SPC Sep 2, 2026 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1257 AM CDT Wed Sep 02 2026

Valid 021200Z - 031200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
AND CENTRAL MT AND FROM THE LOWER GREAT LAKES TO THE MID ATLANTIC...

...SUMMARY...
Severe thunderstorms are possible across portions of the eastern
Great Lakes to the Mid-Atlantic today and tonight. Damaging wind
gusts are the main threat, though some large hail and a few
tornadoes may also occur. Scattered severe gusts and more sporadic
occurrences of large hail appear possible from the northern Rockies
into northern High Plains Wednesday afternoon into night.

...Eastern Great Lakes, Mid Atlantic...
Several low-amplitude impulses embedded within a belt of moderate
mid-level northwest flow of 40-60 kt will move from the lower Great
Lakes into the northeast and Mid Atlantic today and tonight. A
surface low over James bay will trail a slow moving cold front to
the southwest across lower ON, the lakes and into MI/OH with a
second backdoor front stalled across the eastern Hudson Valley and
southern new England. Within the warm sector, a very moist air mass
will be in place over much of the Northeast contributing to large
buoyancy and broad, but uncertain potential for severe thunderstorms
much of the day.

A complex convective scenario is expected across the region
modulated by several rounds of thunderstorms beginning early this
morning. Convection associated with a lead shortwave trough exiting
southern ON will likely support scattered storms along the front
across the lower Great Lakes and NY this morning. Isolated large
hail and damaging winds are possible with these storms as they move
southeastward and encounter a gradually destabilizing air mass
across southern PA and possibly into VA/MD.

Air mass recovery is expected behind this initial condition as the
primary upper trough moves from WI and lower MI into western NY/PA
later in the afternoon. Steep mid-level lapse rates of 7-7.5 C/km
atop boundary layer dewpoints in the upper 60s to low 70s will aide
in destabilization with upwards of 2000-3000+ J/kg of MLCAPE by
afternoon from lower MI into western parts of NY and PA. Storm
development is expected ahead of the approaching trough and cold
front as well as on any residual outflow from the morning storms. A
mix of supercells and line segments is expected with all hazards
possible.

A greater tornado risk may evolve in the evening across southern NY
and central PA, contingent upon air mass recovery in the wake of the
prior storms and presence of a more supercellular mode. NAM/RAP
forecast soundings do show some elongation of low-level hodographs,
and any modifying old pool or outflow boundary could further enhance
low-level shear profiles favorable for tornadoes. Higher tornado
probabilities were considered, but uncertainty on the aforementioned
factors remains large.

...MT/ND...
A compact but strong shortwave trough is forecast to move rapidly
northeastward from the Great Basin to the northern Rockies today and
tonight. 35-50 kt mid-level flow will accompany this feature and
overspread a modestly moist, but warm and unstable air mass across
much of central and eastern MT. Ascent from the approaching
shortwave trough will aid in the development of thunderstorms across
the higher terrain of western MT through the afternoon. Despite
modest buoyancy, steep lapse rate profiles and a deep, well-mixed
boundary layer, will enhance severe-wind-gust potential with these
storms. 30-40 kt of deep-layer shear will promote organization and
clustering with some guidance showing a fast-moving line developing
and moving northeastward through the later afternoon/early evening.
Scattered severe gusts are likely, with peak intensity of 65-80 mph
possible.

Additional storms are possible across portions of eastern MT into
the evening within a zone of warm advection along a nocturnally
strengthening low-level jet. Isolated large hail appears to be the
primary hazard with those storms.

...WY...
Some model guidance shows high-based showers and thunderstorms
developing near the southern fringes of the northern Rockies trough
across WY this afternoon. Modest low-level moisture/buoyancy may
limit convective intensity, but sporadic strong outflow gusts are
possible given a very deeply mixed boundary layer.

...Mid MO Valley into IA and southern MN...
An intensifying low-level jet will likely support an increase in
thunderstorms late this evening/overnight across the MO valley and
parts of the Midwest. Moderate to strong elevated instability and
sufficient vertical shear may exist for a few stronger storms
capable of marginal severe hail. However, overall forcing for ascent
is modest and with building mid-level heights, confidence in a
broader organized severe threat is low.

