422
FXUS63 KLSX 091032
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
532 AM CDT Thu Oct 9 2025

.KEY MESSAGES...

-Near normal temperatures will stick around for another day before a
warming trend kicks off Friday and lasts through much of the period.

-Dry conditions will persist across much of the forecast area into
 next week.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 319 AM CDT Thu Oct 9 2025

As of 3 AM most locations across the area have fallen into the mid
to upper 40s from the efficient radiational cooling of a strong
surface high over the Great Lakes. Temperatures will continue to
fall a few degrees in the remaining overnight hours, and some
locations in the hollows and river valleys may kiss the upper 30s.
Despite the cool start, temperatures will be able to warm into the
low 70s again today thanks to plenty of sunshine and mixing to 850
mb where temperatures are still in the upper single digits to around
10C. Through the day the surface high will slide eastward, while a
surface low will begin to push into the Great Lakes region, driven
by a mid-level low.

The trailing cold front will sweep through the upper Mississippi
Valley overnight, combining with a ribbon of moisture and the low-
level jet across western Missouri to spawn showers and an isolated
thunderstorm. Hi-res and global ensembles continue to show the
highest probabilities for precipitation across western Missouri, and
uncertainty remains in how much these ingredients will overlap over
our CWA. The best chance for rain in our area will be across central
and northeast Missouri Friday morning, closest to the LLJ and the
front. If rain does fall it is not expected to be beneficial, hi-res
guidance indicates a 30-40% chance for at least 0.1" of rain.
Overnight lows will once again bottom out up to 10 degrees below
normal, similar to this morning.

The LLJ and moisture convergence along the shallow front will weaken
through the morning, decreasing rain chances across the western
forecast area through the day. The front will not pass through the
forecast area until overnight, and southwesterly flow ahead of the
front will cause temperatures to warm a few degrees from Thursday
resulting in highs in the mid to upper 70s.

Delia

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 319 AM CDT Thu Oct 9 2025

Divorced from elevated frontogenesis, the passage of this weakening
front will be marked largely by a wind shift. Aloft the mid-level
ridge will persist across the central CONUS, setting up what will
become an Omega Block over the weekend. Southwesterly flow
establishes in the low-levels, increasing warm air advection into
the region Saturday and pushing high temperatures up a few more
degrees. This pattern will persist for much of the forecast period.

The one hiccup is a cut off low that is projected to escape the
western Omega Block trough over the West Coast and swing northeast
into central Canada during the first half of the work week. Some
guidance sources indicate this feature producing a surface low that
will push an associated front through the middle CONUS. The movement
of this feature remains uncertain at this point, likewise the
associated rain chances and temperature ramifications. This
uncertainty is highlighted in the interquartile spread in high
temperatures which has increased to 10-15 degrees Tuesday and
beyond, a change from yesterday. While warm and dry weather are more
favored to prevail through the end of the forecast period, we`ll be
keeping an eye on these features that might bring a relief on both
accounts.

Delia

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 529 AM CDT Thu Oct 9 2025

Fog has failed to develop overnight, leaving dry and VFR flight
conditions through the remainder of the period. Given that fog
did not develop overnight, there is more uncertainty in fog
developing tonight, so I have not included it in this TAF
package. Winds will prevail largely from the east, becoming
southeasterly through the day and into the evening. More sheltered
sites are expected to be light and variable through portions, if
not most of the period.

Delia

&&

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

$$

WFO LSX