037
FXUS63 KILX 020400
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1100 PM CDT Sat Jun 1 2024

.KEY MESSAGES...

- Showers and isolated storms come to an end this evening, turning
  things dry for Sunday.

- There is a 10-30% chance for patchy dense fog tonight.

- Additional chances for showers and storms return early next
  week, including the possibility for some severe storms.

&&

.UPDATE...
Issued at 808 PM CDT Sat Jun 1 2024

A weak area of low pressure was meandering east over the northern
sections of the ILX CWA this evening. Most of the showers over the
past few hours have been confined to a narrow convergence zone
near and east of the IL River, and another area south of I-70.
These will continue to diminish over the next few hours with most
of the area dry before midnight. Low clouds look to blanket the
region tonight. There is a good setup for fog to our west tonight
as ridging approaches the Mississippi Valley by sunrise, but
guidance suggests any dense fog stays west of the area and will
keep a mention of patchy fog in the forecast. Will see a northwest
to southeast gradient on lows as cold advection works in late, for
lows in the upper 50s west of the IL River to the mid 60s in SE
IL.

25

&&

.DISCUSSION...
Issued at 232 PM CDT Sat Jun 1 2024

Surface analysis early this afternoon depicts a broad area of ~1012
mb low pressure centered over western IL. Widely scattered showers
are tied to this feature and will continue through at least early
evening before pushing east into Indiana. Instability on the order
of a few hundred J/kg may lead to a few thunderstorms this
afternoon, especially where pockets of sunshine peak through and
lead to locally higher CAPE. A few cold air funnels have been
reported in western Illinois near the Mississippi River just before
2 pm where wind shear is weak and lapse rates are moderately steep.
The non-supercell tornado parameter has a bullseye of 2 over western
Illinois near the Mississippi River, with pockets nearing 1 west of
I-55 (values of 1 or greater are usually pretty good for cold air
funnels). Wouldn`t be suprised if we get a few reports of funnels
across the area this afternoon before instability wanes this evening.

A brief upper shortwave ridge slides into the area for the second
half of the weekend, turning things drier for Sunday. Surface high
pressure will begin to nose into western parts of the area late
tonight into Sunday, allowing winds to become light and variable.
With recent rainfall moistening the boundary layer, there is some
potential for patchy fog tonight. However, the 01.12Z HREF only
suggests about a ~30% probability or less for visibility to fall
below 1 mile overnight, focusing higher chances of this west of the
area where the center of the high will be located. The latest
guidance does favor visibility dropping to between 2 to 5 miles
tonight, but the chances for dense fog appear rather low at this
time.

Zonal flow sets up overhead by the start of the new week, with what
looks like a more active period characterized by additional chances
for showers and storms. Shower and storm activity could return as
early as Monday morning as a remnant MCS approaches from the west. A
stronger upper wave will track through the northern Plains on
Tuesday, sending a cold front through the Midwest states later
Tuesday night into Wednesday. Southerly flow/moisture advection
ahead of the system should bring in moderately strong instability by
Tuesday afternoon as dewpoints climb into the 70s. However, upper
jet support will be displaced to our west/northwest and the timing
of the cold front passage could limit our severe threat. The CSU-MLP
continues to show Tuesday as our best chance for any severe weather,
though depending on the speed of FROPA, Wednesday could be another
day to monitor.

Temperatures for the first half of the week look to be near or
slightly above normal (low to middle 80s) pending storm activity.
The upper pattern becomes more northwesterly/low meridional by the
end of the week as the previously mentioned upper wave becomes
vertically stacked and remains somewhat stationary north of the
Great Lakes Region. Precipitation chances become a little more
unknown in the extended due to differences in timing and placement
of shortwaves, but a drier period looks to be favored.

NMA

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1100 PM CDT Sat Jun 1 2024

SHRA have diminished, leaving a mix of ceilings ranging from IFR
over eastern IL to VFR in parts of central IL. Trends based on
guidance are for the lower ceilings to expand west overnight, with
IFR ceilings affecting KCMI-KDEC-KBMI. KPIA-KSPI could drop to IFR
at times but primarily expecting MVFR there. A slow rise in
ceilings is forecast after sunrise, turning VFR area wide late
morning through early afternoon.

25

&&

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

$$