317 
FXUS63 KILX 281713
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1213 PM CDT Thu Aug 28 2025

.KEY MESSAGES...

- Seasonably cool conditions continue into early next week, with
  daily highs ranging from the mid 70s to low 80s and lows in the
  50s.

- There is a 15% chance of a light shower north of a roughly 
  Lacon to Paris line through around midday.

- There is a 50-60% chance of showers and storms around the 
  middle of next work week. Confidence remains low in precise 
  timing and any severe weather risk.

&&

.DISCUSSION...
Issued at 134 AM CDT Thu Aug 28 2025

***** SLIGHT SHOWER CHANCES NORTHEAST THIS MORNING *****

At 130am, satellite imagery reveals an area of mid level clouds 
drifting southeastward across the northern half of the Prairie 
State, and regional radar mosaic shows some showers across southwest 
Wisconsin and northern Illinois. Guidance suggests this region of 
isentropic upglide will shift south, clipping our area mid morning 
into early afternoon, ahead of a mid level shortwave trough. Given 
how dry the low levels appear on forecast soundings, most of this 
activity is not expected to reach the surface in our area, but did 
not feel comfortable pop-free given the splotchy QPF in the HRRR and 
FV3 - which are capturing the current precip well; we've included 
around a 15% chance of showers north of a roughly Lacon to Paris 
line from roughly 4am through noon. The cloud cover will keep 
temperatures cooler in those areas this morning, but by mid 
afternoon area- wide low 80s are expected.

The HRRR and NAMNest suggest a few more showers will develop near 
the I-80 corridor this afternoon along a lake breeze off of Lake 
Michigan, with a couple hundred J/kg of shallow SBCAPE apparent on 
NAM and HRRR soundings there. The NAMNest threatens to bring those 
into our area, clipping Marshall County, but as (1) it's the 
outlier, (2) the airmass is becoming increasingly dry by that time, 
and (3) synoptic descent is favored in the wake of the shortwave 
we've left sub-mentionable (<15%) PoPs there for now.

***** COOL AND DRY WEEKEND IN STORE *****

High res guidance suggests a back door cool front will slide in from 
the northeast late tonight into tomorrow, bringing a more stable and 
slightly cooler airmass to much of central IL. High temperatures 
will range from the low 80s across our southwest counties to mid 70s 
along and north of the I-74 corridor. Under the influence of surface 
high pressure, dry and seasonably cool conditions should continue 
right through the weekend with daily highs in the mid 70s to 
around 80 and lows in the 50s.

***** SLIGHTLY WARMER, THUNDERSTORM CHANCES RETURN NEXT WEEK *****

Global deterministic models suggest a stronger trough will dig into 
the region at some point mid next week. With a brief push of warm 
advection ahead of it, temperatures will climb back towards or 
slightly above normal with NBM giving a 30-50% chance for highs > 85 
by next Wednesday. Along its attendant cold front, some showers and 
storms can be expected, with over 70% (40-50%) of raw (calibrated) 
guidance giving us measurable rainfall. The severe set up doesn't 
appear overly impressive at this point, with moisture return into 
our area ahead of the system limited in duration (and following a 
seasonably dry airmass). Of course, a lot can change in the forecast 
between now and then; the feature is currently in the Bearing Sea, 
so it has a long journey through varying airmasses before it reaches 
the Midwest. Conditions turn sharply cooler and breezy behind this 
system; in fact, NBM has a 30% chance for both sub 70 degree high 
temperatures and wind gusts over 30 mph by next Thursday.

Bumgardner

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1208 PM CDT Thu Aug 28 2025

A cold front will settle southward across the region this evening.
There is a low (30%) chance that MVFR ceilings and/or visibility 
emerge in the vicinity of the frontal passage at a few of the 
regional terminals, mainly between 09z-13z. Otherwise, VFR flight 
conditions will be most common through this TAF cycle. With the 
surface front dropping southward, surface winds will gradually 
veer from WNW to NE, perhaps becoming light and variable for a 
time overnight.

MJA

&&

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

$$