656
FXUS63 KILX 101101
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
601 AM CDT Sun Aug 10 2025

.KEY MESSAGES...

- A slight risk (level 2) exists for excessive rainfall northwest
  of the IL river from today through Monday night. While rainfall
  generally should range from 1 to 1.5 inches in this area,
  localized totals 2 to 3 inches or more can not be ruled out.

- There is a marginal risk (level 1 of 5) of severe storms for
  damaging winds west of I-55 this afternoon.

- Warm and muggy conditions will persist through mid week, though
  temperatures will ease back a bit in central IL as clouds become
  widespread next few days. Hot and humid conditions will return
  Friday through Sunday when afternoon heat indices could top 100
  degrees.

&&

.DISCUSSION...
Issued at 345 AM CDT Sun Aug 10 2025

The predawn surface analysis shows 1022-1024 mb high pressure
anchored over the mid Atlantic States and New England, while a
frontal boundary extended from central MN, thru nw Iowa into
eastern Nebraska and KS. A series of MCS`s had convection from
central/northern KS ne through eastern NE, central/southern Iowa
into far nw IL and southern WI and central Lake MI. Nearest
convection to our CWA was near the Quad Cities/Iowa border and
tracking northeast. IR satellite imagery showing mostly clear to
partly cloudy skies overall with bands of mid/high clouds though
clear skies near the Indiana border/Wabash River valley. Temps
were in the low to mid 70s with muggy dewpoints in the lower 70s.
South to SE winds were 5-10 mph in central IL and light to calm in
southeast IL. Very patchy light fog near the Indiana border with
5 mile vsby at Danville with patchy fog more common further east
in west central and sw Indiana.

The latest CAMs show some convection tracking east/ne into the IL
river valley later this morning into mid afternoon and weakening
as it moves toward I-55 during mid/late afternoon. Unstable air
mass again over the area especially this afternoon when ML CAPES
reaching near 3000 j/kg over IL river valley and SB CAPES rise to
4000-5000 j/kg or higher from IL river west. Wind shear remains
weak with 20-30 kts far nw CWA at mid afternoon. SPC Day1 outlook
has marginal risk of severe storms for damaging winds west of an
El Paso to Lincoln to Springfield line this afternoon. An outflow
boundary could get as far east as I-57 during this afternoon but
most of the CAMS are very limited with convection in eastern/se IL
likely to do strong mid/upper level ridge still in place across
the Southeast States including the Ohio and TN river valleys.
Very warm and humid today with highs in the upper 80s to around
90F (lower 90s se of I-70 and mid 80s nw of the IL river).
Afternoon heat indices peak in the mid to upper 90s from the IL
river southeast with Lawrenceville near 100F.

Cold front to slowly push into far nw MO, southeast Iowa and
central WI by dawn Monday and this to spread chances of showers
and thunderstorms further se into central IL tonight and Monday. A
scattered to broken band of convection shown by CAMs to move east
into the IL river valley during this evening and weakening
overnight while eastern/se IL look to stay mostly dry. Outflow
boundary near central IL on Monday could see isolated to scattered
convection develop by Monday afternoon, while southeast IL stays
dry and very warm. Highs Monday similar to today with mid 80s nw
of the IL river, and upper 80s to around 90F se of the IL river
with lower 90s by Lawrenceville.

Areas to our nw have a flood watch in effect today but feel
more widespread and heavy rainfall will be just nw of CWA. Could
see 1-1.5 inches nw of the IL river today through Monday night
while LPMM shows 24 hour pockets of 1.5-3 inches west of the IL
river. WPC has slight risk of excessive rainfall west of the IL
river today though Monday night. They have a 25% risk of exceeding
flash flood guidance today and tonight west of the IL river.

The frontal boundary is forecast to push into far nw IL on Tue and
we have a good chance of showers and thunderstorms into central IL
and in southeast IL too by Tue afternoon. WPC has marginal risk of
excessive rainfall on Tue/Tue night over IL. Highs Tue in the mid
80s over the IL river valley and upper 80s to near 90F in east
central and se IL. The frontal boundary weakens as it pushes down
to near central IL during Wed into Thu and continued chances of
convection, with best chances in the afternoon/early evening
hours. Seasonable highs in the mid to upper 80s Wed/Thu with lower
80s by Galesburg. Still muggy with dewpoints in the upper
60s/lower 70s.

Subtropical ridge to build back northward late this week as 500 mb
heights rise to 592-594 decameters by Fri/Sat. More impressive
heat and humidity returns with afternoon heat indices likely
topping 100F Fri into this weekend. Convection chances appear to
be more isolated and focused during the afternoon/early evening
hours. with storm track being north of IL over upper Midwest and
Great Lakes region.

The Climate Prediction Center (CPC) 6-10 Day outlook for Aug 15-19
has a 70-80% chance of above normal temperatures across IL. CPC`s
8-14 Day outlook for Aug 17-23 has a 50-60% chance of above normal
temperatures across IL. So the warm and muggy conditions look to
continue across central/se IL the next two weeks.

07

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 555 AM CDT Sun Aug 10 2025

A cluster of showers and thunderstorms near the IA/IL border will
expanded southward as it tracks eastward into the IL river valley
later this morning, and then weakens by mid afternoon as it
approaches I-55. Continued Prob30 for TS with MVFR conditions at
PIA from 16-19Z. Latest HRRR model showing a 2nd band of
convection moving into the IL river valley late this afternoon and
early evening and carried Prob30 for TS at PIA from 22Z-02Z for
this possibility. BMI and SPI appear to be on eastern edge of this
convection chance and carried VCSH/TS at these locations from
00Z-04Z. Think DEC and CMI should stay dry next 24 hours with VFR
conditions prevailing as approaching convective bands weaken into
mid/upper level ridge over eastern/se IL. South to SSW winds
around 10 kts with gusts 17-22 kts after 15Z and into the
afternoon, veer SE and decrease to 4-7 kts after sunset.

07

&&

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

$$