892
FXUS63 KLOT 021857
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1257 PM CST Mon Mar 2 2026

.KEY MESSAGES...

- Low chance (15%) for patchy slick spots late tonight into
  early Tuesday morning outside of Chicago.

- Warmer and occasionally wet weather is in store from the mid
  to late week period onward. Confidence is higher in more
  widespread rain late Wednesday night into Thursday and again
  late Friday into early Saturday.

&&

.DISCUSSION...
Issued at 1257 PM CST Mon Mar 2 2026

Through Thursday:

Early this afternoon, most of the area sits in the lower 40s
beneath sunny skies. Easterly winds are keeping conditions
several degrees cooler on the west side of the lake, including
downtown. Dewpoints are all over the place but managed to mix
down into the single digits to around 10 degrees in our
northwest yielding some low RHs out that way. Luckily, generally
light winds are keeping any fire weather concerns at bay. Mid-
high level cloudiness will build during the late afternoon and
evening as temps cool back into the 30s.

A developing mid level shortwave impulse is scooting east
across the Plains this afternoon after spinning up off the lee
of the Rockies early this morning. The wave will move into the
Midwest late tonight bringing with it our next chances for
precip. A leading vort lobe will move over the area very late
tonight into early Tuesday morning and, with the help of some
warm advection and modest upglide, most deterministic camps are
resolving at least trace amounts of light rain or drizzle in
pockets during that window. A wedge of low-mid level dry air may
impinge on precip`s ability to make it to the surface and could
lead to isolated or spotty coverage. But a saturated layer atop
the dry air featuring steep lapse rates and even a little bit
of elevated instability may very well generate precip capable of
punching through that dry air. While an inversion and warm
layer just off the deck supports liquid precip, temperatures at
the surface are forecast to be right around freezing, if not a
couple of degrees below freezing. Should rain/drizzle fall into
sub-freezing temps, a glaze of ice could result in spots. An
increase in low-mid level cloud cover tonight ahead of the wave
can hopefully help keep temperatures up a bit. Sub- freezing
temps appear most attainable near and west of the Fox Valley. In
the forecast, maintained slight chances for freezing rain in
this area into early Tuesday and instances of slick travel will
be possible here and there during the morning commute,
especially off of highways and arterials.

Showers will remain possible during the morning as the wave
gets sheared off atop the area. The better rain chances will be
found across central IL where the better moisture and forcing
will track near a strengthening baroclinic zone that will set up
downstate. Meanwhile, drier air aloft with northward extent
will continue to hinder precip chances across much of northern
IL. Latest high res guidance favors nearly all measurable precip
coverage south of I-80. Behind the low level trough axis
passing during the morning, pressure rises and dry advection
will further focus the greater precip potential across southern
and central IL for the afternoon. The latest RAP and HRRR keep
all precip just south of the CWA during the afternoon.

An axis of moist, confluent air feeding into that baroclinic
zone is expected to keep a steady corridor of rain and possibly
embedded thunderstorms churning across central IL for the latter
half of Tuesday and into Wednesday. Coverage is favored to
largely stay south of the CWA during this period, but there
remains notable model support for portions of our south to be
included in the steadier rainfall, at least at times, late
Tuesday into Wednesday. Depending on how far north that
baroclinic zone can lift, it`s not out of the question that a
couple of embedded thunderstorms could be found in our south as
low level warm advection works to steepen up lapse rates aloft
and generate some elevated instability. The thunder potential
appears significantly better south of the local area.

Precip chances will expand across northern IL late Wednesday
into Thursday as another shortwave tracks through the region
lifting the baroclinic zone north. This will transport 1" of
PWAT and some marginal instability into northern IL. Forcing
doesn`t look fantastic, but we will be in a favorable position
relative to the jet max to see some appreciable, deep lift.
These signs point toward a potential for some healthy showers
Wednesday night and Thursday. Coverage locally remains a bit
uncertain and will be influenced by the track of the low level
wave, but a period of widespread showers is favored among
guidance, namely in the Wednesday night through Thursday morning
window. A few embedded thunderstorms may be possible during
this period as well. Precip chances will come into a lull
Thursday evening behind the departing system.

Doom


Thursday Night through Monday:

Rain chances look to temporally drop off for a period Thursday
night as a region of forced large scale decent sets up overhead
along the backside of the exiting mid-level impulse. This will be
short lived. On Friday, mid-level southwesterly flow will
strengthen as a mid-level jet ejects northeast across the Plains
into the Upper Midwest. This will send a low amplitude mid-level
shortwave racing northeastward into the Upper Midwest sometime late
Friday morning or early Friday afternoon. Scattered showers and
elevated thunderstorms accompanying this feature may impact parts
of northern IL and southern WI into early Friday afternoon, but
outside of this potential, it appears there will be a good amount
of dry time during the day.

Temperatures on Friday are expected to soar well into the 60s to
around 70 for most through the afternoon as a surface warm front
surges northward across IL and IN. However, as is typical this
time of year, onshore flow ahead of this front across far
northeastern IL may keep conditions much cooler through much of the
day until the warm front clears this area. The combination of
these very warm temperatures and unseasonably high dew points,
into the upper 50s to near 60, will support an unstable and well
sheared warm sector in the wake of the earlier day storms.
However, it appears there will not be much of a focus for much
late afternoon and evening convection in our area following the
earlier day impulse. Instead, shower and thunderstorm chances and
coverage look to be the greatest late Friday into Saturday
morning in association with a cold frontal passage.

Rain chances will come to an end following the cold frontal
passage on Saturday, at least for a few days. Temperatures will
generally remain well above average through early next workweek.
Current medium to long-range ensembles point towards a stronger
cold front passage bringing a return to colder conditions by
later next week/mid-March.

KJB

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1100 AM CST Mon Mar 2 2026

Key Messages:

- MVFR CIGs developing late tonight and continuing on Tuesday

- Potential for spotty light precip early Tuesday

Quiet conditions are expected through this evening, with VFR
conditions and light east-southeasterly winds. Thereafter,
lower clouds (MVFR) are expected to develop across the area,
particularly after 09z tonight. These lower clouds are likely to
persist through most of the day on Tuesday, and even lower CIGs
are expected farther south across central IL and IN in closer
proximity to a surface frontal boundary. There also remains a
low chance (20-30%) for a few brief light showers across the
terminals Tuesday morning, but the best chances for rain are
largely expected to remain south of the main terminals.

Winds on Tuesday will remain light from the east-southeast in
the morning, before shifting to the northeast during the
afternoon.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago