SPC Convective Outlook Day 1

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236
ACUS01 KWNS 040552
SWODY1
SPC AC 040550

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Thu Sep 04 2025

Valid 041200Z - 051200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
EAST...

...SUMMARY...
Isolated damaging winds are possible across parts of the Northeast
to the southern Appalachians and Tennessee Valley from late morning
through the afternoon.

...Synopsis...
A vertically stacked cyclone will drift north in northern ON, as an
intense mid-level jetlet and shortwave trough amplifies from the
southern Canadian Prairies across the Upper Midwest/Great Lakes. A
leading cold front will progress east into the Northeast to TN
Valley by this afternoon, with a separate lee trough diurnally
sharpening from VA into NY.

...Southern Appalachians/TN Valley to the Northeast...
Convection will likely be ongoing at 12Z along parts of the
aforementioned cold front from the Lake Erie to northern KY
vicinity. Despite weak mid-level lapse rates, diabatic surface
heating ahead of this activity should yield diurnal increases in
convective coverage/intensity by late morning across parts of the
Cumberland Plateau. This will overlap the northern extent of
moderate buoyancy across the TN Valley where low-level moisture is
richer. Combined with a more westerly component to mid-level flow
near the basal portion of the broad trough, a few semi-discrete and
loosely organized cells should develop southward during the
afternoon. Locally damaging winds and marginally severe hail are
possible, centered on the eastern TN vicinity.

Isolated to scattered multicell clusters and short-line segments may
also evolve in the afternoon from convection along/ahead of the cold
front and lee trough. Weak MLCAPE and poor mid-level lapse rates
will temper convective vigor, with damaging wind potential locally
augmented where pockets of deeper boundary-layer heating occur.

...Mid-MO Valley...
The aforementioned shortwave trough and intense mid-level jetlet
amplifying into the Upper Midwest could support a couple brief
strong storms in the early evening. A narrow corridor of meager
surface-based buoyancy may develop ahead of a sharpening cold front
by late afternoon. Modified moisture return in the wake of a prior
frontal passage will be limited and convection should remain
low-topped given the flimsy buoyancy. Still, the background wind
fields and strengthening forcing for ascent render concern for a few
locally strong gusts and small hail.

...KS...
An accelerating and sharpening cold front will sweep south across
the central High/Great Plains tonight. Undercut/elevated convection
should form to the cold side of this boundary early Friday morning.
Locally strong surface gusts may accompany this activity amid robust
low-level northerlies.

..Grams/Thornton.. 09/04/2025

$$

The "Convective Outlooks" issued by SPC can be thought of as a detailed discussion of the Severe Thunderstorm threat and it's associated risks nationwide. Risk levels range from Marginal to Slight, Enhanced, Moderate, and High and are issued based on the likelihood of 3 major severe weather threats; the risk of tornadoes, damaging winds, and hail. These discussions are often heavily laced meteorological terminology that may be difficult to understand without a background in the field. However understanding these discussions shouldn't be thought of as necessary. Instead, should DuPage county fall under one of these threat levels for severe weather, the response should be to have a heightened level of awareness about the deveoloping weather. Keep an eye on the "Watch County Notification" for any active severe weather watches issued for DuPage county; the "Hazardous Weather Outlook" and "Severe Weather Statement" can also be helpful in explaining the developing risk; additionally, watch for "Active Weather Warnings" and keep an eye on our "Regional Satellite and Radar" products which can be viewed with active watches/warnings or lightning activity.

Hazardous Weather Outlook

See Product Description

907
FLUS43 KLOT 040758
HWOLOT

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
258 AM CDT Thu Sep 4 2025

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-050800-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
258 AM CDT Thu Sep 4 2025 /358 AM EDT Thu Sep 4 2025/

This Hazardous Weather Outlook is for portions of north central
Illinois...northeast Illinois and northwest Indiana.

.DAY ONE...Today and Tonight.

Weather hazards expected...

High Swim Risk Lake Michigan Beaches.

DISCUSSION...

Dangerous swimming conditions will continue today at Indiana Lake
Michigan beaches.


.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Thursday Night into Friday...
Limited Non-Thunderstorm Wind Risk.
High Swim Risk Porter County Lake Michigan Beaches.

DISCUSSION...

Expect dangerous conditions on the lake again Friday, primarily
at Indiana Lake Michigan beaches.

Winds may gust up to 40 mph from the southwest to west late
tonight into Friday morning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be necessary through tonight.

$$

LMZ740>745-050800-
Winthrop Harbor to Wilmette Harbor IL-
Wilmette Harbor to Northerly Island IL-
Northerly Island to Calumet Harbor IL-
Calumet Harbor IL to Gary IN-Gary to Burns Harbor IN-
Burns Harbor to Michigan City IN-
258 AM CDT Thu Sep 4 2025

This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.

.DAY ONE...Today and Tonight.

