SPC Convective Outlook Day 1

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791
ACUS01 KWNS 251959
SWODY1
SPC AC 251957

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Fri Jul 25 2025

Valid 252000Z - 261200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTHEAST AND MID ATLANTIC...PARTS OF THE MID MISSOURI VALLEY...AND
ACROSS THE NORTHERN PLAINS....

...SUMMARY...
Scattered strong to severe thunderstorms remain capable of damaging
wind gusts across parts of New England and the northern Mid-Atlantic
States this afternoon/evening. Severe storms will also be possible
across much of North Dakota as well as eastern Kansas into western
Missouri.

...20z Update Northeast...
Scattered to numerous thunderstorms ongoing ahead of a weak cold
front across the Northeast and northern Mid Atlantic states will
continue to pose a risk for isolated damaging gusts through this
evening. The main focus for storm development/intensification along
the front will continue to shift southeastward this afternoon.
Trimming was done to the MRGL area mainly where the wind shift has
already moved offshore. Otherwise the SLGT risk area was adjusted to
better match the higher storm coverage and threat for damaging
gusts.

...KS/MO...
To the west, scattered severe storms should continue to
develop/intensify this afternoon ahead of an MCV/shortwave trough
across parts of KS and MO. Very moist surface conditions are present
with mid 70s F dewpoints contributing to moderate destabilization
despite weak low and mid-level lapse rates. Enhanced mid-level wind
fields observed by area VADs should support a few stronger storms
including supercells capable of damaging gusts and possibly brief
tornadoes this afternoon and evening.

...Great Basin...
Isolated to scattered high-based thunderstorms remain likely across
northern CA and western NV this evening. Steep low-level lapse rates
will favor dry microburst potential with these storms or any more
persistent clusters of storms able to evolve. Have adjusted the MRGL
risk slightly west to better capture storms developing near the
higher terrain.

Otherwise, see the previous discussion for additional information.

..Lyons.. 07/25/2025

.PREV DISCUSSION... /ISSUED 1142 AM CDT Fri Jul 25 2025/

...Northeast/Mid-Atlantic States...
Midday vapor imagery shows a fast-moving shortwave trough
progressing eastward into Quebec. An associated cold front will move
south-southeastward across New England this afternoon. Relatively
hot/humid conditions ahead of the front will lead to widely
scattered afternoon thunderstorms across southern New England and
eastern portions of New York/Pennsylvania. These storms will track
southeastward toward the coast through the early evening with
damaging winds possible.

...Northern Plains including North Dakota...
An upper ridge remains centered over the central Plains, with a weak
southern-stream trough currently moving across Utah into Wyoming.
Weak lift and increased mid-level moisture ahead of the system will
aid in the development of scattered thunderstorms by late afternoon
across parts of eastern Montana and northeast Wyoming. Thermodynamic
parameters are favorable for large hail in the stronger cells. It
seems that these storms will tend to persist east-northeastward this
evening and pose a risk of hail and locally damaging winds across
North Dakota.

...Eastern Kansas/western Missouri...
Regional WSR-88D VWP data continues to sample modestly enhanced
low/mid-tropospheric flow in relation to a slow-moving MCV, notable
from KEAX where 35-40 kt west-southwesterly flow persists between
3-5 km AGL. With a very moist air mass in place (low to middle 70s F
surface dewpoints), intensifying storms could include supercells
given some likely persistence of the enhanced flow field. Especially
with a convectively reinforced surface boundary, a semi-focused
corridor of damaging winds and brief tornado potential could evolve
this afternoon into early evening.

...Northern California/western Nevada...
Aside from the dry thunderstorm potential (see Fire Weather Day 1
Outlook), sufficient moisture/buoyancy may exist on the eastern and
northern periphery of the slow-moving upper low, where mid-level
temperatures (-12C at 500mb) are semi-cool, to allow for some hail
and/or convectively enhanced wind gusts this afternoon through
around sunset.

$$

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

894
FLUS43 KLOT 252007
HWOLOT

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
307 PM CDT Fri Jul 25 2025

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-262015-
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-
307 PM CDT Fri Jul 25 2025 /407 PM EDT Fri Jul 25 2025/

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

.DAY ONE...Tonight.

Weather hazards expected...

Limited Thunderstorm Risk...with an associated:
Level 1 of 5 Damaging Wind Risk...up to 60 mph.
Elevated Flooding Risk.

DISCUSSION...

Isolated to scattered thunderstorms will continue this afternoon.
Brief torrential rainfall may lead to a continued threat for
isolated instances of flash flooding.

Additional heavy rain producing storms are possible this evening
and overnight, with an additional flash flood potential into
early Saturday morning. Initially, the main threat area will be
west of the Fox Valley, but may expand to include most of the
region tonight.

