ACUS01 KWNS 131239
SWODY1
SPC AC 131238

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0738 AM CDT Wed Aug 13 2025

Valid 131300Z - 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.

...Northern/Central Plains...
The primary upper trough will remain over western/central Canada
today, with quasi-zonal westerly mid-level flow continuing over much
of the northern Rockies/Plains through the period. A
subtle/low-amplitude shortwave trough over parts of ID/western MT
this morning associated with ongoing weak convection is forecast to
advance eastward towards eastern MT/WY and the western Dakotas by
early this evening. Gradually warming low/mid-level temperatures and
a stout cap will likely hinder surface-based convective development
across much of the northern/central Plains until mid to late
afternoon at the earliest. Still, the modest large-scale ascent
associated with the approaching shortwave trough may be sufficient
in tandem with robust daytime heating and localized orographic
effects near the Black Hills to initiate thunderstorms.

Modest low-level moisture will continue to stream northward today
along/east of a surface lee trough. Initially high-based convection
across the northern/central High Plains could pose an isolated
threat for mainly severe gusts as it continues eastwards towards
greater low-level moisture and MLCAPE. The best potential for a more
focused corridor of severe winds and isolated large hail still
appears generally along/east-southeast of the Black Hills towards
central SD and perhaps north-central NE this evening into the early
overnight hours. Here, moderate instability and deep-layer shear
should overlap with a very well-mixed boundary layer, supporting a
severe wind threat with any cluster that can become established amid
a gradually strengthening low-level jet. Some uncertainty still
remains regarding this potential, however, as low/mid-level
temperatures (around 850-700 mb) are forecast to remain quite warm.

...Northeast/Mid-Atlantic...
The Northeast and portions of the Mid-Atlantic will experience the
glancing influence of upper troughing advancing eastward over
Ontario/Quebec today. A moist low-level airmass is already in place
ahead of a weak surface front extending southwestward from the Great
Lakes into the Midwest. Although lapse rates aloft will remain poor
through the afternoon, diurnal heating ahead of ongoing showers and
thunderstorms this morning should promote weak to locally moderate
instability from New England to parts of the Mid-Atlantic. Generally
modest mid-level flow (around 15-25 kt at 500 mb) should tend to
limit deep-layer shear given weak winds at low levels. Even so,
loosely organized clusters may still pose some threat for isolated
damaging winds this afternoon and early evening as convection
spreads eastward amid a boundary layer characterized by steepened
low-level lapse rates.

..Gleason/Leitman.. 08/13/2025

$$
--- SBBSecho 3.28-Linux
 * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (618:250/1)