Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1254 AM CDT Wed Aug 13 2025
Valid 131200Z - 141200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS...
...SUMMARY...
The evolution of an organized cluster of thunderstorms accompanied
by strong to severe wind gusts appears probable across parts of the
central Plains this evening and overnight. Scattered thunderstorms
across the Mid-Atlantic/Northeast may produce sporadic damaging
winds this afternoon.
...Synopsis...
Strong to severe thunderstorm chances today will primarily be
focused across the Mid-Atlantic/Northeast and across the central
Plains. Early-morning water-vapor imagery depicts a broad
upper-level trough across eastern Canada and Great Lakes region with
a diffuse surface front draped from the Midwest southwestward into
the Plains. This wave and its attendant surface front will spread
east through the day, reaching the Mid-Atlantic by around peak
heating when conditions should be adequately unstable for
thunderstorms. Further west, a deepening upper trough will progress
rapidly across the Pacific Northwest and northern Rockies over the
next 24 hours. Ascent ahead of this wave overspreading a dry, but
buoyant, air mass will promote scattered thunderstorms with robust
convection anticipated across the Plains later this
evening/overnight as lift impinges on a more moist/buoyant air mass.
...Central Plains...
05 UTC surface observations show modest moisture return ongoing
across the Plains in the wake of a recent frontal passage. Through
the afternoon, a deepening of the lee trough will promote stronger
moisture return just as lift ahead of the approaching wave and
high-based convection emanating off the central Rockies spreads
east. Deep, well-mixed boundary layers to the west of the surface
trough will promote strong to severe downbursts winds as well as
outflow dominant storms. Most CAM guidance suggest cold pool
consolidation will be adequate for upscale growth of at least one
convective cluster across the High Plains by mid/late evening. This
activity will likely intensify as it encounters richer moisture
within a moderately sheared environment (35-40 knots of effective
shear). This scenario appears to be the most probable based on
ensemble consensus, and hints that strong to severe winds will
likely overspread much of southern SD and northern NE through the
overnight hours. While CAMs show reasonably good agreement on the
trajectory of this system, the exact corridor of propagation remains
uncertain.
A few solutions hint at more cellular development across portions of
SD after roughly 02 UTC as isentropic ascent over an effective warm
frontal zone increases with a strengthening of the nocturnal jet.
Cells developing within the warm advection regime may evolve into
supercells with an attendant risk for large hail given strong
veering between 1-3 km and moderate effective shear. A propagating
cluster may emerge out of this regime, but ensemble support for this
scenario is comparatively weak.
...Mid-Atlantic/Northeast...
00z soundings across the region sampled rich low-level moisture as
well as poor mid-level lapse rates. However, west/southwesterly flow
aloft will advect steeper mid-level lapse rates over the next 12-18
hours. The combination of steepening lapse rates and diurnal heating
of a moist air mass should result in a modestly buoyant, but weakly
capped, environment across the Mid-Atlantic. Focused forcing along
the front coupled with limited inhibition should promote scattered
to widespread thunderstorms by 19-21 UTC. Damaging downbursts will
be possible with this activity - especially where surface
temperatures can warm into the upper 80s and low 90s. Based on
recent ensemble guidance, this appears most probable from southern
PA into the New England region. While deep-layer shear will be
fairly weak, very weak surface winds under 20-25 knot mid-level flow
may provide adequate deep-layer wind shear for a few persistent,
more robust cells and/or clusters.
..Moore/Hart.. 08/13/2025
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/TMSPwj
