585
FXUS63 KLSX 211815
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1215 PM CST Fri Nov 21 2025

.KEY MESSAGES...

- Widespread rain is forecast to continue into this evening.
  Additional amounts of 0.25-0.75" are expected.

- Dry and mild weather is expected this weekend.

- Another round of light rain is likely (70-90%) Monday into
  Monday night ahead of a cold front. This front will bring in
  some colder air for the Thanksgiving holiday.


&&

.SHORT TERM...  (Through Late Tonight)
Issued at 306 AM CST Fri Nov 21 2025

Widespread light rain is ongoing over much of the area and
continues to slowly move north/northeast. The rain should
overspread parts of northeast Missouri and west-central Illinois
by late morning. This area of widespread rain is aided by strong
low-level moisture convergence, low/mid level frontogenesis, and
vorticity advection downstream of a midlevel impulse. By early
afternoon, a surface low begins to approach southeast Missouri.
Isolated to widely scattered showers (and perhaps a couple of
thunderstorms) may develop along/south of the surface low track
this afternoon, with the more widespread/steady light rain
shifting further north more toward northeast Missouri/west central
Illinois.

By early this evening, the stronger forcing for ascent shifts off to
the east. Light rain should be ongoing in northeast Missouri/west
central Illinois and gradually shift southeast with time tonight.
However, as mid/upper level forcing continues to weaken, look for
the rain to decrease in coverage and become even lighter in terms
of intensity. Total additional rainfall amounts of 0.25-0.75" are
expected, with the highest amounts focused near the I-70
corridor. This is where the strongest low/mid level frontogenesis
and low-level moisture advection is this morning. There may be
some totals near or just over an inch along this corridor as well.
The 0Z HREF has relatively good (20-40+%) chances of this
occurring, mainly on the Missouri side.

Temperature wise, areas that stay socked in with low clouds and
persistent light rain will not move too much all day. A steady
northeast wind also will prevent much in the way of warming north
of the surface low track. Highs are expected to be near 50 degrees
north of I-70, with readings increasing further to the south. For
parts of southeast Missouri, some mid (and perhaps upper) 60s are
expected. This region should see a break in the rain and may even
briefly get into the warm sector with some potential at least for
some broken sunshine. Cooler weather will move in from the
northwest behind the departing surface low, with lows ranging from
the mid 30s (northeast Missouri/west central Illinois) to mid 40s
(southeast Missouri/southwest Illinois) tonight.


Gosselin

&&

.LONG TERM...  (Saturday through Thursday)
Issued at 306 AM CST Fri Nov 21 2025

(Saturday - Sunday)

There remains high confidence in a period of dry weather with
seasonably mild temperatures for this weekend. The sun will also
make an appearance for the first time in a few days. Highs in the
mid to upper 50s are forecast on Saturday. For Sunday, look for
highs to reach into the lower 60s. Those readings would be almost 10
degrees above normal for the date.


(Sunday Night - Monday Night)

A midlevel shortwave trough is forecast to move out of the central
Plains and into the Upper Midwest early next week. At the surface, a
cold front is expected to sweep eastward across the CWA. There
remains a strong signal for another round of light rain, but this
next round looks to be much shorter in duration. Consequently,
amounts look to be a lot lighter. Probabilities for at least 0.25"
of rain only top out in the 40-60% range on the LREF from north to
south, and drop to 10-30% for at least 0.50".


(Tuesday - Thanksgiving)

Ensemble guidance is in good agreement that there will be a stronger
mid/upper level trough crossing the Upper Midwest midweek. Clusters
of the 500-hPa height pattern however show moderate to high spread
with the strength and timing of this feature. This in turn leads to
lower confidence in temperatures heading into the Thanksgiving
holiday. That being said, there remains a strong signal for at least
slightly below normal temperatures for the holiday. Even the 90th
percentile has highs in the mid 40s to near 50 degrees. Those values
would still be a few degrees below normal. On the other side of the
coin, a stronger mid/upper level trough would bring in more
anomalously cold air into the region. This scenario would likely
yield highs on Thanksgiving closer to the 10th percentile of the
NBM, with readings in the mid 30s to near 40 degrees. The promising
news (for travel anyway) is that precipitation chances look low
leading up to, and including, the Thanksgiving holiday. LREF
probabilities over any 24-hour period generally stay below 25-30%.


Gosselin

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1141 AM CST Fri Nov 21 2025

IFR flight conditions are expected to prevail across the area
through early to mid morning on Saturday. There is an area of
lifting and scattering ceilings that will try to get into central
and southeast Missouri, however it`s unclear how long the improved
conditions will last given that additional shower activity is
developing in central Missouri at this time. Low pressure will
then move across Missouri this afternoon and evening which will
shift the low level flow to the north and fill in any MVFR/VFR
spots in with IFR ceilings and potentially fog. Rain associated
with this storm system will continue across northern Missouri
into central Illinois at least through the evening hours before
tapering off around 06Z. Isolated showers or perhaps some patchy
drizzle will be possible across much of the area for the remainder
of the night. Ceilings should clear/scatter across most of the
area by 18Z Saturday.

Carney

&&

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

$$

WFO LSX