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FXUS63 KLSX 072314
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
614 PM CDT Tue Oct 7 2025

.KEY MESSAGES...

- Cooler conditions will last through Friday. This weekend we will return
  back to widespread highs in the 80s.

- Dry weather is favored for the rest of this week.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 238 PM CDT Tue Oct 7 2025

The cold front responsible for yesterday`s and today`s rain and
thunderstorms has exited the CWA to the south, and cool air is
rushing in behind it. As of 18z, all sites north of I-70 remain
below 70 degrees, with Mexico, MO failing to achieve even 60
degrees. On the flip side of I-70, some sites like Sparta, IL are
reporting highs well into the 80s. Their warmth won`t last long,
though. Tomorrow morning`s low temperatures will let us know that
the cold air has overtaken us completely as those warmer sites dive
into the low 50s - 15+ degrees cooler than this morning. Further
north where the cool air has already established itself, lows will
fall lower than 45 degrees.

Tomorrow will be a relieving day as high temperatures only reach the
widespread low to mid-70s with portions of northeast Missouri
remaining in the upper 60s. It`s tempting to call this cool weather
and it is relatively, but this is actually normal for early October.
The same can`t be said for Wednesday night/Thursday morning. As
high pressure builds into the region, radiational cooling will
tank low temperatures. The majority of the region is forecast to
fall into the low 40s, which is a far cry from what we`ve become
accustomed to. The HREF shows a 50 - 60% chance of lows below 40
degrees north of I-70. Upper 30s will be localized and more likely
1) closer to the surface high and 2) in valleys and sheltered
areas. If KUIN does hit 39 degrees, it will be the first
occurrence since April 10th.

Jaja

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 238 PM CDT Tue Oct 7 2025

Thursday into Friday morning will be the coolest period of the week.
Highs in the low 70s on Thursday with 30s to 40s dewpoints will make
for a refreshing day. Friday morning lows will be crisp yet again
falling into the upper 30s to mid-40s. It`s possible that low-lying
areas around metro St. Louis reach 39 degrees, though the city
itself will be insulated by the urban heat island. If, somehow, KSTL
did reach 39 degrees, it would be the first occurrence since April
8th.

By Friday, the surface high will slide east, opening us up to
southerly flow and low-level warm air advection. Aloft, ridging will
begin to establish itself in the Mid-Mississippi Valley as well.
This pattern will support a warming trend that will bring us back
into the 80s for highs by Saturday and last through the weekend. A
closed low will dive southeastward through the Great Lakes and
threaten to impact our sensible weather on Friday, but ongoing
frontolysis paired with our very dry air will mitigate any chance at
cooling or rain once associated with the system. With that, the
forecast will remain dry through this weekend.

Jaja

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 614 PM CDT Tue Oct 7 2025

The back edge of the MVFR stratus is advancing southward through
metro St Louis at this hour. While this may slow somewhat as the
sun goes down, dry advection should sustain its advance southward.
Based on current timing, it would move through STL around 01Z.
Although clouds clearing at sunset often leads to the potential
for fog due to low dewpoint depressions at the start of the
nocturnal cooling period, dry advection on a northerly wind should
limit this potential overnight leading to a VFR forecast which
continues through the day Wednesday.

Kimble

&&

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

$$

WFO LSX