893
FXUS63 KILX 071635
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1135 AM CDT Mon Jul 7 2025

.KEY MESSAGES...

- Seasonably very warm and humid conditions are expected during
  this work week across central and southeast IL, with highs in
  the mid to upper 80s today and upper 80s to around 90 Tuesday
  through Friday. Afternoon heat indices peaking in the lower 90s
  through Thursday, and mid upper 90s on Friday afternoon.

- A chance of showers and thunderstorms over southeast IL today,
  mainly this afternoon when locally heavy rain and gusty winds
  are possible with a few thunderstorms. Dry weather prevails
  across the area tonight with a bit cooler and less humid air
  arriving. Then a chance of showers and thunderstorms returns to
  the Illinois Tuesday afternoon and continue through the rest of
  the week, though most of the time it will be dry this week.

&&

.UPDATE...
Issued at 1006 AM CDT Mon Jul 7 2025

A weak frontal boundary is pushing south of I-70 late this morning
with a few showers and storms in the vicinity of the boundary. Dew
points pooling in the low to mid 70s near the front are
contributing to around 1000-1200 J/kg MLCAPE allowing for the
potential for a stronger storm or two over the next couple hours
before the threat shifts south of the forecast area altogether
this afternoon. Weak deep layer shear of only around 15 kt
precludes a more organized severe threat late this morning, but
an isolated damaging downburst wind gust cannot be ruled out, and
some localized pockets of 1-1.5 inch per hour rain rates can be
expected with the strongest storms.

Deubelbeiss

&&

.DISCUSSION...
Issued at 345 AM CDT Mon Jul 7 2025

The 09Z/3 am surface map shows a cool front over central IN/IL,
(just south of I-72 over IL) and over northern MO. South to SW
winds south of the boundary, shift north/ne from I-72 north near
10 mph or less. Dewpoints slowly slipping into the mid to upper
60s from Rushville to Bloomington north while muggy lower 70s
from Lincoln south. Mostly cloudy to overcast skies over central
and eastern IL with mostly clear skies from Galesburg to Rushville
west. Low stratus clouds less than 1k ft over east central IL from
I-55 east. Patchy fog also over parts of east central IL, with
CMI vsby at 1.25 miles and around Galesburg in Knox county with
1.5 mile vsby. Patchy fog to lift by mid morning though low clouds
in eastern IL may linger longer in the morning before breaking up
and lifting into cumulus cloud bases.

Latest CAMs slowly bring the cold front southward through
southeast IL through early this afternoon. Radar mosaic currently
not showing much activity with spotty very light rain showers in
southeast IL from Danville to Effingham southeast. But diurnally
heating of unstable tropical airmass with CAPES rising to near
1500 j/kg in southeast IL this afternoon and PW values 1.8-2.1
inches into mid afternoon in southeast IL to develop bands of
convection mainly southeast of I-70 late morning into mid
afternoon. SPC day1 does not have a marginal risk today in
southeast IL, though a few strong cells possible south of I-70
during early/mid afternoon along with locally heavy rains and
lightning. Air mass not as unstable as yesterday afternoon and low
level lapse rates not as steep, and also wind shear quite weak
again. So this may limit chances of severe storms this afternoon
in SE IL. Highs today mostly in the mid 80s with afternoon heat
indices in the upper 80s to near 90F in central IL, with lower 90s
from I-70 south.

Weakening front moves just south of CWA late today/early evening
with dry wx expected over CWA tonight as weak 1018-1020 mb
Canadian high pressure settles into the Great Lakes region. This
will bring a bit cooler and less humid air into central IL
tonight, with lows overnight in the low to mid 60s central IL
(coolest from I-74 ne) and upper 60s in southeast IL and west
central IL toward MS river valley from Macomb to Jacksonville
west.

A weak northern stream short wave trof moves from the northern
plains tonight into IL by Tue afternoon into the Midwest on Tue
afternoon and returns chances of showers and thunderstorms from
west to east during Tue afternoon. PW values rise back up to 1.5-2
inches during the day Tue and instability increases as CAPES rise
to 1500-3k j/kg over western/sw CWA Tue afternoon. SPC Day2
outlook has marginal risk of severe storms for damaging winds over
western/sw CWA. WPC Day2 ERO also has marginal risk of excessive
rainfall over IL due to tropical PW values returning. Highs Tue in
the mid to upper 80s with heat indices peaking in the lower 90s
Tue afternoon. Associated weak surface low and front from upper
level short wave trof to be near central IL at dawn Wed and to
move into southeast IL by Wed evening keeping chances of
convection going especially afternoon/early evening hours, with
highest pops eastern/se IL. More scattered convection to develop
over central and southeast IL Thu afternoon in tropical airmass in
place.

Another northern stream short wave trof moves into the Midwest
late this week enhancing convection chances Fri afternoon into
Saturday. Very warm and humid condtions to linger over area into
the weekend with highs in the upper 80s to around 90F friday and
afternoon heat indices in the mid to upper 90s and likely the
highest this week. Seasonable highs in the mid to upper 80s this
weekend and still muggy.

07

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1135 AM CDT Mon Jul 7 2025

VFR conditions persist through the 18z TAF period. Diurnal cumulus
will develop with bases around 2k-3kft but will be scattered.
Winds shift from northerly to southerly by late tomorrow morning,
but the winds stay light (< 5 knots), so only show the shift to
easterly at this time.

Copple

&&

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

$$