Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0746 AM CDT Thu Aug 20 2026
Valid 201300Z - 211200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE MID-ATLANTIC...AND FROM THE CENTRAL PLAINS INTO THE UPPER
MISSISSIPPI VALLEY...
...SUMMARY...
Scattered severe storms are possible today and tonight across parts
of the Mid Atlantic, posing a risk for damaging wind gusts. Large
hail and isolated wind damage will be possible with severe storms
from Nebraska into northwest Wisconsin.
...Central Appalachians into the Mid-Atlantic...
Broad upper troughing currently extends from the northern Plains
through New England, with an embedded shortwave trough progressing
across the Mid MS Valley into the Lower OH Valley. Showers and
thunderstorms are ongoing ahead of this shortwave, and the
expectation is that these showers and thunderstorms will continue
weakening this morning. A moist airmass is in place downstream of
this wave (i.e. from the central Appalachians and upper OH Valley
into the Mid-Atlantic), and reintensification and/or new development
is expected ahead of this wave as it continues northeastward into
this diurnally destabilized region.
Surface low associated with this wave is currently over the IN/OH/KY
border vicinity. This low is forecast to deepen slightly as it moves
northeastward just ahead of the parent shortwave trough. Modest
low-level moisture advection will precede this low, and a warm front
is forecast to lift northward across southern PA, northern MD, and
most of NJ. Despite poor lapse rates, ample low-level moisture south
of the front will support moderate buoyancy. Reintensification
and/or new thunderstorm development is expected first near the Blue
Ridge and across the higher terrain of southern PA and northern MD
before increasing in coverage and intensity with eastward extent. A
belt of slightly stronger mid-level flow will precede the shortwave,
resulting 40 to 50 kt of effective bulk shear. This is more than
sufficient to support a mix of supercells and organized line
segments. Damaging wind gusts will be the primary risk, but
southerly winds will enlarge low-level hodographs from the Delmarva
into central NJ, supporting the potential for a couple of tornadoes.
...Carolinas into the Southeast...
Ample low-level moisture and strong heating will result in an
unstable airmass from the Carolinas into much of the Southeast.
Low-level convergence along a cold front that will extend from the
western Carolinas into AR this afternoon will result in scattered
thunderstorm coverage. Vertical shear will be weak, and an
outflow-dominant storm structure is anticipated. Even so, moderate
to strong buoyancy and ample moisture (PW around 2") will support
occasionally strong water-loaded downbursts, particularly from
western TN into AL and MS where high temperatures in the upper 90s
are anticipated.
...Central Plains into the Upper MS Valley...
A reservoir of greater low-level moisture (i.e. dewpoints in the
upper 60s) currently extends from AR/eastern OK northwestward across
much of KS and into NE. Modest low-level moisture advection is
anticipated throughout this corridor today, as a tightening surface
pressure gradient results in stronger southerly surface winds. Mid
60s dewpoints could reach as far north as southwest MN. Moderate to
strong buoyancy will develop within this corridor, with the greatest
buoyancy likely from the CO/KS/NE border vicinity northeastward into
southeast SD. At the same time, a cold front will progress
southeastward across western MN, central SD and western NE,
interacting with this buoyancy to support thunderstorm development.
Thunderstorm initiation is anticipated first across the Upper MS
Valley before expanding southwestward.
Moderate northwesterly flow aloft will support supercell wind
profiles, with elongated/straight hodographs, and the threat for all
severe hazards. Large to very large hail (i.e. greater than 2 inch
diameter) will be the primary severe hazard, particularly during the
early evening as the storms move into greater instability. Isolated
strong to severe gusts (i.e. 55 to 75 mph) are possible as well.
Given the supercellular storm mode and low-level southerly flow, a
low-probability tornado risk also exists.
Some risk for isolated damaging gusts may persist into the early
overnight across southern NE and northern KS if clustering can
occur.
...AZ...
Another round of scattered thunderstorms this afternoon and evening
amid seasonably rich monsoon moisture (dewpoints in the upper 50s to
60s F) and moderate buoyancy. The lower elevations will be
characterized by greater convective inhibition than yesterday, with
the overall buoyancy slightly lower as well. Consequently, despite a
similar upper pattern, the overall potential for strong gusts is
expected to be lower than yesterday. Even so, isolated gusts are
still possible as storms move off the high terrain into the deeply
mixed airmass over the lower elevations.
..Mosier/Bunting.. 08/20/2026
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