469
FXUS63 KILX 111102
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
602 AM CDT Mon Aug 11 2025

.KEY MESSAGES...

- There is a chance of showers and thunderstorms over central IL
  today and tonight, with the best chances west of I-55. Central
  and southeast IL will see a good chance of showers and
  thunderstorms Tuesday, especially Tuesday afternoon and early
  evening.

- There is a marginal risk for excessive rainfall northwest of a
  Champaign to Taylorville line today and tonight, and across the
  area Tuesday and Tuesday night. Very localized heavy rainfall
  could amount to between 1.5 and 3 inches with locally higher
  amounts possible mainly west of I-55.

&&

.DISCUSSION...
Issued at 345 AM CDT Mon Aug 11 2025

The 08Z/3 am surface map shows 1023 mb high pressure near the mid
Atlantic Coast and ridging westward into the OH/TN river valleys.
Meanwhile a frontal boundary extended from central WI through
eastern Iowa into nw MO and central KS. Radar mosaic shows small
band of showers near the Adams/Brown county border and into
central Pike county approaching Pittsfield tracking ENE. MCS with
large area of convection was over central/southern KS into nw and
north central OK. Mild temps were in the lower 70s, with rather
muggy dewpoints in the upper 60s to around 70F.

The main frontal boundary is forecast to stay nw of CWA through
at least sunset Tuesday with our area remaining in a warm and
humid tropical air mass. Better chances of convection today and
tonight will again be focused west of I-55 as some short waves
eject ne from northern MO passing nw of the IL river today. PWATs
are currently 1.5-1.75 inches over central IL (nw of I-70) and
projected to reach 1.75-2 inches over central IL during today and
tonight, and highest over the IL river valley. WPC day1 outlook
has marginal risk of excessive rainfall from Champaign to
Taylorville nw today and tonight. SPC day1 outlook does not have a
marginal risk of severe storms today over CWA, but a few
strongest cells could have gusty winds this afternoon/early
evening over nw half of CWA. Upper level ridge over the Southeast
States still having a stronger influence on the Ohio river valley
including southeast IL to keep them drier through tonight. Highs
today in the mid to upper 80s, ranging from lower 80s by Galesburg
to lower 90s southeast IL, southeast of I-70. Heat indices to
peak in the mid 90s from I-55 southeast this afternoon with upper
90s southeast of I-70.

On Tue a weak upper level trof slowly shifts closer to central IL
with cold front pushing down into nw IL and near the IA/MO border
by sunset Tue. Higher PWATs around 2 inches or more to shift se
over CWA on Tue along with higher chances of convection, into
southeast IL too by Tue afternoon/early evening. WPC Day2 ERO has
marginal risk of excessive rainfall across CWA Tue and Tue
evening. Still pretty warm and humid Tue since south of the front,
with highs in the mid to upper 80s much of central IL and around
90F in east central and southeast IL. Afternoon heat indicies Tue
to reach mid to upper 90s from I-55 southeast with areas southeast
of I-70 near 100F.

A weakening cold front pushes south into central IL by dawn Wed
and into southern IL near I-64 by dawn Thu. This will shift
chances of convection southward, with higher pops south of I-72 on
Wed. WPC Day3 ERO has marginal risk of excessive rainfall over
southeast IL, southeast of I-70 on Wed. Highs Wed in the low to
mid 80s central IL and upper 80s in southeast IL, with heat
indices peaking in mid 90s south of I-70 Wed afternoon. Wed night
appears to be the coolest night this week as weak high pressure
drops down into the western Great Lakes, with lows in the low to
mid 60s central IL and upper 60s in southeast IL. We have a fairly
dry forecast Wed night through Thu, except for slight chance of
showers/thunderstorms south of I-70 Thu afternoon closer to
frontal boundary in southern IL. Seasonable highs Thu mostly in
the mid 80s with upper 80s from I-70 south.

The subtropical upper level ridge builds back into IL by Friday as
500 mb heights rise to 592-594 decameters. Frontal boundary to
lift back north of central IL during Friday with hot and humid air
mass in place Friday through this weekend. Highs in the upper 80s
and lower 90s with afternoon heat indices in the upper 90s and
lower 100s. The best chances of convection/MCS activity appear to
be north of central IL Fri through Sunday but convection chances
may start increasing from the nw next Sunday/Monday.

The Climate Prediction Center (CPC) 6-10 Day Outlook for Aug
16-20 has a 70-80% chance of above normal temperatures across IL.
CPC`s 8-14 Day Outlook for Aug 18-24 has a 45-50% chance of above
normal temperatures over central and southeast IL.

07

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 559 AM CDT Mon Aug 11 2025

Stratus clouds with 300-500 ft ceilings possible at PIA until 14Z
along with MVFR vsbys (3-5 miles) from fog. Stratus clouds get
close to BMI at 13Z/7 am but HRRR keeps these low clouds just nw
of BMI airport but will need to be watched. Otherwise isolated
convection to affect central IL airports today into mid evening
though most of the time should be dry. Latest CAMs are not in best
agreement even with each hour update and with isolated convection
currently north of Jacksonville, carried VCSH at SPI next few
hours and then at PIA after 14Z. Just recently getting isolated
showers appearing near I-72 between DEC and CMI with 4-7k broken
ceilings and tracking ENE. Best chance of isolated to scattered
convection to be from I-55 nw this afternoon/evening and possibly
extending into overnight at PIA. South winds around 5 kts at dawn
to veer SW at 7-10 kts after 14Z and turn south to SSE about 5 kts
at sunset.


07

&&

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

$$