Williamsburg, Missouri Weather Forecast Discussion

597
FXUS63 KLSX 262245
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
545 PM CDT Fri Sep 26 2025
.KEY MESSAGES...
- Warm and slightly above average temperatures are expected for
  the next week, with very little opportunity for more rain.
&&
.SHORT TERM...  (Through Late Saturday Night)
Issued at 148 PM CDT Fri Sep 26 2025
After a round of much needed rainfall early in the week, warm and
dry weather has settled back into the region, and does not appear to
be going anywhere anytime soon. A large area of high pressure has
spread across much of the Mississippi Valley region today, with very
light winds and dry air aloft. While there remains enough residual
moisture to produce some fairweather cumulus clouds across the
Ozarks, most areas are seeing plenty of sun this afternoon.
Temperatures are on track to top out near or slightly above 80
degrees today, which is a few degrees warmer than yesterday thanks
mostly to another day of insolation.
Overnight, light winds and clear skies will lead to efficient
radiative cooling, and this may result in another round of river
valley fog. While today`s mixing and slightly warmer temperatures
may make this slightly more difficult in a few areas, particularly
north of I-70, overnight lows are likely to be similar, and much of
the residual moisture may just end up settling back near the surface
considering that winds remain very weak and moisture advection
minimal. As such, we will likely see more fog in at least a few low
lying river valleys.
BRC
&&
.LONG TERM...  (Sunday through Next Friday)
Issued at 148 PM CDT Fri Sep 26 2025
Very little has changed in the extended forecast period, as we
remain very likely to see a prolonged period of slightly above
average temperatures and dry conditions for the next week.
Over the weekend and into early next week, the synoptic upper
pattern will feature a slowly building ridge across the central
plains which will eventually slide east and become centered over the
Mississippi river valley by Sunday. While a weak surface trough will
approach the area from the north Saturday, this will be very
temporary and surface high pressure will reassert itself Sunday
onward. As a result, Saturday through Tuesday will feature slow
warming, with temperatures climbing from the low 80s tomorrow to the
mid to upper 80s Sunday through Tuesday. These warmer values are
about 10 degrees above seasonal averages for late September, but not
particularly exceptional.
Meanwhile, this stubborn high pressure will lock a dry airmass in
place through mid-week, and precipitation chances are functionally
zero through at least Tuesday, and possibly longer. Around mid week,
there are some hints that the upper flow pattern will begin to break
down, and there is even a chance that residual tropical moisture
from a disturbance currently in the southern Bahamas may get caught
up in easterly flow and retrograde into the lower Mississippi
Valley. So far this has not resulted in a significant increase in
precipitation chances in the 7 day period, but there is a non-
trivial increase in precipitation chances as we approach the very
end of the forecast period, and even a few members that produce
light rain as early as Wednesday. This remains well in the minority
of solutions, although there is a more robust signal for increasing
cloud cover and slightly lower temperatures Wednesday onward.
While we will continue to monitor the trends regarding the
aforementioned tropical disturbance, the forecast for warm and dry
conditions remains on track for most of the next week.
BRC
&&
.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 542 PM CDT Fri Sep 26 2025
River valley fog is expected again tonight, impacting KJEF, KSUS,
and KCPS where conditions are expected to drop to MVFR and then
LIFR overnight. As occurred last night, terminals could bounce
around categories as the fog moves in. Fog will quickly dissipate
in the first hour or two of daytime mixing.
Otherwise, dry and VFR conditions will prevail under a surface
high and light winds.
Delia
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion