Area Forecast Discussion
476
FXUS63 KLSX 151728
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1128 AM CST Sat Nov 15 2025
.KEY MESSAGES...
- Well above average temperatures and breezy southwest winds are
expected again today, with a (slightly lower) chance to touch
daily record highs.
- A brief round of showers is expected (50 to 80%) Monday night,
with a few thunderstorms also possible (20 to 30%).
- Confidence is growing that additional rounds of rain will impact
the area between Wednesday and Friday, with a reasonable
potential for more substantial amounts. Still, forecast
confidence in rain amounts, locations, and day to day timing
remains relatively low.
&&
.SHORT TERM... (Through Late Sunday Afternoon)
Issued at 214 AM CST Sat Nov 15 2025
Another very warm afternoon is expected today, with a limited
potential to approach daily record highs once again. A cold front
will put and end to this heading into Sunday, but this boundary is
not likely to bring any rain with it.
Once again, persistent southwesterly low level flow is expected to
produce another round of well above average temperatures today,
although we have a few more variables to contend with compared to
yesterday. Firstly, a steady stream of mid and high level cloud
cover is expected throughout heating ours, which is likely to stunt
heating (if only slightly). Not only this, but a cold front will
impinge upon northern Missouri during the afternoon, adding a mixed
bag of subtle impacts to the temperature forecast. On the one hand,
this front is likely to shave a couple hours off of the prime
heating hours in our northern areas, and limiting the potential to
hit the record of 75 degrees at Quincy. However, a very slight bump
from compressional warming may also occur ahead of the boundary,
primarily along and south of I-44, although confidence is not high
that this will be enough to counteract the effect of the persistent
cloud cover. Still, the highest forecast values are across the
Ozarks and southwest Illinois, which may make another run at 80
degrees. Elsewhere, low to mid 70s are more likely, and on average
temperatures are more likely to be 1 to 3 degrees cooler than they
were yesterday.
The aforementioned cold front will sweep through the area between
late afternoon and evening, picking up speed after sunset. Behind
the front, much drier air will filter into the area, although the
temperature gradient is not expected to be particularly sharp. This
unique combination of rapidly falling moisture with only a minor
temperature drop may open a very narrow window for some elevated
fire weather conditions (RH near 35%, NW winds of 10-20 mph, dry
fine/dead fuels) across northern Illinois and west-central Illinois.
These conditions are on the margins of what is typically
considered to be "elevated" locally, but there is some potential
for very localized impacts for a few hours in the afternoon.
During the day tomorrow, dry surface high pressure will settle into
the area, with very low humidity and more seasonable temperatures in
the mid 50s to mid 60s. Fortunately, light winds are expected and
this should mitigate the fire weather potential.
BRC
&&
.LONG TERM... (Sunday Night through Friday)
Issued at 214 AM CST Sat Nov 15 2025
A much more active pattern is expected to develop throughout the
work week, likely bringing multiple rounds of rainfall between
Monday night and Friday.
While much of Monday is expected to be dry, a weakening shortwave
and associated surface low remain likely to move through the area
Monday evening and overnight, bringing this week`s first round of
rainfall. While we will start to see some surface recovery as winds
back to the southeast during the day Monday, for the most part the
boundary layer continues to appear largely cool and stable, but with
robust warm/moist advection and isentropic ascent developing just
above this layer as the low approaches. Model guidance continues to
suggest that this will spread modest elevated instability (500-1000
J/kg of MU CAPE) into the region Monday evening and overnight, and
the combination of this and the previously mentioned isentropic lift
will likely produce blossoming elevated showers and a few
thunderstorms during this timeframe. The strongest forcing and
highest ensemble precipitation probabilities remain generally along
and east of the Mississippi River, but all areas will have a
reasonable opportunity (50% or greater) to see at least some light
rain. In the aforementioned higher probability areas (mainly in
Illinois), current ensemble projections suggest anywhere from 1/10
to 1/2 of an inch of rain are well within reason (25th to 75th
percentile). Considering the previously mentioned instability and
sufficient wind shear, we`ll also need to keep a loose eye on the
potential for a stronger storm or two mainly across the Ozarks, but
we have seen little indication that we will see enough surface-based
instability for this to become more than an isolated threat.
While dry conditions are likely Tuesday, confidence remains very low
regarding the temperature thanks to the presence of a stalled, sharp
frontal boundary. We do note that ensemble forecast temperature
spreads have narrowed slightly, 25th-75th percentile values remain
around 15 to 20 degrees area-wide, which reflects the uncertainty
in the position of the boundary. The boundary also appears to be
trending toward a more northerly (and likewise warmer) position,
although the spread remains so large that this should be
approached with caution.
Between Wednesday and Friday, an upper level trough remains likely
to slowly emerge from the desert southwest into the southern Plains,
and eventually through the Mississippi Valley by the end of the work
week. There remains significant variability in the timing and
strength of this feature, with the slower/weaker trough solutions
favoring more delayed precipitation and lower amounts compared to
the faster/stronger solutions. However, differences among members
and clusters have narrowed from yesterday, and likewise our
confidence in widespread and potentially significant precipitation
is increasing.
This is especially true roughly along and south of I-44, as the
storm track favors potentially multiple rounds of
precipitation...first due to isentropic ascent in the early portion
of the event WED/THU, followed by more widespread rain as the main
trough and a deepening surface low moves across the area THU/FRI.
While there is still enough variability at this time range that all
areas remain in play for significant rain (or for the main axis to
shift farther south), the NBM probability of 1 inch or more is much
higher in the previously mentioned areas (60-70%) than farther
north, with a robust signal for even higher amounts (40-60% of 2+
inches) as well. Adding confidence to this potential are ensemble
mean PWAT projections exceeding the 90th percentile for an extended
period, and deterministic model depictions of a dynamic, deepening
low pressure system. While much remains to be determined regarding
the day-to-day details, confidence in a wet mid to late week period
continues to increment upwards.
BRC
&&
.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
NWS LSX Office Area Forecast Discussion
