866
FXUS63 KILX 100859
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
359 AM CDT Thu Jul 10 2025

.KEY MESSAGES...

- There is a 20-30% chance of showers and thunderstorms today and
  Friday, mainly during the afternoon and evening hours and
  highest pops over the IL river valley/nw CWA. There is a
  marginal to slight risk of severe storms over central IL late
  Fri afternoon and Fri evening. There is a 50-60% chance of
  showers and thunderstorms Saturday and some storms could be
  strong Saturday afternoon with gusty winds and locally heavy
  rains.

- Very warm and humid conditions will continue through at least
  Saturday, with Friday being the hottest today with highs in the
  lower 90s, and heat indices in the upper 90s to around 100
  Friday afternoon.

&&

.DISCUSSION...
Issued at 255 AM CDT Thu Jul 10 2025

Predawn surface map shows a frontal boundary from nw Ohio and
northern Indiana (near Fort Wayne and La Fayette IN) and westward
over central IL, south of BMI and PIA and north of Macomb. The
front then turned into a warm front over central Iowa. Radar
mosaic shows a small area of moderate rain showers moving se into
nw Christian county that had developed over central Mason county
a few hours ago. GOES 19 IR and Nighttime Microphysics Satellite
imagery`s show patches of clouds over central IL west of I-57
while clear skies in eastern IL from I-57 east. Patchy fog noted
ne of I-74 and more widespread and denser fog in northeast IL and
Indiana with Pontiac vsby less than 1/4 mile. Lacon and Rantoul
airports vsbys were 3 miles. Fog due to light to calm winds and
moist boundary layer. Latest CAMs show patchy fog developing over
central and eastern IL next few hours and becoming locally dense
in spots. There is a dense fog advisory until 9 am from
Livingston, Ford and Iroquois counties and will monitor our
eastern/ne counties for that possibility or a special weather
statement. The shallow fog should lift between 8-9 am.

MCS/MCV over western parts of MN and Iowa and eastern Nebraska to
weaken during this morning as it tracks eastward toward nw IL by
early afternoon. Outflow boundary from this system to likely
develop broken band of convection along it during midday/early
afternoon as air mass get more unstable with daytime heating, with
MLCAPES rising to 1-2k J/kg over portions of central and nw IL
and Bulk Shear values increasing to 20-30 kts over west central
and nw IL by late afternoon. SPC Day1 outlook keeps marginal risk
of severe storms nw of Knox and Stark counties but will need to
watch for risk of stronger storms later today. Marginal risk is
over far nw IL for gusty winds, hail and isolated tornadoes nw of
Quad Cities to Rockford line from mid afternoon into mid evening.
Locally heavy rains possible too over far northern CWA per HREF
LPMM having pockets of 1-4 inches north of Galesburg to Lacon
line. We have slight chance of convection over central and
southeast CWA this afternoon/evening with 30-40% northern CWA from
Quincy to BMI north. Highs today in the upper 80s to near 90F
with afternoon heat indices peaking in the low to mid 90s.

A stronger short wave trof to dig southeast from the upper
Midwest/northern plains into Iowa Fri evening and to bring more
chances of convection to area Fri afternoon/night especially over
IL river valley. SPC Day2 has marginal risk of severe storms nw of
I-70 with slight risk nw of IL river late Fri afternoon and Fri
evening for damaging winds, large hail (IL river valley) and 2%
risk of tornadoes over Knox, Fulton and Schuyler counties.
SBCAPES rise to 2-3k J/kg Fri afternoon as temps warm into the
lower 90s and dewpoints in the 70s. Heat indices Fri afternoon
reach upper 90s to around 100F and likely the hottest day this
week. We have 20-30% pops Fri afternoon over central and northern
CWA, highest in north then increase pops during Fri night with
40-60% pops by overnight Fri night from I-55 nw. HREF LPMM shows
pockets of 2-4 inches of rain by late Fri afternoon over IL river
valley.

The upper level trof digs into IL Saturday and an associated cold
front moves se into the IL river valley during mid/late Sat
afternoon and through rest of central IL during Sat evening and
into se IL overnight Sat night. This to likely bring showers and
chance of thunderstorms to area on Sat especially Sat
afternoon/evening. SPC Day3 outlook has marginal risk of severe
storms ne of CWA but will need to monitor risk of strong storms in
our area to Sat afternoon/evening along with locally heavy rains.
Highs Sat range from mid to upper 80s over central/nw CWA and
lower 90s se of I-70 where heat indices peak in the upper 90s to
near 100F Sat aftn in southeast IL. Heat indices in 90s over rest
of central IL Sat aftn.

Frontal boundary still close enough to central IL as it moves se
toward Ohio river valley to keep chances of convection around over
central and especially southeast IL. Highs Sunday 83-88F warmest
in southeast IL where heat indices in lower 90s Sunday afternoon.
Heat and humidity build back into area Mon/Tue as upper level
ridge builds over IL with 500 mb heights rising above 591 dm on
Monday. Highs Mon/Tue in the upper 80s to around 90F and
afternoon heat indices in the 90s. Still 20-30% chance of
convection Mon and Tue in tropical air mass especially during
afternoon/evening hours.

07

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1227 AM CDT Thu Jul 10 2025

Main concern in the short term is with potential for stratus/fog
in the KPIA-KCMI corridor, along a weak surface boundary.
Visibility at KPNT has dropped below 3 miles recently, and HREF
probabilities of ceilings below 500 feet are 50-60% just north of
the boundary by 10Z. Will keep this corridor at SCT003 for now and
watch trends closely as we get toward sunrise. However, MVFR
visibility is not out of the question, and have maintained that
potential in the new TAF set.

Getting into the afternoon, some concerns for scattered showers
and storms, some of which depends on leftover features from storms
that will be moving across Iowa later tonight. Kept the PROB30
mention in at all sites, though confidence wanes the further south
and east you get.

Geelhart

&&

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

$$