284
FXUS63 KILX 181427
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
927 AM CDT Sat Oct 18 2025

.KEY MESSAGES...

 - Rain will occur across all of central and southeast Illinois
   today through Sunday morning. Amounts will be greatest along
   and southeast of a Champaign to Springfield line where in
   excess of 1 inch is expected.

 - There is a Marginal Risk (5-15% chance) for severe weather this
   afternoon along/east of I-55...with the primary risk being a
   few 40-50mph wind gusts.

 - Northwesterly wind gusts of 30-40mph will develop behind a
   departing cold front late tonight into Sunday.

&&

.UPDATE...
Issued at 925 AM CDT Sat Oct 18 2025

Mid morning water vapor imagery shows a strong shortwave lifting
across TX/OK and a lower amplitude wave ahead of that over central
MO. Across central Illinois, expect a relative lull (isolated) in
precip coverage in place currently to continue into the early
afternoon, then precip chances will begin to increase again as the
lead shortwave lifts into the area. Precip coverage farther
increases this evening as the stronger wave to the southwest
overspreads the area. Latest RAP suggests some pockets of
1000-1500 J/kg MLCAPE may develop this afternoon, which, when
combined with the increasing shear through the day, should be
sufficient to support a severe thunderstorm or two. RAP also
suggests that strong 0-1km shear of 20-30 kt will be in place
along and south of I-70 along with low LCL heights area-wide, so
will need to keep a tornado threat in mind if strong storms are
able to form this afternoon.

Deubelbeiss

&&

.SHORT TERM...(Today through Sunday)
Issued at 328 AM CDT Sat Oct 18 2025

0730z/230am regional radar mosaic shows a band of scattered showers
and thunderstorms from near Madison, Wisconsin southwestward to
the Kansas City metro. These cells have formed along and ahead of
a pre-frontal trough and are expected to spill into the Illinois
River Valley before dawn. Areal coverage of convection will decrease
after 12z/7am as a short-wave trough currently over northwest Iowa
tracks into Wisconsin and the best synoptic lift shifts into the
Great Lakes. Given loss of forcing, am only carrying chance PoPs
(20-40%) across the area this morning before a stronger short-wave
over New Mexico approaches from the southwest by afternoon.

With renewed lift and a cold front pushing across the Mississippi
River, showers and thunderstorms will become more widespread from
mid-afternoon into this evening...especially along/east of I-55.
00z HREF continues to advertise limited instability due to widespread
cloud cover with mean MUCAPEs peaking at just 500-1000J/kg. The
strongest instability will be focused further upstream across
southern Missouri into Arkansas where MUCAPEs will exceed
1500J/kg. Despite the modest instability, increasing deep-layer
shear will lead to a few strong thunderstorm cells capable of
40-50mph wind gusts along/east of I-55 this afternoon. Further
south, a more robust cluster of strong to severe storms will form
across the Ozarks...then track northeastward into the Ohio River
Valley this evening. Based on the 00z SREF/GEFS 4-hour
neighborhood probability of severe wind, it appears the bulk of
the severe weather will remain along/south of I-64. Will still
need to keep a close eye on radar trends later today...in case the
cells lift further north and perhaps clip the far SE KILX CWA
around Flora and Lawrenceville early this evening.

While the most significant thunderstorms will stay south of central
Illinois, all models show widespread showers with a few embedded
thunderstorms forming area-wide this evening as the short-wave
energy arrives and low pressure deepens along the frontal boundary.
Given the expected trajectory of the best deep-layer moisture,
locations along/southeast of a Champaign to Springfield line will
be favored for the heaviest rainfall. The latest projections
suggest this area will pick up beneficial amounts of 1-2
inches...with isolated spots perhaps topping 2 inches. Further
west, rainfall will generally be 1 inch or less across the
remainder of central Illinois.

As low pressure deepens and lifts into the Great Lakes, a
tightening pressure gradient will lead to strong/gusty winds after
FROPA late tonight into Sunday. The 06z HRRR shows wind gusts of
35-45mph reaching the far western KILX CWA around Galesburg and
Rushville by midnight...then spreading eastward to the I-57
corridor by 4am. After this period of winds potentially gusting
over 40mph, NW winds will ease just a bit...but continue to gust
30-35mph through early Sunday afternoon. Once the pressure
gradient relaxes, winds will decrease substantially toward sunset
Sunday evening.

Barnes

.LONG TERM...(Monday through Friday)
Issued at 328 AM CDT Sat Oct 18 2025

High pressure will build into the Midwest Sunday night, bringing
diminishing winds and chilly overnight lows in the upper 30s and
lower 40s. As the high quickly shifts off to the east, a gusty
return flow will develop on Monday and push afternoon highs back
into the upper 60s to around 70 degrees. The next fast-moving cold
front expected to swing through the area is still on target for
Monday night. While moisture will be limited, think lift will be
strong enough to justify low chance PoPs (20-30%)...especially
along and north of I-74. Once this front passes, much cooler
weather will be on tap for the rest of the week. The coolest day
will be Tuesday when highs only reach the upper 50s and lower 60s
and overnight lows dip into the middle to upper 30s. If winds are
able to decrease sufficiently, this may provide the next
significant opportunity for frost. Stay tuned for more details
over the next few forecast cycles. After that, temperatures will
warm back into the upper 60s to near 70 degrees by the end of the
week.

Barnes

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 602 AM CDT Sat Oct 18 2025

Isolated showers will track across much of central Illinois this
morning...with showers/storms becoming more widespread by late
afternoon into tonight. Latest CAMs continue to suggest
convection developing and lifting northward to the I-72 terminals
by 20z/21z...then further north to KPIA by around 23z. Think this
initial push of precip will be the most likely timeframe for
thunder, so have included a TEMPO group at all sites accordingly.
The primary thunder area will quickly shift eastward early this
evening...with showers lingering through the entire night.
Ceilings will initially be VFR, but will drop to MVFR when the
steady precip develops later today, then remain MVFR through 12z
Sun. Winds will be SW with gusts over 20kt today, then will veer
to NW and increase markedly after a cold front passes tonight.
Based on HRRR wind gust forecast, have introduced NW gusts of 35kt
at KPIA/KSPI by 07z...then further east to KCMI by 10z.

Barnes

&&

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

$$