146
FXUS63 KILX 300430
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1130 PM CDT Sun Sep 29 2024

.KEY MESSAGES...

- Aside for patchy fog each of the next two nights, no other
  weather-related impacts are forecast for central Illinois
  through Saturday.

&&

.UPDATE...
Issued at 713 PM CDT Sun Sep 29 2024

Regional radar mosaics show isolated showers continuing from
southwest Illinois into western Ohio. Water vapor imagery shows
drier air building southward with time, so the lingering rain
should diminish from north to south this evening. Have extended
some 20% rain chances over the southeast third of the forecast
area for another 2-3 hours.

A fairly large clear area has emerged across locations northwest
of I-55, but additional clouds continue to stream southwest from
Indiana. Some adjustments have been made to the sky trends for
this evening as a result. Getting past midnight, low stratus is
expected to become more predominant over eastern Illinois, though
skies become partly cloudy once again west of I-55.

Geelhart

&&

.DISCUSSION...
Issued at 157 PM CDT Sun Sep 29 2024

Residual low-level moisture and forcing associated with the
remnants of Helene will result in isolated showers this afternoon
and again Monday afternoon in areas south of a Paris to
Shelbyville line. Any diurnal showers that do develop will be
light and transient, with 48-hr QPF totals only offering a few
hundredths of precip. Perhaps the greater nuisance will be
forecasting clouds and fog the next couple nights.

While the fog probabilities offered by both the hi-res ensemble
(HREF) and blended guidance (NBM) are low for tonight and Monday
night (currently a 10-30% chance for visibility < 3 miles), there
are a select few deterministic, hi-res solutions such as the HRRR
that paint areas of dense fog (< 0.5 mile) throughout southeast
Illinois Monday night. Any coverage of fog tonight will be
confined west of I-55, where some partial clearing occurs, while
any fog that develops Monday night could be confined to areas east
of I-55 where soils remained damp from residual daytime
cloudiness. Of these next two nights, the synoptic set-up for fog
looks more favorable Monday night, and we will continue to
monitor trends in guidance.

The Tuesday - Saturday Night time frame continues to look mostly
dry despite a pair of shortwave troughs and attendant cold fronts
pushing through our region. Simply put, we will lack the moisture
return ahead of these fronts, with low-level flow mostly from the
north along the Gulf coast through next Saturday. Additionally,
strong mid-level ridging to our west throughout the week should
mitigate any recycled Pacific moisture from reaching central
Illinois as well. These trends are well-depicted by both WPC`s
7-day QPF and CPC`s 6-10 day precip outlook, which signal very
little precip.

Otherwise, temperatures are trending a hint above normal through
the next week as temperatures surge into the low 80s on Monday and
Thursday ahead of the cold fronts but then slump into mid-to-low
40s behind the fronts.

MJA

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1130 PM CDT Sun Sep 29 2024

Skies have mostly cleared across the terminals late this evening,
but cloud cover continues to stream southwest out of Indiana.
Upstream obs are showing MVFR ceilings across central Indiana,
and new HREF guidance continues to show this advecting into
Illinois, reaching KCMI toward 09-10Z and KBMI/KDEC toward 12Z.
Highest probabilities (60-70%) of sub-1000 foot ceilings remain
focused in the KBMI-KCMI corridor, for a few hours between 11-15Z.
While conditions improve over most of central Illinois around mid
morning or so, the MVFR conditions at KCMI are likely to continue
into mid afternoon.

Geelhart

&&

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

$$