SPC Convective Outlook Day 1

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811
ACUS01 KWNS 210047
SWODY1
SPC AC 210045

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 PM CDT Sun Apr 20 2025

Valid 210100Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MID
MISSISSIPPI VALLEY INTO WESTERN TENNESSEE...

...SUMMARY...
Severe thunderstorms will spread across the mid Mississippi Valley
into western Tennessee this evening. A few tornadoes remain
possible, along with the threat of wind and perhaps some hail.

...01z Update...

Strong negative-tilt short-wave trough is ejecting northeast across
eastern KS/western MO early this evening. This feature is
contributing to an elongated band of convection that currently arcs
from western IL-southeast MO-central AR-southeast TX, coincident
with the primary synoptic cold front surging east. Over the last few
hours the most concentrated corridor of supercells has shifted into
eastern AR where no less than four distinct supercells are spreading
across western portions of ww156. Latest model guidance suggests the
LLJ will increase across northern MS/western TN/KY later this
evening. There is some concern this activity may spread a bit
farther downstream than depicted in earlier day1 convective outlook.
Forecast sounding for MEM at 06z exhibits more than adequate SBCAPE
for robust updrafts, and strong shear is favorable for the
maintenance of these storms. Will adjust the SLGT/MRGL Risks east to
account for this scenario.

..Darrow.. 04/21/2025

$$

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.

Hazardous Weather Outlook

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646
FLUS43 KLOT 202026
HWOLOT

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
326 PM CDT Sun Apr 20 2025

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-220000-
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-
326 PM CDT Sun Apr 20 2025 /426 PM EDT Sun Apr 20 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 tonight...with an associated:
Level 1 of 5 Damaging Wind Risk...up to 60 mph.

DISCUSSION...

A cold front will bring widespread showers and embedded
thunderstorms late this evening through tonight. While widespread
severe weather is not expected, stronger storms will have the
potential to generate locally gusty winds especially across
western Illinois.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Monday...
Limited Non Thunderstorm Wind Risk.
Tuesday...
Limited Thunderstorm Risk...with an associated:
Level 1 of 5 Severe Thunderstorm Risk.
Thursday night and Friday...
Limited Thunderstorm Risk.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be necessary through tonight.

GENERAL STORM MOTION OF THE DAY:

Moving toward the east-northeast at 45 to 50 mph.

$$

LMZ740>745-220000-
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-
326 PM CDT Sun Apr 20 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...

Hazardous conditions for small craft.
Limited Thunderstorm Risk.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Monday...
Gale force winds and very hazardous waves.
Tuesday night...
Limited Thunderstorm Risk.
Friday and Saturday...
Hazardous conditions for small craft are likely.

$$

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

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855
ACUS02 KWNS 201706
SWODY2
SPC AC 201704

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1204 PM CDT Sun Apr 20 2025

Valid 211200Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorm potential appears low on Monday.

...Synopsis...
An upper low/shortwave trough over the Upper Midwest on Monday
morning will lift northeast across the Great Lakes into southern
Ontario and western Quebec by Tuesday morning. Meanwhile, another
upper shortwave trough over the northern Rockies will develop
eastward to the northern Plains. At the surface, an area of low
pressure will move from Wisconsin to Quebec through the period with
a trailing cold front moving from the Ohio Valley to the
north-central Appalachians and into the Mid-Atlantic. This front
will be more stationary across the Mid-Mississippi Valley and may
start to move north by the end of the period across south-central
Texas.

...Ohio Valley/Lower Great Lakes to the TN/Lower MS
Valleys/Southeast TX...
A narrow corridor of mid 60s dewpoints may be present across the
Ohio Valley on Monday which could result in some weak instability
despite extensive cloud cover and poor lapse rates. Robust vertical
shear could result in a few stronger storms capable of isolated
damaging wind gusts, but the limited instability should keep the
threat minimal overall.

Better-quality boundary layer moisture, slightly better lapse rates,
and the potential for some warming may result in greater instability
farther south, perhaps up to 1000 J/kg MLCAPE. However, vertical
shear will be very weak where this better instability is forecast to
develop. A couple of strong storms will be capable of locally strong
gusts or small hail, but a lack of stronger vertical shear will
likely limit longevity of any stronger/better organized updrafts,
precluding severe probabilities.

...Northern Plains...
Cold temperatures aloft with the upper shortwave trough will support
steep midlevel lapse rates from MT into the northern Plains
vicinity. As weak instability develops across the northern Plains,
scattered thunderstorms are possible. A well-mixed air mass could
support an isolated severe wind threat, particularly across
southwest South Dakota and vicinity where mid-level flow will be
strongest.

Additional thunderstorms may develop overnight across eastern SD
into southern MN/northern IA on the nose of a developing low-level
jet. This activity may produce small hail into early Tuesday
morning.

..Bentley.. 04/20/2025

$$

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

837
ACUS03 KWNS 201927
SWODY3
SPC AC 201926

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0226 PM CDT Sun Apr 20 2025

Valid 221200Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE SOUTHERN HIGH PLAINS...

...SUMMARY...
Isolated severe thunderstorms are possible on Tuesday across
portions of the southern Plains.

...Synopsis...
Modest west-southwesterly flow is forecast from the Southwest to the
southern Plains on Tuesday with a stronger mid-level jet across the
northern Plains and a sharpening trough in the Pacific Northwest. A
weak mid-level shortwave trough (indicated by most guidance) is
forecast to cross New Mexico during the afternoon which would result
in a sharpening dryline and perhaps some lee cyclogenesis.

...Southern High Plains into southern Kansas...
Low-level moisture advection and strong heating across the southern
High Plains will lead to moderate to strong destabilization ahead of
the dryline. As this airmass becomes uncapped by early to
mid-afternoon and ascent increases ahead of the approaching
mid-level shortwave trough, expect scattered thunderstorm
development. A deeply mixed boundary layer and 25 to 35 knots of
shear will support supercells capable of large hail and severe wind
gusts. Storms will likely congeal into an MCS by later in the
evening as the low-level jet strengthens with some severe wind
threat which could continue into the overnight hours.

A remnant frontal boundary will likely be in place across southern
Kansas Tuesday afternoon which will likely be an additional focus
for potential severe storms Tuesday afternoon. Moisture/instability
remains more questionable across southern Kansas, and shear is not
forecast to be quite as strong amid somewhat veered low-level flow
ahead of the front. Therefore, a marginal risk (level 1 of 5) has
been maintained at this time.

...Central Iowa to southern Wisconsin and Northern Illinois...
Moisture recovery along a warm frontal zone may lead to some weak
instability from eastern Iowa into southern Wisconsin and northern
Illinois. Sustained isentropic ascent may provide sufficient forcing
for isolated to scattered thunderstorm development through the day.
Despite the lack of moisture, cool temperatures aloft and steep
lapse rates may support the potential for isolated large hail and
damaging wind gusts.

..Bentley.. 04/20/2025

$$

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

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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

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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.

Winter Weather Warnings

No active Winter Weather 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.