SPC AC 020059
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 PM CDT Tue Sep 01 2026
Valid 020100Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL PLAINS AND MIDWEST AS WELL AS THE MID ATLANTIC...
...SUMMARY...
Scattered strong to severe thunderstorms remain likely into tonight
across parts of the northern/central Plains and Upper Midwest, and
parts of southern New York into the Mid-Atlantic. Large hail and
damaging winds should be the main threats.
...Southern NY/The Mid Atlantic...
A mid-level shortwave trough and enhanced west-northwesterly flow
were observed from the Northeast/Mid Atlantic States to the lower
Great Lakes this evening. A front was draped from northwest to
southeast across southern NY/New England, with numerous showers and
storms ongoing along and south of it this evening. The air mass here
is unstable and moderately sheared which is supporting organized
supercells and short linear segments. Damaging gusts remain likely
through this evening, along with some hail and perhaps a brief
tornado, especially near the from across southeastern PA and NJ
where low-level sear is maximized. Convection should eventually
begin to weaken with the loss of diurnal heating and as it
approaches the coast later this evening.
...Central Plains and Midwest...
Several supercells have developed ahead of a weak surface low along
a stalled front from NE into SD. A very unstable air mass (MLCAPE of
3000+ J/kg) is in place and extended downstream of the cluster
across eastern SD, northern IA and southern MN. A belt of strong
mid-level westerly flow along the front will continue to support
organized storms. Upscale growth is possible this evening with one
or more clusters or an MCS expected to eventually develop and track
across portions of northern IA and far southern MN. This will pose a
threat for severe wind gusts and perhaps a tornado along the front
through tonight.
Farther southwest along the surface lee trough, scattered high-based
storms were ongoing in eastern CO and western KS. Buoyancy and shear
are much weaker, but steep lapse rates and T/TD spread of 30-40
degrees could support a sporadic severe gusts with these storms
before they weaken near sunset.
...Great Lakes...
A secondary mid-level vort max and upper low, currently over the
western Great lakes, may serve as a focus for additional storm
development tonight across eastern WI and lower MI. The eastern
portions of the quasi stationary front remain very warm and
unstable. As ascent from the upper low/shortwave approach after
midnight, they may support a modest enhancement of the southwestern
low-level jet. Warm advection at the nose of this feature could
allow for a cluster of thunderstorms to develop and intensify. The
large elevated buoyancy and 40-50 kt westerly flow would favor a
risk for hail and damaging gusts before moving into southern ON by
12z Wed. However, confidence in how this scenario evolves remains
low and only 5% wind/hail probabilities will be maintained given the
uncertainty in storm development.
...Coastal Southeast Texas/Southwest Louisiana...
Tropical Storm Edouard will continue tracking northwestward across
southeast TX and southwest LA per latest NHC forecasts. Some
enhancement to the low-level wind field and hodographs has been
noted in outer bands along the northern portions of the circulation.
This may support transient updraft rotation with any cells. A brief
tornado or two may occur across parts of coastal southeast
TX/southwest LA through tonight as the system weakens.
..Lyons.. 09/02/2026
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 011730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Tue Sep 01 2026
Valid 021200Z - 031200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE EASTERN
GREAT LAKES INTO MID-ATLANTIC AND OVER THE NORTHERN ROCKIES...
...SUMMARY...
Severe thunderstorms are possible across portions of the eastern
Great Lakes to the Mid-Atlantic Wednesday into Wednesday night.
Damaging wind gusts are the main threat, though some large hail and
a few tornadoes may also occur. Widely scattered severe gusts and
more sporadic occurrences of large hail appear possible from the
northern Rockies into northern High Plains Wednesday afternoon into
night.
...Synopsis...
A belt of 40-50+ kt mid-level winds will spread from the Great Lakes
into the Northeast in tandem with a series of low-amplitude
disturbances. Elsewhere, a negatively tilted shortwave trough and
attending mid-level jet streak will progress through the northern
Rockies Wednesday afternoon and evening. At the surface, the primary
baroclinic zone is expected to extend from low pressure over James
Bay through the Great Lakes and mid MO Valley into the northern High
Plains. A backdoor front/quasi-stationary boundary will reside over
the Mid-Atlantic, the specific location of which will be dictated by
the extent of outflow associated with early-day storms and the
strength of low-level ridging stretching from the Gulf of St.
Lawrence through the Northeast.
...Great Lakes into the Mid-Atlantic...
As alluded to in the synopsis, thunderstorms may be ongoing at 12Z
Wednesday from portions of WI and MI into NY and PA within a zone of
forcing for ascent associated with a lead short-wave trough. The
strongest storms will be capable of isolated occurrences of large
hail and/or damaging winds as they spread east-southeast through the
lower Great Lakes and Mid-Atlantic Wednesday morning. In the wake of
the early-day convection, prevailing west-northwest mid-level flow
will maintain a plume of relatively steep mid-level lapse rates
(e.g., 7 C/km) atop boundary layer dewpoints in the upper 60s to low
70s, yielding MLCAPE upwards of 2000-3000+ J/kg by afternoon from
lower MI into western parts of NY and PA.
