Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

614
FXUS63 KLSX 081105
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
605 AM CDT Thu Oct 8 2026

.KEY MESSAGES...

- Warm and dry conditions are expected through Saturday, with
  temperatures approaching 90 degrees and near daily records
  tomorrow (Friday).

- Confidence is growing that parts of southeast Missouri and
  southwest Illinois will see some rain late Saturday through
  Sunday due to remnants of Hurricane Isaias, but there remains
  some uncertainty in the track that will impact where this rain
  falls and amounts.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 333 AM CDT Thu Oct 8 2026

For the next few days the status quo continues, as high pressure and
a dry, continental airmass will dominate area weather
conditions. This means we will continue to see dry weather, with
perhaps a few more degrees of warming as we close out the work
week. As we begin our Thursday morning, surface observations
reveal that a very weak cold front has settled into the area,
although calling it "cold" is quite a stretch. Essentially this
amounts to a subtle wind shift, and right along the stalled
boundary these winds have become nearly calm. The combination of
this and continued clear skies as allowed for a another round
of patchy river valley and steam fog, which is resulting in
reduced visibilities in a few of our fog-prone spots (like the
Chesterfield Valley, for one specific example). As has been the
case for the last few mornings, this shallow fog will dissipate
quickly after sunrise as mixing begins. For the remainder of the
day, light winds and nearly full sunlight can be expected, and
temperatures will rise into the low to mid 80s. For reference,
this is roughly 10-12 degrees above the seasonal average, but
just a bit shy of daily records.

For tomorrow though, surface high pressure is expected to slide just
a bit further east, opening the door for renewed south-southwesterly
low level flow and modest warm air advection. This, combined with
very subtle downsloping in the lee of the Ozarks (although the
direction isn`t quite perfect for this), should bump temperatures a
degree or two warmer, and several areas are likely to make a run at
90 degrees. This would be much closer to local daily records, which
range from 89 (UIN/STL) to 91 (COU) on 10/9. Currently the NBM
deterministic forecast highs are very near the center of the model
distribution, and we may even be undershooting the forecast highs by
a degree or two if downsloping becomes a more significant factor.
Either way, it will be unseasonably warm Friday, whether we break
daily records or not.

Meanwhile, humidity is expected to remain rather low (min RH 20-
30%), particularly across the southern half of the area where
temperatures will be warmest, and we will need to keep an eye on the
potential for localized elevated fire weather conditions Friday
afternoon. Currently it appears that forecast wind speeds are a bit
too low to result in widespread issues, but a slight increase in
wind speeds could drive more active fire behavior, which would
likewise be worthy of more prominent messaging.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 333 AM CDT Thu Oct 8 2026

As the weekend approaches, attention turns to the approach of the
remnants of Hurricane Isaias, which is forecast to make
landfall along the Gulf Coast late tomorrow, and graze southeast
Missouri and southwest Illinois as an extratropical cyclone
sometime between late Saturday and early Sunday. Model consensus
regarding the track of this hurricane and its remnant circulation
has improved over the past 24 hours, although at this time range
there is still plenty of uncertainty. At some point as this low
approaches the Bootheel it is likely to turn eastward, and exactly
how quickly this occurs will determine who sees rain and how
much. A fast turn to the east would keep most of the area
relatively dry, while a slower turn that allows the circulation to
drift further north would result in both greater coverage and
rain amounts. Even in the more bullish solutions, rain amounts
would likely be of the "beneficial" variety, as 75th-90th
percentile amounts only just approach 1 inch along our
southeastern border. On the flip-side, 10th-25th percentile
amounts only result in a few hundredths to near 1/10th of an inch,
so there is still a reasonable chance that most of the area
misses out. In any case, increased cloud cover is likely to stunt
our heating in some areas Saturday, although we will likely remain
above average.

Another "sneaky" potential to keep an eye on Saturday is for another
day of limited elevated fire weather conditions. While we expect
humidity to steadily increase, thus may not occur until late
Saturday, and breezy southeast winds may result in pockets of
elevated conditions here and there. There are a lot of things that
would need to overlap in order to realize this threat, but a slower
arrival of the remnant circulation and its associated cloud
cover/humidity would make this threat a bit more realistic. By
sometime late Sunday, whatever rain does manage to make it this
far north should come to an end. By Monday, southwesterly low
level flow is expected to resume in earnest, and the ambient upper
ridge will reassert itself. As such, a quick rebound to near-
record temperatures appears likely, with renewed potential for
elevated fire weather conditions. The coverage of this threat will
of course be influenced by how much rain falls the day prior, but
if the drier solutions pan out, there is a higher ceiling for
more widespread elevated conditions.

From Tuesday onward, day-to-day details become much less
predictable, as the upper flow pattern appears to gradually shift
eastward and weaken. This will make the area more prone to
meaningful cold fronts, and eventually precipitation, but exactly
how quickly this unfolds is the key. A high degree of variance
exists among ensembles, with massive temperature spreads (15-20+
degree interquartile ranges) Tuesday onward due to the presence of
an oscillating surface front. Meanwhile, another lull in
precipitation chances appears likely immediately in the wake of the
passing tropical remnants TUE/WED, but ensemble precipitation
chances steadily increase Thursday onward as more substantial
troughs/cold fronts begin to encroach on the weakening ridge.
Overall, while the potential for more warm extremes seems lower
beyond Monday, it is a bit early to make many bold proclamations
regarding temperature/precipitation specifics until we get a better
handle on the position of that frontal boundary.

&&

.AVIATION /12Z TAFS THROUGH 18Z FRIDAY/...
Issued at 603 AM CDT Thu Oct 8 2026

VFR conditions are expected for a majority of the TAF period. An
hour or two of intermittent LIFR fog may impact SUS and CPS at
the start of the period, but this will dissipate shortly
thereafter. Some patchy fog will again be possible at the same
terminals at the end of the period (in addition to JEF), but
slightly increasing south winds may limit this potential, and it
has been omitted from the TAF for the time being.

Otherwise, clear skies and light, variable winds will prevail at
all other sites.

&&

.CLIMATE...
Issued at 219 PM CDT Wed Oct 7 2026

Record high temperatures are possible between Friday 10/9 and Monday
10/12. Here are current records at each of our 3 official climate
stations:

                    KSTL            KCOU            KUIN
Friday 10/9       89/1938         91/1893         89/1938
Saturday 10/10    92/1963         92/1963         89/1963
Sunday 10/11      94/1963         89/1962         88/1962
Monday 10/12      90/2024         94/1899         88/1975

&&

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

&&

$$

SHORT TERM...19
LONG TERM...19
AVIATION...19
CLIMATE...Gosselin