376
FXUS63 KLSX 050905
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
405 AM CDT Fri Sep 5 2025

.KEY MESSAGES...

- Cloudy and mild conditions can be expected today as a cold front
  moves through the area, with intermittent light rain possible.

- Mild and dry conditions will persist through Monday, with a
  steady warm up expected through the work week.

- Very little opportunity for meaningful rain exists for the next
  week.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 318 AM CDT Fri Sep 5 2025

The primary item of interest today and tomorrow continues to be a
slowly progressing cold front, which will usher in both cooler
temperatures and a limited opportunity for some light rain.

As we start the morning, the aforementioned cold front is located
across northwest Missouri and southern Iowa, with a more diffuse
remnant surface front much farther south across Arkansas. Over the
course of the morning, a subtle shortwave will pivot around the base
of a much larger synoptic trough across the upper great lakes and
Ontario, which will both add some mid and upper level frontogenesis
and help to drive the cold front south through the morning. While
forcing will increase through the day today, precipitation will be
battling progressively drier air in the low levels, so much so that
any precipitation that does manage to work it`s way through this
layer is likely to be very light. We will likely see steady cloud
cover through the day and plenty of virga, but with 6-8k ft cloud
bases and very little elevated instability, it will be difficult to
produce accumulating rain aside from a few pockets here and there.

Later in the evening, another shortwave will pivot around the base
of the trough, and we`ll also likely see a resurgence of mid-level
moisture ahead of this feature. As this shortwave moves through, a
reinforcing shot of cooler air will finally drive the surface front
completely through the area this evening overnight, producing an
increase in low-level convergence as it does so. The combination of
these factors should help to push more precipitation through the dry
low levels and to the surface later in the evening, but mainly
across southeast Missouri and southwest Illinois.

Given all of the above, it`s difficult to see a scenario that
results in widespread accumulating precipitation. What`s more likely
is that most areas will see a cloudy day, with perhaps a few brief
periods of light rain that doesn`t amount to much more than a few
hundredths of an inch. This is most likely along and south of I-70.
Meanwhile, temperatures will be highly variable, with highs only
likely to reach the upper 60s to mid 70s along and north of the I-44
corridor, to perhaps near 80 degrees across southeast Missouri and
southwest Illinois.

BRC

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 318 AM CDT Fri Sep 5 2025

Behind today`s cold front, a large surface high will steadily build
into the region and remain in the area through the weekend and into
early next week. This will lead to a rather non-descript period
featuring mild temperatures and minimal chances for precipitation.
From Saturday through Monday, confidence is quite high that we will
see afternoon temperatures topping out in the mid 70s to near 80
degrees, with a slight upward turn as early as Monday. This is
roughly 5 to 10 degrees below seasonal averages for early September,
and these comfortable temperatures will also be accompanied by low
humidity. In other words, it should be a great weekend to head
outside.

Over the course of the work week, mid and long range ensemble
guidance continues to project that an upper level ridge will
steadily build and southerly flow will resume across the central
Plains. Both of these factors will almost certainly lead to a steady
warming trend across our area, in spite of the fact that the the
axis of the upper ridge will likely remain to our west throughout
the forecast period. While confidence is high that a warming trend
is on the way, there remains some uncertainty regarding both how
quickly we will warm up and the upper-end potential, primarily due
to continued variance in the upper flow pattern evolution among
ensemble members. In spite of this, NBM guidance suggests that there
is a greater than 50% chance that we will climb back above normal
(roughly 85 degrees) by Wednesday, increasing to 70+% by the end of
the work week, and maximum temperature forecast spreads have shrunk
to 5 degrees or less throughout this period.

Meanwhile, precipitation chances remain rather low throughout the
extended period. We do see a very slight increase in precipitation-
producing members late Tuesday through the end of the week as more
moisture-rich southerly flow inches eastward, but these solutions
remain firmly in the minority. As such, our extended stretch of
mostly dry weather appears much more likely than not to continue for
the next week.

BRC

&&

.AVIATION...  (For the 12z TAFs through 12z Saturday Morning)
Issued at 400 AM CDT Fri Sep 5 2025

VFR conditions are expected to prevail throughout the 12Z TAF
period, with only a few limited exceptions. Mid level cloud cover
will steadily increase through the day, along with widespread
virga. A few pockets of light rain will likely reach the surface
during the afternoon and evening, but this is not likely to
significantly reduce visibilities or lover ceilings below VFR. Any
such reductions would also likely be very brief were they to
occur. Occasionally gusty northwest winds will be possible during
the day, mostly at UIN, but winds are not likely to be strong
enough to cause noteworthy impacts.

BRC

&&

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

$$

WFO LSX