Belleville, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

310
FXUS63 KLSX 190412
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1012 PM CST Thu Dec 18 2025

.KEY MESSAGES...

- A Wind Advisory remains in effect through midnight tonight as wind
  gusts occasionally reach 45 mph this evening.

- Anomalous warmth is expected through the Christmas holiday.


&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 247 PM CST Thu Dec 18 2025

Regional radar and surface observations show that our first cold
front and associated convection are departing the CWA. The pacific
nature of this first front has conditions quickly clearing and
drying in its wake ahead of a second, more potent cold front. This
second cold front is entering northeastern Missouri as of this
writing, an will quickly march east-southeastward across the CWA
this evening. There is a low chance (less than 20%) for a quick
round of sprinkles with the immediate FROPA.

Radar imagery across Iowa shows an area of post-frontal snow showers
beneath the axis of an upper-level trough. With the axis pivoting
east-southeastward through the evening, this area of snow showers is
expected to clip northeastern Missouri, west-central Illinois, and
south-central Illinois. This solution is supported by several CAMs.
Model soundings show limited moisture, particularly in the near-
surface layer, leading to low confidence in impacts. Supporting this
is strong post-frontal winds that will blow any snow that falls (a
dusting at most) off of smooth, paved surfaces. These winds may at
times reach Wind Advisory criteria (45 mph), particularly for areas
north of I-70. Therefore, our Wind Advisory will continue through
midnight.

As the surface low responsible for these FROPAs moves further into
the Great Lakes tomorrow, winds will continue to weaken as the
pressure gradient slackens. Deep northwesterly flow will advect a
seasonable air mass into the Midwest, with area temperatures topping
out right at to just below climatological normals.

Elmore

&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 247 PM CST Thu Dec 18 2025

Early Saturday, guidance consensus is that a low-amplitude trough
will be moving through the Upper Midwest; its surface low traversing
the US-Canadian border. While this will track well north of the CWA,
the attendant cold front will sweep through the Middle Mississippi
Valley late in the day. Ahead of the front, south-southwesterly flow
will help boost temperatures anomalously into the upper 40s to mid
50s, supported by narrow ensemble spread. Limited moisture return
ahead of the front and a lack of upper-level forcing leads to high
confidence in a dry FROPA, with 95%+ of global ensemble members
showing dry conditions. Given the shallowness of the trough, deeper
northwesterly flow remaining north of the CWA, and the center of the
post-frontal air mass also passing north of the CWA, temperatures
will drop only to around seasonal normals for Sunday.

While specifics in the phasing of the upper-levels becomes
increasingly divergent through next week, the consensus is that an
upper-level ridge will increasingly amplify over the central CONUS,
pushing an anomalously warm air mass into the Midwest. By Wednesday,
low-level temperatures will be at the 99th percentile of model
climatology (mid to upper teens C) for the GEFS, GEPS, and ENS,
climatologically favoring surface temperatures reaching the mid to
upper 60s, with 70s and high temperature records within reach
Wednesday and Thursday. See the climate section below for more
information. A minority of ensemble members show a front sagging
into the region through this portion of the period, with growing
consensus just beyond the period of a FROPA.

Elmore

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1011 PM CST Thu Dec 18 2025

Other than a brief period of MVFR ceilings at KUIN and a few linger
flurries, dry and VFR flight conditions will prevail this TAF
period. Strong northwesterly winds will become lighter through
daybreak Friday with gusts also largely diminishing. Winds will turn
to southerly during the afternoon and evening as a surface high
pressure passes. Marginal LLWS is expected Friday night as a
southwesterly low-level jet develops atop persisting light southerly
winds.

Pfahler

&&

.CLIMATE...
Issued at 201 AM CST Thu Dec 18 2025

Above normal temperatures are forecast around Christmas, with
record temperatures within reach. Records for our three climate
sites and the years that they occurred are listed below.

   KLSX  KCOU  KUIN
12/2473(2021)74(2021)69(2021)
12/2571(1889)74(1889)66(2019)


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Wind Advisory until midnight CST tonight for Audrain MO-Boone MO-
     Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-
     Marion MO-Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike
     MO-Ralls MO-Reynolds MO-Saint Charles MO-Saint Francois MO-
     Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-
     Shelby MO-Warren MO-Washington MO.

IL...Wind Advisory until midnight CST tonight for Adams IL-Bond IL-
     Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey
     IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
     Pike IL-Randolph IL-Saint Clair IL-Washington IL.

&&

$$

WFO LSX