Area Forecast Discussion

928
FXUS63 KLSX 310502
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1102 PM CST Tue Dec 30 2025

.KEY MESSAGES...

- There is no significant chance for precipitation into early
  next week.

- Temperatures are expected to be within a few degrees of normal
  through Saturday, but warming to well above normal Sunday into
  early next week.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 243 PM CST Tue Dec 30 2025

A high amplitude mid-upper level pattern with a longwave trough
over the eastern U.S. and ridge over the west will persist at
least through the end of the week. This will keep the Mid
Mississippi Valley stuck in northwest flow aloft through the short
term. A surface high currently over Texas is expected to drift
east/southeast into the Gulf through Wednesday into Wednesday
night. Westerly flow will prevail across the Mid Mississippi
Valley as this happens which will allow temperatures to continue
to moderate from yesterday and last night`s chill. Lows tonight
will be around 10 degrees warmer in the mid to upper 20s and highs
Wednesday will likewise be up to 10 degrees warmer than today in
the low to mid 40s. Short range guidance shows a weak short wave
moving across the Upper Midwest and Great Lakes in the northwest
flow on Wednesday night. The surface reflection of the wave drags
a cold front into southern Missouri by 12Z Thursday morning.
Thursday morning lows will therefore be a little cooler in the low
to mid 20s, mostly along and north of the I-70. Precip is not
expected with this cold front as the aforementioned high will be
lingering in the Gulf which will block moisture return.

Carney

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 243 PM CST Tue Dec 30 2025

The the mid-upper pattern persists through the end of the week,
though it does attenuate somewhat with time.  Temperatures will be a
bit cooler again north of the cold front on Thursday, but will
moderate slowly through the end of the week as the pattern slowly
attenuates.  Deterministic guidance shows another short wave moving
from the Central Plains into the Lower Mississippi Valley Thursday
night into Friday. This produces a Gulf Coast low which tries to
sling some moisture back into southern Missouri, but current
indications are that cooler and drier air from high pressure to the
north will undercut the moisture keeping our area dry.  The GFS and
ECMWF continue to attenuate the pattern Sunday through Tuesday,
although the LREF is showing a considerable amount of uncertainty in
how fast/how much this will occur.  While a warm up does appear
likely to occur, the LREF high temperature IQRs increase from around
4-5 degrees on Saturday, to as much as 10 degrees Sunday through
Tuesday.  Dry weather is very likely to persist with fewer than 10%
of the LREF members showing any precipitation.

Carney

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1051 PM CST Tue Dec 30 2025

VFR flight conditions with light westerly winds will continue
overnight ahead of an approaching cold front to the north. Behind
the front, a period of MVFR ceilings along with light
northwesterly winds are expected by early to mid morning, with the
highest confidence in MVFR ceilings occurring at KUIN and the St.
Louis metro terminals. A second cold front drops into the area
from north to south Wednesday night switching surface winds from
westerly to northerly and potentially bringing another round of
MVFR ceilings with it.

Peine/Pfahler

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion