ACUS01 KWNS 271240
SWODY1
SPC AC 271238

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0738 AM CDT Thu Aug 27 2026

Valid 271300Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC/NORTHEAST...AND THE CENTRAL PLAINS...

...SUMMARY...
Scattered strong to severe thunderstorms are possible across parts
of the Northeast and Mid-Atlantic today. Damaging winds, severe
hail, and a tornado or two may accompany these thunderstorms. Large
to very large hail and severe gusts are also possible across parts
of southwest South Dakota into western/central Nebraska and
northwest Kansas.

...Mid-Atlantic/Northeast...
An elongated mid/upper-level trough with closed low over Hudson Bay
will encompass much of the eastern CONUS today. Embedded within this
large-scale troughing, a mid-level shortwave trough with modestly
enhanced southwesterly winds (around 25-35 kt) will advance
northeastward through the day across the Mid-Atlantic and Northeast.
At the surface, a weak low over eastern Ontario will develop into
Quebec this afternoon, with a trailing cold front advancing
southeastward across the Mid-Atlantic/Northeast through the period.
Stronger daytime heating is forecast with southward extent across
the Mid-Atlantic ahead of the cold front, with cloud cover
potentially limiting heating somewhat across the Northeast. Even so,
a zone of moderate instability should develop by this afternoon
across these regions, with sufficient deep-layer shear for some
updraft organization. Current expectations are for thunderstorms to
gradually increase in coverage and intensity by 17-20Z ahead of the
surface front and a lee trough along/east of the Appalachians. A mix
of multicells and supercells should pose a threat for both severe
hail and damaging winds, especially from the northern Mid-Atlantic
northward into NY and vicinity. A tornado or two may also occur,
with modest hodograph curvature noted in various NAM/RAP forecast
soundings from northern MD northeastward to western New England.

...Central Plains...
The central Plains will be sandwiched between upper ridging over the
Southwest and upper troughing over eastern Canada today, with modest
northwesterly flow aloft persisting through the period. Large-scale
ascent is forecast to remain rather weak/nebulous, with some
guidance suggesting a weak mid-level impulse will crest the ridge
and aid convective initiation across parts of southwest SD into
western/central NE this afternoon. A corridor of greater low-level
moisture (generally 60s surface dewpoints) will be in place across
this region. Daytime heating of this moist airmass coupled with the
presence of steep mid-level lapse rates will help foster moderate to
locally strong instability and erode lingering MLCIN by 19-21Z.
While robust convective development and overall coverage still
remains somewhat uncertain given the weak forcing, a rather
favorable environment for supercells will exist. Any sustained
supercells will be capable of producing large hail (some 2+ inches)
as they track south-southeastward through the late afternoon into
the evening. The potential for severe/damaging gusts is also
uncertain, as most guidance does not show a cluster developing this
evening. An isolated threat for severe hail/gusts may also exist
farther west/south across the CO Front Range to Raton Mesa vicinity,
although deep-layer shear should be weaker across these areas.

...Northern Rockies/High Plains...
A mid-level jet on the southeast periphery of upper troughing over
the eastern Pacific and western Canada will translate northeastward
across the northern Rockies today. Enhanced west-southwesterly flow
and lift associated with this jet will likely aid isolated to
scattered thunderstorm development this afternoon across parts of
the northern Rockies, with this activity spreading into the adjacent
High Plains through the evening. While low-level moisture will
remain limited/shallow across these regions, steep low/mid-level
lapse rates amid a well-mixed boundary layer coupled with moderate
to strong deep-layer shear should support a threat for isolated
severe gusts with the high-based convection that develops.

...Great Basin...
High-based thunderstorms should also develop this afternoon across
portions of northeast NV into northwest UT and southeast ID. While
low/mid-level winds and related thunderstorm organization will
likely be somewhat weaker/limited compared to areas farther north,
steep lapse rates and large DCAPE will support potential for strong
to severe outflow gusts as this convection spreads northeastward
into the early evening.

...South-Central/Coastal Texas into Southern Louisiana...
Ongoing thunderstorms across southern LA may pose a threat for gusty
winds this morning before they move offshore. Additional
thunderstorms may develop this afternoon from parts of south-central
TX towards the upper TX Coast, with isolated severe/damaging
downburst winds possible given ample moisture/instability forecast.
Weak deep-layer shear should limit the overall severe threat.

..Gleason/Broyles.. 08/27/2026

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