The strongest storms this afternoon and tonight will be capable
of producing strong and gusty winds.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Saturday...
Limited Flooding Risk.
Limited Thunderstorm Risk...with an associated:
Level 1 of 5 Severe Thunderstorm Risk.
Sunday...
Limited Thunderstorm Risk...with an associated:
Level 1 of 5 Severe Thunderstorm Risk.
Limited Excessive Heat Risk.
Monday...
Elevated Excessive Heat Risk.
Tuesday...
Limited Thunderstorm Risk.
Limited Flooding Risk.
Elevated Excessive Heat Risk.
Wednesday...
Limited Thunderstorm Risk.

DISCUSSION...

Lingering thunderstorms Saturday will bring the chance for
torrential rainfall and localized flooding, particularly during
the morning, mainly north of I-80. There is a threat for a few
strong to severe storms in the afternoon, mainly south of I-80.

Heat and humidity may once again build to dangerous levels at
times Sunday through Tuesday. The hottest conditions look to occur
on Monday.

.SPOTTER INFORMATION STATEMENT...

Given the limited nature of any severe threat, spotter activation
is not expected, but reports of flooding or severe weather are
appreciated.

GENERAL STORM MOTION OF THE DAY:

Moving toward the east to northeast at 15 mph this afternoon,
then 20 to 25 mph tonight.

$$

LMZ740>745-262015-
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-
307 PM CDT Fri Jul 25 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...

Limited Thunderstorm Risk...with an associated:
Level 1 of 5 Thunderstorm Wind Gust Risk...up to 40 knots.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Saturday...
Limited Thunderstorm Risk...with an associated:
Level 1 of 5 Severe Thunderstorm Risk.
Sunday...
Limited Thunderstorm Risk.
Tuesday and Wednesday...
Limited Thunderstorm Risk.

$$

Carlaw

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

795
ACUS02 KWNS 251726
SWODY2
SPC AC 251725

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1225 PM CDT Fri Jul 25 2025

Valid 261200Z - 271200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
NORTHERN ROCKIES...CENTRAL HIGH PLAINS AND THE DAKOTAS AS WELL AS
THE MIDWEST INTO THE MID-ATLANTIC...

...SUMMARY...
Strong to severe thunderstorms accompanied by potentially damaging
wind gusts are possible Saturday afternoon/evening in parts of the
Upper Midwest/Lower Great Lakes into portions of the Mid-Atlantic.
Isolated to widely scattered severe storms are also likely across
the Northern Rockies, central High Plains, and northern Plains.

...Synopsis...
The overall synoptic regime will largely remain in place over the
next 48 hours across the country, characterized by a persistent
upper ridge over the Southeast with longwave troughing west of the
Rockies. A diffuse frontal zone draped from the upper OH Valley into
the central Plains this morning should largely remain in place
across the upper Midwest/Great Lakes region and will act as a foci
for thunderstorm development through the afternoon. To the west, a
low-amplitude impulse currently off the coast of southwest CA will
propagate into the central Rockies/High Plains around peak heating.
This will support isolated to scattered thunderstorm development
that may persist into the overnight hours across the northern
Plains.

...Eastern North Dakota...
Two rounds of severe thunderstorms appear possible across eastern ND
and far northwest MN tomorrow afternoon and overnight. A weak
surface front emanating out of the southern Canadian prairies will
impinge on the northern edge of a plume of 70-75 dewpoints as it
moves into northeast ND and far northwest MN. Steep mid-level lapse
rates advecting into the region coupled with rich low-level moisture
should support 3000-4000 J/kg MLCAPE by late afternoon. 30-40 knot
mid-level flow will provide adequate deep-layer wind shear for
organized storms, including the potential for a few supercells
capable of large hail and severe winds. Increasing capping with
southward extent should limit the spatial extent of this threat.
Morning guidance hints at the passage of an MCS across the Dakotas
overnight as a result of upscale growth of convection over the High
Plains. Given the steep lapse rates in place upstream per 12z RAOBS
and the passage of weak mid-level wave during the overnight period,
this scenario appears plausible. However, deterministic solutions
vary regarding the intensity of the potential MCS, and nocturnal
cooling coupled with warm 850-700 mb temperatures at the base of the
EML cast uncertainty onto how intense surface winds will be. Higher
risk probabilities may be needed for either of these scenarios as
forecast uncertainty become resolved.

