FXUS63 KILX 210801

AFDILX



Area Forecast Discussion

National Weather Service Lincoln IL

301 AM CDT Mon Sep 21 2026



.KEY MESSAGES...



- Much cooler weather will prevail this week as high

  temperatures only reach the 60s and lower 70s everywhere north

  of I-70 today through Wednesday. 



&&



.DISCUSSION...

Issued at 301 AM CDT Mon Sep 21 2026



07z/2am surface analysis shows a slow-moving cold front

extending from West Virginia to southern Missouri while a 1030mb

high pressure is anchored over Ontario. An influx of cooler/drier

air from the northeast has led to mostly dry conditions north 

of the I-72 corridor early this morning. However further south, 

the nocturnal low-level jet continues to interact with the 

departing boundary to trigger clusters of showers and 

thunderstorms. The precipitation has been most widespread

along/south of a Jacksonville to Mattoon line, and this will

continue to be the case for the next couple of hours before the

best forcing shifts E/SE into the Ohio River Valley and the

showers taper off toward dawn. Despite a prominent decrease in

areal coverage, think widely scattered showers will continue to

be possible throughout the day as an upper low spinning over 

Nebraska slowly pivots eastward. Forecast soundings suggest the 

low overcast currently in place will persist as well, resulting 

in a cloudy and cool day. High temperatures will range from the 

middle to upper 60s along/north of I-72 to the upper 70s far 

southeast around Flora and Lawrenceville. 



Isolated showers will persist tonight into Tuesday morning as 

the upper low gradually shifts into north-central Illinois. Once

this feature pushes to the east, synoptic subsidence on its 

back side will lead to an end to the very light precip and 

partial clearing by Tuesday afternoon. Highs on Tuesday will be

similar to today, ranging from the middle 60s far north to the

middle 70s south of I-70. As skies clear and winds diminish,

radiational cooling will lead to the coolest night of the

forecast period Tuesday night. Overnight lows will drop into the

lower to middle 50s, but may dip into the upper 40s in a few

low-lying rural locations west of I-57. Probabilities for temps

below 50 degrees have lowered across east-central Illinois 

where partial cloud cover and a lingering breeze may limit 

cooling: however, the 00z NBM still indicates a 50-60% chance 

northwest of the Illinois River.



After that, the departing upper low is progged to linger over the

Mid-Atlantic...creating a blocking pattern across the eastern 

CONUS. As a result, upper heights will gradually rise as ridging

builds over the Midwest by the end of the week through early 

next week. The end result will be mostly dry weather with slowly

warming temperatures climbing back into the upper 70s/lower 80s

by next Sunday/Monday. 



&&



.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...

Issued at 1206 AM CDT Mon Sep 21 2026



As of 05Z this evening, we're starting to see the next round of

showers blossom over portions of west central Illinois just west

of SPI. These showers and eventually a few occasional storms 

will continue to expand and spread east along the I-72 corridor 

overnight, tapering off just after daybreak Monday morning. 

Meanwhile IFR ceilings have developed across central Illinois 

and expected to persist overnight through Monday morning. Some 

improvement back to MVFR is eventually expected during the 

afternoon or evening Monday. Northeast winds will prevail

through the period. There will be a few occasional gusts to

around 20 kt.



&&



.ILX WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



KEY MESSAGES...Barnes

DISCUSSION...Barnes

AVIATION...Deubelbeiss