540
ACUS01 KWNS 061252
SWODY1
SPC AC 061251

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0751 AM CDT Sun Sep 06 2026

Valid 061300Z - 071200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE SOUTHERN APPALACHIANS INTO THE SAVANNAH RIVER VALLEY...AND OVER
PARTS OF WESTERN AND CENTRAL MONTANA...

...SUMMARY...
Widely scattered damaging wind gusts are likely across portions of
the Southeast this afternoon and early evening. Widely scattered
large hail occurrences are expected across portions of western and
central Montana this afternoon and evening. Additional areas at risk
for isolated severe wind and hail are parts of the Interior West,
over the northern and central High Plains, and from the eastern
Dakotas and western Minnesota into the Ozark Plateau and Gulf Coast
states.

...Southern Appalachians through coastal SC and GA...
A moist airmass is in place across the region this morning, with
recent surface analysis revealing a reservoir of low to mid 70s
dewpoints. Strong heating is anticipated across this region today,
with afternoon temperatures reaching the low to mid 90s. This strong
heating will destabilize the airmass and contribute to
moderate/strong buoyancy, with MLCAPE around 2000-2500 J/kg likely
during the late afternoon. A subtle shortwave trough will progress
through the northwesterly flow aloft extending over the area,
interacting with this destabilized airmass to support thunderstorm
development. Vertical shear will generally be weak, limiting updraft
organization and promoting a predominantly outflow-dominant storm
mode. Even so, steep low-level lapse rates and abundant moisture
will promote the potential for damaging wind gusts with any
longer-lived multi-cells or line segments. Updraft augmentation due
to storm interactions could also result in isolated hail.

...Ozark Plateau into the Gulf Coast States...
A corridor of greater low-level moisture arcs from the Southeast
states through Arkansas and Missouri. Daytime heating will
destabilize this airmass, helping to support thunderstorm
development in areas of low-level confluence. Weak forcing for
ascent and vertical shear are expected to limit storm organization.
However, the degree of instability will support briefly intense
pulse-type storms capable of locally damaging wet microbursts during
the afternoon and early evening hours.

...Eastern Dakotas and western Minnesota into the lower Missouri
Valley...
A linear MCS continues to push eastward across the central Plains
this morning. A notable vorticity maximum has developed within the
northern portion of this line. Its motion appears to be more
northeasterly than the line itself, and new development is occurring
downstream of this vorticity maximum across south-central/southeast
SD and adjacent northeast NE. A corridor of relatively greater
low-level moisture (i.e. dewpoints in the low 70s) exists downstream
of this vorticity maximum and attendant MCS from eastern SD through
western IA and into northern MO. General expectation is for
thunderstorm coverage and intensity to increase later this
morning/early afternoon as the vorticity maximum/remnant MCS
interact with this moist and diurnally destabilizing airmass. Much
of this development is expected to occur along or to the immediate
cool side of the surface boundary that extends through portions of
the middle and lower MO Valley. Occasionally strong updrafts could
result in isolated hail and/or damaging gusts, but the weak
mid-level flow and associated modest deep-layer shear should limit
storm organization and contribute to clustered multicellular mode.

...Northern Plains into the northern/central High Plains...
Modest height falls may begin to impinge on northern/central High
Plains during the early evening as a low-amplitude shortwave trough
moves a belt of stronger southwesterlies just west of the region.
This modest ascent will augment low-level convergence along the lee
trough to support isolated to widely scattered thunderstorm
development where the lingering convective inhibition can be
overcome. This appears most likely across southeast WY and northeast
CO where persistent low-level easterly flow could keep dewpoints in
the 60s. High-based, outflow-dominant storms will support the
potential for isolated strong to severe gusts.

Increasing mid-level flow will support stronger deep-layer vertical
shear farther north (into eastern MT and western ND), but stronger
convective inhibition may linger, casting doubt whether storms will
initiate. If initiation is realized, storm motion could take it into
the more moist and buoyant airmass north of the surface low where
thermodynamic profiles are favorable for large to very large hail.
Will maintain 5% wind/hail probabilities but introduce a CIG1 for
hail given the conditional potential.

...Northern Great Basin into the northern Rockies...
Increasing height falls and strengthening mid/upper-level flow will
spread across the region today ahead of a vigorous shortwave trough
pivoting through the base of a Pacific Northwest upper low.
Thunderstorm development is anticipated over the higher terrain
before then progressing northeastward towards lower elevations.
Deep-layer vertical shear of 40 to 50 kt will support supercells,
with large hail as the primary severe risk. Greater buoyancy is
expected across central MT, but low-level stability will likely
persist across this region as well, potentially limiting the
severe-wind and tornado potential.

Weaker instability is forecast from northeast NV and northern UT
into central and eastern ID. However, the presence of steep lapse
rates and kinematics mentioned above may yield a few severe storms
capable of severe wind gusts.

..Mosier/Lyons.. 09/06/2026

$$