155
FXUS63 KLOT 302335
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
635 PM CDT Fri Oct 30 2026

.KEY MESSAGES...

- Periods of showers and/or drizzle are expected at times
  through the weekend, though the highest chances/coverage is
  expected tonight into Saturday morning.

- Additional periods of wet weather are likely next week.

&&

.DISCUSSION...
Issued at 100 PM CDT Fri Oct 30 2026

There is a mid-level trough over west central Texas (via SPC
Mesoanalysis) that is expected to gradually move northeastward over
the southern Plains today/tonight. Additionally, a stout 100+ knot
upper jet is located over southeastern Ontario, placing northern
Illinois in the right entrance region of its location and therefore
in an area increased upper level divergence. For know, a near
surface dry airmass has been winning the day keeping all activity on
KLOT radar currently showing up in the western portions of the
forecast area to mainly virga, to maybe a few sprinkles. As a plume
of increased moisture and warm air advection moves into the area
this evening and in the overnight, there is a better chance for
increased coverage for light showers into Saturday morning. Given
the unfavorable time of day, thunder is not expected. Although
slightly steepening low/mid-level lapse rates keeps the chances non-
zero, but below formal forecast mention.

As the upper level jet streak weakens and moves east tomorrow
morning, the mid/upper level trough is expected to move over the
western Great Lakes Saturday afternoon and evening. With weaker
forcing and a lingering dry boundary layer air mass, confidence is
lower for precipitation tomorrow evening. Slight chance PoPs were
maintained for tomorrow night for the isolated chance for a light
shower, if not just sprinkles/drizzle during any trick-or-treating.
Certainly not any kind of washout, some areas will probably remain
completely dry. But enough of a nuisance to keep precip mention in
the forecast through Sunday morning.

A pseudo-stationary upper level cutoff low west of Seattle, WA is
projected to finally move eastward over the intermountain west on
Sunday as another short wave currently near Baja California moves
northward, merging with the low, further amplifying the trough early
next week. While specific details still need to be ironed out,
models are showing fairly good agreement that this trough will
induce surface cyclogenesis east of the Rockies and that will move
over the Great Lakes in the middle of next week bringing better chances
for widespread rain. Behind this system, a cooler airmass will drop
temperatures down to make it feel a little more autumn-like.

DK

&&

.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 635 PM CDT Fri Oct 30 2026

The primary forecast concern this period is the chance of
showers and timing.

Scattered showers south and southwest of the terminals currently
are expected to slowly drift north tonight into Saturday morning
and guidance has been showing an overall decrease in shower
coverage overnight, with perhaps the best chances for showers
across northwest IL and at RFD. Opted to continue only prob
mention for the rest of the terminals and primarily for Saturday
morning. Isolated showers will remain possible Saturday
afternoon with perhaps another chance of showers late Saturday
evening through Sunday morning.

While cigs may lower into low vfr or perhaps briefly into high
mvfr with any periods of showers, confidence is very low for
mvfr cigs and expect mainly prevailing vfr cigs through the
period.

Easterly winds at or below 10kt will continue tonight, becoming
more southeasterly Saturday and possibly south/southeast
Saturday evening. cms

&&

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

&&

$$

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