Area Forecast Discussion

069
FXUS63 KLSX 201112
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
512 AM CST Tue Jan 20 2026

.KEY MESSAGES...

-While temperatures will be close to normal today and Wednesday, bitterly
 cold air will return this weekend.

-There is a slight chance (20%) of a wintry mix late tonight and early
 Wednesday over southeast Missouri, with a better chance (30-
 50%) chance of snow this weekend.


&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 341 AM CST Tue Jan 20 2026

Temperatures early this morning have dropped into the single digits
and teens.  Winds have already switched out of the southwest behind
a surface high centered over the Mid South which will move off to
the east today.  While there will be some clouds early on today, it
should turn out to be at least a partly sunny day across most of the
area.  This combined with south-southwest winds will push highs into
the 30s and lower 40s this afternoon, with the warmest highs in
central Missouri.

Expect tonight to be mainly dry until late before there is an
increase in low level moisture ahead of mid level trough that will
move across the Midwest.  The NAM develops some light QPF with this
system, while the RAP/HRRR/GFS develops QPF just to the southeast of
the CWA.  Have introduced 20 PoPs for a light wintry mix with no
accumulation after 3 am over the far southern CWA.  This slight
chance will linger into Wednesday morning before the system moves
off to the east.

A cold front associated with the mid level trough will move through
the area late tonight and early on Wednesday.  Winds will turn out
of the west behind the front and advection will be weak allowing
highs to warm back up into the 40s on Wednesday afternoon.

Britt

&&

.LONG TERM...  (Wednesday Night through Monday)
Issued at 341 AM CST Tue Jan 20 2026

The global models remain dry late Wednesday through Friday as we
will be in west-northwesterly flow aloft with a strong surface high
dropping southeast out of Canada.  The latest model guidance is
showing that the high will move across the Midwest and Great Lakes
Friday into Sunday which will supply very cold and dry air to the
region. High temperatures are looking to be 15 to 25 degrees below
normal during this timeframe with lows in the single digits
including below zero values in the north.

There remains quite a spread in the southern stream system that
looks to affect the area Saturday night into Sunday night.  The
global models are showing more spread with how far north the QPF
will get with this system, though the latest run has shown a general
northern shift with the precipitation in the CWA.  With this said,
it will be fighting the very dry air being advected in from the
surface high, and the LREF is still showing a wide spread in
snowfall amounts, with most ensemble members pointing toward the low
end of any accumulating snow over the southern part of CWA.

Britt

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 504 AM CST Tue Jan 20 2026

Dry and VFR conditions are expected through the period. Southwest
winds will pick up between 14-18Z between 10-14 knots, and then
increase again with gusts to 20 knots this evening. A
southwesterly low level jet between 45-50 knots will cause LLWS
after 04Z.

Britt

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion