964
FXUS63 KILX 111849
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
149 PM CDT Mon Aug 11 2025

.KEY MESSAGES...

- Daily chances for showers and thunderstorms will continue
  through midweek with the highest chances on Tuesday afternoon (40-60%)
  as a cold front slowly works through the area.

- Seasonable temperatures are expected this week with things
  turning hot by the weekend. There is a 30-50% chance for heat
  indices over 100 degrees Friday through Sunday with the higher
  probabilities in west-central and southern Illinois.

&&

.DISCUSSION...
Issued at 149 PM CDT Mon Aug 11 2025

...Daily Precipitation Chances Through Midweek...

Upper analysis shows a large upper trough positioned over the
north- central CONUS/south-central Canada with a blocking high
over the Atlantic Ocean. At the surface, ridging in place from the
Mid- Atlantic states westward into the middle Mississippi Valley.
A nearly stationary front remains positioned northwest of here
and stretches from central Wisconsin into south-central Iowa.
Widely scattered showers and thunderstorms will be common once
again today, especially this afternoon into early evening with the
focus being near/west of I-55. Storms have the potential to
develop fairly quickly due to strong instability, but will
struggle to remain organized under a weakly sheared environment.
Similar to previous days, slow storm motions and high PWATs will
lead to the threat for locally heavy rainfall with any storms.

By Tuesday, a shortwave trough will allow the parent trough to begin
pivoting eastward into the Great Lakes Region and push the
previously mentioned front into central Illinois as a cold front.
This will support higher precipitation chances across the area (40-
60%), especially during the peak heating of the afternoon into early
evening hours. Strong instability and slightly better shear with the
front may lead to the development of few stronger thunderstorms.
However, better chances for severe storms will be confined north of
here, closer to the upper wave. Storm motions will once again be
slow on Tuesday with even higher PWATs due to dewpoints pooling near
the front. Because of this, a threat for heavy rainfall/localized
flooding will once again be a concern, especially where heavy rain
has fallen in previous days.

The front will slowly exit the area later Wednesday, with some
lingering shower/storm chances continuing in southeast parts of the
state through Wednesday afternoon.

...Drier, Then Heating Up...

A drier period looks to take shape for the end of the week into
the start of the weekend as flow aloft transitions to upper
ridging. Forecast guidance depicts a few overnight MCS`s working
across the Northern Plains into the Upper Mississippi Valley late
this week into the weekend. These look to stay north of us with
our next chance for rain holding off until later in the weekend or
early next week tied to a cold front.

Until then, temperatures will gradually climb underneath the
building ridge. High temperatures Friday through the weekend
peaking in the upper 80s to low 90s with heat indices flirting
with Heat Advisory criteria (105 degrees) on Saturday and Sunday.
There is 30-50% chance heat indices rise above 100 degrees Friday
through Sunday, with the higher probabilities being in west-central
and southern parts of the state.

NMA

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1211 PM CDT Mon Aug 11 2025

Persistent convection that has been near KPIA/KBMI the last few
hours has finally lifted northeast. Best chances of any
redevelopment will be near KPIA, and will include a PROB30 at this
site for early evening. However, pop-up showers/storms can`t be
ruled out at KBMI/KSPI, but chances are too low to mention at this
time.

Going into Tuesday morning, some more substantial rain chances are
expected, as a cold front begins to approach. Will include VCSH
for now, at KPIA/KBMI/KSPI, with better thunder chances after the
current forecast period.

VFR conditions will prevail the next 24 hours, with any ceilings
generally at or above 10kft.

Geelhart

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$