695
FXUS63 KILX 292333
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
633 PM CDT Sun Jun 29 2025

.KEY MESSAGES...

- Tropical heat and humidity to linger into Monday over central
  and southeast IL. Heat indices in the mid 90s to near 100
  degrees this afternoon to be in the low to mid 90s Monday,
  highest in southeast IL. Conditions cool slightly for Tuesday
  and Wednesday, with highs in the mid 80s and heat indices
  below 90 degrees.

- Isolated to scattered storms are forecast through Monday.
  Locally heavy rainfall is possible, and there is a marginal risk
  (level 1 of 5) of severe storms on Monday afternoon and evening.
  The primary hazard with any severe storms will be strong winds.

&&

.DISCUSSION...
Issued at 245 PM CDT Sun Jun 29 2025

An MCV over central MO was weakening as it is tracking eastward
toward IL. Bands of convection were moving into west central and
sw IL by mid afternoon. Isolated to scattered showers and
thunderstorms were also over eastern IL into Indiana with these
cells tracking ne. Unstable airmass in place over central IL with
MLCAPES 1500-2500 j/kg and SB CAPES of 2500-4000 j/kg. PW values
were high too, from 1.70-2.10 inches, highest over southeast IL
and have been slowly advecting northward today. Heat and humidity
also continues this afternoon with heat indices in the mid to
upper 90s from Lincoln and Decatur ne and mid 80s to lower 90s sw
where more cloud cover today.

MCV to track eastward over central and southern IL this evening
and into Indiana overnight, and will continue to produce isolated
to scattered convection into this evening. A few pulsey strong
cells possible with gusty winds until sunset but main threat with
be locally heavy rains over 1 inch in less than 1 hour possible
along with cloud to lightning strikes. Another muggy night ahead
with lows in the lower 70s. Could be some patchy fog overnight and
early Mon morning with light winds if we get enough clearing. But
currently we have mostly cloudy skies tonight and should limit
extent of fog development compared to last two nights.

A cold front over eastern MN into nw Iowa and southeast NE to push
se into nw IL Monday morning, then then move se through central
IL during Monday afternoon and thru se IL during early to mid Mon
evening. This front will likely bring a band of showers and
scattered thunderstorms thru the CWA during Monday afternoon and
evening. SPC Day2 outlook continues marginal risk of severe storms
with damaging winds possible over entire CWA, though better
chances appear to be east of the IL river. WPC also has marginal
risk of excessive rainfall Mon afternoon/evening from I-55 east.
Warm and humid Monday with highs in the mid to upper 80s, warmest
in eastern/se IL. Heat indices peak in the low to mid 90s, warmest
in southeast IL with heat indices likely reaching upper 90s by
Lawrenceville.

Mid/upper level trof moves into IL by overnight Monday night with
cold front pushes east of IL, and also chances of showers and
thunderstorms shifting eastward of CWA. Weak high pressure settles
into the MO and mid MS river valley Tue/Wed returning drier wx
along with more seasonable temperatures and humidity levels. Lows
Mon night range from low to mid 60s over the IL river valley and
upper 60s to around 70F in southeast IL. Highs Tue in the mid 80s,
lows Tue night in the low to mid 60s, and highs in the mid to
upper 80s on Wed. Very isolated afternoon convection possible Thu
and Fri though most areas should be dry as upper level ridge
builds back into IL, with temps and humidity levels gradually
rising back up late this week. Highs in the upper 80s to near 90F
on Thu, lower 90s Friday and Saturday. Afternoon heat indices in
the lower 90s Thu afternoon climb into the upper 90s to around
100F next weekend.

07

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 633 PM CDT Sun Jun 29 2025

Isolated convection lingers across central Illinois early this
evening...with 2320z/620pm radar imagery showing most of the
storms along/southeast of a KDNV to K1H2 line. Further west, a few
cells are percolating across the Illinois River Valley as
well...so cannot rule out a stray shower or storm for the next few
hours. Areal coverage will be minimal and confidence is not high
enough to include in the TAFs at this time. After a mostly dry
night and Monday morning, a cold front will trigger scattered
convection by late Monday afternoon. Given a more focused forcing
mechanism passing through the region at peak heating, have opted
to carry PROB30 for thunder at all terminals from 20z Monday to
00z Tue. Winds will be S at less than 10kt tonight, then will veer
to SW and increase to 8-12kt on Monday.

Barnes

&&

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

$$