Tornadoes and Hail in Illinois, April 2, 2026

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
242 PM CDT Thu Apr 2 2026

.KEY MESSAGES...

- Scattered severe thunderstorms through mid evening with a
  tornado potential, highest along/west of the Fox Valley.

- Strong gusty south winds, gusting at times to 45-50 mph are
  expected this afternoon, outside of thunderstorms.

- There is another threat for severe thunderstorms Friday
  afternoon through Saturday morning, though the threats are
  conditional on placement of boundaries and system arrival
  timing.

- A transition toward a quieter, but cooler, pattern is on track
  to arrive early next week.

&&

.MESOSCALE...
Issued at 203 PM CDT Thu Apr 2 2026

A couple of different convective regimes with accompanying
severe threat late this afternoon into this evening. The most
obvious is with rapidly develop intense convection across
northern MO into southern IA in the quickly destabilizing warm
sector. There is some uncertainty with respect to the eventual
extent of coverage with this convection, but whatever there is
would likely begin to get into our western CWA early this
evening. By the time it approaches, there will likely be some
slight decrease in MLCAPE and corresponding slight increase in
MLCIN after sunset. If the convection is well organized or
intense, then those subtle changes in boundary layer instability
may not be a terribly detrimental factor with respect convective
intensity, at least not initially. If convection is a bit weaker
or less organized, then the subtle instability changes could
result in weakening as this convection approaches or gets into
our western CWA.

The second potential convective regime, which is lower
confidence, is that the current elevated convection over western
IL could become rooted in the boundary layer this afternoon.
The 18z KILX sounding depicted noteworthy warm layer near 500mb,
however mesoanalysis data has 500mb temps 2-4C colder upstream.
As these cooler mid-level temps advect east across Illinois
this afternoon, that should result in a corresponding increase
in instability. Certainly seems plausible that as this occurs,
that the currently elevated storms over western IL could
increase in coverage and eventually become rooted in the
boundary layer. This change in the inflow layer of the storms
would also result in marked increase in storm intensity/severe
potential.

Area VWPs depict a very impressive kinematic profile all across
the region. So any boundary layer rooted convection that does
become sustained would likely become supercellular, at least
initially. The very large 0-1km looping hodograph with strong
streamwise vorticity would support a threat for tornadoes with
any sustained strong supercells either with the upstream
activity over IA/MO or if the elevated convection becomes rooted
in the BL this afternoon over IL.

There is still somewhat low confidence in which, if either,
convective scenario will occur with a severe weather threat in
CWA, the environmental shear profiles means that we will need to
closely monitor convective trends closely this afternoon.

- Izzi

&&

.DISCUSSION...
Issued at 242 PM CDT Thu Apr 2 2026

Specific severe potential discussed above in the recent
mesoscale discussion but more broadly, low pressure over
southern IA will move northeast across southern WI this evening.
A warm front is currently lifting north across far northern IL
with temperatures warming into the upper 60s/lower 70s and
dewpoints generally in the lower 60s. Current thunderstorms
across far northwest MO/southwest IA are expected to continue
moving east/northeast through the afternoon and into northwest
early by early evening. Cams have generally been in good
agreement with the current activity along the I-39 corridor
slowly increasing in coverage and intensity. They have also been
in fair agreement with additional development along/east of I-57
and will need to monitor for the potential for additional
thunderstorms developing across this area. Any of the
thunderstorms that develop will have the potential to be severe.

Southerly winds have steadily increased south of the warm front
and further increasing winds are possible with gusts to 45 mph.
While the best potential for these higher gusts may be generally
south of I-80, have maintained the wind advisory as is until its
expiration at 00z.

Southeast winds ahead of the cold front will allow for areas of
fog across far northeast IL for the next hour or two until the
warm front lifts north into southern WI.

The showers and storms will end from northwest to southeast this
evening into the early overnight hours, with dry conditions then
expected through at least midday Friday. A warm front is
expected to lift north to about I-80 on Friday while northeast
winds gradually increase north of I-80. There is a chance of
showers and thunderstorms Friday afternoon, mainly in the warm
sector, but confidence is low for trends and maintained chance
pops for much of the area, mainly in the late afternoon. It
appears the best chance for showers and thunderstorms will be
later Friday evening through Saturday morning ahead of a strong
cold front. The front looks to be east of the area by mid
morning Saturday, ending any severe threat, but there may be
lingering precipitation through midday Saturday. cms

Sunday Onward:

In the wake of this system, a period of drier weather is
expected to close out the weekend as a surface high moves into
the Mississippi Valley. However, the upper trough is expected to
stall over the Great Lakes which will result in nearly constant
northwest flow resulting in seasonably cool high temperatures
in the 40s to lower 50s for Sunday and again on Monday.

