709
FXUS63 KLOT 010848
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
348 AM CDT Thu Oct 1 2026

.KEY MESSAGES...

- Periods of rain, at times heavy, will continue through this
  evening. Additional rainfall up to 1-2" (and possibly narrow
  corridors in excess of 2") may lead to localized flooding and
  river rises.

- Dry and seasonably cool conditions are expected this weekend
  into early next week.

&&

.DISCUSSION...
Issued at 348 AM CDT Thu Oct 1 2026

Regional radar imagery shows an expansive area of showers
ongoing across the region early this morning, with the earlier
focused axis of torrential rainfall in eastern Nebraska having
since scattered out for the most part. A broader area of steady
rainfall, with embedded higher rainfall rates, is beginning to
set up across northeast Iowa, far northwest Illinois, into
southwest Wisconsin initially this morning. This favors mainly
lighter rain and somewhat intermittent coverage for much of the
area through the morning before this activity ultimately drifts
back south into northern Illinois toward mid-late morning.

Meanwhile a separate area of renewed heavier shower development
will likely occur in response to the phasing of a disturbance
lifting northeast from the southern KS/MO border with a separate
disturbance moving into southern IA, eventually reaching the
area toward the afternoon. In contrast to yesterday, there is a
brief window when a narrow corridor of weak instability (up to
250-500 J/kg MLCAPE) may develop in response to this feature as
it moves through the area into early evening. The presence of
weak instability and near-record moisture content (2"+ PWATs)
would support higher rainfall rates, potentially locally in
excess of 1"/hr. While guidance has been fairly consistent in
the cold front progressing steadily across the area today, any
training of heavier showers and isolated embedded thunderstorms
may still yield localized corridor(s) of rainfall amounts in
excess of 2". The threat of flooding would be mainly tied to
these narrow corridors of higher amounts. However, confidence in
if and where these ultimately set up remains low and
accordingly, plan to hold off on any additional flood-related
headlines. Widespread rainfall amounts of 1-2" will still lead
to some rises on area rivers and streams.

In the wake of this evening`s cold front, persistent northerly
winds and cold air advection will lead to a seasonably cool
end to the work week on Friday with high temperatures in the
60s, lowest along the lakeshore.

The upper level pattern transitions toward a more zonal WNW to
ESE orientation this weekend into next week. Temperatures
remain near seasonable to seasonably cool with lower and more
comfortable humidity. Several low-amplitude waves will move
within the upper jet to our north and swing mainly dry cold
fronts across the area at times.

Petr

&&

.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 118 AM CDT Thu Oct 1 2026

Key Messages:

- Periods of rain will continue through this evening before
  rain tapers off.

- MVFR and IFR ceilings and visibilities are expected at times
  through this evening.

- A northerly wind shift will occur behind a cold front this
  afternoon.


Waves of showers will continue to pass through the C90 airspace
through the remainder of this morning. Primarily VFR conditions
will be favored at the Chicago metro terminals during this
time, though brief MVFR visibility reductions may occur at times
beneath the steadier showers.

A more solid band of rain will set up over the Chicago metro
during the early-mid afternoon, allowing for prevailing MVFR to
IFR conditions to make a return for several hours. This band
will likely set up over RFD earlier, with conditions expected to
deteriorate there by the mid-late morning. There remains only
about a 20% chance that isolated embedded thunderstorms within
this broader rain band may affect the terminals during the
afternoon (mid-late morning at RFD), so have continued to
withhold on any formal TSRA or VCTS mentions in the TAFs. The
rain will then taper off from northwest to southeast during the
evening, with VFR conditions returning at some point thereafter.

Lastly, during today`s rainfall, a cold front will drop across
the area from northwest to southeast. This will result in a wind
shift from southwesterly to northerly winds between midday and
the mid-late afternoon.

Ogorek

&&

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

&&

$$

Visit us at weather.gov/chicago