599
FXUS63 KLSX 231104
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
604 AM CDT Sun Aug 23 2026

.KEY MESSAGES...

- Temperatures will remain in the 80s across most of the area
  this week with relatively low humidity. While there are
  intermittent low chances for rain, the weather should be dry
  for the majority of the week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 333 AM CDT Sun Aug 23 2026

A ridge of high pressure extending south from Canada into the Mid
Mississippi Valley will control our weather today.  Light northwest
flow at the surface will keep temperatures 3-5 degrees below normal
in the low to mid 80s, as well as allow relatively dry air to
continue to filter into the region.  The ridge will drift east
tonight, and winds will become light and variable, and then turn to
the south-southwest along and east of the Mississippi.  Forecast
soundings suggest there will be intermittent mid and high ceilings
moving into the area from the northwest during the evening. However,
there should be sufficient time with clear to scattered clouds that
radiational cooling will allow temperatures to drop to near the dew
point in the mid 50s to low 60s in most locations. Slightly warmer
temperatures in the mid 60s are likely in central Missouri where the
wind turns back to the south earlier and there will likely be more
clouds.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 333 AM CDT Sun Aug 23 2026

The general long wave pattern remains in place through next week
with a ridge over the Intermountain West and a trough extending
south from Canada through the Great Lakes Region into the Southeast
U.S. The trough attenuates somewhat early in the week allowing the
ridge to build eastward a bit which will warm temperatures from the
low 80s on Monday into the mid and upper 80s Tuesday and Wednesday.
Deterministic guidance shows two weak short waves moving across the
Mississippi Valley Monday and Tuesday.  While these waves are weak
and fast-moving, they do force some weak low level cyclogenesis over
the Plains which turns 805mb flow to the southwest over Missouri.
The southwest flow produces some modest moisture convergence but
relatively dry southeast surface flow from the retreating high over
the Ohio Valley will undercut this moisture convergence.  Models
spit out some light QPF which grazes central and some of eastern
Missouri, but the chance that much measurable rain will reach the
ground looks low due to the dry low levels.  A more substantial
short wave dives through the Midwest Wednesday which pushes a cold
front through Missouri and Illinois Wednesday night.  Guidance is
inconclusive on precipitation chances as the front moves through low
level moisture return looks limited ahead of it.  Regardless, the
short wave briefly re-amplifies the eastern long wave and front
brings slightly cooler air into the Mid Mississippi Valley.
Temperatures fall 2-5 degrees for the end of the week back into the
low to mid 80s.

&&

.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 600 AM CDT Sun Aug 23 2026

Localized fog will reduce the visibility to 1SM or less in river
valleys through 13Z. Otherwise VFR flight conditions are
expected to prevail through the period. Light northwest flow
will become light and variable this evening, and then gradually
turn to the southeast tonight into Monday morning.

&&

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

&&

$$

SHORT TERM...Carney
LONG TERM...Carney
AVIATION...Carney