757
FXUS63 KILX 281731
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1231 PM CDT Thu Aug 28 2025

.KEY MESSAGES...

- There is a very low (10%) chance central and southeast Illinois
  exceeds 1 inch of rainfall over the next 7 days, and only a
  medium (40%) chance of exceeding one-quarter inch. Source(s):
  NBM (13z) and LREF (00z) QPF.

- There is a low (20%) chance for thunderstorms next Wednesday, and
  severe weather is not anticipated at current time.

- At least some signal for near-record low temperatures is
  emerging for late next week, particularly in the
  Thursday/Friday timeframe.

&&

.DISCUSSION...(through next Thursday)
Issued at 1228 PM CDT Thu Aug 28 2025

A robust mid-level shortwave trough is currently observed digging
into the eastern Great Lakes region, accompanied by a backdoor
cold front progressing southward along the I-80 corridor. While
the latest HREF guidance indicates a low (10-30%) probability of
scattered showers this afternoon, particularly in areas near and
north of I-74, the expectation is for a more prevalent increase in
mid-level cloudiness and only a few sprinkles. This idea is
influenced by poor low-level moisture, as evidenced by the 12z
KILX raob, and relatively weak forcing (sfc convergence) along the
front.

The cold front will settle south of the region overnight, with
surface high pressure building into the Great Lakes region for
Friday. Dry, mild and otherwise low-impact weather will then
extend through at least Monday as central Illinois finds itself
positioned beneath an atmospheric blocking pattern. The average
temperature through the holiday weekend will range 3-5 degrees F
cooler than what is considered normal for late August and early
September, with daily highs near 80 and overnight lows in the mid
50s.

A notable pattern change begins to take shape between Tuesday and
Thursday as the polar jetstream buckles over the Canadian Prairies
and sends a digging trough southward into the Great Lakes region.
This trough and its attendant cold front will mark the return of
shower and thunderstorm chances (30%) for central Illinois.

For some added commentary into the middle of next week, it is
worth mentioning a dislocation between the latest global
deterministic output (GFS, ECMWF, CMC) versus the blended/ensemble
output (NBM, ECMWF AIFS). Global models (Scenario A) suggest a
faster and deeper progression of the upper-level trough into the
Great Lakes by late Wednesday into Thursday. Conversely,
blended/ensemble guidance (Scenario B) indicates a slower,
shallower evolution of the upper trough, largely keeping the cold
core northward in Ontario. Regardless, both scenarios predict at
least one, if not multiple, cold fronts moving through central
Illinois next week. In either case, the moisture flux ahead of the
front appears limited, originating from the Pacific rather than
the Gulf, so significant rainfall is not anticipated. The primary
differences between scenario A and scenario B involve the shear
and forcing preceding the front, as well as the temperatures
following it. If scenario A unfolds, central Illinois could see
more organized convection mid-next week, followed by chilly
overnight lows by the end of the week. Some global models (GFS and
ECMWF) are forecasting surface dew points in the low 30s for next
Thursday night, which could help us challenge record low
temperatures.

MJA

&&

.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.
&&

$$