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FXUS63 KILX 100139
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
839 PM CDT Wed Jul 9 2025

.KEY MESSAGES...

- After a brief lull in the precip chances today (<20%) there
  will be daily chances (20-50%) for showers and storms
  particularly during the afternoon and evening hours Thursday
  through the middle of next week.

- Temperatures will generally be seasonable (highs in the mid 80s)
  the rest of the week and weekend with Friday being the warmest
  day with highs around 90F.

&&

.UPDATE...
Issued at 839 PM CDT Wed Jul 9 2025

Extended coverage of isolated showers for the evening given more
widespread than expected coverage in radar obs, however latest
trends suggest coverage will be near zero by 9 pm. Otherwise, main
feature of concern overnight is potential for fog by morning. High
pressure ridging across the area at the surface suggests mostly
clear skies should continue, allowing good radiational cooling and
light winds, so model guidance depicting patchy to widespread fog
in most models appears on track. Followed model consensus of first
development in east-central to northeast IL around 3 AM, spreading
southwestward to areas northeast of a Galesburg-Springfield-
Lawrenceville line by sunrise. Otherwise, lows in the mid to upper
60s look on track for tonight.

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&&

.DISCUSSION...
Issued at 144 PM CDT Wed Jul 9 2025

Weak surface ridging is in place across central Illinois this
afternoon which is resulting in generally fair weather across the
region. While an afternoon or evening isolated pop-up shower or
storm cannot be completely ruled out today, most of the area will
be dry through tonight. By Thursday, surface ridge axis will inch
east into Indiana with a bit of a mixed picture on convective
chances through the day. Dew points will creep back up into the
lower 70s for much of the area contributing to moderate
instability across the region. GFS advertises around 1500 J/kg
MLCAPE which will be weakly capped (generally less than 30 J/kg
MLCIN). Despite the atmosphere primed for thunderstorms, synoptic
scale forcing will be well west of the area with eastern portions
of Illinois still under the influence of the surface ridge. Still,
some of the CAMs suggest a convectively induced vort max will
move into portions of central Illinois Thursday late
afternoon/evening and could serve as the focus for some scattered
storm development. Should this occur, a few stronger storms will
be possible with damaging downburst winds and locally heavy rain
due to slow storm motions the primary concerns. Week flow aloft
and weak deep layer shear will keep the threat for a more
organized severe threat low.

On Friday, a more robust trough is progged to move east along the
Canada/US border while a southern stream wave lifts from the
central Great Plains into the Upper Midwest. A deepening surface
low over the Upper Midwest will lift a warm front across central
Illinois through the day. Temperatures will warm to around 90
degrees within a broad warm sector while dew points further climb
into the mid 70s. Strong instability will result with MLCAPE
values exceeding 3000 J/kg expected by Friday afternoon and
evening. Mid level warm air advection could drive some showers and
storms during the day Friday, but the main concern will be Friday
evening as storms grow upscale over the mid Missouri Valley in
response to a developing low level jet. These storms will congeal
into a line and move east along the instability gradient into
portions of Illinois late in the evening and overnight. While
there will be a gradually diminishing severe threat with time
through the overnight hours, it`s possible that some of these
storms could reach and maintain severe levels as they push into
the state. Uncertainty in some of the placement/timing details
remains which keeps the SPC D3 marginal risk right on our doorstep
for the time being.

Depending on the evolution of storms Friday night and placement of
remnant outflow boundaries Saturday (impacting the location of
the effective cold front), there will be some potential for
additional strong to severe storms over the weekend. Areas further
north in the state will be less warm with highs back in the lower
to mid 80s, but closer to the effective front across the southern
half of the state temps will continue to run warmer with highs
near 90F.

Deubelbeiss

&&

.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 607 PM CDT Wed Jul 9 2025

A ridge of high pressure across the central IL terminals should
bring an early end to isolated -SHRA by around 01Z-02Z this
evening, then enough clearing and light winds that areas of fog
could form late tonight. As a general theme, model guidance
develops fog first over east-central to northeast IL around 08Z,
then expand it southwestward through much of central IL by
sunrise. Have therefore included MVFR vsbys by 09Z-10Z, with a
tempo for IFR 10-12Z, then anticipate fog lifting by 13Z. There is
a chance for isolated to scattered thunderstorms developing after
20Z-22Z Thursday, and have included PROB30 for TSRA. Winds WNW
4-8 kts this evening, becoming light and variable overnight, then
returning from the SW after 13Z at around 4-8 kts.

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&&

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

$$