Area Forecast Discussion

083
FXUS63 KLSX 081938
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
138 PM CST Thu Jan 8 2026

.KEY MESSAGES...

- There remains a limited potential for a brief tornado or two
  across mainly areas along and south of I-70 late this afternoon
  through the evening, but confidence is low overall. Sporadic
  damaging wind gusts are also possible.

- Some some light rain may change over to snow briefly late Friday
  night through Saturday morning across northeast/central
  Missouri, confidence remains low that impactful accumulations
  will occur.

- A sharp cooldown is expected this weekend, along with brisk west
  winds.

&&

.SHORT TERM... (Through Late Friday Afternoon)
Issued at 128 PM CST Thu Jan 8 2026

The most pressing item of concern within this forecast period
continues to be the potential for isolated severe
showers/thunderstorms this afternoon through the evening, as there
remains a limited potential for brief tornadoes and/or occasional
damaging wind gusts. The bulk of this discussion will focus on
today`s threat, with a shorter section focusing on the limited
potential for light snow accumulations tomorrow night and Saturday
morning.

As of 1 PM, all eyes are on the approach of a round of widespread
showers and a few sporadic thunderstorms, which is now encroaching
upon central Missouri. This activity is remnant from much more
robust convection that produced severe weather across central
Oklahoma earlier this morning, including a couple of likely
tornadoes. Fortunately, waning instability later in the morning has
caused this activity to gradually weaken, with a significant drop in
lightning activity and only a few stronger line segments moving
through the Springfield, MO area.

However, mesoanalysis and high resolution model guidance continues
to suggest that a strong low level jet will rapidly transport a warm
and moisture-rich airmass northeastward into our area this afternoon
and evening. This trend has resulted in a slight increase in
instability projections in high resolution model guidance over the
past several runs this morning, and while the amounts are still
marginal (250-750 J/kg MLCAPE) and mid-level lapse rates remain
poor thanks to some mid level subsidence, this is just enough
instability to be a concern for severe thunderstorms within this
very strongly sheared environment (55-70 kt effective bulk shear).
Meanwhile, we will also need to keep an eye on the potential for
clearing clouds and a resulting instability boost, although this
seems unlikely to occur ahead of the current shower activity in
our area, and moreso to our west and possibly into Central
Missouri later in the afternoon and early evening. More on that
later.

In any case, while our confidence remains relatively low that we
will get strong enough updrafts that are able to adequately tap into
the ample low level shear and helicity, there remains a concern for
a tornado or two associated with one or more QLCS`s or low-topped
supercells across parts of our area from roughly 3 PM through 9 PM,
and possibly even a couple hours later if the strong warm/moist
advection persists. This also remains most likely across southeast
Missouri and southwest Illinois, but it wouldn`t be a complete shock
to see this as far north as the I-70 corridor and STL metro area.
The primary driver of this is the abundant low-level shear (50-65kt
0-3km / 40-50kt 0-1km shear) and long, curved hodographs, which will
be more than sufficient for tornadoes if the resulting helicity can
be adequately stretched. Isolated damaging wind gusts also remain
possible, along with perhaps some small hail (less than 1/2 inch).
While the forward speed of this activity is likely to slow as it
becomes aligned more parallel to the mean flow, most of the initial
activity will exit the area to the east before midnight.

Just behind this initial activity, we will also need to watch for a
potential secondary development late in the evening, particularly if
stratus clears soon to our northwest and we can get a bit of extra
heating. CAMS have hinted at this to varying degrees, with some
developing robust convection just behind this initial line. However,
most suggest that this later activity would be weaker and within a
more stable, and less strongly sheared environment, so our
confidence is very low that it would pose a significant threat.

Finally, the cold front will slowly move southeast through the
night, and aside from a few straggling showers along the boundary
itself it should put an end to the bulk of our precipitation.
Meanwhile, gusty southerly winds during the day (15-25 mph with
gusts to 35) will veer to the west as the boundary moves through,
but likely will remain elevated through the night before turning to
the northwest and weakening considerably by tomorrow morning. Dry
conditions remain most likely tomorrow, with much cooler
temperatures in all areas aside from our far southeast in the
vicinity of the stalled front.

BRC

&&

.LONG TERM... (Friday night through Next Thursday)
Issued at 128 PM CST Thu Jan 8 2026

Overnight Friday, attention turns to the next approaching system,
which is more accurately described as the merger of two separate
systems - both a southern stream and northern stream shortwave -
into a larger trough. While the bulk of the resulting impacts from
such a dynamic evolution are likely to occur to our northeast across
the Great Lakes area, we do catch the early stages of this merger,
and we still expect a round of light, frontogenetically driven
precipitation to move through our area late Friday night through
Saturday.

While latest model guidance has shifted the precipitation slightly
farther south, it has not done so with temperatures, so our expected
impacts remain relatively unchanged, and generally minor. Surface
temperatures for our area remain a bit on the warm side, and so
while we will likely see a changeover to snow for a brief period in
parts of our area Saturday morning, the chance for impactful
accumulations on roadways remains quite low. 90th percentile amounts
(worst case) in0 ensemble guidance are only up to about 1/2 inch,
which is in line with previous forecasts. It should also be noted
that some of the higher-end forcing parameters (notably 500-700mb
omega) have reduced slightly, reducing our confidence in brief,
rate- driven accumulations, even though there are a few soundings
in deterministic models that maintain a saturated dendritic growth
zone for a brief period.

Otherwise, the primary story over the weekend remains the drop in
temperatures, which remains on track with afternoon highs generally
in the 30s to low 40s. Sunday also remains the coldest day of the
weekend. Breezy west winds will add a bit of bite to those
values also, although much of this will occur Saturday through
Sunday morning before weakening Sunday afternoon.

Temperatures remain likely to warm again briefly Monday and Tuesday,
with another cooling trend expected Wednesday onward. There are
some hints of light precipitation with a passing clipper system
Wednesday, but little can be said about its potential impact at
this stage.

BRC

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1120 AM CST Thu Jan 8 2026

An active TAF period is expected at all terminals, with multiple
potential aviation hazards.

First, multiple rounds of showers will impact all terminals
between the start of the period and the overnight hours. While
some of this has already occurred, a reinforcing round of showers
will arrive at COU/JEF shortly after the start of the period, and
gradually move east before impacting UIN/STL/SUS/CPS from late
afternoon through the evening. A few lightning strikes are
possible with this activity, although observations suggest that
upstream lightning has diminished significantly in the past
couple of hours. Given the latter trend, confidence is too low to
include TS in the TAF at this time. However, visibility and
ceiling reductions are likely, along with gusty winds, which will
be in addition to the already gusty ambient southerlies that will
persist through late evening.

We may also briefly approach LLWS criteria through the day today
thanks to very strong winds above the surface, but considering
that surface winds will also be gusty and there is minimal
directional turning, we have excluded mention from the TAF.

Late evening through the overnight hours, a cold front will move
through the area, which will shift winds to the west and
eventually northwest. This will also push the more significant
showers east of our local terminals (aside from one last brief
round right along the front itself). This will also likely bring
widespread low stratus to all terminals tomorrow morning through
the end of the period. Wind speeds will also weaken considerably
tomorrow morning through the end of the period.

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion