311
FXUS63 KLSX 031140
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
540 AM CST Wed Dec 3 2025

.KEY MESSAGES...

- Up to a dusting of light snow is possible (40-60%) this
afternoon and evening along I-70 and I-64.

- Well below average temperatures are expected tonight and Thursday
night, with near daily record lows at Quincy.

- Another round of light wintry precipitation is possible (20-40%)
  late in the weekend.


&&

.SHORT TERM...  (Through Late Tonight)
Issued at 335 AM CST Wed Dec 3 2025

Temperatures have dropped into the teens and the 20s early this
morning as most of the area is experiencing strong radiational
cooling over the snowpack.  Parts of the southern and eastern CWA
are seeing low clouds holding on or expanding in recent hours with
some fog over the far southern CWA.  Couldn`t rule out some patchy
freezing fog in the far southern CWA early this morning.  Regional
radars are showing a stripe of returns that the CAMS have moving
into the northern CWA by 12Z. Can`t rule out that there wouldn`t be
flurries or light snow over northeast Missouri with this so will
maintain 20 PoPs.

The better chance for precipitation will be with the mid level
frontogenesis that will develop this afternoon and this evening. The
NAM/GFS is showing the placement of the band closer to the I-70
corridor which is farther south than it was forecast to be this time
yesterday.  The HREF is still supporting 40-60% PoPs along and
behind the front as it move southeast through the CWA this afternoon
and this evening.  Even with the cold start, temperatures over the
central CWA will be able to climb up into the upper 30s allowing for
some rain to mix with the snow before it changes to all snow. The
band of snow will shift off to the south of I-70 this evening and
eventually dissipate as the upper trough moves off to the east.  QPF
totals are still expected to be very light with this narrow band
(<0.05"), so still expect most areas to see just a dusting of snow.
However, the HREF LPMM is still showing spotty 1" amounts indicating
that there could be some locally higher amounts.

Temperatures tonight are forecast to drop into the single digits and
teens tonight.  The low tonight at Quincy will be close to the daily
record low of +2F set back in 2006.

Britt

&&

.LONG TERM...  (Thursday through Tuesday)
Issued at 335 AM CST Wed Dec 3 2025

It will be dry, but colder behind the front on Thursday with highs
in the teens and 20s.   Low temperatures will drop back into the
teens and single digits again on Thursday night with the coldest
readings across northeast Missouri into west central Illinois.  Here
again, the daily record low at Quincy on Thursday night of +6F set
back in 2005 is jeopardy.

There will be several additional chances for precipitation from late
this week into early next as the LREF continues to show low-
amplitude northwesterly flow across the region through the period.
The first chance (20%) will be on Thursday night where southeastern
Missouri will be on the northern periphery of system resulting is a
slight chance (20%) of a wintry mix.  There will then be a break
through early in the weekend before the LREF is showing a deeper
trough in all of its clusters by late in the weekend.  Here again,
the NBM`s current 20% PoPs on Sunday-Sunday night are likely washed
out by timing/strength differences by the individual members this
far out since the LREF 24 hour PoPs are closer to 60%.  We will have
to watch for the potential for wintry mix with this system.  The
LREF is showing additional chances with weak shortwave troughs into
early next week.

Britt

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 517 AM CST Wed Dec 3 2025

Low clouds with ceilings between 1000-2000 feet AGL are expected
to linger at the St. Louis area terminals through 17Z. Then the
focus to snow changes to this afternoon. There will be a chance
for light snow early this afternoon at UIN (30%) with
accumulations not likely. There will also be a narrow band of
light snow that will affect COU/JEF between 20-01Z and the St.
Louis area terminals between 23-05Z with MVFR/possible IFR
ceilings and visibilities. Any accumulations are expected to be
minor at this point (<1/2"). A front will move through the
terminals causing winds to shift out of the northwest around 20Z
at UIN, around 21Z at COU/JEF, and in the St. Louis metro area
around 23Z.

Britt

&&

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

$$

WFO LSX