425
FXUS63 KLSX 021129
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
529 AM CST Tue Dec 2 2025

.KEY MESSAGES...

- Seasonably cold temperatures will continue through the weekend, with
  a reinforcing shot of cold air expected late Wednesday into
  Thursday.

- There will be a chance (20-40%) for light snow over northeast
  Missouri and west central Illinois on Wednesday afternoon.


&&

.SHORT TERM...  (Through Late Tonight)
Issued at 326 AM CST Tue Dec 2 2025

The last snow band of snow has moved east of the area early this
morning leaving just low clouds in the low level cyclonic flow over
the area.   These low clouds will clear out of the area as the
surface high centered over western Missouri moves east across the
CWA by this afternoon.  Temperatures will be chilly once again today
with the snowpack, the cold start, and the morning clouds with
high temperatures ranging from the mid 20s over south central
Illinois to the mid 30s over central and southeast Missouri. Lows
tonight will drop back into the teens and lower 20s before clouds
begin to stream in over the northeast half of the CWA ahead of the
next shortwave trough.

Britt

&&

.LONG TERM...  (Wednesday through Monday)
Issued at 326 AM CST Tue Dec 2 2025

There is good agreement between the NAM/GFS that a shortwave trough
will move through the Midwest and Great Lakes Wednesday night
pushing an attendant cold front southeast through the CWA with a
reinforcing shot of cold air.  Both models are showing some light
QPF behind the front on Wednesday afternoon over northeast Missouri
and west central Illinois, but this area will lie under the right
entrance region of the upper jet and modest mid-level
frontogenesis. The 00Z HREF PoPs are higher than the NAM, so went
with a 20-40% chance for light snow tomorrow afternoon in this
region. These values may very well be too low given that the LPMM
is suggesting that there could be up to another 1" of snow
somewhere in this area tomorrow afternoon.

Then the LREF is showing a low amplitude northwesterly flow late
week which pushes the southern stream system south of the area on
Friday. There is a deeper trough that will move through the
Midwest over the weekend with each the determistic models showing
different timing bringing precipitation through the area. The LREF
24 PoPs are higher at STL (50%) than the NBM (20%) which reflects
the timing differences, so we will have to watch for the
possibility for a wintry mix over the weekend. The LREF is also
showing another trough moving through the Midwest by early next
week.

Temperatures are expected to stay below normal into early next week
given the current snowpack and the NBM generally showing highs
staying in the 20s and 30s.  Lows on Wednesday and Thursday nights
over northeast Missouri into west central Illinois will likely drop
into the single digits where there good radiational cooling over
the fresh snow cover.

Britt

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 509 AM CST Tue Dec 2 2025

Low clouds with ceilings between 800-1500 feet are expected to
improve through the morning and clear out at UIN by 15Z and at
COU/JEF by 16Z and at the St. Louis area terminals around 20Z.
West to northwest winds at 7 to 10 knots will turn out of the
south late this afternoon.

Britt

&&

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

$$

WFO LSX