291 

ACUS02 KWNS 221732

SWODY2

SPC AC 221730



Day 2 Convective Outlook  

NWS Storm Prediction Center Norman OK

1230 PM CDT Sat Aug 22 2026



Valid 231200Z - 241200Z



...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF

CENTRAL AND EASTERN MONTANA AND PARTS OF THE EASTERN GREAT BASIN

INTO THE CENTRAL ROCKIES...



...SUMMARY...

Strong thunderstorm activity posing at least some risk for severe

hail and wind appears possible across parts of the northern Rockies

and Great Plains, and across parts of the eastern Great Lakes to the

Northeast, Sunday through Sunday night.



...Synopsis...

Upper ridging will prevail across the western CONUS as an upper

trough slowly traverses the Northeast tomorrow (Sunday). A mid-level

impulse will crest the upper ridge tomorrow afternoon across the

northern Rockies while a small impulse embedded in the

aforementioned upper trough overspreads the northern Appalachians.

From the northern Rockies to northern High Plains, as well as parts

of the Northeast, stronger flow above the boundary layer will

promote adequate vertical wind shear, in tandem with buoyancy, to

promote strong to severe thunderstorms. Elsewhere from the central

Rockies to the Gulf/Carolina coastlines, strong surface heating amid

pockets of low-level moisture will support scattered thunderstorm

development, with an isolated severe storm possible.



...Northern Rockies...

By mid to late afternoon, a well-mixed boundary layer should develop

beneath a plume of cooler temperatures aloft (e.g. 8+ C/km mid-level

lapse rates) with the passage of the aforementioned mid-level

impulse. A belt of stronger mid- to -upper level westerly flow will

also accompany this impulse, resulting in elongated hodographs and

30-40 kts of effective bulk (speed) shear coinciding with the steep

low- and mid-level lapse rates. Multicells and transient supercells

should develop, accompanied by a risk of severe gusts and perhaps an

instance or two of hail. A gust over 75 mph is possible.



...Northern High Plains into South Dakota...

Convective evolution and morphology remains unclear in this region.

Steep lapse rates will emanate from the northern Rockies and

overspread a moistening warm sector (e.g. mid 60s F dewpoints),

yielding 2000+ J/kg MLCAPE. Modestly curved and elongated hodographs

suggest multicells and supercells as the main storm mode, at least

initially. Severe gusts/hail would accompany these storms if they

can become sustained. There is also some indication by the latest

CAMS that storms may merge into a cold-pool-driven MCS, though

guidance consensus is weak on this scenario. Nonetheless, any MCS

development that does occur would support severe gusts, including a

75+ mph gust.



...Portions of the eastern Great Basin to the central Rockies...

A cluster of multicell storms should develop around the eastern

Great Basin into the central Rockies by afternoon peak heating.

Stronger flow aloft will glance the region to the north, atop a

strongly mixed boundary layer. Forecast soundings show classic

inverted-V profiles extending to 500 mb, with surface-500 mb lapse

rates reaching at least 9 C/km. As such, severe gusts are possible

with the stronger multicells that form.



...Portions of the Northern Appalachians into New England...

By afternoon, surface temperatures should warm well into the 70s F

as earlier showers and thunderstorms make way for at least partly

clearing skies. While not overly steep, mid-level lapse rates

exceeding 6.5 C/km will result in marginal buoyancy, amid stronger

flow aloft (yielding elongated hodographs). A couple instances of

damaging gusts/hail will be possible with the stronger multicells

that manage to sustain themselves.



...Gulf to Carolina Coastlines...

A heated and moist boundary layer should develop by afternoon given

the presence of mid 70s F surface dewpoints and temperatures rising

well into the 80s F. Such rich low-level moisture will support

2000-4000 J/kg MLCAPE from LA to extreme eastern NC despite

mid-level lapse rates only reaching 6-6.5 C/km. Across the Gulf

Coast, pulse-cellular storms are expected given weak flow aloft,

with damaging gusts originated from wet downbursts the main threat.

Along the Carolina Coastline, southwesterly mid-level flow will be a

bit stronger given the upper trough glancing by to the north.

Multicells capable of isolated severe gusts are possible. Locally

higher severe probabilities may be needed in future Day 1 outlooks

if greater storm coverage becomes apparent.



...Portions of southern Arizona...

Locally stronger southeasterly mid-level flow will pivot around the

upper ridge and overspread a deep and dry boundary layer by late

afternoon/early evening. Meanwhile, surface temperatures around 100

F, amid 60 F surface dewpoints and overspread by modestly cooler

temperatures aloft, will yield 9+ C/km tropospheric lapse rates and

over 2000 J/kg MLCAPE. Given the modest flow aloft and

aforementioned buoyancy, a few organized multicells may occur,

accompanied by an isolated severe gust threat.



..Squitieri.. 08/22/2026



$$