ACUS01 KWNS 230611
SWODY1
SPC AC 230609

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0109 AM CDT Sun Aug 23 2026

Valid 231200Z - 241200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHERN PLAINS...MUCH OF CENTRAL MONTANA...AND PORTIONS OF THE
EASTERN GREAT BASIN...

...SUMMARY...
Strong-to-severe thunderstorms capable of large hail and damaging
winds will be possible across portions of the northern Rockies and 
northern Plains. Additional severe thunderstorms capable of damaging
winds will be possible across portions of northern Utah.

... Synopsis ...

A sub-tropical mid-level ridge will remain in place across much of
the West on Sunday, with a large-scale trough taking shape across
much of the East. A seasonably strong short-wave trough will crest
the ridge over southern Canada, with an attendant jet streak in its
basal region moving across Montana. Broadly northwest mid-level flow
will exist from the northern Plains east toward the Appalachians,
between the western ridge and eastern trough.


... Intermountain West ...

A well-mixed boundary layer will develop during the afternoon as
cooler mid-level temperatures associated with the approaching
short-wave trough overspread the northern Rockies. Scattered
thunderstorms should develop during the early to mid-afternoon
within an environment with steepening mid-level lapse rates.
Effective shear on the order of 30-40 knots will support multicell
clusters and transient supercell structures capable of producing
large hail and damaging wind gusts.

Farther south, multicell clusters should develop across eastern
Nevada and western Utah during the late afternoon. Modest mid-level
flow on the north side of the subtropical ridge, coupled with steep
low-level lapse rates (inverted-V profiles) should support efficient
downward momentum transfer with any sustained thunderstorm updraft.


... Northern Plains south into the Central High Plains ...

A plume of steep mid-level lapse rates will advect out from the
northern Rockies and overspread a moistening warm sector. The result
will be afternoon MUCAPE values between 2000-3000 J/kg. Although
vertical shear is not overly strong, forecast soundings/hodographs
suggest enough shear to support multicells and transient supercell
structures. Large hail will be possible with these initial
thunderstorms. With time, congealing outflows should support some
potential for upscale growth toward an MCS. Steep lapse rates will
support severe winds (some significant) with any organized
thunderstorm cluster.


... Northeast US ...

Early morning convection should dissipate enough to support at least
filtered sunshine during the late morning and early afternoon. This
will support temperatures warming into the 70Fs to perhaps low 80Fs.
This, when combined with upper 50Fs to low 60Fs dewpoints will
support between 500-1000 J/kg MUCAPE during the afternoon. Vertical
ascent downstream of the eastern trough will support clusters of
thunderstorms across the region. Modest mid-level lapse rates should
limit a more robust hail threat, but the degree of ascent and
instability will support a marginal risk of severe hail and damaging
wind.


... Northern Gulf Coast toward the Coastal Carolinas ...

Strong diurnal heating of a moist boundary layer (dewpoint
temperatures in the 70Fs) should support MUCAPE values between
3000-4000 J/kg during the afternoon. High precipitable water values
will support water-loaded updrafts capable of producing isolated
damaging downbursts with the strongest cells.


... Southern Arizona ...

Seasonably strong southeasterly mid-level flow will develop along
the periphery of the mid-upper-level ridge. This enhanced flow will
overspread a deeply mixed boundary layer (inverted-V) during the
afternoon. In spite of the deeply mixed boundary layer, precipitable
water values in excess of 1" will exist across the area during the
late afternoon. This will support at least isolated thunderstorm
clusters capable of producing damaging wind gusts.


... Southeast Kansas, Northeast Oklahoma, Southwest Missouri, and
Northwest Arkansas ...

A low amplitude mid-level trough will move southeast across the
Central US on Sunday, within the broader northwest flow. Although an
isolated thunderstorm cannot be ruled out with this feature during
the afternoon, the more likely scenario is the environment across
Kansas and Missouri remains capped during the afternoon.

By late evening, the mid-level trough/jet streak should be across
southern Missouri or northeast Arkansas, placing northeast Oklahoma
and southeast Kansas in the right entrance region of the mid-level
jet. Guidance is pretty confident in developing a strong low-level
jet across the southern Plains in response to this mid-level jet.
The result will be increasing warm-air advection/isentropic ascent
during the overnight. This will lead to scattered thunderstorm
development, with movement off to the east-southeast. Mid-level
lapse rates should only be on the order of 6.5 C/km, but
cloud-bearing shear around 30-40 knots should support strong
updrafts. DCAPE values between 500-1000 J/kg will support at least
marginally severe downbursts capable of wind damage.

..Marsh/Weinman.. 08/23/2026

$$