the northern Great Basin.

...20z Update...

...Northern Rockies/Plains and Great Basin...
Subtle adjustments were made to the existing Marginal/Slight risk
areas based on ongoing convective trends. Recent CAM/TLE guidance
suggests that upscale growth of convection into one or more linear
clusters may result in localized corridors of greater
damaging/severe wind coverage across portions of northern Utah and
central Montana. The evolution of this scenario remains somewhat
uncertain, however, which precludes the addition of 30% wind
probabilities at this time. See MCDs 2099, 2100, and 2101 for
additional short-term details.

...Coastal Carolinas...
Recent mesoanalysis and observational data depict modestly elongated
hodographs and effective shear around 35 kts in place across
portions of the Coastal Carolinas. Despite poor mid-level lapse
rates, this may allow for the occurrence of isolated, marginally
severe hail with the most robust updraft cores. Thus, a targeted 5%
hail probability area was included with this update, which is
similarly supported by AI/ML guidance and recent CAM solutions.

Elsewhere, the forecast remains largely on track, with only minor
adjustments made based on the latest forecast and observational
trends. See the discussion below for additional details.

..Chalmers/Moore.. 08/23/2026

.PREV DISCUSSION... /ISSUED 1135 AM CDT Sun Aug 23 2026/

...Great Basin into the Northern Rockies/High Plains...
Water-vapor imagery this morning shows an eastward-migrating
shortwave trough over the Pacific Northwest.  A belt of 40-50 kt of
west-southwesterly mid-level flow will overspread the northern
Rockies and adjacent High Plains of central/eastern MT by this
afternoon.  Heating along with ascent attendant to the disturbance
will favor initial storm development over the higher terrain over
southwest/western MT.  Steepening lapse rates over the High Plains
will favor the potential for scattered severe gusts as thunderstorms
move/develop over the plains during the late afternoon and evening.
A mix of multicells and supercells may yield a risk for severe hail
early before upscale growth into linear clusters (60-80 mph gusts)
likely evolves during the evening.

A somewhat separate area of convection should develop this afternoon
across parts of the northern Great Basin and Upper Snake Valley.
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.
Very steep lapse rates will favor ample evaporative cooling in the
stronger downdrafts.  Scattered severe gusts (60-80 mph) are
possible with the stronger thunderstorm cores and outflow.

...Northern/Central Plains...
Morning surface analysis places a moisture plume (lower to mid 60s
deg F dewpoints) extending from the TX-OK Panhandles
north-northwestward through eastern CO/NE Panhandle and into the
Black Hills vicinity.  It is within this corridor moderate to strong
instability is forecast by mid-late afternoon along/east of a lee
surface trough.  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 from northeast CO northward into the western
Dakotas.

Farther south, high-based convection is forecast to slowly
spread/move east of the Raton Mesa into the TX-OK Panhandles during
the early evening.  Very steep lapse rates and inverted-V profiles
will favor evaporative cooling and an isolated threat for severe
gusts with the stronger downdrafts and outflow surges.

...Northeast...
Midday satellite imagery shows an upper trough/low over Ontario with
a series of embedded shortwave impulses rotating through its base.
A lead disturbance over the Lower Great Lakes will continue to
rotate northeastward across the western portion of the Northeast and
influence scattered thunderstorm development this afternoon.
Heating of an adequately moist airmass but relatively meager
mid-level lapse rate environment will result in weak buoyancy
developing through mid afternoon as convection deepens.  Around
30-35 kt of deep-layer shear will support some updraft organization
mainly in the form of bands of storms.  An isolated risk for strong
to locally severe gusts is expected across much of this region this
afternoon.  Towards early evening, an upstream impulse will approach
the Lake Erie vicinity with some uptick in storm coverage and
perhaps a lingering risk for wind damage before this activity
weakens by the mid evening.

...Southeast...
Isolated to scattered thunderstorms will likely develop along/south
of a weak front draped across the lower MS Valley into the Gulf
Coast states, and continuing northeastward into the Carolinas.  An
isolated threat for strong to locally severe gusts may result in
pockets of wind damage with the more intense wet microbursts.

...Northeast Oklahoma/Southeast Kansas into the Ozarks...
Some modest increase in isentropic ascent associated with
a 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 localized severe
gusts.

...Arizona...
On the western periphery of a mid-level anticyclone centered over
eastern NM, weak southeasterly mid-level flow will remain across
southern/central AZ.  Model guidance only depicts weak buoyancy
across much of central and southern AZ, with the exception of
perhaps over far southern AZ.  Nonetheless, hot temperatures and a
deeply mixed boundary layer lend some potential for a localized
microburst risk.

$$