Weather hazards expected...

Hazardous conditions for small craft east of Gary Indiana today.
Gale force winds and very hazardous waves expected tonight.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Friday...
Gale force winds and very hazardous waves through the morning.

$$

KJB

Visit us at www.weather.gov/chicago

The "Hazardous Weather Outlook" contains information regarding any and all weather expected to occur within the region that could be hazardous to travel, life or property. This is one of our most highly recommended products to check on a daily basis, and it some cases multiple times per day should significant weather be expected to affect DuPage county.

SPC Convective Outlook Day 2

See Product Description

694
ACUS02 KWNS 040602
SWODY2
SPC AC 040600

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Thu Sep 04 2025

Valid 051200Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS STRETCHING FROM
NORTHERN TEXAS NORTHEAST INTO SOUTHERN OHIO...

...SUMMARY...
Strong thunderstorms will be possible from the southern Plains into
the Ohio and Tennessee Valleys during the afternoon into the
overnight hours. Isolated large hail and damaging winds may be
possible with the strongest storms.

... Synopsis ...

A seasonably strong/cold midlevel low will persist across Ontario,
with an attendant larger-scale trough persisting across much of the
eastern United States. A potent midlevel shortwave trough will be
across the Upper Great Lakes at the start of the period and will
quickly rotate around the upper low into Quebec through the period.
In its wake a midlevel ribbon of higher vorticity will be left
behind from Iowa northeast across Michigan. Upstream from this, the
midlevel height field will begin to respond to another shortwave
trough rotating around the Ontario low.

At the surface, a surface low will quickly lift northeast from
northern Michigan through Ontario and into Quebec through the
forecast period. A cold from will extend southwest from this low and
will push south and east as the surface low lifts northeast.
Although somewhat diffuse initially, the temperature gradient across
the cold front will rapidly strengthen through the day.

... Ohio and Tennessee Valleys ...

Diurnal heating should allow afternoon temperatures to warm into the
80Fs and 90Fs across the region. Given surface dewpoint temperatures
in the mid 60Fs perhaps as far north as southern Ohio, this heating
will result in most-unstable CAPE values in excess of 2000 J/kg
across the area. The region will also be on the periphery of the
stronger midlevel flow, yield effective shear of around 40 knots.

Thunderstorms should develop by late afternoon in response to
increasing large-scale ascent associated with both differential
vorticity advection and frontal circulations. Given the degree of
instability and effective layer shear, initial thunderstorms may
exhibit supercellular structures. However, given the
temperature-dewpoint spreads on the order of 20F+ the expectation is
that thunderstorms should tend to favor upscale growth toward linear
segments. As such, thunderstorms may initially pose a hail threat,
especially across western Kentucky and Tennessee, but should
transition to more of a wind threat with eastward extent.

Across portions of Kentucky and southern Ohio, a short-window,
conditional tornado threat may evolve as thunderstorms develop in
the vicinity of the surface boundary. As thunderstorms interact with
or cross over the boundary, strong northeasterly surface winds will
enlarge low-level hodographs supporting at least some tornado
threat.

... Greater Arklatex Region ...

The surface cold front across the region is expected to strengthen
during the day as it slowly moves south. During the evening into the
overnight hours, strong warm-air advection on the nose of a
strengthening low-level jet may support thunderstorm development on
the cool side of the cold front. Despite surface temperatures in the
60Fs and low 70Fs, steep mid-level lapse rates atop the colder
surface layer may support isolated large hail.

..Marsh.. 09/04/2025

$$

The "Convective Outlooks" issued by SPC can be thought of as a detailed discussion of the Severe Thunderstorm threat and it's associated risks nationwide. Risk levels range from Marginal to Slight, Enhanced, Moderate, and High and are issued based on the likelihood of 3 major severe weather threats; the risk of tornadoes, damaging winds, and hail. These discussions are often heavily laced meteorological terminology that may be difficult to understand without a background in the field. However understanding these discussions shouldn't be thought of as necessary. Instead, should DuPage county fall under one of these threat levels for severe weather, the response should be to have a heightened level of awareness about the deveoloping weather. Keep an eye on the "Watch County Notification" for any active severe weather watches issued for DuPage county; the "Hazardous Weather Outlook" and "Severe Weather Statement" can also be helpful in explaining the developing risk; additionally, watch for "Active Weather Warnings" and keep an eye on our "Regional Satellite and Radar" products which can be viewed with active watches/warnings or lightning activity.

SPC Convective Outlook Day 3

See Product Description

865
ACUS03 KWNS 040716
SWODY3
SPC AC 040715

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0215 AM CDT Thu Sep 04 2025

Valid 061200Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
NORTH CAROLINA NORTHWARD INTO SOUTHERN PENNSYLVANIA...

...SUMMARY...
Strong thunderstorms are expected from northern North Carolina into
southern Pennsylvania on Saturday. The strongest storms may pose a
threat for damaging winds.

... Discussion ...

A surface cold front will slowly move east across the eastern US on
Saturday. Along and ahead of this front, surface temperatures should
warm into the upper-80Fs to low-90Fs from the Mid-Atlantic region
southward into the Carolinas, with surface dewpoint temperatures in
the upper-60Fs to low-70Fs. As a result a corridor of instability
perhaps as great as 2000 J/kg will develop from North Carolina
northward into the Mid-Atlantic area.

Isolated to scattered thunderstorms should develop during the
afternoon along the slow moving front across the Carolinas into the
Mid Atlantic. Despite deep layer shear on the order of 40 knots and
2000 J/kg CAPE, poor mid-level lapse rates and precipitable water
values around 1.75 inches should limit the overall severe threat to
the potential for isolated damaging thunderstorm winds.

..Marsh.. 09/04/2025

$$

The "Convective Outlooks" issued by SPC can be thought of as a detailed discussion of the Severe Thunderstorm threat and it's associated risks nationwide. Risk levels range from Marginal to Slight, Enhanced, Moderate, and High and are issued based on the likelihood of 3 major severe weather threats; the risk of tornadoes, damaging winds, and hail. These discussions are often heavily laced meteorological terminology that may be difficult to understand without a background in the field. However understanding these discussions shouldn't be thought of as necessary. Instead, should DuPage county fall under one of these threat levels for severe weather, the response should be to have a heightened level of awareness about the deveoloping weather. Keep an eye on the "Watch County Notification" for any active severe weather watches issued for DuPage county; the "Hazardous Weather Outlook" and "Severe Weather Statement" can also be helpful in explaining the developing risk; additionally, watch for "Active Weather Warnings" and keep an eye on our "Regional Satellite and Radar" products which can be viewed with active watches/warnings or lightning activity.

Special Weather Statement

See Product Description

No active Special Weather Statement for DuPage County.

The "Special Weather Statement" details notable weather either occuring or expected to occur, but does not necessarily have to be considered severe or hazardous. This is a supplementary product issued by the National Weather Service to help describe noteworthy weather. It's terminology should be reasonably easy to understand by the general public.

Watch County Notification

See Product Description

No active Watch County Notification for DuPage County.

The "Watch County Notification" will contain updates regarding active severe weather watches that pertain to DuPage county. This may be for a newly issued watch, or the cancelation of an existing watch. Severe weather watches come in two forms; Severe Thunderstorm and Tornado, and it should be noted that a Severe Thunderstorm Watch does NOT rule out the possibility of tornadoes occuring. It generally means that the tornado threat is minimal while damaging winds and hail are still likely. See our "Watch, Warning, and Advisory Criteria" for more detailed information on the differences and critera for watches, warnings and advisory for all forms of weather.

Winter Weather Statement

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No active Winter Weather Statement for DuPage County.

The "Winter Weather Statement" is a product aimed at the general public that will discuss impacts caused by winter weather. This may include information about watches, warnings and advisories as well as details about impactful winter weather that may not warrant the issuance of a watch, warning or advisory.

Severe Weather Statement

See Product Description

No active Severe Weather Statement for DuPage County.

The "Severe Weather Statement" is a product aimed at the general public that will discuss impacts caused by severe thunderstorms. This may include information about watches and warnings as well as details about impactful "sub-severe" weather that may not warrant the issuance of a watch or warning which sometimes may come when a watch or warning has been canceled.

Non-Precip Statement

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No active Non-Precip Statement for DuPage County.

The "Non-Precip Statement" is aimed at the general public and will detail notable weather that is either occuring or expected to occur, but does not relate to any form of precipitation. These would include but are not limited to high winds, reduced visibility or extreme temperatures.

Active Weather Warnings

Tornado Warnings

No active Tornado Warnings.

Severe Thunderstorm Warnings

No active Severe Thunderstorm Warnings.

Flood Warnings

No active Flood Warnings.

General Tornado/Severe Weather Safety

1. A Tornado or Severe Thunderstorm Warning is issued when it has been reported, or when it has been detected via National Weather Service radar. It is to be interpreted that this event is occuring and is expected to affect all warned areas. Those within the warning need to take action immediately.
2. If under a warning remain calm and if it is necessary to seek shelter. Students and Employees should head to their nearest designated shelter area. The route to these shelter areas are posted in all rooms on campus and signs are placed in the hallways to direct you to the nearest shelter area. Review these instructions and be familiar with where your nearest shelter is. Stay indoors, away from windows and large unsupported ceilings. Faculty should account for their students and Supervisors should account for their areas employees.
3. If outside, take shelter in the nearest building.
4. After the storm has passed, dial Police at 911 to report any injuries or damage to buildings.
5. If the building is severely damaged, evacuate the building as soon as possible after the storm has passed.