SPC Convective Outlook Day 1

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496
ACUS01 KWNS 171947
SWODY1
SPC AC 171946

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0246 PM CDT Wed Sep 17 2025

Valid 172000Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE RATON
MESA AND SOUTHERN COLORADO FRONT RANGE INTO PORTIONS OF THE SOUTHERN
HIGH PLAINS....

...SUMMARY...
Isolated severe thunderstorms are possible, mainly during late
afternoon to mid-evening, across parts of the south-central High
Plains. The most likely corridor is from the southern Colorado Front
Range/Raton Mesa into the western Texas and Oklahoma Panhandles,
where large hail, severe gusts, and a brief tornado are possible.

...20z Update...
The previous forecast largely remains on track with only minor
adjustments made to reflect recent convective trends. Latest GOES
imagery and regional radar mosaics show convective initiation
underway across the TX Panhandle into western OK along a diffuse
frontal zone. This activity will likely pose some hail/wind threat
as it spreads northeast into a well-mixed, but modestly sheared
environment. Further west across the High Plains, low-level winds
are becoming easterly as anticipated by morning guidance. This
increasing upslope flow regime will promote thunderstorm development
by early evening as well as aid in convective organization via
elongation of low/mid-level hodographs. Recent CAM guidance
continues to depict the best signal for robust convection across
southeast CO into adjacent portions of NM/OK/TX within the Slight
risk corridor. See the previous discussion below and MCD #2091 for
additional details.

..Moore.. 09/17/2025

.PREV DISCUSSION... /ISSUED 1140 AM CDT Wed Sep 17 2025/

...Front Range/Raton Mesa and south-central High Plains...
A prominent upper trough will continue to pivot over the northern
High Plains with a base-embedded shortwave trough/speed max
spreading southeastward over Colorado toward the south-central High
Plains by tonight. A related front will continue to settle
south-southeastward with moist low-level upslope flow in its wake
across southeast Colorado/Raton Mesa vicinity and the nearby
south-central High Plains. Buoyancy will be adequate for some
supercells as flow aloft strengthens and low-level winds take on
more of an easterly component. Bouts of large hail can be expected,
with severe-caliber winds also possible, particularly with the
southernmost development toward the Panhandles. A brief/low-end
tornado risk may also exist near the boundary and within the
immediate post-frontal environment.

...South-central/eastern Kansas to Iowa/Missouri...
MCV/modest-strength cyclonic flow aloft and zones of moderate
destabilization to the east of the residual early day convection and
cloud debris seems likely to influence a redevelopment and
intensification of convection this afternoon. Even with some
MCV-related flow enhancement, deep-layer shear will remain weak
overall, but some episodic severe storms could occur with locally
damaging winds and some hail.

...Southern Louisiana...
As a cumulus field continues to develop/expand late this morning per
visible satellite imagery, scattered thunderstorm development is
likely this afternoon. As the boundary layer warms and destabilizes,
thermodynamic profiles will become favorable for the possibility of
some localized downbursts.

...Southern Minnesota/northern Wisconsin...
A few strong storms and perhaps a locally severe storm or two could
occur this afternoon into evening as the upper trough interfaces
with the front and moderately unstable environment, especially with
eastward extent away from residual early day cloud cover/scattered
precipitation. However, very weak deep tropospheric winds should
keep any pulse-type severe potential rather marginal/localized
overall.

$$

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

045
FLUS43 KLOT 170905
HWOLOT

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
405 AM CDT Wed Sep 17 2025

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-180915-
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-
405 AM CDT Wed Sep 17 2025 /505 AM EDT Wed Sep 17 2025/

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

.DAY ONE...Today and Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Friday through Sunday...
Limited Thunderstorm Risk.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be necessary through tonight.

$$

LMZ740>745-180915-
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-
405 AM CDT Wed Sep 17 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.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Friday and Saturday...
Hazardous conditions for small craft are likely.
Saturday and Sunday...
Limited Thunderstorm Risk.

$$

Yack

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

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156
ACUS02 KWNS 171732
SWODY2
SPC AC 171730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Wed Sep 17 2025

Valid 181200Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL IA
INTO WESTERN MO...EASTERN KS...NORTHWEST AR...OK...AND THE SOUTHEAST
TX PANHANDLE...

...SUMMARY...
Strong to locally severe storms are possible from parts of the
Midwest into the east-central and southern Plains on Thursday.

...Synopsis...
Little change to the overall pattern is expected on Thursday, with
a mid/upper-level trough expected to persist over the
northern/central Plains. Within the broader trough, distinct
mid/upper-level lows initially over northeast MT and central SD may
begin to consolidate by Thursday night, as a convectively enhanced
midlevel shortwave moves through the base of the trough from the
central Plains into the lower MO Valley vicinity. Farther west, a
mid/upper-level trough related to the remnants of Tropical Cyclone
Mario will move across parts of southern/central CA through the
period.

...Parts of the east-central and southern Plains into the Ozarks and
Upper Midwest...
A weak surface low is forecast to move eastward across eastern SD on
Thursday. A weak surface front will extend southward from the low
across western MN/IA into eastern KS, and then southwestward into
parts of OK and the TX Panhandle. The south and east extent of this
front will be influenced by rather extensive early-morning
convection. To the east of any remnant morning convection and cloud
debris, moderate destabilization and steepening of low-level lapse
rates will be possible from northeast OK into parts of MO/IA.
Scattered storm development is expected during the afternoon.
Deep-layer shear will remain rather weak, but a few weakly organized
cells or clusters could evolve and pose some threat of locally
damaging wind.

Farther southwest along the trailing portion of the front,
deep-layer shear will be somewhat stronger across parts of OK into
the TX Panhandle, as midlevel winds veer to west-northwesterly.
Storm coverage with southwest extent is rather uncertain, with the
primary midlevel shortwave trough becoming increasingly removed from
the region, but an isolated organized cell or two may evolve and
pose some threat for hail and/or strong gusts.

...Southwest...
Increasing moisture and the approaching mid/upper-level trough will
support at least scattered storms across parts of southern/central
AZ into southeast CA and far southern NV. Some modest enhancement to
midlevel flow may overspread this region during the afternoon, but
deep-layer shear is currently expected to remain rather weak. As a
result, storms may remain disorganized, but localized downbursts
cannot be ruled out, especially where stronger pre-storm heating
occurs.

..Dean.. 09/17/2025

$$

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

381
ACUS03 KWNS 171910
SWODY3
SPC AC 171909

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0209 PM CDT Wed Sep 17 2025

Valid 191200Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe storms are not currently expected on Friday.

...Synopsis...
A mid/upper-level trough is forecast to remain in place across the
central/northern Plains and Upper Midwest on Friday, as an embedded
midlevel cyclone moves eastward across SD. Scattered diurnal storm
development will be possible from the ArkLaTex into much of the MS
Valley, within a relatively moist and moderately unstable
environment. With weak deep-layer flow/shear expected across this
region, the threat for organized severe storms currently appears
low. Late in the period, elevated storms may develop within a
low-level warm advection regime across parts of KS/OK.

Farther west, a midlevel shortwave trough is forecast to move from
central CA toward the Great Basin, while a broader mid/upper-level
trough remains offshore of southern CA. This pattern will favor
potential for scattered storms across parts of the Southwest, with
at least isolated storm development possible from central/northern
CA into adjacent parts of NV.

..Dean.. 09/17/2025

$$

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.