664
FXUS63 KILX 202231
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
531 PM CDT Thu Aug 20 2026

.KEY MESSAGES...

- There is a marginal risk of Severe Thunderstorms late Friday
  afternoon and Friday evening northwest of a Shelbyville to
  Danville line. Damaging winds and large hail are the primary
  threats, with tornadoes also a risk (2-<5%) north of Peoria.

- A persistent northwest flow will keep temperatures and
  humidity levels in check the next several days, with
  seasonable highs in the upper 70s to mid 80s and lows in the
  upper 50s to mid 60s into mid next week.

&&

.DISCUSSION...
Issued at 240 AM CDT Thu Aug 20 2026

Scattered to broken cumulus cloud was mainly south of I-72 while
ample sunshine/few cumulus clouds over northern CWA. North to NE
flow has brought in some drier air with dewpoints in the upper
50s/lower 60s from I-74 ne, and upper 60s to around 70F from
Macomb to Decatur to Paris south. 19Z/2 pm temps were in the
upper 70s and lower 80s. Weak 1018-1020 mb high pressure was
over Lake Huron and ridging sw over southeast Iowa into northern
MO. The cold front has pushed southward into nw KY, far nw TN
and into central AR. Radar mosaic shows a narrow band of
convection over far southern IL and far sw IN near I-64 and
drifting slowly se.

Weak high pressure ridge to drift se over IL during overnight
into Fri morning, bringing fair wx and light winds. Diurnally
driven cumulus field to dissipate around sunset. Patchy shallow
ground fog could develop during overnight into early Fri morning
with CAMs showing more of this fog forming in east central/ne IL
and along river valleys (IL/Wabash/Sangamon). Any fog that does
develop during overnight should lift by mid Fri morning. Lows
overnight in the upper 50s to near 60F in central IL and lower
60s in southeast IL from I-70 southeast.

IL will be entrenched in a northwest upper level flow through at
least the middle of next week, with upper level high pressure
ridge over the Southwest States and upper level low/trof over
eastern Canada and Northeast US. A couple of northern stream
short waves to track se over the Midwest every few days, with
the 1st one over northern MN to move into the Western Great
Lakes Friday, pushing a cold front se across IA/WI on Friday and
into nw IL Fri evening. Steep mid level lapse rates and
increasing instability and wind shear by late Fri afternoon
(MUCAPES 2-3k j/kg nw of IL river by late Fri afternoon)
supports SPC`s Day1 update marginal risk of severe storms nw of
Champaign to Shelbyville line late Fri afternoon and Fri
evening. Widely scattered thunderstorms to form ahead of cold
front over northern/nw IL late Fri afternoon and moving into
central IL during Friday evening as weakening by late Fri
evening. Highs Fri in the low to mid 80s, warmest sw CWA and
south of I-70. Dewpoints in the mid 60s to lower 70s Fri,
highest nw of the IL river. Convection chances could linger
early overnight Fri night in east central IL as cold front
sweeps through CWA and thru southeast IL Sat morning. Chances
chances on Saturday appear to be east of IL over Indiana and sw
of IL over MO though isolated convection may occur near the
Wabash river valley on Saturday.

Reinforcing drier and a bit cooler air arrives Sat night through
Monday night as another weak high pressure system settles into
the region and upper level trof deepens over the northeast third
of the US. Lows in the upper 50s/lower 60s Sat night thru Mon
night with mid to upper 50s for lows Sunday night. Highs 80-85F
Sat and 75-80F Sun/Monday and back to 80-85F Tue. More short
wave energy tracks se from the central/northern Plains during
middle of next week and could bring next chance of showers and
thunderstorms, with best chances around Wednesday. Seasonable
highs in the low to mid 80s Wed/Thu with dewpoints in the mid to
upper 60s.

The Climate Prediction Center (CPC) 8-14 Day Outlook Aug 28-Sep
3 has a 33-40% chance of above normal temperatures over central
and southeast IL with precipitation trending near normal. So
this nicer weather pattern could go another two weeks.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 522 PM CDT Thu Aug 20 2026

A passing mid-level ridge axis and its attendant surface high
pressure will support mostly clear skies and light/variable
winds throughout this TAF period. The brief exception comes
early Friday morning, when patchy fog could bring MVFR/IFR
visibility restrictions. This possibility has been covered by a
TEMPO group from 08z-12z across all regional terminals.

&&

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

&&

$$

KEY MESSAGES...07
DISCUSSION...07
AVIATION...07/MJA