194
FXUS63 KILX 181842
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
142 PM CDT Sat Jul 18 2026

.KEY MESSAGES...
- Scattered Severe Storms Today: Scattered thunderstorms will move
  through central Illinois this afternoon and evening. The
  primary threat is localized damaging wind gusts from
  collapsing storms, along with downpours capable of producing 1
  to 2 inches of rainfall.

- Wildfire Smoke Sunday: Smoke from Canadian wildfires will filter
  southwest across the area overnight, creating hazy skies
  through the day Sunday. Those sensitive to pollution should
  take precautions.

- Severe Weather Risk Late Monday: There is growing confidence
  in a more organized severe weather threat late Monday and
  Monday night. Severe storms capable of damaging winds and
  locally heavy rain are expected to sweep southeast into the
  region.

- Dry and Cooler Late Week: A strong high-pressure system
  brings a return to quiet weather from Wednesday through
  Friday. Expect dry conditions with comfortable, slightly
  below-normal temperatures in the low to mid-80s.

&&

.DISCUSSION...
Issued at 138 PM CDT Sat Jul 18 2026

Short Term Forecast & Convection Today...
A west-east oriented frontal boundary currently resides near
the I-80 corridor in northern Illinois and is making a slow
southward progression into central Illinois. Ahead of this
front, a warm and humid air mass remains in place with
temperatures in the upper 80s to low 90s and dew points in the
low to mid 70s. RAP guidance indicates MLCAPE values will peak
in the 2500-3000 J/kg range this afternoon, though deep-layer
shear remains modest at 20-25 kt. Given the lack of robust
forcing and sub-optimal shear profiles, expect convective
coverage to remain scattered, with some storm clustering likely.
The primary hazard with this activity will be damaging wind
gusts from collapsing cores. Additionally, with modest storm
motions of 20-25 mph to the southeast, locally heavy rainfall is
possible. HREF LPMM guidance highlights localized swaths of 1-2
inches of rain, which the ground should be able to handle given
current 3-hour flash flood guidance generally running between 2
and 3 inches. Activity should wane after sunset, though
lingering storms may persist into the overnight hours across
portions of east-central and southeast Illinois.

Sunday Air Quality...
Canadian and Upper Midwest wildfire activity continues to
produce a significant smoke plume across portions of the Great
Lakes and Upper Midwest this afternoon. Near-surface smoke
guidance from the HRRR suggests this plume will filter southwest
across central Illinois behind the cold front overnight
tonight, lingering through the day Sunday. This smoke, combined
with a post-frontal airmass, will likely inhibit insolation
Sunday, resulting in temperatures slightly below normal, with
highs topping out in the mid-80s. Slow improvement is expected
through the day Monday as the front lifts back north across the
region with south/southwest winds overspreading the area helping
to clear out the smoke.

Monday Severe Weather Potential...
The front is expected to lift back north across the region on
Monday, allowing south-to-southwest flow to re-establish,
pushing temperatures back into the upper 80s to lower 90s. With
dew points surging into the mid-to-upper 70s, strong instability
will develop, with MLCAPE values peaking around 3000 J/kg
Monday afternoon and evening. As a shortwave trough digs across
the Upper Midwest, deep-layer shear is forecast to increase
significantly to 40-50 kt, creating a favorable parameter space
for organized severe thunderstorms. Storms should initiate over
the upper Midwest Monday afternoon, with a strengthening low-
level jet supporting maintenance and propagation southeast along
the instability gradient into central Illinois by late evening
and overnight. This period warrants close monitoring for severe
weather potential.

Extended Period...
By Tuesday, storms are expected to clear the area along a
trailing cold front. The remainder of the work week, from
Wednesday onward, will feature dry conditions and slightly
below-normal temperatures as a strong Canadian High settles
across the Midwest. Highs are expected to remain in the low to
mid-80s with no notable precipitation chances through the latter
half of the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1213 PM CDT Sat Jul 18 2026

A slow moving cold front will sag south across central Illinois
late this afternoon and evening. Scattered thunderstorms are
expected along the front, some of which could be strong to
severe. Westerly winds ahead of the front will veer to northwest
then northeast in its wake. As winds turn northeasterly
overnight, smoke from Canadian wildfires is expected to
overspread the area. Confidence is low in any impacts to
visibility but upstream obs will need to be closely monitored as
smoke approaches central Illinois.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Air Quality Alert from midnight tonight to midnight CDT Sunday
night for ILZ027>031-036>038-040>057-061>063-066>068-071>073.

&&

$$

KEY MESSAGES...Deubelbeiss
DISCUSSION...Deubelbeiss
AVIATION...Deubelbeiss