..Lyons/Wendt.. 09/02/2026


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SPC Sep 2, 2026 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


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


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SPC Sep 1, 2026 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Tue Sep 01 2026

Valid 012000Z - 021200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHERN NEW YORK INTO THE MID-ATLANTIC...AND THE NORTHERN/CENTRAL
PLAINS INTO THE UPPER MIDWEST...

...SUMMARY...
Scattered strong to severe thunderstorms should occur this afternoon
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.

...20Z Update...
Only minor changes were made with this update. The MRGL Risk was
expanded slightly southward into northwest KS, where an evolving
storm and additional towering cumulus will pose a risk of isolated
large hail and locally severe gusts -- aided by an elongated
hodograph (around 30 kt of effective shear) and sufficient buoyancy.

In the northern/central Plains, some consideration was given to
adding 30-percent wind probabilities in parts of southeast SD,
northeast NE, and northwest IA. Here, guidance is in good agreement
that an upscale-growing cluster will pose a relatively greater
severe-wind risk. However, given the late expected timing, higher
probabilities were withheld at this time.

For details on the near-term severe risk, see MCDs 2184 and 2185.

..Weinman.. 09/01/2026

.PREV DISCUSSION... /ISSUED 1128 AM CDT Tue Sep 01 2026/

...Mid-Atlantic/Southern New York...
A mid/upper-level anticyclone will remain centered over the TN
Valley/Mid-South today, with a mid-level shortwave trough forecast
to move eastward across Ontario through the period. In between these
features, a belt of enhanced west-northwesterly flow will exist
across the Great Lakes into the Mid-Atlantic. Latest surface
observations show a front draped from northwest to southeast across
southern NY/New England, with cloud cover and precipitation ongoing
across these areas. Current expectations are for destabilization to
occur along/south of the front through the afternoon, with modestly
steepened mid-level lapse rates present across MI (reference 12Z
observed APX/DTX soundings) forecast to advect southeastward across
the Mid-Atlantic. Moderate to strong instability will likely develop
by mid afternoon across PA/NJ, with 30-40 kt of deep-layer shear
fostering updraft organization.

While there is still some uncertainty regarding overall convective
development and evolution this afternoon/evening owing to nebulous
large-scale ascent, most high-resolution guidance develops isolated
to widely scattered thunderstorms along/south of the front,
particularly over eastern PA into NJ and vicinity. Supercells with a
severe hail/wind threat will be possible initially, and enough
low-level shear may exist near the front for a tornado or two as
well. Whether convection can grow upscale into one or more clusters
also remains uncertain. But if this occurs, then the threat for
damaging winds may increase late this afternoon into the evening
given the rather favorable environment forecast.

...Northern/Central Plains into the Upper Midwest/Great Lakes...
A mid-level shortwave trough over the northern/central Rockies and
adjacent High Plains this morning will translate northeastward today
over the northern/central Plains. A moist and unstable airmass will
reside along/south of a front forecast to extend generally west to
east across parts of southern SD/northern NE into southern
MN/northern IA. Robust thunderstorm development appears increasingly
likely by 21-23Z across north-central NE as large-scale ascent
preceding the shortwave trough overspreads the destabilizing warm
sector. Latest NAM/RAP forecast soundings across this region show up
to 1500-2500 J/kg of MLCAPE and strong deep-layer shear, which will
likely support supercells initially. With steepened low/mid-level
lapse rates and elongated/nearly straight hodographs at mid levels
depicted, some potential for 2+ inch hail may exist with these
supercells. A tornado or two also appears possible as low-level
shear gradually increases after 02/00Z. With time, a bowing cluster
is expected to develop across eastern SD/northeast NE this evening,
and subsequently track eastward across southern MN/northern IA with
a severe/damaging wind threat overnight. Some risk for damaging
winds and hail may continue into early Wednesday morning across
parts of WI and Lower MI as well.

