691
FXUS63 KILX 171134
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
634 AM CDT Fri Jul 17 2026

.KEY MESSAGES...

- Persistent heat and humidity will continue to build through
  Saturday over central and southeast IL. Heat indices peak in
  the upper 90s to around 100 degrees this afternoon, and
  100-105 degrees Saturday afternoon. Very warm and humid
  conditions look to continue early next week especially on
  Monday afternoon when heat indices likely reach the upper 90s
  and lower 100s.

- Scattered thunderstorms (30-50% coverage) are possible today
  mainly during the afternoon and early evening. Locally heavy
  rain is the primary concern though a few cells could have
  gusty winds this afternoon.

- A cold front pushing south over IL brings a potential for
  strong to severe thunderstorms late Saturday afternoon and
  evening with damaging winds the primary threat. Locally heavy
  rains also possible. More storms possible Monday night into
  Tue morning with passage of a stronger cold front.

&&

.DISCUSSION...
Issued at 400 AM CDT Fri Jul 17 2026

Predawn surface map shows a weak frontal boundary in northeast
IL from sw of Peru and Kankakee with widespread surface smoke
along and northeast of this front with vsbys 1-3 miles and some
areas even below 1 mile closer to Chicago metro like Gary, IN.
Radar mosaic shows much of CWA currently dry with isolated
showers over nw Indiana, northern IL and southeast Iowa.
Scattered to broken mid level clouds with bases around 10k ft
over central IL especially from IL river se. Patchy fog noted
mainly from I-72 south with mainly MVFR vsbys at airports. We
mentioned patchy fog from I-72 south early this morning and
lifting by 13-14Z. Mild temps were in the low to mid 70s and at
or a few degrees above dewpoints.

Latest CAMs take surface front back ne of IL by early afternoon
and should stay the smoke with it. A weak mid level short wave
trof over IL today to interact with a moist/unstable air mass
with MUCAPES reaching 2000-2500 j/kg late morning/afternoon in
central and eastern IL and 1500-2000 k/kg in west central IL.
SPC keeps marginal risk of severe storms east of IL today,
though feel we could see a few stronger cells with gusts winds
this afternoon over central and eastern CWA. The RAP13 non
supercell parameters show chance of funnel clouds again this
afternoon over central and eastern IL. Very high PWATS today of
1.9-2.3 inches supports heavy rains from slow moving cells. HREF
LPMM continues to show a few cells with 1.5-3 inches of rain in
less than 6 hours today east of the IL river. WPC Day1 ERO has
marginal risk of excessive rainfall today over eastern IL. Very
warm and humid today with highs in the upper 80s to near 90F
with afternoon heat indices in the upper 90s to around 100F.
Diurnally enhanced convection to wane during this evening
especially after sunset with muggy lows overnight in the lower
70s.

A thermal ridge to move over IL on Saturday and likely bring our
highest heat indices of this heat wave that started earlier this
week. Highs Saturday in the lower 90s with afternoon heat
indices 100-105F and a few spots likely higher. Part of our area
may need a heat advisory Saturday afternoon especially if less
convection occurs Sat afternoon. An amplifying short wave trof
moving into the eastern Great Lakes Saturday to push a cold
front southward through central IL late Sat afternoon and
evening and likely bring a round of convection with it.
Moderately unstable airmass with CAPES 2-3k j/kg while wind
shear values 20-25 kts. SPC has marginal to slight risk of
severe storms over CWA late Sat afternoon/evening for mainly
damaging winds. The slight risk is northeast of a Bloomington to
Terre Haute line over east central IL. The stronger forcing and
winds will be further east over OH/PA/NY/MD where 30% chance of
damaging winds.

Quiet weather returns to area on Sunday as weak high pressure
settles into the Great Lakes region, with more sunshine and
seasonable highs in the mid to upper 80s over CWA. Still rather
muggy with dewpoints in the upper 60s/lower 70s, highest
dewpoints over sw CWA and southeast IL. Monday will see SSW to
SW winds develop and returning the hot and humid air mass to
central/se IL. Highs in the upper 80s/lower 90s with afternoon
heat indices upper 90s in eastern IL and 100-105F over western
half of CWA west of highway 51. A strong northern stream short
wave track into the Great Lakes late Mon afternoon and Monday
night, pushing a stronger cold front southward across CWA
overnight Mon night into Tue morning over southeast IL. This
will likely bring another round of showers/thunderstorms and
possible strong to severe storms and heavy rains. SPC Day4
outlook for Mon night has a 15% risk severe northern CWA and
SPC Day5 outlook for Tue has a 15% risk over Wabash river
valley in southeast IL. Still very warm and humid Tue with highs
in the upper 80s central IL and lower 90s southeast IL with
dewpoints in the upper 60s central IL and low-mid 70s southeast
IL. Dry weather along with cooler and less humid air finally
ushers into central/se IL from Tue night into Thu with highs in
the lower 80s Wed/Thu and lows in the low to mid 60s Tue night
through Thu night.

Wildfire Smoke... The western Ontario and northern MN wildfire
activity continues to produce a considerable smoke plume for a
3rd day across the Great Lakes into the mid Atlantic States.
Near surface smoke plume with vsbys 1-3 miles common currently
northeast of a Henry to Chenoa to Danville line, so affecting
extreme northeast CWA early this morning. Current HRRR near-
surface smoke guidance indicates the southwest edge of this
smoke plume should stay northeast of I-74 this morning and begin
retreating back to the northeast later this morning and
afternoon. Air Quality Alerts continue today over northeast IL
and central and northern Indiana. A secondary, more favorable
window for smoke advection into central Illinois appears
possible on Sunday behind the passing cold front, though
guidance suggests this may be in a lower concentration than is
currently being observed to our northeast today.

The Climate Prediction Center 6-10 Day Outlook for July 22-26
has 33-40% chance of below normal temperatures over central and
northeast IL with precipitation trending toward normal. CPC 8-14
Outlook for July 24-30th has temperatures trending near normal
over central and northeast IL with sw and west central IL
slightly above normal temps. Precipitation trending near normal
across IL during last week of July.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 634 AM CDT Fri Jul 17 2026

Thunderstorms currently northeast of the KBMI and KCMI terminals
should be taken northeast away from KBMI/KCMI by the light
steering flow. Brief instances of MVFR visibility in light fog
may occur through about 13z. Otherwise, maintained PROB30 groups
for storms this afternoon, though confidence has decreased
somewhat particularly for sites near and west of KBMI-KAAA-KSPI.
Light winds are forecast, except potentially near
thunderstorms.


&&

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

&&

$$

KEY MESSAGES...07
DISCUSSION...07
AVIATION...AAT