981
FXUS63 KILX 141750
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1250 PM CDT Mon Jul 14 2025

.KEY MESSAGES...

- Areas of dense fog have developed overnight. A Dense Fog
  Advisory is in effect for north of I-70 until 10am.

- Additional chances for strong thunderstorms and flooding return
  by the middle of the week (Wednesday - Thursday) and again by
  next weekend (Saturday).

- Heat indices will get up to 100-105 degrees on Wednesday, before
  a cold front sweeps through Wednesday night.

&&

.DISCUSSION...
Issued at 318 AM CDT Mon Jul 14 2025

Patchy dense fog is hanging around central IL this morning. Some
areas are seeing very limited visibilities. There is a Dense Fog
Advisory out until 15z (10am), but the conditions should start to
improve between 8-10am as the sun erodes the fog layer.

Today will be a dry, but quite typical summer day. Highs today will
being the upper 80s, with lows upper 60s to low 70s. Most of the
area will be dry today. A stationary front is draped across
southeastern Il today. There are some low chance POPs (20% or
less) in our southeast 6 counties this afternoon, but should stay
mostly to our south.

Tomorrow, better shower and storm chances return (30-60%), as the
stationary front starts to shift northward. The storms won`t be
anything organized. They will be of the typical scattered middle
July, popcorn variety. However, any storms that do occur could
produce decent rainfall locally. Forecast soundings show a long,
skinny CAPE profile, slow storm motions (~15-20 knots), and PWATs
around 2-2.3 inches, which would support very heavy rainfall and
localized flooding risk. SBCAPE values are around 2500-3500 J/kg
(depending on the model), with no CIN and low shear. Severe threat
is not expected, but strong wind gusts would be possible within any
stronger downbursts.

Wednesday, there is a marginal risk for severe weather north and
west of the IL River. This will connected to how Tuesday`s storms
evolve on if the risk increases or not. Timing is looking to be an
overnight issue. Currently, the models are showing PWATs around 2
inches, astronomical SBCAPE values (>4000 J/kg), MLCAPE around 2000-
3000 J/kg, and DCAPE around 1000 J/kg. Slow storm motions are shown
on forecast sounds, so another flooding threat? We shall see.

Beyond day 3, periodic chances for showers and thunderstorms exist
into the weekend.

The hottest day of the week looks to be Wednesday with highs around
90s and heat indices 100-105 degrees. Then a cold front will swing
through, dropping daytime temperatures back into the 80s, perhaps
even below normal for mid July.

Copple

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1249 PM CDT Mon Jul 14 2025

The moisture from this morning`s dense fog was deep enough to
linger until midday as an MVFR cumulus layer across portions of
central IL. Visible satellite loops are not showing much clearing
in those clouds through 1730z. However, we still expect a gradual
improvement as the sun works to mix out some of that moist layer,
per the ILX 12z sounding. All sites should see VFR cloud conditions
by 20z. VFR conditions should prevail until Tuesday morning,
although pockets of MVFR fog will be possible between 09z and 13z
tomorrow morning. Confidence is not high enough to add those
conditions at this point, but it will bear watching.

A stationary front will lift north toward I-70 tomorrow morning,
helping to increase MVFR clouds from south to north and increase
rain potential for our southern TAF sites. SPI and DEC will have
the better chances for sprinkles as early as 15z, but we left off
precip for the 18z update.

Winds will remain light through tomorrow, with a general southerly
flow pattern prevailing.

Shimon

&&

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

$$