Belleville, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

514
FXUS63 KLSX 232050
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
250 PM CST Tue Dec 23 2025

.KEY MESSAGES...

- Unseasonably warm temperatures will continue through Saturday. A
  relatively high degree of uncertainty remains exactly how warm
  each day will get.

- A strong cold front will move through the region Saturday night
  into Sunday morning. The Arctic airmass behind the front will
  drop temperatures 40+ degrees by Monday.

&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 248 PM CST Tue Dec 23 2025

A weak east-west oriented front is draped along the I-70 corridor
this afternoon. Short-range guidance shows this front remaining
nearly stationary tonight, and then drifting north into northern
Missouri and central Illinois on Wednesday. Warm moist air
interacting with cooler air in the frontal zone will continue to
produce widespread cloudiness generally along and south of I-70
tonight. Short range guidance suggests that low level warm/moist
advection will increase tonight ahead of a weak 850mb wave. The
RAP and most CAMs show spotty light QPF/weak simulated
reflectivity developing over southern Missouri during the late
evening or early overnight period due to this warm advection. The
precip then moves northeast through the remainder of the night
into Wednesday. Have therefore expanded the patchy drizzle in the
forecast to cover much of the area. Wednesday`s temperatures are
tricky with the clouds and drizzle potentially limiting diurnal
rises, but mid 60s to low 70s should be attainable south of the
front during the afternoon, particularly if there are breaks in
the clouds. Have less confidence in temperatures across northeast
Missouri into west central Illinois which will be closer to the
front and have the chance for patchy drizzle lingering into the
afternoon.

Carney

&&

.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 248 PM CST Tue Dec 23 2025

Models show the the 850mb flow turning more to the west and parallel
to the front on Wednesday night.  At the same time, a strong surface
high drifts across southern Canada and the Upper Midwest which
strengthens north/northeast flow across Iowa and northern Illinois.
This pushes the front back to near the I-70 corridor on Christmas
Day.  Both the NBM and LREF are showing up to 10 degrees difference
between the 25th and 75th percentile for highs in the vicinity of
the front on Christmas Day indicating a high degree of uncertainty.
However, with the front that far south, it`s not looking very likely
that high temperature records will be in danger on Christmas Day.

Most guidance shows a weak surface wave developing along the front
Thursday night which pulls the front back to the north to near the
Missouri/Iowa border before 12Z FRiday morning.  The wave pushes the
front down into southern Missouri by Friday afternoon, but cold
advection north of the front is very weak to non-existant.  The
deterministic NBM guidance shows temperatures ranging from the mid
70s in southeast Missouri to the mid 60s in west central Illinois.
This would be near record territory for St. Louis, Columbia, and
Quincy. However, the high temperature IQRs range from 7 to 10
degrees, and the deterministic NBM highs are at or near the 75th
percentile.  This leads to a lower confidence temperature forecast
for Friday.  Saturday is very similar, with another wave developing
over Kansas which brings warm air back northward just ahead of a
very strong cold front.  Again the deterministic NBM highs are close
to the 75th percentile and would tie or break records at Columbia
and St. Louis.  However the IQRs are around 8 degrees so it remains
a low confidence temperature forecast.

A high amplitude mid level short wave digs into the Midwest Saturday
night and continues east into the Great Lakes Sunday/Sunday night.
This will bring our recent streak of unseasonably warm weather to an
abrupt end as an Arctic front crashes through the Mid Mississippi
Valley late Saturday night into early Sunday morning.  Temperatures
may rise slightly in the morning after sunrise, but will likely fall
through the afternoon when the real cold advection ratchets up.
There may be some frontogenetically forced precip behind the front
on Sunday afternoon across parts of southeast Missouri into southern
Illinois, but most models suggest that anything that falls in our
area will be light rain, possibly and briefly mixed with a little
snow right before ending.  The Arctic airmass behind the front will
push temperatures back below normal for Monday and Tuesday with lows
in the teens and Monday`s highs will struggle into the mid and upper
20s in most locations.  Tuesday looks a little warmer as the surface
high slides into the lower Mississippi Valley with highs warming
into the 30s.

Carney

&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1145 AM CST Tue Dec 23 2025
A front is nearly stationary along the I-70 corridor this
afternoon. Current thinking is that this front will remain nearly
stationary until Wednesday morning when it will begin drifting
northward. While flight conditions have largely improved to MVFR
and VFR, IFR ceilings will linger across parts of central and
southeast Missouri and south central Illinois this afternoon.
Stratus is expected to redevelop and lower to IFR along and south
of the front tonight. Additionally, patchy drizzle and fog
overnight and Wednesday morning will likely lower the visibility
to 1SM or less at times.

&&

.CLIMATE...
Issued at 220 PM CST Mon Dec 22 2025

Well above normal temperatures are expected for much of Christmas
week. Record high temperatures are within reach on several days.
Daily record highs for each site are listed below.

 St Louis    Columbia    Quincy
12/2473(2021)74(2021)69(2021)
12/2571(1889)74(1889)66(2019)
12/26   70(1942)    69(1942)    63(1942)
12/27   72(1971)    71(1946)    70(1946)

The all time December record highs are listed below.

St Louis - 76 most recently on Dec 3, 2021
Columbia - 76 most recently on Dec 15, 2021
Quincy - 75 on Dec 15, 2021


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX