092
FXUS63 KLSX 252053
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
253 PM CST Tue Nov 25 2025

.KEY MESSAGES...

- Behind a cold front later today, dry weather and below normal
  temperatures are forecast Wednesday through Friday.

- Widespread precipitation is expected Friday night through
  Saturday. There is the potential for the season`s first snowfall
  accumulation by Saturday morning.

&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 249 PM CST Tue Nov 25 2025

A strong surface low will track across southern Minnesota this
evening. A cold front stretches south of the system through the
eastern Plains into northern Texas. Low level moisture flows from
the western Gulf through the Great Lakes with a broad distribution
of dewpoints in the 50s. Overcast skies are favored through late
this afternoon/early evening as the front remains to the northwest.

The cold front enters NW/C Missouri between 22z-23z, progressing
through the metro around 01z and through Illinois counties between
01z-04z. The front may be accompanied by a few sprinkles or very
brief shower with localized, low probabilities (<40%) for anything
measurable. Surface observations show very dry air behind the front
with dewpoints in the teen/20s across the northern Plains. This air
mass will be funneled into the region tonight as high pressure
builds southeast out of Montana. Clouds initially attempt to clear
from west to east. However, RAP shows an area of mid-level RH at 90-
100% rotating southeastward behind the system. This will draw
additional cloud cover over NE Missouri into Illinois counties
through early Wednesday morning with clearing favored over central
and southeast Missouri. Despite cloud cover, strong cold air
advection will cool temperatures tonight with lows in the 30s
Wednesday morning.

In addition to the cold, dry air, a strong low level jet core of 50-
55 kts extends from Minnesota into northern Missouri and west-
central Illinois. This will provide the dynamics for gusty winds
tonight into Wednesday morning. RAP model soundings show 40-45 kts
at the top of the inversion around 850-875mb, fortunately through
diurnal min., which limit the depth of mixing. HREF ensembles
suggest 30-35 mph gusts will be common with probabilities
approaching 60% across southeast Missouri to near 100% around
Quincy, Illinois. Probabilities quickly decrease to 10-15% for gusts
at or above 45 mph near the Iowa/Missouri/Illinois borders. Consider
this a more of a high-performance, sub-advisory scenario for
locations north of I-70, where occasional gusts near 40 mph will be
possible (HREF 50% probs).

Gusts near 30 mph could linger as late at 18z near Quincy, but
outside that, conditions improve through the late afternoon/evening.
Gusts subside from southwest to northeast from mid-morning through
late afternoon. Temperatures only rise in to the 40s Wednesday
with lows falling into the 20s Thursday morning.

Maples

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 249 PM CST Tue Nov 25 2025

(Thursday - Friday)

An elongated surface ridge will extend from southern Canada through
the northern Gulf Thursday morning with high pressure centered over
the northern Plains. The surface high builds southeast and crosses
over the Mid-Mississippi Valley through the day Friday. Mostly sunny
conditions are expected through the day Thursday and into the first
part of Friday. Return flow at the back side of the surface ridge
paves the way from increasing moisture and cloud cover in the later
half of Friday. Conditions remain dry with below normal temperatures
to end the week. The coldest air is favored for Thursday
night/Friday morning as high pressure crosses the region. Clear
skies and light winds will send temperatures into the mid-teens to
low-20s areawide.

(Friday Night - Saturday Night)

The weekend system continues to peak interest with the potential for
the first snow accumulation of the season. Unfortunately, the system
is still well off the west coast and provides little additional
information with few notable trends in the latest guidance.

Global deterministic guidance (GFS/ECM) has represented two
scenarios, both of which result in at least some snow, but vary on
specifics beyond that. The ECM has been the slightly stronger
solution, which would pull warm air northward quicker than what has
been the weaker GFS solution. EOF clusters have indicated a trend
toward the deeper, slightly stronger upper trough with no one model
significantly weighted in any of the clusters. While this may be the
first sign of where trends will take us, I`d like to see this
indication repeated in later runs to build confidence.

One positive is that Friday evening remains dry with time lagged
LREF showing the onset of precipitation just after midnight Friday
night. Considering it being a holiday weekend and a late night
onset, it may limit the impact to Saturday morning. Then, the
question is how long snow hangs on into Saturday. As upper vorticity
crosses the Rockies and enters the Plains, a weaker vort quickly
ejects west-to-east across the southern U.S. GFS model soundings
show mid/upper levels saturate aloft of 850mb, while air becomes
increasingly dry below this level. Dewpoint depressions of 15-20
degrees at 03z Saturday. Temperatures in the low to mid-30s are
marginal for accumulation (especially on roadways) with recent
warmth, but wetbulbing should effectively cool the surface layer by
at least a few degrees Saturday morning. Precipitation is expected
to develop and expand in coverage as the upper trough closes in on
the Mid-Mississippi Valley. This also provides lift through the DGZ
after 06z Friday night, which then persists through roughly 12z-15z
Saturday morning. This suggests the potential exist for a 6-8 hour
period during diurnal mins that would support accumulating snowfall.

Latest LREF ensembles show 50% of the members supporting at least 1
inch of snowfall running parallel with the Mississippi River from
northeast Missouri through St. Louis and location to the north and
east from there. The same area yields 40-50% of the members with 2
inches and 20-30% with greater than 4 inches. The key will be how
quickly warm air advects northward Saturday to gradually chance snow
to rain over much of influence the mid-level warm layer has on
location to the northeast of the St. Louis Metro. Should lift be
able to be utilized in the DGZ and not too much moisture is
committed to saturated the dry layer, we could see a 6-8 hour period
of efficient snowfall (TBD) with some slick conditions Saturday
morning. Warm air seems to eventually win out Saturday afternoon
with a transition to rain over much of the area with cooler air
wrapping back in behind the system as it exits early Sunday. A very
brief window exists for flurries or light snow on the back side,
more specifically north of I-70, but most precipitation will come to
an end as cold, dry air is pulled southward into the area.

(Sunday - Tuesday)

From Sunday into next week, the main story will be the cold, dry air
that settles in with not strong indication for warmth through the
end of the period. High pressure builds in over the center of the
country with a longwave upper trough consuming just about all of the
Lower 48. The pattern shows multiple upper shortwaves embedded
within the pattern, most of which are weak and some of which comes
via clippers. The expanse of the cold air shunts moisture south and
most of what passes over in moisture-starved. While the NBM scatters
slight chance PoPs (15-25%) across the region Sunday through
Tuesday, this is likely a product of low potential with wide spread
in the track of these systems. Clippers are rarely well predicted
even a few days out, let along one week. The main message here is
the winter-like pattern that stretches into next week. Temperatures
will be well below normal with highs in the 30s and lows in the
teens and 20s.


Maples

&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1139 AM CST Tue Nov 25 2025

Low clouds have remained lock in over the region with bases
generally ranging 500-1000 feet early this afternoon. A cold front
will approach from the northwest this evening, arriving at central
MO and KUIN between 22z-00z and metro terminals 01z-03z. Much
drier air will help erode the low level moisture with bases
gradually lifting to MVFR this afternoon/evening and VFR tonight.

Once the front passes, winds will be become quite strong with
west-northwesterly gusts near 25 knots becoming common overnight.
The strongest winds cross the region early Wednesday morning with
gusts exceeding 30 knots at times. The best wind potential will
be around KUIN with a few gusts reaching 35 knots a times. Winds
slowly subside through the day Wednesday with VFR persisting
through the end of the period.

Maples

&&

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

$$

WFO LSX