427
FXUS63 KLOT 081820
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
120 PM CDT Tue Sep 8 2026

.KEY MESSAGES...

- Showers and a few storms will move across the area late
  tonight through Wednesday.

- Thursday and Friday look pleasant.

- The next opportunities for rain will arrive this weekend and
  continue into early next week.

&&

.DISCUSSION...
Issued at 120 PM CDT Tue Sep 8 2026

Per a recent subjective surface analyses, a 1000 mb surface low
pressure system is moving across southern Manitoba well to the
north of a surface high pressure system parked along the
Atlantic coast. A cold front extends southward from the low
pressure system through northern Minnesota and across the
central Plains. Ahead of the front, a broad ribbon of somewhat
unfocused low-level isentropic ascent is supporting areas of
showers and thunderstorms from Nebraska northeastward into
central Wisconsin. A pocket of relative dry air is present
southeast of the axis of isentropic ascent, which is leading to
a pleasant day across the Lower Great Lakes.

This afternoon and evening, the upper-level wave currently
supporting showers and thunderstorms across eastern Nebraska
will shift eastward into Iowa and support the
expansion/invigoration of thunderstorms. After sunset, radar
data to our west may look rather intimidating with what may be
several clusters of strong to severe storms moving toward the
Mississippi River. Thankfully, the environment east of the river
will be hostile for thunderstorms to maintain their intensity,
so the expectation remains for thunderstorm clusters to
gradually weaken as they traverse eastward into northern
Illinois through the night. Peak coverage of activity through
daybreak should be mainly along and north of I-88 and west of
I-39.

With time, the axis of remnant showers will drift southward
through the area from sunrise through early afternoon on
Wednesday. Coverage should then decrease with time from north to
south through the afternoon as a cold front works across the
area. Redevelopment of thunderstorms along the front appears to
be a largely unfavored scenario given limited opportunities for
destabilization tomorrow. In all, the next 24 hours doesn`t look
like a complete washout across our area with most areas favored
to get less than 0.5" of an inch of total rainfall.

Temperatures tomorrow will be modulated by remnant showers and
cloud cover. While there are some prospects for clearing from
north to south through the afternoon, did opt to cut back NBM
temperatures to largely advertise highs around 80 degrees.
Tomorrow night, a few waves propagating along the front should
allow for additional waves of showers and a few storms primarily
south of our area. Did cut back on NBM PoPs to paint low-end
chances (20-40%) for showers near the US-24 corridor through
daybreak Thursday.

A surface high pressure system will slide through the region
Thursday and Friday leading to quiescent conditions. Both days
will be characterized by mostly sunny skies, light winds, and
highs around 80 degrees. A series of upper-level waves may
provide the opportunity for a few windows for precipitation this
weekend into early next week.

Borchardt

&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1226 PM CDT Tue Sep 8 2026

Key Aviation Messages for the current TAF period:

- Showers are expected overnight into tomorrow morning with
  isolated thunderstorms possible

VFR conditions prevail this afternoon with light southwest
winds. No change in the chances for an afternoon lake breeze.
It will be monitored through the day, but models continue to
project that any breeze that does develop should remain east of
the Chicago terminals.

As a front moves southward, showers will develop over the area
after midnight tonight. Some embedded showers may reduce
conditions down to MVFR, otherwise, on-again-off-again showers
can be expected into the early afternoon. Isolated embedded
thunder is possible (during the same MVFR timeframe), but
chances were too low for formal mention in the TAF. Winds will
become westerly behind the showers tomorrow.

DK

&&

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

&&

$$

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