017
FXUS63 KILX 141917
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
217 PM CDT Sun Sep 14 2025

.KEY MESSAGES...

- The next weather system has trended slower, and now mostly dry
  conditions are expected to prevail through the daytime hours on
  Thursday, with highs in the 90s.

- Occasional rain chances return late week into the weekend
  (20-40% each day). Total rainfall amounts are unlikely to exceed
  1" (less than 20% chance).


&&

.DISCUSSION...
Issued at 215 PM CDT Sun Sep 14 2025

*** TODAY ***

It`s another hot day as central Illinois remains positioned
directly beneath the upper level ridge axis. In fact, it will
likely be among the hottest days this year, as temps have already
climbed as high as 95 or 96 degrees in some spots as of
1830z/130pm. While these conditions are well-above normal for mid-
September, record setting heat still looks unlikely as the record
warm highs are in the triple digits at each of our official
climate sites (Peoria, Springfield, Lincoln). Dewpoints in the
mid/upper 60s this afternoon will result in peak heat indices in
the upper 90s/near 100 degrees.

Satellite imagery shows scattered diurnal Cu forming along and
south of a Macomb to Mattoon line as of 19z/2pm, but forecast
soundings from the overly moist NAM still show a modest layer of
CIN (capping) above the LCL (cloud base), which combined with very
weak forcing will make it quite difficult for storms to initiate
this afternoon/evening. Any development that does occur will be
isolated, at best, and likely won`t form until the early evening
hours. Maintained a 10-15% chance of storms across west-central
IL.

*** THIS WEEK ***

The most notable change in the forecast for the upcoming week is a
slowing trend in the arrival of the next system. This is because
the upper ridge axis tilts northeast in time, forming a Rex block
(high pressure poleward of low pressure) over the eastern US. This
block will act to slow the progression of an approaching closed
upper low, and upper lows already have a tendency to arrive slower
than projected by models.

These changes were well captured by the latest NBM guidance, which
trended slower with PoPs. The expectation is now that high temps
will remain above 90 through at least Thurs, and mostly dry
conditions (aside from a very low chance, 10% or less, of a storm
across west-central IL each afternoon) will prevail. As has been
noted previously, this is bad news for the worsening drought
conditions and increases the potential for field fires during
harvest activity. The good news is that sustained wind speeds
should generally stay below 10 mph each day through Thurs, which
will help limit the risk of rapid fire spread.

The slow-moving upper low is expected to arrive late week and
meander around the area into the weekend, resulting in several
periods with at least a chance (20-40%) of precip and a cooling
trend in the temperatures. The potential for total rainfall
amounts of over 1" through the end of next weekend remains low
(20% or less), but there is at least a modest signal (30-40%) for
a half inch of rain. I`m a bit skeptical that signal holds though,
as guidance tends to overdue rainfall amounts in the medium/long
range during drought.

Erwin

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1258 PM CDT Sun Sep 14 2025

VFR conditions will prevail at all TAF sites next 24hrs. No
significant clouds, except for some high cirrus, are expected
through the period, but will still carry FEW250. With high
pressure ridge over the top of the area, winds are very variable.

Auten

&&

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

$$