Area Forecast Discussion

496
FXUS63 KLSX 091736
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1136 AM CST Fri Jan 9 2026

.KEY MESSAGES...

- Cooler weather returns for the next several days, though still
  mostly above normal for this time of year.

- A period of light rain or snow is expected tonight into Saturday
  morning, otherwise there are no significant precipitation
  chances in the forecast.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 229 AM CST Fri Jan 9 2026

As of 2AM this morning, low pressure was pushing northeast through
southern Wisconsin with a cold front extending SSW from the low
through about the St Louis area down into northwest Arkansas. This
front is shoving aside the recent warm and humid air mass, replacing
it with a cooler and drier air mass, though still above normal in
both respects for this time of year. Most locations will have seen
their daily high temperature occur early this morning shortly after
midnight, with a drop into the 40s expected by daybreak. Cloudy
skies this morning will eventually give way to some sun by this
afternoon as cold advection slackens. The temperature likely holds
steady through most of the day, in the 40s, though a modest rebound
into the low 50s is possible especially if the clouds clear sooner.

Although the wave that brought us last night`s front has moved off
to the northeast, it`s just the first of a two part system. The
second portion of this wave is still hanging back over the Four
Corners region this morning, bringing snow to the Colorado Plateau
before tracking this snow out into the High Plains today. This wave
moves off to the northeast and through our region tonight bringing
our next best chance of precipitation. As the wave moves east,
though, it loses access to a lot of the moisture it was working
with, as the mid level wave becomes separated from the surface wave
well to the south. So while we still see some mid and upper level
lift move through, it will lose intensity as it moves out of the
Plains and into the Mississippi Valley tonight, reinvigorating a bit
on Saturday as it gets wound into a broader upper low over the Great
Lakes. As it moves across our region it will still be just cold
enough aloft for snow, but surface temperatures are still mild and
mostly above freezing. So most locations are likely to see some
light rain, and although some snow may mix in especially in the
northern CWA, it is not expected to lead to any accumulations.

Kimble

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 229 AM CST Fri Jan 9 2026

As an upper low gets wound up over the Great Lakes on Saturday it
latches on to another cooler air mass which slides southward behind
it. This brings a shift to northwest winds in our region Saturday
night with another drop in temperature. This time back to near or
below normal for this time of year. We have rather high confidence
in highs only in the 30s on Sunday with NBM interquartile range only
at about 3 degrees indicating guidance is latching on to how cold
this air mass is.

This cold doesn`t last very long, though. The upper low over the
Great Lakes moves east into New England and the surface high driving
this cold air mass moves east out of the Southern Plains on Sunday
into the Tennessee Valley for Monday. This sets up a return
southwest flow on Monday beneath an expanding ridge aloft,
initiating a warm up for our area Monday into Tuesday. Widespread
50s are expected, with NBM probability of 60 degrees rising up to as
high as 30 percent south of the Missouri River on Tuesday.

As we move toward the middle of next week, another trough drops into
the Upper Midwest and Great Lakes Tuesday into Wednesday, this time
latching on to a bit more cold air dredged out of northwest Canada
and northern Alaska where it has been building for much of the
winter. The cold air returns to our area in two waves, the first
behind a cold front Tuesday night into early Wednesday, and the
second behind another digging trough late in the week (Friday or
Saturday). While this general idea holds well among all the
available guidance, the amount and intensity of cold air which gets
pulled our way does vary. Notably the 00Z operational GFS has
trended colder behind the first wave, as has the 00Z ECMWF, though
some timing differences fade this out a bit in the blends. Latest
NBM forecast of temperatures trending colder, back to near seasonal
normals, is in the right direction though perhaps still a bit on the
warm side.

As far as precipitation goes, latest NBM keeps precipitation chances
at 20 percent or less through the extended forecast. Cyclonic flow
around an upper low has a tendency to bring smaller patches of light
precipitation in waves around the parent low, as seen in most of the
deterministic guidance. However, timing and track uncertainties tend
to blend out these chances in the longer range forecast. For
example, among the 00Z low resolution ensemble guidance, 70 to 80
percent of members produce measurable precipitation in the 48 hours
ending Thursday evening, with about half of those falling as snow.
However, timing that into 12-hour chunks for our official forecast
leads to considerably lower chances each forecast period. In short,
we have greater confidence that we`ll see another round of light
precipitation later this week than is indicated in the official
daily forecast alone. We do think this would be light precipitation,
though, as the source region for this trough is the Arctic and it
remains disconnected from a more substantial moisture source.

Kimble

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1128 AM CST Fri Jan 9 2026

Lingering MVFR stratus continues to impact I-70 corridor terminals
at the start of the period, and will do so for another few hours
before scattering later in the afternoon. Some model guidance also
maintains patches of this low cloud cover through the evening as
well, particularly in the vicinity of JEF/COU, but it is more
likely that both terminals will return to VFR categories for at
least a few hours.

Overnight through early tomorrow morning, MVFR to IFR stratus and
a round of light rain are expected to move into most local
terminals. At UIN, some of this rain may also mix with snow, but
confidence is low that this will occur and even lower that snow
will accumulate on runway surfaces. However, this would likely
create visibility restrictions if it occurs. We have included a
PROB30 mention of rain transitioning to snow to account for this
possibility.

Stratus is expected to erode as a cold front ushers in gusty
west-northwest winds late in the period, although scattered low
cumulus may persist. Just beyond the period Saturday
afternoon/evening, some snow flurries and/or sprinkles will be
possible, but impacts are not currently expected from this.

BRC

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion