Area Forecast Discussion

276
FXUS63 KLSX 181148
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
548 AM CST Sun Jan 18 2026

.KEY MESSAGES...

- Today will be warmer than Saturday with southwest winds. While
  measurable precipitation is unlikely today, scattered flurries
  continue to be possible, mainly across northeast Missouri and
  west central Illinois.

- Another cold front will move through tonight which will bring
  the area another shot of Arctic air. The combination of
  northwest winds and very cold temperatures will push wind chill
  values to -10 to -15 Monday morning across parts of northeast
  Missouri and west central and south central Illinois. A Cold
  Weather Advisory has therefore been issued for these areas.

- Dry and warmer weather is expected Tuesday through Thursday.


&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 347 AM CST Sun Jan 18 2026

Latest GOES-E water vapor imagery shows a short wave moving
southeast through the Dakotas this morning.  This wave will continue
to the southeast into the Mid Mississippi Valley by 00Z this
evening. Meanwhile, at the surface, high pressure will move from the
southern Plains to the Gulf Coast today.  This will produce a
southwest wind for our area which will help temperatures rise into
the low to mid 30s across Missouri and upper 20s to around 30 in
Illinois this afternoon.  The southwest flow will not produce much
moisture return though with the blocking high stretching out across
the Gulf Coast.  Forecast soundings are showing a deep dry layer
from the surface up to between 850-800mb across the forecast area
today.  All deterministic short range guidance is dry today, and the
HREF and NBM probabilities for measurable precipitation are less than
10% today.  Have therefore removed mention of measurable precip
today, though a few flurries are still possible across northeast
Missouri and west central/south central Illinois where it looks like
the forcing from the short wave will be strongest.

The short wave drags another shot of Arctic air into the Mid
Mississippi Valley tonight.  Short range guidance is in good
agreement with temperatures dipping into the mid single digits to
low teens behind the front on Monday morning.  Northwest flow stays
fairly strong with sustained winds of 15 to 20 mph across parts of
northeast Missouri and west central and south central Illinois.
morning.  These winds combined with the cold temperatures will
produce wind chill values as low as -15.  Have therefore issued a
Cold Weather Advisory for these areas for Monday morning.  Between
persistent northwest flow and the cold start to the morning,
afternoon highs struggle to reach the upper teems to mid 20s.

Carney

&&

.LONG TERM...  (Monday Night through Saturday)
Issued at 347 AM CST Sun Jan 18 2026

Medium range guidance continues to show warmer temperatures for
Tuesday through Friday.  The upper level long wave pattern becomes
less amplified which keeps the coldest air bottled up across the
Northern Plains and Upper Midwest.  The cold surface high which
brings Monday`s cold temperatures moves east into the Tennessee
Valley on Tuesday and then off the East Coast on Wednesday.
Persistent southwest flow on the west side of the high pushes
temperatures back to near normal in the mid to upper 30s on Tuesday
and then slightly above normal in the upper 30s to mid 40s
Wednesday. The deterministic GFS and ECMWF then dig another upper
level short wave into the Ohio Valley Wednesday night into Thursday
morning which drags another cold front through Missouri and
Illinois.  LREF cluster analysis is showing a good deal of variance
with the amplitude of the trough as it moves through. This
translates to a lower confidence temperature forecast for Thursday
as high pressure builds across the region behind the front.  While
Thursday does look cooler than Wednesday, even the 25th percentile
highs stay well above freezing in the mid to upper 30s for most of
the area.  Deterministic guidance is showing another strong cold
front moving into Missouri and Illinois in the Friday/Saturday time
frame.  Both the LREF and NBM are showing a considerable amount of
variation in temperatures with temperature IQRs of 15+ degrees both
days.  While the end of the week does look cooler, potentially with
precip associated with the frontal passage, confidence in the
details remains quite low.

Carney

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 540 AM CST Sun Jan 18 2026

An area of MVFR ceilings with bases between 2500-3000ft over south
central/southwest Illinois will continue moving eastward and out
of the forecast area by 14Z. Otherwise, VFR conditions are
expected to prevail through the period in most locations today.
There is a possibility that ceilings may fall below 3000 ft this
afternoon across northeast Missouri and west central Illinois with
snow flurries, however confidence in this occurring is low.
Southwest winds will become gusty this afternoon, and then turn to
the northwest this evening as a cold front moves through the
region. VFR flight conditions are expected to continue behind the
front in most locations, though there is a chance that ceilings
will fall below 3000 ft again across northeast Missouri and west
central Illinois late this evening.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Cold Weather Advisory from 3 AM to 10 AM CST Monday for Knox MO-
     Lewis MO-Marion MO.

IL...Cold Weather Advisory from 3 AM to 10 AM CST Monday for Adams IL-
     Brown IL-Calhoun IL-Greene IL-Jersey IL-Macoupin IL-
     Montgomery IL-Pike IL.

&&

$$

WFO LSX

NWS LSX Office Area Forecast Discussion