485
FXUS63 KILX 081327
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
827 AM CDT Tue Jul 8 2025

.KEY MESSAGES...

- There will be daily chances (20-50% coverage) for isolated to
  scattered showers and thunderstorms through the rest of the
  week, mainly during the afternoon and evening hours. There is a
  marginal risk (level 1 of 5) for severe storms this afternoon
  into mid evening across much of central Illinois, south of
  highway 24.

- Seasonable July heat and humidity will prevail through this
  weekend, with afternoon highs generally in the mid 80s to near
  90, and afternoon heat indices peaking in the lower 90s this
  week, except 95 to 100 on Friday afternoon.

&&

.UPDATE...
Issued at 822 AM CDT Tue Jul 8 2025

A decaying line of thunderstorms is pushing across the lower
Illinois River Valley as of 8am this morning with a gust front
surging well ahead of the main line. A few new updrafts forming
along the gust front have failed to maintain themselves owing in
part to weakening instability with eastward extent and moderate
convective inhibition. Expect this line to continue to weaken as
it struggles eastward. Once this line eventually fades, anticipate
a brief lull in convective coverage late this morning before
storms redevelop early this afternoon with an attendant severe
risk. Of particular note will be an MCV currently over far NE MO
and SE IA that could serve as one of the triggers for storm
development later today in addition to the aforementioned outflow
boundary.

Deubelbeiss

&&

.DISCUSSION...
Issued at 350 AM CDT Tue Jul 8 2025

Predawn surface map shows weak 1018-1019 mb high pressure over
Lake MI and eastern IL and western Indiana. A warm front was near
the IL/MO border and MO/IA border extending westward to 1012 mb
low along the western NE/KS border. An MCS was over nw MO, south
central and sw Iowa and into southeast Nebraska and northeast KS
and tracking southeast and KC metro and toward Kirksville MO. A
few isolated showers were over northern IL north of I-80 past few
hours, while quiet wx prevailed over central/se IL with clear to
mostly clear skies. Patchy fog had developed over the Wabash river
valley with Terre Haute IN vsby at 1.5 miles.

MCS to weak next few hours as it tracks se over central MO but it
will lay out outflow boundaries that will push eastward into west
central IL later this morning and into central IL during this
afternoon. Also have a weak upper level trof shifting eastward
into IL by late today and evening. Likely will see redevelopment
of scattered thunderstorms near this eastward moving boundary with
daytime heating and instability increasing. Though convection will
be more isolated in southeast IL this afternoon/evening. HREF
MLCAPES elevate to 1500-2000 J/kg this afternoon sw of I-74 with
weak bulk shear values of 15-20 kts. SPC Day1 outlook has expanded
marginal risk of severe storms for damaging winds further ne into
central IL and now covers areas south of highway 24 (south of
Peoria) this afternoon into mid evening. PW values increasing to
1.75-2.2 inches north of I-70 during this afternoon and will
contribute to localized heavy rain threat. The HREF LPMM still
shows pockets of 1.5-3 inches of rain north of I-70, with a few
isolated spots of 3-5 inches similar to what we saw on Sunday
afternoon/early evening. Highs in the mid to upper 80s today with
dewpoints rising into the upper 60s/lower 70s this afternoon with
SSW flow. Heat indices to peak from 90-95F this afternoon (coolest
by Galesburg).

Convection chances to wane later this evening and overnight with
muggy lows in the upper 60s to around 70F (lower 70s by
Lawrenceville). The weak upper level trof moves into Indiana
during Wed where best chances of convection will be. We have
chance pops Wed afternoon in eastern/se IL and slight chances as
far west as the IL river. SPC Day2 outlook does not have a
marginal risk of severe over CWA, but may be a few stronger cells
Wed afternoon in eastern IL with gusty winds, and locally heavy
rains near the Indiana border. Highs Wed back in the mid to upper
80s with afternoon heat indices around 90F to lower 90s.

Central IL will be between wx system Wed night and Thu with weak
upper level trof pushing further east of IL and next short wave
trof tracking se from the Northern Plains into Iowa on Thu where
better chances of convection will be. We have mainly slight
chances of convection Thu afternoon south of I-74. Highs Thu in
the upper 80s and afternoon heat indices in the lower 90s.

A stronger northern stream short wave trof to drop down from the
Northern Plains and into IL late Friday afternoon and Fri night
bringing a better chance of more organized convection that could
be strong to severe as airmass is quite unstable and we will see
more wind shear with this wx system. Highs around 90F on Fri with
dewpoints in the low to mid 70s and afternoon heat indices in the
mid 90s to near 100F (highest over the IL river valley). Still
pretty good chances of convection on Saturday especially eastern
IL as frontal boundary moves through eastern/se IL. Highs Sat in
the mid to upper 80s with Lawrenceville near 90F where heat
indices in the mid 90s in southeast IL Sat afternoon.

Convection chances to diminish from nw to se on Sunday and
seasonable temperatures prevailing early next week.

07

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 616 AM CDT Tue Jul 8 2025

Main aviation concern will be with development of thunderstorms
early afternoon in west central Illinois, spreading east through
early evening. Time frame remains fairly similar to the previous
TAF set, starting around 19-20Z near KSPI/KPIA and reaching KCMI
toward 00Z. Within the stronger storms, short periods of MVFR or
IFR visibility are likely, along with some strong wind gusts over
30 knots. Outside of the storms, VFR conditions will prevail.

Geelhart

&&

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

$$