...Northern Rockies into the Northern/Central High Plains...
An upper-level impulse currently off the southern CA coast is
forecast to phase favorably with peak heating over the northern
Rockies/central High Plains. This will promote thunderstorm
development within the higher terrain of southern MT and northern WY
and along a surface trough draped across the western Plains by late
afternoon. Strong daytime heating under a plume of steep mid-level
lapse rates and on the western fringe of a low-level moisture plume
will result in deeply mixed profiles with around 500-1000 J/kg
MLCAPE. Moderate mid-level flow within the CAPE-bearing layer may
support adequate deep-layer shear for a supercell or two across
MT/northern WY, but weaker shear with southward extent will limit
storm organization/longevity. Regardless, thermodynamic profiles
will be very favorable for strong to severe downburst winds.

...Midwest to Mid-Atlantic...
A weak mid-level impulse/MCV emanating out of the Plains will
promote scattered showers and weak thunderstorms across the Midwest
at the start of the forecast period. Lingering showers and clouds
casts some uncertainty regarding diurnal heating/destabilization,
but rich boundary-layer moisture already in place will likely
support MLCAPE values upwards of at least 2000 J/kg by late
afternoon. Areas along the composite frontal zone that can
destabilize will likely see thunderstorm development by
mid-afternoon as the MCV propagates east across the Midwest/Great
Lakes. Augmented mid-level winds attendant to this feature will
support 0-6 km bulk shear values on the order of 20-30 knots, which
in conjunction with mean flow along the boundary, should promote a
mix of semi-discrete cells and loosely organized clusters capable of
damaging to severe winds and perhaps large hail.

Further east across southern PA into the Mid-Atlantic, thunderstorm
development is anticipated by mid to late afternoon both within the
central Appalachians and along a diffuse frontal zone. Despite weak
mid-level lapse rates, rich low-level moisture should support
widespread MLCAPE values of around 1500 J/kg with minimal capping.
Easterly low-level winds under northwesterly mid-level flow will
provide sufficient hodograph elongation for organized cells/clusters
with an attendant threat for damaging/severe winds.

..Moore.. 07/25/2025

$$

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

982
ACUS03 KWNS 251923
SWODY3
SPC AC 251923

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0223 PM CDT Fri Jul 25 2025

Valid 271200Z - 281200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THE EASTERN
DAKOTAS INTO PORTIONS OF THE UPPER MISSISSIPPI RIVER VALLEY AND
ACROSS THE MID-ATLANTIC AND PORTIONS OF NEW ENGLAND...

...SUMMARY...
Severe thunderstorms are possible from the eastern Dakotas into the
Upper Mississippi Valley as well as across portions of the
Mid-Atlantic and New England region.

...Synopsis...
An upper ridge currently over the Southeast will gradually shift
west over the next 48-72 hours into the south-central U.S.
Strong/severe thunderstorm chances will largely be focused on the
north/northeastern periphery of the ridge as shortwave impulses
embedded within strong westerly mid-level flow overspread buoyant
air masses.

...Eastern Dakotas into the Upper MS Valley...
Forecast confidence remains low for Sunday across the eastern
Dakotas into portions of the upper MS Valley. A low-amplitude
mid-level wave is forecast to round the apex of the mid-level ridge
through the afternoon/evening across ND/MN. A residual MCS from
overnight Saturday may accompany this wave, though the intensity of
this MCS by Sunday morning remains uncertain. However, this will
have a direct impact on thunderstorm development/evolution Sunday
afternoon. Several deterministic solutions (most notably recent NAM
and ECMWF runs) suggest either a re-intensification of the MCS
and/or new convective development along an outflow boundary across
MN by late afternoon. Given forecast MLCAPE of 3000-4000 J/kg and
30-40 knots of deep-layer wind shear, this activity could strengthen
into a well-organized, severe MCS through the late evening hours as
it propagates southeastward along a warm frontal zone into parts of
IA and/or WI. Other solutions, including the high-res RRFS, depict a
weaker early-morning MCS and more limited thunderstorm coverage
through late evening. Ensemble guidance shows similarly dichotomous
solutions. Severe risk probabilities were maintained as-is given
then spread in solutions, but higher risk highlights will likely be
needed if guidance begins to coalesce around the NAM/ECMWF
solutions.

...Mid-Atlantic into parts of New England...
A weak surface trough/cold front is forecast to push eastward across
the Northeast/Mid-Atlantic region through peak heating. A moist air
mass will likely remain in place through the weekend and will
promote widespread MLCAPE values of at least 1000 J/kg along with
limited capping. West/northwesterly flow aloft coupled with modest
low-level winds should support adequate deep-layer wind shear for a
few strong/severe thunderstorms as convection develops by mid/late
afternoon.

..Moore.. 07/25/2025

$$

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

See Product Description

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

• Issued: 07/25/25 11:43 am - Expires: 1 Hours8 Minutes

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.