The upper trough is forecast to start pushing east of the Great
Lakes on Monday as an upper ridge builds over the central
CONUS. As a parting gift a final shortwave is progged to round
the backside of the trough Monday night which could bring us one
more period of rain showers during this timeframe, That said,
there is a lot of variability in guidance as to how much
moisture will be available Monday night as the wave moves
through so there is a chance that the rain avoids northern IL
and northwest IN all together. For now though will advertise a
20-40% chance for rain. After Monday night, the upper ridge will
be moving into the Great Lakes which will promote dry
conditions for the middle of next week with temperatures
moderating towards more seasonable values in the mid to upper
50s.

Yack

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 102 PM CDT Thu Apr 2 2026

Key Messages:

- Thunderstorms likely this afternoon with another round of
  storms possible this evening.

- Strong non-thunderstorm wind gusts to 30-40 kts expected this
  afternoon, with locally stronger gusts possible during
  thunderstorms.

- MVFR/IFR ceilings expected at times during the TAF period.

A low pressure system moving through the region will bring
another round of scattered to numerous thunderstorms to the
area this afternoon. The strongest thunderstorms may produce
strong to locally damaging winds and IFR visibilities. Some
tornado threat could materialize too, but confidence in that is
low near the terminals. Another round of storms may then occur
this evening as a cold front sweeps through the area from west
to east. Confidence in this round of storms occurring is lower,
but have maintained the inherited TEMPO groups that highlight
that potential for now.

Strong southerly non-thunderstorm wind gusts to 30-40 kts are
also expected today south of a warm front that is moving
northward through the area early this afternoon. Winds will
shift westerly tonight behind the aforementioned cold front with
gusts to around 30 kts continuing through the evening before
subsiding overnight. A prevailing easterly wind direction is
then expected tomorrow afternoon as today's low pressure system
distances itself from the area and another low pressure system
develops and approaches from the west.

Lastly, MVFR and IFR ceilings are expected at times during the
TAF period. These lower ceilings will likely prevail tonight,
though how long they last into tomorrow remains a point of
uncertainty with the going forecast.

Ogorek

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory until 7 PM CDT this evening for ILZ006-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-
     ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

IN...Wind Advisory until 7 PM CDT /8 PM EDT/ this evening for
     INZ001-INZ002-INZ010-INZ011-INZ019.

LM...Gale Warning until 9 PM CDT this evening for the IL and IN
     nearshore waters.

     Dense Fog Advisory until 4 PM CDT this afternoon for Winthrop
     Harbor to Wilmette Harbor IL.

     Small Craft Advisory from 9 PM this evening to 4 AM CDT Friday
     for the IL and IN nearshore waters.

&&

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Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
249 PM CDT Thu Apr 2 2026

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-032000-
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-
249 PM CDT Thu Apr 2 2026 /349 PM EDT Thu Apr 2 2026/

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 3 of 5 Tornado Risk.
     Level 3 of 5 Damaging Wind Risk...up to 70 mph.
     Level 2 of 5 Large Hail Risk...up to quarter size.
  Limited Flooding Risk.
  Elevated Non Thunderstorm Wind Risk.

DISCUSSION...

Scattered thunderstorms are expected this afternoon and continue
into this evening. Some of these thunderstorms may be severe.
Damaging winds in excess of 70 mph and possible tornadoes will be
the primary severe threats. The greatest threat of tornadoes will
be across northwest Illinois, along and west of the Fox Valley.

Locally heavy rainfall will accompany these thunderstorms, and
this may result in some instances of flooding, particularly in low
lying areas.

Gusty southerly winds up to 45 to 50 mph are expected outside of
thunderstorms through early this evening.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Friday...
  Limited Flooding Risk.
  Limited Thunderstorm Risk...with an associated:
     Level 1 of 5 Severe Thunderstorm Risk.
Saturday...
  Limited Flooding Risk.
  Limited Thunderstorm Risk.

DISCUSSION...

Additional waves of showers and thunderstorms are possible Friday
afternoon into Saturday morning. A few storms may be severe.

Localized river flooding will be possible as recent heavy rains
result in continued river rises.

.SPOTTER INFORMATION STATEMENT...

Spotters will likely be needed through this evening.

GENERAL STORM MOTION OF THE DAY:

Moving toward the northeast at 45 to 55 mph.

LMZ740>745-032000-
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-
249 PM CDT Thu Apr 2 2026

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.
  Elevated Thunderstorm Risk...with an associated:
     Thunderstorm Waterspout Risk
     Level 2 of 5 Thunderstorm Wind Gust Risk...up to 55 knots.
     Level 1 of 5 Hail Risk...up to quarter size.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

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

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