SPC Convective Outlook Day 1

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886
ACUS01 KWNS 191955
SWODY1
SPC AC 191954

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0254 PM CDT Sat Jul 19 2025

Valid 192000Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL AND NORTHERN HIGH PLAINS INTO THE MIDWEST...AND PARTS OF
VIRGINIA INTO NORTH CAROLINA...

...SUMMARY...
Scattered strong storms with a severe wind/hail threat are likely
this evening across the northern High Plains into the Midwest, with
a couple of tornadoes possible over western Nebraska. A few damaging
gusts also remain possible with storms over Virginia into North
Carolina.

...20Z Update...
Substantial changes have been made to the 20Z Day 1 Convective
Outlook update. First, Slight risk probabilities have been dropped
across portions of the Great Lakes into the OH Valley region. Storms
ongoing over this part of the CONUS have not shown robust severe
potential thus far. Ongoing storms are also overturning the
troposphere during peak heating, casting doubts on adequate airmass
modification/destabilization for a renewed organized severe threat.
Nonetheless, an isolated damaging gust or brief tornado could occur
with a stronger storm that can become sustained, hence the
maintenance of a Category 1/Marginal Risk.

Wind-driven Slight risk probabilities have been added over portions
of the MO River Valley, joining the Slight risk across the High
Plains and Midwest areas. From eastern NE into northern IL,
thunderstorms are expected to develop along the warm-frontal
low-level boundary this evening given enhanced convergence driven by
a low-level jet. Furthermore, there is some concern that supercells
could congeal into an MCS across central NE and potentially
propagate eastward along this boundary early tonight, fostering a
damaging gust threat.

Otherwise, ongoing multicells over VA into NC will continue through
the afternoon with a damaging gust threat. Supercells and small
bowing segments are also still expected across the central/northern
High Plains this afternoon and evening, accompanied by severe wind
and hail. A couple of tornadoes may accompany any more robust,
sustained supercells over western into central NE with the onset of
low-level jet development this evening.

..Squitieri.. 07/19/2025

.PREV DISCUSSION... /ISSUED 1130 AM CDT Sat Jul 19 2025/

...Midwest/Great Lakes...
An ongoing sub-severe MCS continues east-southeast across IL with an
attendant warm advection cluster of thunderstorms downstream over
the lower Wabash Valley. Considerable convective overturning
coupled with convective cloud debris have acted to limit
destabilization thus far across IL into western IN and northward
into the southwest Great Lakes. Have reduced severe probabilities
this outlook update for northern IL into WI due to limited
destabilization, and models converging on limited storm coverage
through the remainder of the day and their depiction of primary
thunderstorm activity tonight occurring farther south/southwest over
IA into central IL towards daybreak.

However, downstream of the ongoing thunderstorm clusters over IL/IN,
gradual heating will probably support some intensification of storms
into the afternoon. Isolated to perhaps scattered damaging winds in
small clusters appear to be the primary severe hazard. Other
thunderstorm development is possible over Lower MI where a
wind-damage threat may materialize with the stronger storms that
develop this afternoon. Later this afternoon but more likely into
tonight, additional storms are forecast to develop on the trailing
outflow with an attendant risk for mainly hail/wind.

...Virginia/North Carolina...
A west-east draped frontal zone resides over southern PA to the
north of this region. However, a very moist low-level airmass
featuring lower to mid 70s dewpoints will continue to
heat/destabilize through mid-late afternoon and promote the
development of moderate buoyancy. Despite weak mid-level lapse
rates, high PW (around 2 inches) will promote water-loaded
downdrafts capable of strong to severe gusts and scattered wind
damage with the more organized cluster(s). Around 15-25 kt of
mid-level westerly flow will favor eastward-moving storm activity.
The severe risk is expected to concentrate during the 20-01 UTC
period as storms move towards central VA and into eastern VA by this
evening.

...Northern/Central Plains...
Water-vapor imagery shows a mid-level impulse moving eastward across
the northwest quarter of MT this morning. This will continue
eastward towards eastern MT and the western Dakotas by early
evening. Weaker mid-level westerly flow will remain farther south
into the central High Plains. At the surface, a lee trough will
extend southward from eastern MT to eastern CO. Generally low to mid
60s surface dewpoints should exist this afternoon along/east of the
lee trough, with upper 60s to lower 70s F dewpoints present near a
remnant front/boundary in NE.

Scattered thunderstorms will likely develop initially over the
higher terrain of the northern/central Rockies this afternoon, with
additional development farther east along the lee trough. As this
convection spreads eastward into a moderately to strongly unstable
airmass across the northern/central High Plains, it should
strengthen. Weak low-level winds are forecast to veer and increase
with height through mid/upper levels, supporting strong deep-layer
shear and the potential for supercells. Scattered large hail will be
possible with any supercells that can persist, with most guidance
indicating a greater concentration of severe thunderstorms across
eastern MT into western ND, and separately across western/central
NE. Given the presence of steep mid-level lapse rates and 40-50+ kt
of deep-layer shear, isolated very large hail appears possible.
Recent model guidance indicates a few supercells may develop across
west-central NE late this afternoon into the evening. Some
enlargement of the hodograph during the evening combined with moist
low levels may support a couple hour window for a locally higher
tornado risk compared to within this broader region.

$$

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

498
FLUS43 KLOT 192000
HWOLOT

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
Issued by National Weather Service Lincoln IL
300 PM CDT Sat Jul 19 2025

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-202000-
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-
300 PM CDT Sat Jul 19 2025 /400 PM EDT Sat Jul 19 2025/

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

.DAY ONE...Tonight.

Weather hazards expected...

Elevated Thunderstorm Risk...with an associated:
Level 1 of 5 Tornado Risk.
Level 2 of 5 Damaging Wind Risk...up to 60 mph.
Level 1 of 5 Large Hail Risk...up to quarter size.
Elevated Flooding Risk.

DISCUSSION...

Scattered thunderstorms and locally heavy rain are possible late
tonight, mainly south of I-80. Severe potential is generally low.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

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

DISCUSSION...

Thunderstorms with torrential rain and localized flash flooding
may persist south of I-80 on Sunday.

Dangerous heat and humidity are possible the middle of next week.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed after midnight tonight.

GENERAL STORM MOTION OF THE DAY:

Moving toward the east-southeast at 40 mph.

$$

LMZ740>745-202000-
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-
300 PM CDT Sat Jul 19 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:
Thunderstorm Waterspout Risk
Level 2 of 5 Thunderstorm Wind Gust Risk...up to 40 knots.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Sunday...
Limited Thunderstorm Risk.
Thursday and Friday...
Limited Thunderstorm Risk.

$$

Shimon

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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476
ACUS02 KWNS 191731
SWODY2
SPC AC 191730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Sat Jul 19 2025

Valid 201200Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHEAST...AND OVER THE DAKOTAS...

...SUMMARY...
A few severe thunderstorms with damaging wind gusts and some hail
are possible Sunday across parts of New England into the northern
Mid Atlantic. Scattered severe hail and wind are also possible over
the central Dakotas.

...Northeast...
An upper trough will pivot eastward across Quebec, with cooling
aloft from NY into New England. Low pressure will deepen into
southern New England during the afternoon, with a cold front
progressing southeastward across the region, and nearing the coast
around 00Z. A moist air mass will remain ahead of the front, with
MUCAPE up to 2000 J/kg possible. This will occur beneath 40-50 kt
midlevel westerlies, resulting in a few long-lived cells producing
localized hail. As storm coverage maximizes during the late
afternoon, a few small bowing structures will be possible, with
corridors of damaging gusts as well.

...Dakotas...
A broad upper trough will remain from the Pacific Northwest into the
northern Rockies, with minor shortwave ridging over the northern
Plains where midlevel temperatures will still remain cool. A surface
trough will develop from southeast MT into the western SD/NE/KS,
where heating will be strong. Moderate uncapped instability and
moist southeast winds east of the surface trough should yield
clusters of storms developing from central ND into SD, moving
southeastward through evening. Large hail is likely, along with
aggregating/severe outflow/wind.

...Mid MS and OH Valleys...
Although well south of the upper trough, modest west/northwest flow
aloft will remain over the Midwest and OH Valley, near a stalled
front with 70s F dewpoints. Tall/moist CAPE profiles with high PWAT
suggest sporadic multicelluar clusters of storms will be possible
from southeast IA into KY/WV during the afternoon. Localized wind
damage will be possible. Higher probability corridors cannot be
ruled out in later outlooks as predictability increases on the
mesoscale.

..Jewell.. 07/19/2025

$$

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

090
ACUS03 KWNS 191933
SWODY3
SPC AC 191932

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0232 PM CDT Sat Jul 19 2025

Valid 211200Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
NORTHERN PLAINS...AND FROM THE TENNEESSEE VALLEY TO SOUTH
CAROLINA...

...SUMMARY...
At least isolated severe storms appear likely across parts of the
northern Great Plains and parts of the Tennessee Valley into
southern Atlantic Seaboard Monday through Monday night.

...MT into the northern Plains...
A positive-tilt upper trough will remain over the Pacific Northwest
on Monday, with an upper ridge over the Plains. Moderate southwest
to west winds aloft will exist over MT and into ND and northern MN
around the periphery of the ridge, with midlevel temperatures
remaining relatively cool.

At the surface, low pressure will deepen over the central High
Plains with strong heating, and southeast winds around a Great Lakes
high will maintain a westerly push of moist air with 70s F dewpoints
across the Corn Belt. Farther northwest, lower 60s F dewpoints will
be common into much of eastern MT. This will result in strong
instability NE/IA into the Dakotas, with lack of large-scale ascent
the primary mitigating factor to a larger area of severe potential.

That said, it is likely that at least isolated severe storms develop
over western NE into the Dakotas where the air mass gets uncapped.
Conditionally, large hail and damaging winds will be possible.
Farther west into MT, this region is also likely to see at least a
few severe storms. Given the upper ridge, storm coverage and
potential capping into the evening may mitigate the overall threat.
As such, will maintain a broad area of 5% probabilities at this
time, though higher probabilities may be needed in later outlooks
cycles as predictability increases.

...TN Valley southeastward to the SC Coast...
A weak low is forecast over SC during the afternoon as a cold front
pushes south across VA and NC. The air mass across the region will
remain very moist, with pockets of stronger instability. Scattered
storms are likely within the instability axis, possibly in
association with residual boundaries from the previous night's
convection over the OH Valley. Otherwise, sufficient surface
convergence and terrain effects should support widely scattered
development from the southern Appalachians toward the SC Coast, with
locally strong to damaging downbursts in the high PWAT environment.

..Jewell.. 07/19/2025

$$

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.