Tornadoes and Hail in Illinois, March 19, 2025

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
256 PM CDT Wed Mar 19 2025

.KEY MESSAGES...

- Level 3 of 5 severe thunderstorm into early this evening.
  Main threat being possible tornadoes.

- Accumulating wet wind whipped snow late tonight across
  portions of the area. Hazardous travel possible late tonight
  into the early Thursday morning commute.

- Seasonal conditions this weekend into early next week with
  several chances for precipitation, highest on Sunday

&&

.MESOSCALE...
Issued at 159 PM CDT Wed Mar 19 2025

No big changes to thinking.

The 18z ILX special sounding shows very little boundary layer based
instability. Interestingly, the destabilization today is not going
to come from down below, but from above via strong mid level cold
air advection. Guidance suggests that over the next couple of hours
strong cold air advection aloft overtop of the axis of low/mid 50
degree dewpoints should lead to a blossoming area of MLCAPE of 500
to perhaps nearly 1000 J/kg.

We're already starting to see convective initiation around north of
the St. Louis area, likely associated with this colder air aloft
moving in. Continued cold air advection aloft in advance of these
storms could result in modest, but sufficient destabilization in
advance of these new storms developing near St Louis.

Low level wind profiles have grown increasingly favorable on KILX's
VWP over the past few hours with a backing and strengthening of the
low level flow.

The magnitude of the tornado threat is likely going to hinge on low
level CAPE, which is going to driven to some extent to the
boundary layer moisture. Really a fine line between a rather big
problem and not much problem at all and unfortunately, it is
very challenging to figure out which side of the line we will
end up. Given the forecast wind profiles and growing confidence
in sufficient destabilization taking place, concern is
increasing a bit. Storm scale details will also play a role in
potential tornado threat, including the storm mode and coverage,
which we may start to get a better handle on in the next hour
or so.

Previous meso AFD below...

- Izzi

Issued at 1145 AM CDT Wed Mar 19 2025

A couple of spokes/arcs of elevated showers/thunderstorms are
currently moving across northern Illinois late this morning.
Objective analysis depicts a pocket of 500 J/kg of MUCAPE
centered over northern IL with effective shear of up to 50kt.
While instability it modest, the strong shear has allowed for
some transient supercells embedded within these bands. Wet bulb
zero heights are quite low, so these cells have been producing
lots of small hail, though a couple of the more organized
looking cells have briefly teetered with severe limits. These
elevated storms should continue the next hour or two with a
mostly small hail threat, though an isolated severe hail
producing storm certainly can't be ruled out.

The period of greater interest is this afternoon as dryline
currently over Missouri accelerates eastward into Illinois. A
plume of modest low level moisture continues to quickly advect
northward across Illinois and eastern Missouri in advance of
this dryline. There is a plume dust showing up nicely on the
GOES dust RGB that has gotten wrapped into this cyclone and
covers a sizable swath of the warm sector to the east of the
dryline. While this dust will probably limit insolation some,
it, along with some mid level cloudiness, could help facilitate
the moistening of the boundary layer by preventing shallow low
level moisture from mixing out. Visible satellite imagery shows
there is a narrow axis of clearing to the west of the mid-level
cloudiness and dust and ahead of the advancing dryline, which is
where guidance suggests an axis of relatively weak boundary
layer based instability will develop this afternoon across
Illinois.

While surface dewpoints should be no higher than the 50s this
afternoon, very cold air aloft (-20C to -22C at 500mb) will
become juxtaposed overtop these 50 degree dewpoints allowing
boundary layer to become unstable. With that said, there is
some spread in guidance among the various models regarding just
how much boundary layer destabilization will take place, with
these differences largely the result of differences in low
level moisture. The RAP and HRRR have consistently been the most
aggressive with low level moisture, even pooling some upper 50
degree dewpoints just south of the sharp warm front that is (and
will remain) parked near I-80. Meanwhile, other guidance is more
muted with dew points remaining in the lower 50s.

Regardless of moisture, shear profiles are forecast to become
very favorable for supercells and tornadoes this afternoon.
Forecast hodographs late this afternoon depict strong low level
shear with a significant portion of the low level shear
oriented in the streamwise direction, which tends to portend a
more significant tornado potential. If the more substantial
destabilization outcomes were to take place (dew points in the
mid to upper 50s), then threat would exist for tornadic
supercells ahead of the advancing dryline and south of the
strong warm front this afternoon. The most susceptible area is
well highlighted in the SWODY1 enhanced (level 3 of 5 risk).
However, if the models with the more modest low level
moisture/instability profiles were to verify, then severe and
tornado threat would be lower, though not zero. Close
mesoanalysis and monitoring of the quickly evolving environment
will be important today.

It is important to note that the difference instability between
tornadic supercells and just strongly sheared non-severe
showers in a set-up like this tends to be very sharp and there
is no magic number. We will continue to closely monitor
observational trends heading into and through the afternoon to
assess the severe threat later this afternoon.

- Izzi

&&

.DISCUSSION...
Issued at 250 PM CDT Wed Mar 19 2025

Mid evening Through Thursday:

As the dryline moves east of the area this evening, the severe
threat will depart with it. While there may be a brief lull in
the precipitation, the surface low will slowly move east through
the area. North winds will drive cold air advection and drop
temperatures below freezing overnight, with a wet bulb
temperatures falling to the freezing mark across the I-39
corridor as far south as northern La Salle county. Precipitation
will change over to wet slushy snow accumulations through
Thursday morning.

The storm system's deformation axis will be fairly potent, and
there will be a period of heavy wet snow accumulation with
several hour period of 0.75-1" per hour rates. However, there
are several limiting factors preventing higher confidence in the
forecast: location of the heavier snow and moisture. Over the
last couple days, models have trended the corridor of higher QPF
with the better forcing along with the center of the low a bit
farther south. Even at this time window, it is difficult to
have high confidence in the exact location. Additionally, the
amount of QPF will drive snow totals, and model guidance has not
been in great agreement. The RAP remains on the higher end of
the QPF spectrum, and if this solution were to manifest itself,
forecasted snow totals could be underdone. Right now the highest
confidence in higher totals, currently forecast between 2 to 3
inches, is from southern Lee County to northern Livingston
County northeastward approaching the west and southwest suburbs,
with 1 to 2 inches fore the rest of the forecast area. Finally,
the low level thermal profiles are marginally supportive for
rapid road accumulations, though that could be overcome by the
heavier snow rates.

Impacts during the overnight period will not be just from the
snow. Winds will switch to the north tonight and eventually to
the northwest around midnight. A strong northerly low level jet
will increase with winds at 925 mb 50+ knots. Surface wind gusts
are expected to be up to 45 mph overnight. A wind advisory was
issued last night on the midnight shift and that seems
reasonable. And while snow totals are on the lower side, when
coupled with winds this strong, visibilities can be lowered and
with the potential for some convective snow showers increasing
snow rates at times up to an inch an hour. It can make fore
slippery, if not hazardous, travel. Strong consideration was
given to potentially issuing a Winter Weather Advisory with the
mix of brief heavy rates and visibility reductions from wind.
But given the uncertainty on the location of the heaviest rates,
short lived period, and the window being an unfavorable time of
day and marginal low level temperatures,  it was held off for
now. This is something the evening shift can hone in on for the
thermal profiles during the period of heavy snow rates.

The last bit of uncertainty with this system is the exact time
that this low moves through and east of the area. There is a
strong possibility that this system is still lingering over the
Chicago Metro area during the early part of the morning rush.
With the potential for snow showers having slightly higher
rates, some slippery travel is still possible tomorrow morning,
especially across the Chicago metro area into Northwest Indiana.

Once the low exits to the east, conditions will dry for a
quieter Thursday. Winds will remain out of the northwest driving
cooler temperatures maxing out in the 40s (maybe only in the
upper 30s for areas closer to the Wisconsin stateline). For
more information about the extended forecast, see the previous
discussion below.

DK/KMD

Thursday Night through Wednesday:

Following a much cooler day on Wednesday behind the departing
storm system, winds will turn southerly and modest low level
warm advection will commence ahead of an upper Great Lakes low
and impending cold front. This should keep temperatures from
dropping off too much during the night. Nonetheless, Thursday
night will be cool with lows forecast in the upper 20s, maybe
staying up near freezing in and around the city. The continued
feed of mild low level air during the day will pull highs back
into the middle and upper 50s in the afternoon. Friday also
looks to be on the breezy side with a potent low level jet
moving over ahead of the front. Made the decision to again bump
winds in the forecast beyond the NBM's solution to include some
30-35 mph gusts area-wide during the afternoon. Although,
looking at forecast soundings, gusts could possibly be closer to
40 mph for a majority of the afternoon. Some filtered sunshine
during the morning will give way to building cloud cover through
the day in anticipation of this front and an associated precip
potential.

Guidance is in better agreement on this system than 24 hours
ago and the GFS has finally dropped the idea that a surface low
pressure center will embed itself along the front before moving
overhead. The front should move into our northwest late Friday
evening and work across the CWA through the night. There remains
quite a bit of discrepancy in precip coverage; the GFS and NAM
are more aggressive than the Euro coming in with a sharper front
and more layer moisture. Anywhere from isolated to a period of
densely scattered showers are on the table. It's possible too
that a brief window of snow or a rain/snow mix materializes
toward the end of the event as the low levels cool behind the
front. At this point, no noteworthy impacts are anticipated with
this system. Saturday will be dry with clearing skies and highs
back down in the 40s.

Another, more interesting northern stream Pacific origin trough
will pass through the Great Lakes region on Sunday. This system
packs a bit more punch than Friday night' system, and will
likely have a bit better moisture feed and thus precipitation
chances are correspondingly in the likely category. There are
still some timing discrepancies to resolve. Confidence is high
that temperatures Sunday night into early Monday will support a
mix or even a changeover to snow (across north central IL),
though it is not clear how much of the storm's deformation axis
will affect northern IL.

Northwest flow will remain in place behind this system early
next week, and this will keep temperatures cooler than normal.
Subtle weak waves may bring low end precipitation chances at
times.

Doom/KMD

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1216 PM CDT Wed Mar 19 2025

Primary aviation concerns include:

- Ongoing showers with embedded thunder through early afternoon

- Period of strong to severe thunderstorms this afternoon

- Wind shift from northeast to northwest this evening with gusts
  above 30kt overnight

- Transition from rain to snow overnight, ending by daybreak

Scattered showers will continue moving across the airspace early
this afternoon associated with steepening mid-level lapse rates
in advance of an approaching cyclone. A few thunderstorms cannot
be ruled out within the broader region of showers, but will
leave a formal mention of -TSRA out of the TAFs for now. With
the warm front expected to remain stalled south of the terminals
through the afternoon, winds will remain out of the east to
northeast. Cigs should remain VFR through the afternoon, as
well.

During the late afternoon, clusters of thunderstorms will sweep
across the terminals potentially accompanied with hail and
damaging winds. The inherited TEMPO groups centered around 00Z
remain appropriate.

A sharp northwesterly wind shift will occur behind the
thunderstorms this evening. There is high confidence in gusts
exceeding 30kt and medium confidence in occasional gusts to 40kt
generally between 00 and 12Z with the strongest gusts between
06 and 10Z. At the same time, ongoing rain showers will
transition to snow, especially after 06Z. While snow may
struggle to accumulate at the terminals due to relatively warm
grounds, a slushy inch or two cannot be ruled out on grassy or
elevated surfaces. In addition, visibility may be sharply
reduced during the period of strongest winds and falling snow.
Finally, cigs will lower to IFR overnight as snow is falling.

Conditions will improve from west to east toward and especially
after daybreak Thursday as precipitation ends and cigs scatter.
Winds will be slow to ease, with gusts up to 30 kt through noon.

Borchardt

&&

.MARINE...
Issued at 413 AM CDT Wed Mar 19 2025

A period a gale fore winds and very hazardous waves is
anticipated along southern Lake Michigan nearshore waters today
into Thursday. Southerly gales will be possible as early as this
afternoon along the Indiana nearshore waters and maybe reaching
as far north as the Chicago shore. The northward extent of
gales during the day today will be dictated by the position of a
warm front that will cut across the far southern reaches of the
lake this afternoon. A period of gusty, potentially severe
thunderstorms is also expected over the lake from mid-afternoon
through early evening today. As the front pulls away to the
south this evening, a surge of gale force winds will drive down
the lake from the north and remain into Thursday morning before
winds steadily subside. The NNW flow will lead to significant
waves up to 16 ft and occasional waves over 20 ft along the
Indiana nearshore waters Thursday morning.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory from 10 PM this evening to 7 AM CDT Thursday for
     ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ103-ILZ104-ILZ105-ILZ106-
     ILZ107-ILZ108.

     Wind Advisory until 7 AM CDT Thursday for ILZ023-ILZ032-ILZ033-
     ILZ039.

IN...Wind Advisory from 10 PM this evening to 7 AM CDT Thursday for
     INZ001-INZ002.

     Wind Advisory until 7 AM CDT /8 AM EDT/ Thursday for INZ010-
     INZ011-INZ019.

LM...Gale Warning from 9 PM this evening to 1 PM CDT Thursday for
     the IL and IN nearshore waters.

     Small Craft Advisory until 9 PM CDT this evening for the IN
     nearshore waters.

&&

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Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
1056 AM CDT Wed Mar 19 2025

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-201600-
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-
1056 AM CDT Wed Mar 19 2025 /1156 AM EDT Wed Mar 19 2025/

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

.DAY ONE...Today and Tonight.

Weather hazards expected...

  Limited Thunderstorm Risk...with an associated:
     Level 3 of 5 Tornado Risk.
     Level 2 of 5 Damaging Wind Risk...up to 60 mph.
     Level 2 of 5 Large Hail Risk...up to one inch in diameter.
  Elevated Non Thunderstorm Wind Risk.
  Limited Snow Risk tonight.

DISCUSSION...

Waves of showers and thunderstorms will move across the area today. The
main threat with the morning storms would be strong to near severe
hail up to quarter size. A few storms this afternoon and early
evening may also be strong to severe and feature damaging winds
and hail. A few tornadoes may occur, especially along and south
of I-80, possibly as far north as I-88.

Strong southerly winds are expected this afternoon near and south
of the Kankakee River valley with gusts of 45 to 50 mph. Winds
will then turn northwesterly late this evening and gust to around
45 mph across the entire area into early Thursday morning.

A period of wind-whipped wet snow is anticipated overnight
tonight. Slushy accumulations are possible, especially on cooler
surfaces such as bridges and overpasses, and periods of poor
visibility are likely overnight. Impacts may stretch into parts
of the Thursday morning commute.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Thursday...
  Limited Snow Risk early in the morning.

.SPOTTER INFORMATION STATEMENT...

  Spotters will likely be needed this afternoon and evening.

GENERAL STORM MOTION OF THE DAY:

  Moving toward the northeast at 50 mph.

LMZ740>745-201600-
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-
1056 AM CDT Wed Mar 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...Today and Tonight.

Weather hazards expected...

  Gale force winds.
  Limited Thunderstorm Risk...with an associated:
     Thunderstorm Waterspout Risk in the Indiana nearshore.
     Level 2 of 5 Thunderstorm Wind Gust Risk...up to 50 knots.
     Level 1 of 5 Hail Risk...up to one inch in diameter.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Thursday...
  Gale force winds and extremely hazardous waves.
Friday through Sunday...
  Hazardous conditions for small craft are likely at times.

DK/KMD

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Special Weather Statement
National Weather Service Chicago/Romeoville
1044 AM CDT Wed Mar 19 2025

ILZ019-191615-
La Salle IL-
1044 AM CDT Wed Mar 19 2025

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN LA SALLE COUNTY
THROUGH 1115 AM CDT...

