ACUS01 KWNS 300602
SWODY1
SPC AC 300600

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Mon Jun 30 2025

Valid 301200Z - 011200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHERN PLAINS MIDWEST AND MID ATLANTIC AS WELL AS THE NORTHWEST...

...SUMMARY...
Scattered strong to severe thunderstorms remain possible across
parts of the southern Plains, Ohio Valley, Midwest and the
Mid-Atlantic today. A couple of severe thunderstorms also cannot be
ruled out over parts of the Pacific Northwest.

...Synopsis...
A broad upper trough is forecast to intensify as it moves
southeastward across the Great Lakes and Midwest through tonight. At
the same time, sub-tropical ridging will build over the Plains,
keeping stronger flow aloft displaced to the north. To the west of
the ridge, an upper low will overspread portions of the West Coast.
At the surface, a weak cold front will sag southward from the
Midwest to the southern Plains. Numerous thunderstorms are likely
ahead of the front with isolated damaging gusts and hail possible.

...Midwest and Great lakes...
Ahead of the slow-moving cold front, rich low-level moisture with
dewpoints in the 70s F will be in place from MO/IL into Lower MI. A
messy surface pattern, with multiple remnant outflows and cloud
debris will likely modulate diurnal heating to some degree through
the early afternoon. With little inhibition, scattered to numerous
thunderstorms are expected by mid afternoon as ascent from the
approaching upper trough overspreads the unstable air mass. Several
loosely organized bands or clusters of strong pulse storms are
likely. Weak mid-level flow and poor lapse rates suggests minimal
potential for greater storm organization. Though high PWATS near 2
inches will support heavy water loading and microburst potential,
with the stronger storms.

...OH valley to the Mid Atlantic...
A similar pattern to the Midwest, with somewhat higher storm
coverage, is expected from OH eastward into PA and the Mid Atlantic.
Scattered to numerous thunderstorms should develop by late morning
amid strong surface heating ahead of a subtle shortwave trough over
the OH valley. 20-30 kt of mid-level flow could support some
clustering of storms by early afternoon. Despite mediocre mid-level
lapse rates less than 6 C/km, the high PWAT air mass and some
consolidation of outflows could support isolated damaging wind
potential across eastern OH, southern NY into PA and the Mid
Atlantic states.

...Southern Plains to the Ozarks...
Scattered thunderstorms should develop by mid afternoon ahead of
sagging cold front from the TX Panhandle across the southern Plains
and western Ozarks. Beneath the northern fringes of the building sub
tropical high, strong heating and rich boundary-layer moisture will
support large buoyancy (MLCAPE (3000-4000 J/kg). Scattered
thunderstorm development is likely ahead of the front, and along
remnant outflows from overnight convection. Despite modest vertical
wind shear, the large buoyancy may still support occasional strong
to severe storms with the primary risk of damaging gusts and
occasional hail.

...Northern CA into southern OR...
Ahead of the weak upper low over southern CA, southerly flow will
aid in increasing mid-level moisture across parts of northern CA and
southern OR. Ample heating, weak synoptic ascent and typical
terrain-induced circulations will encourage scattered high-based
thunderstorm development through the afternoon. Nearly dry adiabatic
lapse rates from deep mixing of the boundary layer to near 500mb
will favor strong downdrafts capable of isolated severe wind gusts.
MUCAPE (~1000 J/kg) and 20-30 kt of southerly shear, may also
support marginally severe hail with the strongest cores.

..Lyons/Darrow.. 06/30/2025

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