SPC Convective Outlook Day 1

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278
ACUS01 KWNS 212000
SWODY1
SPC AC 211958

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Tue Oct 21 2025

Valid 212000Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE SOUTHERN GREAT LAKES...

...SUMMARY...
Isolated strong to locally severe gusts are possible this afternoon
over parts of the southern Great Lakes.

...20Z Update...
Minimal changes were made with this update. The MRGL risk area was
trimmed behind an eastward-moving band of low-topped convection in
southeast Lower MI, where temperatures have dropped into the lower
50s. As these storms continue eastward across the remainder of far
southeast Lower MI and northern OH this afternoon, strong to locally
severe gusts (45-60 mph) will remain possible -- aided by steepened
pre-convective boundary-layer lapse rates and 35-40-kt flow below 2
km AGL (per VWP data).

Farther south, the TSTM area was trimmed behind the
southeastward-moving cold front in the Southeast, and in the
southern Appalachians where convection has generally outpaced the
remaining buoyancy.

..Weinman.. 10/21/2025

.PREV DISCUSSION... /ISSUED 1125 AM CDT Tue Oct 21 2025/

...Synopsis...
Morning water-vapor loop and upper-air data indicate a midlevel low
tracking east-southeastward over the upper Midwest -- accompanied by
cold 500-mb temperatures (around -28C). This feature will continue
eastward across the Great Lakes through the period, while a cold
front moves from the Upper OH Valley to the Atlantic Coast. Within
the base of the midlevel low, an embedded vorticitiy maximum will
move across the Lower Great Lakes through the afternoon, while a
related surface front/wind shift overspreads IN, OH, and Lower MI.

...Southern Great Lakes...
In the wake of a weakening band of showers along the departing front
over the upper OH Valley, mostly clear skies will promote
boundary-layer heating/steepening low-level lapse rates (shallow
inverted-V profiles) beneath the midlevel cold pocket -- yielding
marginal destabilization across parts of northern OH and southeast
Lower MI. As widely scattered convection along the secondary surface
front/wind shift spreads/develops into this environment, a modest
uptick in updraft intensity is possible this afternoon. Given strong
deep-layer flow flanking the midlevel low, isolated strong-locally
severe convectively enhanced wind gusts (45-60 mph) will be possible
during the late afternoon into early evening time frame. Small hail
will also be possible with any shallow cellular convection.

...Central Gulf Coast vicinity...
A warm, moist, and uncapped air mass ahead of the tail-end of the
cold front will support isolated thunderstorms across parts of east
TX into southern LA this afternoon. While moderate surface-based
buoyancy and around 25 kt of effective shear could promote a couple
strong storms along the front, warm temperatures aloft and minimal
large-scale forcing for ascent should generally limit upward
accelerations in updrafts.

$$

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

713
FLUS43 KLOT 211948
HWOLOT

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
248 PM CDT Tue Oct 21 2025

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-222000-
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-
248 PM CDT Tue Oct 21 2025 /348 PM EDT Tue Oct 21 2025/

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

.DAY ONE...Tonight.

Limited Non-Thunderstorm Wind Risk.

Westerly winds will gust to 40 mph through this evening with a
few gusts to 45 mph possible through early this evening.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Early Thursday Morning...
Limited Frost and Freeze Risk Outside of Chicago.
Early Friday Morning....
Elevated Frost and Freeze Risk Outside of Chicago.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be necessary through tonight.

$$

LMZ740>745-222000-
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-
248 PM CDT Tue Oct 21 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...Tonight.

Weather hazards expected...

Gale force winds and very hazardous waves.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Wednesday...
Gale force winds and very hazardous waves.
Thursday...
Hazardous conditions for small craft are likely.
Sunday and Monday...
Hazardous conditions for small craft are likely.

$$

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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696
ACUS02 KWNS 211657
SWODY2
SPC AC 211655

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1155 AM CDT Tue Oct 21 2025

Valid 221200Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not forecast on Wednesday or Wednesday night.

...New England...
An occluded cyclone will steadily move northeast from the Lake Huron
vicinity into QC during the period. The low-level warm conveyor
ahead of the bent-back occluded front will pivot northeast across
and eventually out of New England through the day. Meager buoyancy
is anticipated where strong deep-layer shear can persist over
eastern/coastal New England midday into the afternoon. Scattered
low-topped showers should dominate, with isolated embedded
thunderstorms possible. Despite weak convective intensity, fast
low-level south-southeasterlies, mainly across ME, might foster a
few locally strong gusts.

...Southwest...
A compact shortwave trough moving across southern CA into the Lower
CO Valley will aid in scattered thunderstorms from the Sierra NV
Mountains to the Four Corners vicinity on Wednesday afternoon and
evening. Much of this activity should be high-based and low-topped
over lower elevations. Meager buoyancy and weak lower-level flow
will minimize severe potential. But a few locally strong gusts are
possible amid large surface temperature-dew point spreads.

..Grams.. 10/21/2025

$$

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

587
ACUS03 KWNS 211927
SWODY3
SPC AC 211927

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 PM CDT Tue Oct 21 2025

Valid 231200Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL NM
TO CENTRAL OK...

...SUMMARY...
Isolated severe storms are possible beginning late afternoon
Thursday across parts of the Southwest and continuing into Thursday
night over the southern Great Plains.

...Southwest/Southern Great Plains...
A compact shortwave trough over the Lower CO Valley will reach the
southern Rockies by early Friday, as a separate impulse moves across
northern Baja/Gulf of CA. This will reinforce a positive-tilt
orientation to the broader trough and support only a weak lee
surface cyclone over the southern High Plains.

Another day of low-level moisture return from the TX Coastal Plain
should yield a plume of moderate buoyancy reaching the Permian Basin
to southwest OK by Thursday afternoon. More limited moisture is
anticipated farther north/west, supporting weak buoyancy. But this
will be compensated by stronger large-scale ascent accompanying the
leading shortwave impulse. Scattered thunderstorms are expected over
the Four Corners by mid-afternoon, with isolated storms arcing
southeast to southward over central to eastern NM. Sufficient
deep-layer shear will exist for a few supercells as storms mature in
the late afternoon, capable of producing isolated severe hail/wind.
A mesoscale corridor of more concentrated supercell potential may
evolve downstream on Thursday evening as storms impinge on the
aforementioned moderate buoyancy plume in west TX. Otherwise,
increasingly widespread elevated convection should occur on Thursday
night from west TX through much of OK. This should foster a rather
messy mode, with transient supercells/semi-organized clustering
relegated to the southern portion of the broader convective plume.
An isolated severe threat may persist in this regime overnight.

..Grams.. 10/21/2025

$$

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

See Product Description

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.