Coffeen, Illinois Weather Forecast Discussion

606
FXUS63 KLSX 301135
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
635 AM CDT Tue Sep 30 2025
.KEY MESSAGES...
- Warm and dry conditions persist through Monday.
&&
.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 211 AM CDT Tue Sep 30 2025
There`s nothing new under the sun today with mid/upper level ridging
aloft and surface riding extending from the eastern Canadian
Provinces, through the Great Lakes and into the mid-Mississippi
Valley. Mainly clear skies are being maintained with calm to light
and variable surface winds again this morning. Unlike the last few
mornings, river steam/valley fog isn`t expected to be as prevalent
with a little more wiggle room between morning lows (upper 50s/low-
60s) and crossover temps (mid-50s). Factoring in micro-climate
behavior may produced a brief, localized fog potential in the
notably cooler, outlying valleys with limited impact. There will be
little change in sensible conditions today with highs reaching the
mid to upper 80s. Tonight`s low will not be far off from this
morning`s (mid-50s to near 60).
Between Tuesday night and Wednesday, mid/upper ridging very slowly
inches east of its current position as the strong surface ridge over
Canada shifts southeast of the Hudson Bay. Scattered to occasionally
broken high clouds arrive from the west as northeasterly surface
flow pulls slightly drier air into west-central Illinois and
northeast Missouri. Temperatures could be a few degrees cooler over
northern sections of the CWA, where clouds may be a bit thicker.
Otherwise, it`s a similar story elsewhere with mid/upper 80s.
Maples
&&
.LONG TERM...  (Wednesday Night through Monday)
Issued at 211 AM CDT Tue Sep 30 2025
It`s a persistent forecast as we continue through the later half of
the work week into the weekend. Upper level ridging shifts into the
Ohio Valley and gives way to an upper trough to the west. In the
meantime, the Canadian surface ridge works its way down the eastern
seaboard into the mid-Atlantic with its influence extending westward
into the mid-Mississippi Valley. The surface ridge, in tandem with a
broad mid-level ridge overhead, will keep the area warm and dry at
least through the weekend and likely into Monday next week. The lack
of spread (3-5 degrees) in the NBM interquartile data stretches all
the way through Monday, resulting in higher than normal confidence
through the next 5-6 days.
The pattern may show some hint of change by next Tuesday. This is
when the 3-5 degree spread mentioned above more than doubles. The
ridge shifts further east with a longwave trough digging into the
west. There will be two things to watch 1) A cold front at the
leading edge of the trough that slows up in speed over the central
U.S. 2) Convective behavior over the northern Gulf. The dramatic
increase in ensemble spread stems from a couple items. One is the
timing of the front to the north or whether it even entirely makes
it through the area. Second is the eventual northward transport of
moisture and just maybe increasing rain chances heading into
midweek. However, at that length in time and multiple factors coming
into play, confidence drops significantly. It does favor a cooler
pattern with the absence of the ridge and increasing cloud cover.
How cool it will get is still in question.
Maples
&&
.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 633 AM CDT Tue Sep 30 2025
Localized brief visibility reductions have been more prevalent
near this morning around the Mississippi, Missouri and Illinois
River confluence with little indication of impacts elsewhere.
Light and variable winds will turn out of the northeast late this
morning into the afternoon but is expected to remain below 10
knots. VFR conditions are expected to persist through the end of
the period.
Maples
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion