220
ACUS01 KWNS 132012
SWODY1
SPC AC 132012

Day 1 Convective Outlook RESENT 1
NWS Storm Prediction Center Norman OK
0312 PM CDT Wed Aug 13 2025

Valid 132000Z - 141200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTH DAKOTA AND NORTH-CENTRAL NEBRASKA...

...SUMMARY...
Scattered severe wind gusts and isolated large hail may occur across
parts of the northern/central Plains this evening and overnight.
Thunderstorms across portions of the Northeast and Mid-Atlantic may
produce occasional damaging winds this afternoon.

...20Z Update...
The western portion of the Marginal Risk area in the Mid-Atlantic
was trimmed, where convective overturning and cloud debris should
generally limit the severe risk. Farther west, the Marginal Risk was
expanded slightly northward into southwestern ND. Recent
high-resolution guidance is in relatively good agreement, depicting
a cluster of high-based storms evolving in an environment
characterized by weak-moderate surface-based buoyancy and 30-40 kt
of effective shear. Severe wind gusts and isolated large hail will
be possible with these storms. For details on the near-term severe
risk in the northern Plains, see MCD #1939.

..Weinman.. 08/13/2025

.PREV DISCUSSION... /ISSUED 1146 AM CDT Wed Aug 13 2025/

...Northern/Central Plains...
Recent satellite imagery shows a low-amplitude shortwave trough
moving through southwest MT. This shortwave is forecast to continue
eastward along the MT/WY border vicinity today, before continuing
through the Dakotas/NE tonight. The airmass preceding this shortwave
across southeast MT/northeast WY is relatively dry, with dewpoints
currently in the low to mid 50s. Greater low-level moisture is in
place farther east, with dewpoints increasing into the low 60s
across south-central SD and north-central NE. Southerly low-level
flow is anticipated throughout the day, helping to offset some of
the mixing expected amid strong diurnal heating. This should result
in a modestly moist, deeply mixed airmass across the southeast
MT/northeast WY/western SD vicinity by the late afternoon when the
forcing for ascent attendant to the approaching shortwave reaches
the region. This modest large-scale ascent show work in tandem with
robust daytime heating and localized orographic effects near the
Black Hills to initiate thunderstorms.

High-based storms are anticipated initially, which could result in
strong outflow with any more mature storms. A few instances of hail
as possible as well. Greater low-level moisture and buoyancy will be
in place farther east (i.e. into more of western/central SD), which
will combine with persistent large-scale forcing for ascent and a
strengthening low-level jet to support upscale growth into a
convective line. This should foster a continued threat for damaging
gusts into south-central SD and far north-central NE this evening.
The threat should diminish with eastern extent given nocturnal
stabilization and increasing convective inhibition.

...Northeast/Mid-Atlantic...
Dewpoints currently range from the low 70s over the northern
Mid-Atlantic into the low 60s across northern NH/VT. Thunderstorms
are already developing within this moist and moderately buoyant
airmass as large-scale ascent attendant to upper troughing advancing
eastward over Ontario/Quebec glances the region. Deep-layer vertical
shear is expected to remain weak throughout the day (i.e. effective
bulk shear generally less than 25 kt), which should limit overall
storm strength and organization. Even so, steep low-level lapse
rates could aid in the development of occasionally damaging gusts
with any of the deeper convective cores. Greater buoyancy could
result in a relatively higher probability for damaging gusts from
the NY Hudson Valley into eastern PA/NJ. Refer to recently issued
MCD #1938 for additional information.