...Coastal Southeast Texas/Southwest Louisiana...
Tropical Storm Edouard will continue tracking northwestward today,
per latest NHC forecasts. Some enhancement to the low-level wind
field and hodograph is noted on the latest VWP and 15Z special
observed sounding from KLCH. This may support transient updraft
rotation with any cells on the north to northeast side of Edouard's
circulation, and a brief tornado or two may occur this
afternoon/evening across parts of coastal southeast TX/southwest LA
as filtered diurnal heating supports modest destabilization.


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SPC Sep 1, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Tue Sep 01 2026

Valid 011630Z - 021200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHERN NEW YORK INTO THE MID-ATLANTIC...AND THE NORTHERN/CENTRAL
PLAINS INTO THE UPPER MIDWEST...

...SUMMARY...
Scattered strong to severe thunderstorms should occur this afternoon
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.

...Mid-Atlantic/Southern New York...
A mid/upper-level anticyclone will remain centered over the TN
Valley/Mid-South today, with a mid-level shortwave trough forecast
to move eastward across Ontario through the period. In between these
features, a belt of enhanced west-northwesterly flow will exist
across the Great Lakes into the Mid-Atlantic. Latest surface
observations show a front draped from northwest to southeast across
southern NY/New England, with cloud cover and precipitation ongoing
across these areas. Current expectations are for destabilization to
occur along/south of the front through the afternoon, with modestly
steepened mid-level lapse rates present across MI (reference 12Z
observed APX/DTX soundings) forecast to advect southeastward across
the Mid-Atlantic. Moderate to strong instability will likely develop
by mid afternoon across PA/NJ, with 30-40 kt of deep-layer shear
fostering updraft organization.

While there is still some uncertainty regarding overall convective
development and evolution this afternoon/evening owing to nebulous
large-scale ascent, most high-resolution guidance develops isolated
to widely scattered thunderstorms along/south of the front,
particularly over eastern PA into NJ and vicinity. Supercells with a
severe hail/wind threat will be possible initially, and enough
low-level shear may exist near the front for a tornado or two as
well. Whether convection can grow upscale into one or more clusters
also remains uncertain. But if this occurs, then the threat for
damaging winds may increase late this afternoon into the evening
given the rather favorable environment forecast.

...Northern/Central Plains into the Upper Midwest/Great Lakes...
A mid-level shortwave trough over the northern/central Rockies and
adjacent High Plains this morning will translate northeastward today
over the northern/central Plains. A moist and unstable airmass will
reside along/south of a front forecast to extend generally west to
east across parts of southern SD/northern NE into southern
MN/northern IA. Robust thunderstorm development appears increasingly
likely by 21-23Z across north-central NE as large-scale ascent
preceding the shortwave trough overspreads the destabilizing warm
sector. Latest NAM/RAP forecast soundings across this region show up
to 1500-2500 J/kg of MLCAPE and strong deep-layer shear, which will
likely support supercells initially. With steepened low/mid-level
lapse rates and elongated/nearly straight hodographs at mid levels
depicted, some potential for 2+ inch hail may exist with these
supercells. A tornado or two also appears possible as low-level
shear gradually increases after 02/00Z. With time, a bowing cluster
is expected to develop across eastern SD/northeast NE this evening,
and subsequently track eastward across southern MN/northern IA with
a severe/damaging wind threat overnight. Some risk for damaging
winds and hail may continue into early Wednesday morning across
parts of WI and Lower MI as well.

...Coastal Southeast Texas/Southwest Louisiana...
Tropical Storm Edouard will continue tracking northwestward today,
per latest NHC forecasts. Some enhancement to the low-level wind
field and hodograph is noted on the latest VWP and 15Z special
observed sounding from KLCH. This may support transient updraft
rotation with any cells on the north to northeast side of Edouard's
circulation, and a brief tornado or two may occur this
afternoon/evening across parts of coastal southeast TX/southwest LA
as filtered diurnal heating supports modest destabilization.

..Gleason/Moore.. 09/01/2026


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