822
FXUS63 KILX 101802
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
102 PM CDT Sun Aug 10 2025

.KEY MESSAGES...

- There is a low chance (15% or less) for severe thunderstorms
  this evening in areas near and west of I-55. Potential hazards
  include thunderstorm wind gusts up to 60 mph and cloud-to-ground
  lightning.

- There is a medium chance (15-40%) for flash flooding this
  evening in areas near and west of I-55 where very localized
  heavy rainfall could amount to between 2 and 5 inches.

&&

.DISCUSSION... (through Saturday night)
Issued at 1251 PM CDT Sun Aug 10 2025

The current synoptic pattern features a broad mid-level trough
positioned over the central U.S. with an axis of rich low-level
Theta-E/PWATs in the vicinity of a weak baroclinic zone extending
from roughly James Bay to the Texas Caprock. A subtle low-level
jet veering into the region beneath multiple embedded shortwave
impulses will help force convection on a daily basis through at
least Tuesday.

The placement of these showers and storms will favor areas near and
west of I-55 where the key synoptic ingredients (sfc front, LLJ,
high PWATs, etc.) will remain aligned. In fact, the sfc front
will make very little eastward progress over the next 48 hours as
the stronger upper-level forcing sails into Quebec and leaves an
increasingly diffuse baroclinic zone in its wake. Convective
outflows and remnant MCVs could theoretically increase
shower/storm potential east of I-55, but we see very little signal
for this within the current suite of hi-resolution guidance. This
thinking aligns well with both convective (SPC) and excessive
rainfall (WPC) outlooks, which favor areas west of I-55 through
Monday night. Its not until Tuesday that a digging, mid-level
trough emerges from the Canadian Prairies and drives the sfc front
into central Illinois, pushing the higher shower/storm chances
east of I-55.

Convective chances, or at least coverage, should diminish
Wednesday and Thursday as the sfc front washes out over the area.
Both moisture and forcing for ascent over central Illinois will
be notably lesser than in previous days, but with a front draped
somewhere across the region, keeping some mention of PoPs (30%
chance) is both warranted and wise.

By the end of the week, the synoptic scale pattern will become
amplified, causing the effective sfc boundary to shift back
northward across our area. This change will bring back hotter and
more humid weather, with triple-digit heat index values possible
by next weekend. Additionally, the shift will lead to more
unstable conditions and potential for MCS activity.

On the whole, high-impact weather should be limited across
central Illinois over the next week. The chances for severe storms
will be tamped down by relatively weak mid-level flow. Any
damaging wind threat would have to come from either a localized
downburst from a pulse updraft, or a well-developed cold pool from
an upstream MCS. Localized flash flooding could be the more
likely risk. Overall, we have a very August-like air mass in place
this week. It would not be unusual for a scattered thunderstorm
cluster to train/backbuild and put down 2-5 inches of rain over a
couple hour period. The possibility always looms in a pattern
like this. You just hope it misses the larger population centers.

MJA

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1227 PM CDT Sun Aug 10 2025

A decaying line of showers and thunderstorms is pushing eastward
across Interstate 55 early this afternoon. Both ceilings and
visibility have returned to VFR across all regional terminals,
and this trend is expected to persist through the remainder of the
afternoon. We are monitoring another line of showers and
thunderstorms that may potentially enter the terminals between
23z-04z. Confidence and coverage remain low enough to warrant only
a PROB30 mention for TSRA at this point in time, but trends will
be monitored and amendments will be made as needed. Otherwise,
breezy southerly winds will persist through this afternoon ahead of
the cold front.

MJA

&&

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

$$