Area Forecast Discussion

527
FXUS63 KLSX 021103
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
503 AM CST Fri Jan 2 2026

.KEY MESSAGES...

- Near average temperatures through the weekend will warm to
  well- above average next week.

- The chance of rain is less than 15 percent through early next
  week, but a more appreciable opportunity for rain (40 to 50
  percent chance of 0.25") exists late in the week.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 311 AM CST Fri Jan 2 2026

Rich low-level moisture and weak northeasterly flow has allowed
areas of dense fog to develop across portions of south-central and
southeastern MO this morning. If this dense fog persists and
expands, a Dense Fog Advisory may be needed, but visibilities could
fluctuate as radiational cooling is perturbed by thickening upper-
level clouds and stratus that is expanding slowly southward. There
are signals for the widespread stratus to begin scattering this
afternoon across IL as drier air filters in, but additional, thick
upper-level clouds will still limit insolation. Therefore, diurnal
warming of temperatures will be limited with high temperatures
staying in the 30s F. Over 85 percent of HREF membership keep light
rain associated with an upper-level trough traversing the Mid-
Mississippi River Valley south of the CWA including our southeastern
MO counties.

Friday night through Saturday morning, additional upper-level
shortwave troughs will pass but there is little support for any
measurable rainfall in the CWA with a lack of deep moisture and
large-scale ascent. In the wake of these shortwave troughs, clouds
will decrease on Saturday as low-level flow backs to the northwest
and subsidence ensues. Since insolation, therefore, will be greater
on Saturday, high temperatures will be slightly warmer, in the mid-
30s to mid-40s F.

Pfahler

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 311 AM CST Fri Jan 2 2026

Upper-level flow over the Mid-Mississippi River Valley will evolve
from northwesterly to broadly anticyclonic early next week, enabling
a period of low-level southwesterly flow and WAA following warm
frontal passage between Sunday and Monday. As a result, NBM high
temperatures are tightly clustered [interquartile range (IQR) of
5 F or less] on temperatures warming from the upper 30s F and 40s
F on Sunday, to the 50s and 60s F Monday. Temperatures become
increasingly spread in the NBM through mid-week as a series of
upper-level shortwave trough have the potential to force a weak
cold front into the CWA. That being said, 90 percent of ensemble
model membership suggest that these shortwave troughs and the
front will be insufficient for any measurable precipitation.

Global model guidance is in relative agreement that the upper-level
flow pattern across the CONUS will begin to amplify during the
second half of next week including a shortwave trough ejecting
northeastward through the Central Plains and Mid-Mississippi River
Valley around Thursday. Timing and amplitude differences are
apparent, but ensemble model membership containing measurable
rainfall across the CWA has been increasing, 24-hour probabilities
of over 0.25" of rainfall now around 40 to 50 percent. Ensemble
model guidance and analog guidance both indicate that this round of
rainfall could be part of a wetter pattern that continues beyond
current 7-day forecast period. In terms of temperatures, confidence
is high that mild conditions will persist with the NBM 25th
percentile of temperatures remaining above average despite IQRs
nearing 10 F.

Pfahler

&&

.AVIATION...  (For the 12z TAFs through 12z Saturday Morning)
Issued at 500 AM CST Fri Jan 2 2026

Flight conditions are expected to gradually improve today with
visibilities already rising to/above 6SM and IFR to MVFR ceilings
rising and then scattering. How quickly this improvement takes place
is uncertain with a return to VFR flight conditions possible any
time between early afternoon and later this evening. Light
northeasterly will prevail throughout the TAF period.

Pfahler

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion