612
FXUS63 KLSX 152025
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
225 PM CST Sat Nov 15 2025

.KEY MESSAGES...

- Much cooler, albeit still seasonably mild temperatures will
  arrive by Sunday.

- Although there is a 50 to 80 percent chance of showers and a few
  thunderstorms Monday evening/night, confidence continues to
  increase in more widespread and substantial rainfall in the
  Wednesday-Friday timeframe.


&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 224 PM CST Sat Nov 15 2025

At the surface, a cold front is actively traversing the CWA,
reaching the I-44 and I-70 corridors this afternoon. A warm start to
the day, mostly clear skies, and delayed post-frontal CAA has
contributed to another day of well-above average high temperatures
in the 70s to near 80 F (just shy of the daily record at KSTL).
Behind the front, decreasing dewpoints and slow-to-cool temperatures
are anticipated to sporadically reduce RH to near 35 percent in
northeastern MO/west-central IL late this afternoon. With sustained
winds of 10 to 15 mph, brief (1 or 2 hours) elevated fire weather
conditions are expected at most before temperatures cool more
quickly around sunset.

Low-level northwesterly to northerly flow and CAA behind the front
will usher a much cooler, albeit still seasonably mild airmass into
the Mid-Mississippi River Valley by Sunday. The airmass will also be
quite dry (PW approaching 10th climo percentile) with dewpoints
falling into the 20s and teens F yielding remarkably low afternoon
RH of 15 to 25 percent. Fortunately, an arriving surface anticyclone
and slackening winds will preclude conventional elevated fire danger
conditions from behind met in addition to the cool temperatures.

Pfahler

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 224 PM CST Sat Nov 15 2025

On Monday, an upper-level shortwave trough is progged to track
across the Central Plains and Upper Midwest will weakening as it
encounters unfavorable, confluent northwesterly flow. An attendant,
weak surface cyclone and a wing of strong low to mid-level WAA ahead
of the warm front will be catalysts for showers developing during
the afternoon/evening across MO, with greatest coverage anticipated
along/east of the Mississippi River Monday night when deeper
moisture arrives. Model guidance also general aligns with 250 to
1000 J/kg of elevated instability being present and supporting
thunderstorms, but any thunderstorms will be elevated and, perhaps,
capable of some small hail. Although probabilities of measurable
rainfall Monday afternoon into Tuesday morning are high (60 to 80
percent) in ensemble model guidance across that area, rainfall will
be transient with probabilities of over 0.25" at 20 percent or less.
With the CWA north of the warm from on Monday, high temperatures
will remain similar to Sunday.

Model guidance has come into much better agreement on the track of
the weak surface cyclone across the CWA on Tuesday, somewhere near
or just north of the I-70 corridor. As a result, NBM interquartile
ranges have narrowed below 10 F, closing in on high temperatures in
the upper 60s and 70s F along/south of I-70 in the warm sector and
low to mid-60s F to the north. Mostly dry conditions are expected on
Tuesday with large-scale forcing weakening and a capping inversion
limiting the potential for any initiation of showers directly with
the cyclone and its surface fronts.

A more substantial round of rain event is forecast across the Mid-
Mississippi River Valley sometime between Wednesday and Friday as
model guidance have depictions of an upper-level trough ejecting
northeastward from the Desert Southwest toward the region. These
depictions still vary with regards to timing and the
amplitude/structure of the trough, which will impact the
timing/duration of rainfall more specifically across the CWA along
with amounts. Initially on Wednesday into Thursday, precipitation
will be largely driven by the interaction of strengthening southerly
WAA/isentropic ascent with a lingering front from Tuesday`s cyclone.
Highest rolling 6-hour probabilities of rain in ensemble model
guidance remain largely across northern AR and southern MO, but
additional precipitation associated more directly with the trough
and its maturing surface cyclone Thursday into Friday is
corresponded with much higher probabilities extending northward into
the CWA. In terms of total rainfall, NBM probabilities of over 1"
are 60 to 80 percent along and south of the I-70 corridor with
probabilities of over 2" at 40 to 60 percent supported by an
anomalous PW projected to exceed the 90th climatological percentile
and the potential for a longer duration event. The threat of heavy
rainfall will need to at least be monitored across the broader
region, but the range of possible scenarios captured by latest
deterministic and ensemble model guidance suggest this potential is
greater to the south of the CWA within higher probabilities of
instability and greater consensus on the initially stationary front
being present.

Pfahler

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1127 AM CST Sat Nov 15 2025

With prefrontal SCT to BKN MVFR cumulus quickly lifting through the
beginning of the TAF period, VFR flight conditions are most likely
to prevail going forward. A dry cold front will continue to pass
through the region this afternoon, veering westerly/southwesterly
winds to northwesterly. Winds will slacken this evening with gusts
largely diminishing and winds gradually veering further to northerly
by Sunday morning.

Pfahler

&&

.CLIMATE...
Issued at 429 AM CST Fri Nov 14 2025

Daily record high temperatures will be within range today (11/15),
although the chance of reaching or exceeding these values is
slightly lower than yesterday.

St. Louis (STL): 81 degrees (1971)
Columbia (COU): 78 degrees (1950)
Quincy (UIN): 75 degrees (1950)

BRC


&&

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

$$

WFO LSX