319
FXUS63 KILX 121826
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
126 PM CDT Fri Jun 12 2026

.KEY MESSAGES...

- Another round of thunderstorms will impact central Illinois
  Saturday night. There is a Slight Risk (level 2 of 5) for
  severe weather along and southwest of a Peoria to Mattoon
  line...with the primary risk being damaging wind gusts.

&&

.DISCUSSION...
Issued at 126 PM CDT Fri Jun 12 2026

High pressure will ensure a mild/dry night across central
Illinois as overnight low temperatures drop into the upper 50s
and lower 60s. Skies will initially be clear this evening:
however, an increase in mid/high clouds will be noted late. A
short-wave trough tracking out of the central Rockies will
interact with a 40-45kt nocturnal 850mb jet to trigger clusters
of convection across Kansas into central/southern Missouri after
midnight. As this activity shifts eastward, it will be
encountering a drier and more subsident airmass across Illinois
and will therefore be decreasing in intensity and areal
coverage. While some models suggest completely dry conditions,
others such as the HRRR and 12km NAM indicate at least scattered
showers/thunder reaching south-central Illinois Saturday
morning. Have therefore opted to carry slight chance PoPs (20%)
along/south of a Macomb to Mattoon line from morning through
mid-afternoon.

A cold front currently upstream across the Northern Plains will
settle southward...bringing a better chance for showers and
thunderstorms by Saturday evening. While moisture return will
initially be limited, the NAM is indicating a narrow band of
70+ dewpoints immediately along and ahead of the boundary
across southern Iowa/northern Missouri. With MUCAPE in excess of
3000J/kg and 0-6km shear of 35-45kt, a broken line of
convection will develop along the front to the N/NW of the KILX
CWA by late afternoon. These storms will then drop southeastward
into the area during the evening, accompanied by an attendant
scattered damaging wind risk. MUCAPE values rapidly decrease
after sunset, so the exact eastward/southward extent of the
severe risk is uncertain. The updated Day 2 Convective Outlook
from SPC has subsequently pulled the risk to the southwest,
dropping locations along and east of a Peoria to Mattoon line
back into the Marginal Risk (level 1 of 5) category. Based on
current trends showing the greatest instability and strongest
LLJ further southwest across the Ozarks, this seems reasonable.
Am therefore expecting a broken line of thunderstorms with
scattered damaging wind gusts to spill into the Illinois River
Valley as far east as the I-55 corridor during the mid to late
evening...followed by a weakening of the storms as they push
into east-central and southeast Illinois overnight.

Once the cold front passes, high pressure will build in from the
Northern Plains and a period of cool and dry weather is expected
for Sunday and Monday with highs only in the lower to middle
70s. After that, the next chance for precipitation will begin to
come into the picture perhaps as early as Tuesday: however,
most indications suggest the primary chance for showers/thunder
in the extended holding off until late Wednesday into Thursday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1244 PM CDT Fri Jun 12 2026

VFR conditions will prevail through the entire 18z TAF period.
Skies will initially be mostly clear this afternoon and evening:
however, a gradual increase in mid-level cloudiness AOA 12,000ft
is anticipated tonight as a disturbance approaches from the
west. Convection will develop in advance of the disturbance and
on the nose of the nocturnal jet across Kansas into central/southern
Missouri overnight, and some of this activity may spill into
south-central Illinois Saturday morning. Model solutions vary,
so confidence in precip at the TAF sites remains poor. Have
opted to lower cloud bases at all sites and introduce VCSH at
KSPI/KDEC after 14z/15z accordingly. Winds will be light through
tonight, then will become SW and increase to 10-15kt Saturday
morning.

&&

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

&&

$$

KEY MESSAGES...Barnes
DISCUSSION...Barnes
AVIATION...Barnes