At 1043 AM CDT, Doppler radar was tracking a strong thunderstorm near
Grand Ridge, or near Streator, moving northeast at 50 mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor hail damage to vegetation is possible.

Locations impacted include...
Kangley, Grand Ridge, Naplate, Ottawa, Marseilles, Dayton, Wedron,
and Streator.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4152 8883 4143 8860 4136 8859 4113 8887
      4116 8898
TIME...MOT...LOC 1543Z 211DEG 45KT 4120 8891

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

Kluber

Special Weather Statement
National Weather Service Chicago/Romeoville
1051 AM CDT Wed Mar 19 2025

ILZ005-006-191630-
Lake IL-McHenry IL-
1051 AM CDT Wed Mar 19 2025

...A STRONG THUNDERSTORM WILL IMPACT NORTHERN LAKE AND EASTERN
MCHENRY COUNTIES THROUGH 1130 AM CDT...

At 1050 AM CDT, Doppler radar was tracking a strong thunderstorm over
Crystal Lake, moving northeast at 50 mph.

HAZARD...Nickel size hail.

SOURCE...Radar indicated.

IMPACT...Minor hail damage to vegetation is possible.

Locations impacted include...
Oakwood Hills, Wauconda, Port Barrington, Fox Lake, Ridgefield,
Winthrop Harbor, Round Lake Beach, Hainesville, Pistakee Highlands,
Huntley, Grayslake, Gurnee, Channel Lake, Round Lake Heights,
Lakewood, Russell, Wadsworth, Volo, Round Lake, Crystal Lake, Long
Lake, Third Lake, Lake Catherine, Grandwood Park, and Zion.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4249 8780 4243 8780 4215 8836 4215 8841
      4222 8853 4250 8820
TIME...MOT...LOC 1550Z 227DEG 45KT 4225 8835

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH

Kluber

Preliminary Local Storm Report
National Weather Service Chicago IL
1112 AM CDT Wed Mar 19 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1105 AM     Hail             1 ESE Johnsburg         42.38N 88.22W
03/19/2025  E0.50 Inch       McHenry            IL   Public

&&

sb

Preliminary Local Storm Report
National Weather Service Chicago IL
1123 AM CDT Wed Mar 19 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1056 AM     Hail             1 WNW Prairie Grove     42.28N 88.29W
03/19/2025  E0.70 Inch       McHenry            IL   Public

&&

sb

Preliminary Local Storm Report
National Weather Service Chicago IL
1126 AM CDT Wed Mar 19 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1107 AM     Hail             1 SSW Fox Lake Hills    42.39N 88.14W
03/19/2025  E0.50 Inch       Lake               IL   Public

&&

sb

Special Weather Statement
National Weather Service Chicago/Romeoville
202 PM CDT Wed Mar 19 2025

ILZ012-013-103-191930-
Kane IL-DuPage IL-Northern Cook IL-
202 PM CDT Wed Mar 19 2025

...STRONG THUNDERSTORMS WILL IMPACT KANE...DUPAGE AND NORTHWESTERN
COOK COUNTIES THROUGH 230 PM CDT...

At 201 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Sugar Grove to near Oswego. Movement was
north at 60 mph.

HAZARD...Half inch hail.

SOURCE...Radar indicated.

IMPACT...Minor hail damage to vegetation is possible.

Locations impacted include...
Glendale Heights, Valley View, Carol Stream, Lily Lake, Kaneville,
Aurora, West Dundee, Wheaton, West Chicago, South Elgin, South
Barrington, Gilberts, Montgomery, Wayne, Dupage Airport, Glen Ellyn,
St. Charles, Sugar Grove, Roselle, Barrington Hills, Sleepy Hollow,
Hoffman Estates, Elk Grove Village, Winfield, and Carpentersville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4200 8794 4199 8794 4199 8792 4173 8816
      4172 8838 4178 8857 4215 8847 4215 8824
TIME...MOT...LOC 1901Z 199DEG 53KT 4180 8853 4164 8827

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...<30 MPH

Kluber