791
FXUS63 KLSX 071700
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1100 AM CST Fri Nov 7 2025

.KEY MESSAGES...

- After another warm day temperatures will start to cool Saturday
  before dropping dramatically Sunday and Monday.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 312 AM CST Fri Nov 7 2025

Showers and a thunderstorm or two have exited the area ahead of a
cold front pushing into the region this morning. Morning mid-level
water vapor imagery shows a large trough stretching from the Rockies
to the East Coast, with shortwave pushing through the area this
morning. The shortwave will help push the cold front across the CWA
this morning, clearing out the overnight cloud over as dry air
surges into the region in its wake. The mild post frontal air will
have no impact on temperatures today. In fact, the warm start thanks
to overnight southwesterly flow and cloud cover combined with
another day of full sunshine will result in temperatures up to 5
degrees warmer today than yesterday.

By Saturday the mid-level trough will be centered over the Hudson
Bay, but its influence will continue to extend across the eastern
2/3 of the CONUS. A shortwave within the cyclonic flow will push
into the forecast area Saturday, bringing a surface low east along I-
70 into the mid-Mississippi Valley. Moisture return ahead of this
system will be largely limited, and the best moisture will be north
of the forecast area. Any rain that falls from this system is
expected to be light across the CWA, and probabilities of exceeding
0.10" of rain peak around 35% across the far northern CWA. Delia

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 312 AM CST Fri Nov 7 2025

The low will push east out of the forecast area overnight Saturday
into Sunday and a very strong Arctic airmass will storm into the
region behind. This will pull 850 mb temperatures into the negative
low teens, near the 2.5 climatological percentile for this time of
year. Confidence is high both in the strength of this airmass and
the resulting surface temperatures with only 3 degrees of
interquartile spread for highs Sunday and Monday, peaking in the
upper 30s to low 40s areawide. Overnight lows will plummet into the
upper teens to mid 20s, the coolest night we`ve seen so far this
side of summer. While the low will exit the region before most of
this Arctic airmass has taken hold of the forecast area, the NBM is
keeping a smattering of slight chance PoPs lingering through Sunday.
This is due to uncertainty in the strength of the deformation zone
and low-res grid spacing with some of the global models. While I
cannot rule out a spot of light rain, perhaps mixed with a snowflake
or two, on Sunday from the deformation zone, no accumulation is
expected and most will remain dry.

By Tuesday the strong mid-level trough will lift into Quebec, while
a ridge will stall over the West Coast. Subsequent northwesterly
flow will establish over the central CONUS, while in the low-levels
southwesterly flow will establish, advecting warm and dry air into
the region along a low-level jet. This is a classic fire weather set
up that will need to be watched for increasing fire danger.

The cluster analysis shows the northwest flow hanging on across the
region as we remain stuck between the ridge to the west and the
exiting and weakening trough to the east. This will continue to
leave the region open to shortwaves sliding down from Canada,
resulting in uncertainty surrounding the surface flow. So while
there is a clear warming trend into next work week back to near to
above normal temperatures, the details of how warm remain uncertain.


Delia

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1059 AM CST Fri Nov 7 2025

West/northwest winds around 10 knots are expected through the
afternoon. A few gusts to near 20 knots are expected at KUIN.
Winds will subside this evening. A clear sky tonight will
gradually give way to increasing mid/high level clouds late
tonight into Saturday morning, but VFR conditions should prevail.
Some light rain may move into northeast Missouri late Saturday
morning, but the better rain chances hold off at KUIN until the
afternoon.

Gosselin

&&

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

$$

WFO LSX