846
FXUS63 KLSX 140901
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
301 AM CST Fri Nov 14 2025

.KEY MESSAGES...

- Unseasonable warmth is expected today and tomorrow, with the
  potential to reach near daily record highs.

- A brief round of rain is likely Monday (50-80%). Confidence is
  also growing that an active pattern will bring more
  opportunities for rain Wednesday through Friday.

&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 251 AM CST Fri Nov 14 2025

Unseasonably warm conditions remain the primary weather story both
today and tomorrow, thanks to persistent southwesterly winds and a
ridge of high pressure aloft. In fact, daily record high
temperatures will be possible each day, with tomorrow slightly
favored for this.

As we approach sunrise, some patches of low/mid level stratus is
evident on satellite imagery, but this is expected to diminish
during the day. Weak southerly flow is in place thanks to a surface
low pressure system to our north, but so far low level moisture has
been slow to return. As the day progresses, the surface pressure
gradient will increase and wind speeds will increase in kind,
beginning a period of steady warm/moist advection. While surface
dewpoints will slowly increase, it likely will not be enough to
produce noteworthy cloud cover aside from a smattering of
fairweather cumulus, and the combination of warm air advection and
insolation will produce temperatures well into the 70s area-wide.

While surface winds are expected to weaken slightly overnight
tomorrow in response to the loss of afternoon heating, they will
quickly resume in the morning and continue to increase during the
afternoon. Meanwhile, a cold front will advance toward the area
throughout the day, and potentially reach northern Missouri as early
as noon. This will help to increase the pressure gradient ahead of
the boundary, and as a result, surface winds are likely to be a bit
breezier Saturday compared to Sunday (with gust speeds as high as 25
mph possible). This should help to increase the low level warm air
advection, but on the other hand, increasing mid and high level
clouds may counteract this warming slightly, and decreases forecast
confidence in the temperature forecast a bit. Not only this, but the
advancing cold front also adds a bit of uncertainty, as some areas
across northern Missouri and western Illinois may see slightly
cooler temperatures than Friday, while areas ahead of the boundary
may benefit from some compressional warming.

In any case, confidence is very high that both days will see well
above normal temperatures. Confidence in the final values is highest
Friday, and slightly lower Saturday. However, the potential ceiling
may also be slightly higher in some areas on the warm side of the
frontal boundary on Saturday.

Finally, in spite of the gradual moisture advection ahead of the
front, it does not appear likely that it will be enough to produce
precipitation. It will, however, likely be enough to keep humidity
levels high enough to preclude significant fire weather concerns,
although we may need to keep an eye on parts of southwest Illinois
where currently NBM humidity forecasts dip close to 40%.
Southwesterly flow does tend to result in lower than predicted
humidity levels, and such an outcome may get us within range of
"elevated" conditions.

BRC

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 251 AM CST Fri Nov 14 2025

While quiet conditions are expected Sunday, a more active pattern is
set to return to the region beginning late Monday, with multiple
opportunities for precipitation through the end of the work week.

On Sunday, the previously mentioned cold front will usher in surface
high pressure, keeping things dry and seasonably cool. While an
amplified longwave ridge will develop across the central CONUS,
deterministic guidance continues to suggest that a shortwave will
fight its way through this ridge and into the middle Mississippi
River valley late Monday, bringing with it a brief round of rain.
While the shortwave itself is somewhat washed out in ensemble
guidance considering its relatively small scale and some
lingering timing variability, precipitation is well represented
among members (40 to 70% chance of .10 inches or more). While
this likely will not be a washout, confidence is increasing that
most areas have a chance to see at least some light rain during
this period, with highest chances east of the Mississippi River.

Meanwhile, some non-trivial elevated instability is also noted in
LREF and NBM ensemble guidance, with a greater than 50% chance of
MUCAPE above 500 J/kg Monday evening across much of the area. These
probabilities fall off significantly for surface-based instability
thanks to Sunday`s cold front, but it does leave open the
possibility of a few rumbles of thunder.

Forecast confidence decreases significantly beyond Monday night,
both in terms of precipitation and temperatures. While confidence is
increasing that a southwesterly jet stream pattern will develop
across the area over the latter half of the week, considerable
variability in the day-to-day details exists among members. For
starters, there is massive spread (20+ degrees) in the
temperature forecast Tuesday onward, likely owing to the uncertain
position of the surface front following Monday night`s shortwave,
followed by the potential for multiple rounds of precipitation
from mid to late week.

Regarding the latter, confidence continues to grow that
southwesterly flow aloft will develop Wednesday onward, punctuated
by the arrival of a more significant upper trough sometime late in
the week. This is increasingly likely to provide multiple
opportunities for rain over the latter half of the week. While this
potential is increasing as a general concept, very little agreement
exists regarding the day-to-day timing of precipitation and amounts,
other than to say that probabilities are highest as the
aforementioned trough moves across the area late in the period. Even
still, while temperature forecasts remain very uncertain, currently
there is a negligible signal for wintry precipitation over the next
week, and we would likely have to realize the lowest outlier
temperature forecasts for this to be realized. We may, however, need
to keep an eye on the potential for thunderstorms late in the week,
although again confidence is very low in this potential at this
time.

BRC

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1000 PM CST Thu Nov 13 2025

Dry and VFR flight conditions will continue through the TAF period
although there is potential for some low-VFR clouds at times Friday.
A modest southwesterly low-level jet will extend over the area
through Friday morning, but any LLWS is expected to be too marginal
for impacts. Light winds will persist.

Pfahler

&&

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

$$

WFO LSX