175
FXUS63 KILX 301106
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
606 AM CDT Thu Jul 30 2026

.KEY MESSAGES...

- Calm weather today across the area with light winds, highs in
  the mid 80s, and comfortable humidity levels.

- Moderate to heavy rainfall and localized flooding concerns
  Friday and Saturday as a wave of widespread showers and
  thunderstorms spreads in. The NBM probability of exceeding 2
  inches is highest (50-60%) NW of a Havana to Peoria line.

- Below normal temperatures from clouds and precipitation on
  Friday and Saturday will transition to more seasonable warmth
  and humidity by early next week.

&&

.DISCUSSION...
Issued at 235 AM CDT Thu Jul 30 2026

*Calm Conditions Persist Through Tonight*

A 1017 mb surface high is currently meandering eastward across
northern/central Illinois, promoting clear skies, light E/NE
winds, and comfortable conditions. Efficient radiational cooling
is allowing temperatures to cool into the low 60s (some spots
could locally dip into the upper 50s by daybreak). At the same
time, GOES-19 nighttime microphysics imagery reveals some patchy
shallow fog has been developing in Vermilion and Edgar
counties, though is transient in nature and poses minimal risk
for notable visibility reductions. Any rural fog will quickly
burn off as the sun rises this morning.

As the anticyclone drifts into Indiana today, winds will veer to
become southeasterly by midday. Dew points near 60 degrees and
afternoon highs in the mid 80s will keep conditions
comfortable. As the next weather system begins to approach, thin
cirrus clouds will begin to spill into central Illinois this
morning, gradually thickening into the afternoon, filtering out
more sunshine.

*Heavy Rain and Localized Flooding on Friday and Saturday*

A mid-level shortwave traversing across Montana and the Dakotas
atop the ridge today will become further enhanced by
convective/MCS activity in the northern Plains before digging
southeastward through the Midwest. This system is a bit unusual
for late July, with a sfc low pinwheeling its way through the
area Friday and Saturday, accompanied by a wave of showers and
thunderstorms. The chance of thunderstorms is highest Friday
night as elevated instability (MUCAPE of 1000-1500 J/kg)
overspreads central and southeastern Illinois. SPC SWODY2 keeps
the risk for severe weather just to our southwest, as the main
instability axis will reside in Missouri Friday afternoon.
However, will have to monitor the speed of the sfc low, as a
quicker progression could push this risk more into western
Illinois. On Saturday, lingering showers and storms underneath
the low may have the tendency to produce a few cold air funnels
(mainly across SE IL), given the vorticity-rich environment in
place.

The precipitation associated with this system could result in
heavy rainfall and flooding in some areas, given PWATs in the
1.9-2.2 inch range and deep column moisture. WPC Day 2 (Friday)
ERO has a slight (15-39%) risk of excessive rainfall across
much of the area, mainly west of I-57. On Saturday, WPC
maintains a marginal (5-15%) risk of flooding east of the
I-55/I-155 corridor. Slow storm motions and training of
convective cells is the main concern. Broader precipitation
shield along the northern side of the low will promote steady
light-moderate rain rates. There remains some disagreement among
guidance on the exact track of this system (GFS/NAM weaker &
further south, ECMWF stronger & further north). In the scenario
of a stronger low, a more well-defined mid-level dry slot could
slightly reduce rainfall totals across central IL, keeping the
bulk mainly north, though confidence in this is low. The initial
push of showers is expected Friday AM from west to east and
should conclude sometime late Saturday. While there will be some
lingering low-level dry air across central IL ahead of this,
top-down saturation should occur rather quickly. The global
models suggest the potential for a deformation zone along the NW
side of the system, which would keep rainfall going into the
evening, so this will have to be monitored.

*Seasonable Temperatures Return by Next Week*

Widespread clouds and precipitation on Friday and Saturday will
put a lid on temperatures, with afternoon highs as low as the
mid 70s both days. On Friday, our southeastern counties should
see the rain hold off until the early afternoon, allowing a few
extra hours for temperatures to climb into the low-mid 80s. Some
clouds may linger on Sunday, but surface high pressure will
begin to build back in and clear skies out through Tuesday. Each
day, high temperatures will climb an additional 1-2 degrees (to
the mid 80s), with dew points in the mid-upper 60s.

By Wednesday, a piece of a cutoff mid-upper low over TN/KY may
drift back up into the area as it joins the jet stream,
bringing a low (20-30%) chance of showers across our southeast.
Otherwise, a cold front hung up in the Midwest should remain
northwest of the ILX CWA, though may begin nosing into the area
mid-week.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 606 AM CDT Thu Jul 30 2026

VFR conditions expected through the period. A little diurnal
cumulus development is expected late morning, but the main cloud
ceilings will develop later in the period, though primarily at
high levels.

&&

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

&&

$$

KEY MESSAGES...Moeller/Geelhart
DISCUSSION...Moeller/07
AVIATION...Geelhart