Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1222 AM CDT Sat Sep 05 2026
Valid 051200Z - 061200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
THE OHIO VALLEY INTO THE SOUTHERN MID-ATLANTIC AND CAROLINAS...
...SUMMARY...
Severe thunderstorms capable of mainly damaging gusts are possible
across portions of the Ohio Valley into southern Mid-Atlantic and
Carolinas on Saturday afternoon and evening. Isolated occurrences of
large hail and severe wind gusts also appear possible over parts of
the northern and central Plains Saturday into Saturday night.
...Synopsis...
A prominent mid-level ridge will persist over the central CONUS
between upper lows over the Pacific Northwest and the Gulf of St.
Lawrence into NB/NS. Several weak disturbances (some of convective
origin) will progress through the periphery of the ridge, serving as
foci for thunderstorm development. At the surface, an area of low
pressure is forecast over the western Dakotas with an associated
boundary --the location of which may be modified by convective
outflow-- extending into the OH Valley and southern Mid-Atlantic.
The eastern extension of the boundary will begin to push south as a
cold front Saturday afternoon into night as high pressure builds
into the Great Lakes.
...Ohio Valley into the Carolinas...
A mature to decaying MCS is expected to be ongoing 12Z Saturday over
portions of the middle to upper OH Valley, aided by a subtle
mid-level disturbance/possible MCV. There is considerable
variability across the 00Z convection-allowing models in the
longevity and extent of the convective system over the central
Appalachians into southern Mid-Atlantic through the remainder of the
morning. Should the MCS remain intact, isolated occurrences of
damaging wind are possible.
Renewed thunderstorm development is likely by afternoon along the
residual MCS cold pool and/or synoptic front as temperatures in the
90s to around 100 combine with boundary-layer dewpoints in the low
to mid 70s to yield MLCAPE up to 2000-3000+ J/kg with steepening
low-level lapse rates. Additionally, the models indicate some
enhancement of mid-level winds in association with the
disturbance/MCV moving through the southern Mid-Atlantic during the
afternoon, which may yield more organized multicells and line
segments with the predominant hazard being damaging wind gusts into
the evening.
Farther to the west, additional strong to severe storms appear
possible along and ahead of the composite boundary from the vicinity
of the OH River south into the Cumberland Plateau where widely
scattered damaging wind gusts also appear possible.
...Northern and Central Plains...
A band of elevated thunderstorms is expected to be ongoing 12Z
Saturday, centered over eastern SD. That activity is expected to
diminish through the morning with the cessation of the nocturnal
low-level jet; however, isolated occurrences of large hail and
severe wind gusts appear possible prior to dissipation. In the wake
of the early-day storms, the presence of steep low/mid-level lapse
rates and richer boundary-layer moisture with eastward extent will
contribute to a moderately to strongly unstable air mass by
afternoon with MLCAPE of 2000-3500+ J/kg.
Nebulous forcing for ascent and capping relating to the proximity of
the mid-level ridge axis lead to uncertainty in the specific details
regarding the location and extent of surface-based thunderstorm
development during the afternoon into evening. However, the presence
of the surface low, outflow-modified surface front, and a lee trough
over the High Plains will be candidates for storm development. The
strongest deep-layer shear (30-40 kt) is forecast to the north of
the surface low and composite boundary over ND and northern SD into
western MN where a conditional risk of supercells capable of large
hail and severe wind gusts exists. Elsewhere, high-based pulse and
multicell storm modes appear possible with the primary hazard being
widely-spaced severe wind gusts.
The isolated severe threat may persist into the overnight hours in
the vicinity of a nocturnally strengthening low-level jet.
...Western Montana...
A belt of enhanced mid/upper-level flow will exist across the
region, to the east of the upper low over the Pacific Northwest.
Heating along the high terrain coupled with the possible influence
of a weak mid-level disturbance is expected to support an increase
in high-based showers and a few thunderstorms during the afternoon
and evening. While lapse rates will be steep with strong deep-layer
shear, the absence of appreciable moisture will limit MLCAPE to
generally less than 250 J/kg. As such the potential for severe wind
gusts is currently too low to warrant 5% wind probabilities.
..Mead/Chalmers.. 09/05/2026
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