389
FXUS63 KILX 092124
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
324 PM CST Sat Nov 9 2024

.KEY MESSAGES...

- Low visibility in fog and drizzle is anticipated late tonight
  into early Sunday morning...particularly along/west of the I-57
  corridor. Motorists are advised to drive with caution.

- The next chance for showers will arrive by Wednesday: however,
  significant rainfall is not expected.

&&

.SHORT TERM...(Tonight through Sunday)
Issued at 324 PM CST Sat Nov 9 2024

21z/3pm surface analysis shows a 1006mb low over southern Nebraska
with an occluded frontal boundary arcing southeastward into the
Ozarks. Showers have developed ahead of this feature and have been
spilling into central Illinois since midday. While the airmass was
initially quite dry, ceilings have gradually lowered to 4,000-8,000ft
and measurable precip has been noted in most locations west of the
I-57 corridor. With continued top-down moistening, showers will
become more widespread and heavier across the entire KILX CWA this
evening. Instability will remain meager:however, NAM MUCAPE values
of 200-400J/kg will be enough to support isolated thunder mention.

The showers/thunder will shift eastward overnight and mainly be
confined to the far E/SE CWA by dawn Sunday. As the precip ends,
the CAMs are suggesting lowered visibilities overnight. Thanks to
weak lift in the saturated boundary layer, think patchy fog/drizzle
will develop once the showers depart. The lowered visibilities
will be primarily contained to locations along/west of the I-57
corridor through the overnight hours...followed by rapid visby
improvement from SW to NE across the area by early Sunday morning.
12z HREF shows a 30-40% chance of visibilities dropping below 1
mile.

Once the fog dissipates, skies will become partly to mostly
sunny across a good chunk of central Illinois on Sunday as drier
air advects in from the southwest. HRRR/RAP shows low cloud cover
potentially wrapping back into the N/NW CWA toward midday as the
Nebraska low lifts into the Great Lakes. The other big weather
story for Sunday will be the increasing winds. Given at least
partial clearing and the development of deep-layer mixing, SW
wind gusts will range from 20-30mph at times. The sunshine and SW
breeze will help boost afternoon highs several degrees warmer
than today...ranging from around 60 in the Illinois River Valley
to around 70 south of I-70.

Barnes

.LONG TERM...(Monday through Next Saturday)
Issued at 324 PM CST Sat Nov 9 2024

Quiet weather is anticipated for both Monday and Tuesday before
the next short-wave trough arrives by mid-week. Models have been
trending weaker with the system, with the 12z ECMWF now showing a
1006mb surface low passing well to the north of Illinois across
southern Canada during the day Wednesday. This is in stark
contrast to its previous runs that showed a much more amplified
upper pattern and a deeper/further south surface low. The weaker
solution is in better alignment with the current positive phase of
the North Atlantic Oscillation (NAO). As a result, think only
scattered showers will accompany a progressive cold frontal
passage on Wednesday...followed by a return to dry weather by the
end of next week.

Barnes

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1154 AM CST Sat Nov 9 2024

Ceilings will gradually lower as the atmosphere moistens from the
top-down late this afternoon into this evening. Based on latest
upstream obs and consistent forecast from the RAP/HRRR, have
lowered ceilings to MVFR at KPIA/KSPI by 01z...then further
northeast to KCMI by around 03z. Showers will become more numerous
across the area as well and cannot rule out a few rumbles of
thunder this evening, although confidence is too low to include in
the TAFs at this time. Once the band of showers lifts N/NE out of
the area, time-height cross-sections suggest enough lift within
the saturated boundary layer to produce a period of drizzle
tonight into early Sunday morning. Based on forecast soundings and
RAP/HRRR forecast, have lowered visbys to 2-3 miles and ceilings
below 1000ft after the 04z-07z time frame. It appears the dry
slot associated with the storm system will surge into central
Illinois from the southwest during the morning, resulting in an
end to the drizzle and a brief scattering of the clouds after
12z/13z. Will need to keep a close eye on low-level moisture
potentially wrapping back into the area toward midday as low
pressure passes to the northwest of Illinois. Latest HRRR suggests
MVFR ceilings returning to at least the terminals along/west of
I-55 before 18z Sun.

Barnes

&&

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

$$