Additional thunderstorms are expected during the afternoon from
lower MI through the lower Great Lakes, aided by weak disturbances
aloft and the moderate to strong instability forecast across the
warm sector. The presence of 35-45 kt of effective bulk shear will
support organized storm modes including supercells and bowing
structures capable of large hail potentially approaching two inches
and damaging wind gusts into Wednesday night. Tornado potential will
be conditional on storm mode; however, the models do indicate
stronger low-level winds and resultant larger SRH developing from
southwest ON into NY and PA Wednesday afternoon into evening, where
the greatest potential for a few tornadoes will exist.
...Northern Rockies into northern High Plains...
The presence of steep low/mid-level lapse rates and forcing for
ascent attendant to the short-wave trough are expected to foster an
increase in thunderstorms over western MT Wednesday afternoon amidst
a kinematic environment featuring around 30 kt of southerly
deep-layer shear. NAM and RAP-based forecast soundings indicate the
presence of a relatively deep, well-mixed boundary layer, which will
enhance severe-wind-gust potential, especially as storms merge into
clusters. Given the strength of the short-wave trough and consistent
model signal for scattered storms in a favorable thermodynamic
environment, an upgrade to level-2/Slight Risk was included in this
forecast.
Additional storms appear possible across portions of eastern MT into
western ND Wednesday evening within a zone of warm advection along a
nocturnally strengthening low-level jet. Isolated occurrences of
large hail appear to be the primary hazard with those storms.
...Mid MO Valley into IA and southern MN...
Neutral to slight mid-level height rises are forecast across the
region Wednesday afternoon into night with the nebulous forcing for
ascent leading to uncertainty in whether storms will develop near
the surface boundary. As such, no severe weather probabilities will
be included in this forecast, despite a favorable overlap of
moderate to strong instability and sufficient vertical shear.
..Mead.. 09/01/2026
WUUS02 PTSDY2
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 011930
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 PM CDT Tue Sep 01 2026
Valid 031200Z - 041200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE UPPER
OHIO VALLEY TO MID-ATLANTIC COAST...
...SUMMARY...
At least widely scattered severe storms, accompanied by damaging
gusts and perhaps some large hail, appear likely across portions of
the Ohio Valley to the Mid-Atlantic coast on Thursday. More isolated
severe storms capable of large hail and damaging winds appear
possible over the North Dakota-Minnesota Red River Valley into the
upper Midwest Thursday afternoon into night.
...Synopsis...
Broader-scale troughing is forecast over the western CONUS with
low-amplitude ridging from the upper MS Valley and upper Great Lakes
into the Southeast. Between the ridge and an upper low over QC,
latest model guidance indicates the progression of a short-wave
trough and associated 40-50 kt jet streak from the lower Great Lakes
through the Mid-Atlantic and portions of New England. Other more
subtle disturbances are depicted within the periphery of the ridge
over the Great Lakes into the upper MS Valley.
At the surface, an area of low pressure is forecast over the Dakotas
on Thursday with an associated warm front slowly lifting north
through the upper MS Valley and upper Midwest. The boundary is
expected to stretch east through the Great Lakes into the
Mid-Atlantic with the specific location of the boundary dictated by
the extent of thunderstorm activity and associated convective
outflow Wednesday night into Thursday morning.
...Great Lakes and Ohio Valley to Mid-Atlantic Coast...
One or multiple thunderstorm complexes may be ongoing Thursday
morning from the Great Lakes through the Northeast, aided by forcing
for ascent attendant to the previously mentioned mid-level
disturbances. The presence of the early-day storms leads to
uncertainty in the extent of air mass overturning that occurs, and
where the strongest instability will develop by afternoon. As such,
the Marginal Risk probability envelope has been broadened slightly
over the Mid-Atlantic with the Slight Risk probabilities remaining
unchanged.
The overlap of 30-40+ kt of deep-layer shear with a moist and
potentially moderately to strongly unstable warm sector will
conditionally support supercell and bowing storm modes with an
attendant risk for damaging wind gusts and large hail from Thursday
afternoon into evening.
...North Dakota-Minnesota Red River Valley into the upper Midwest...
A plume of steep mid-level lapse rates/EML is forecast to overly a
moist boundary layer, yielding a moderately to strongly unstable air
mass by afternoon in the vicinity of the warm front. The instability
will coincide with up to 40-50 kt of deep-layer shear, conditionally
yielding a very favorable severe storm environment. However, capping
concerns and the timing of any weak disturbances cresting the ridge
axis limit predictability, with only an areal increase in the
Marginal Risk probabilities included in this forecast. A categorical
upgrade to a level 2/Slight Risk may become necessary in subsequent
forecasts.
..Mead.. 09/01/2026
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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