414
FXUS63 KLOT 020451
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1051 PM CST Sun Mar 1 2026

.KEY MESSAGES...

- Warmer and occasionally wet weather will materialize from the
  middle of the week through the middle of next week.

&&

.DISCUSSION...
Issued at 138 PM CST Sun Mar 1 2026

Through Monday Night:

A surface high pressure system is centered
over the Upper Great Lakes and continues to serve as the
primary influence on weather in our local area. East to
northeasterly winds on the southern side of the surface high
continues to provide a stead feed of relatively dry onshore flow
from Lake Michigan. Hence, in spite of mostly sunny skies, high
temperature this afternoon will top off in the mid to locally
upper 30s.

Upper-level cloud cover will increase this evening as an upper-
level wave propagates eastward toward the Ohio River Valley. At
this point, we still favor a dry forecast for our area given (1)
the strongest DCVA associated with the wave will focus well
south of our area, and (2) the aforementioned surface high
pressure system will continue to feed dry low-level air through
the area. As a result, any reflectivity echoes that develop
within regions of mid-level frontogenesis south of Interstate 80
this evening and tonight should be relegated to virga.
Overnight lows look to settle in the low to mid 20s.

Tomorrow, the surface high pressure system will shift toward
the northeastern United States leading to winds gradually
turning from east to southeasterly. Modest warming of the column
via mid-level subsidence in tandem with largely opaque but
still somewhat sunny conditions will help boost high
temperatures to the mid to upper 40s. The exception will be
along the Illinois shoreline of Lake Michigan where
southeasterly onshore flow will hold readings in the upper 30s.
Cloud cover will thicken tomorrow evening as low-level warm air
advection ramps up ahead of a series of storm systems organizing
in the central US. Chances for showers will increase after
midnight and especially after daybreak Tuesday, as discussed
below.

Borchardt


Tuesday Onward:

A mild and active stretch of weather is expected across the
central CONUS midweek into the upcoming weekend as zonal flow
early this week transitions to deep troughing across the west
half of the CONUS. An expansive Bermuda High will foster a
persistent feed of Gulf and Caribbean moisture toward the
central CONUS through the period, resulting in an unseasonably
moist airmass (PWATs over 300% of normal at times) in and around
the region. While this pattern favors axes of heavy rain over
the mid-Mississippi and Ohio River valleys, it remains to be
seen where those axes set-up and whether they align over the
same location and result in flooding concerns.

Broad low-level isentropic ascent combined with modest moisture
transport will bring the first area of precip over at least
southern portions of the area on Tuesday, with the greater focus
for a more robust swath of rain with embedded elevated
convection over the southern half of Illinois. However, a weak,
low-amplitude disturbance quickly tracking from Montana to the
western Great Lakes may result in a broader light rain shield
and areas of drizzle over most of the area Tuesday morning into
the afternoon.

The spread in the ensemble camps remains high Wednesday through
Thursday, owing to the differences in the evolution of the
western trough. However, those camps are coming into better
agreement that a lead wave over the central Rockies will cross
the southern Great Lakes on Thursday. It remains to be seen if
higher precip rates (enhanced by waves of convection) will focus
over or south of the forecast area late Wednesday night into
Thursday, but latest trends are beginning to favor at least
higher chances of appreciable rainfall amounts over the
southeast third of the area during this time.

We continue to monitor for the potential for more organized
convection in or around the area on Friday as a large portion of
the western trough ejects toward the mid to upper-Mississippi
River Valley. Even at this lead time, the various ensemble
systems have a strikingly strong signal centered on Friday for a
northward surge of anomalous dew points in the 50s to possibly
60F+ in spots coinciding with an approaching cold front and
seasonably strong wind fields. The official forecast indicates
60 to 80 percent PoPs area-wide Friday through Friday night and
southeast of I-55 early Saturday morning, owing to a sizable
portion of guidance members with a slower cold front passage.

Kluber/Castro

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1051 PM CST Sun Mar 1 2026

VFR conditions are expected through the TAF period. East-
northeast winds around 5-10 kts will prevail tonight before
turning southeasterly through Monday morning. Speeds will then
likely increase into the 10-15 kt range before easing again
Monday evening.

A disturbance will move across the area late Monday night into
Tuesday morning. At this time, precipitation chances through the
end of the ORD/MDW extended TAFs is under about 25 percent.
However, instability is forecast to develop aloft, and it`s
possible that some isolated convective activity develops. If
this occurs, some narrow west-east bands of precipitation could
become heavy enough to break through dry air below 10 kft.
Wetbulb temperatures would be below freezing during this time,
leading to a potential for some very spotty FZRA, but chances
for this again remain quite remote at this point.

Carlaw

&&

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

&&

$$

Visit us at weather.gov/chicago