Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

725
FXUS63 KLSX 290332
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1032 PM CDT Sat Mar 28 2026

.KEY MESSAGES...

- Elevated fire danger conditions are expected across a broad area
  tomorrow afternoon due to breezy southwest winds and low
  humidity.

- Very warm temperatures are expected once again Monday and
  Tuesday, with highs well into the 80s.

- A cold front late Tuesday or early Wednesday brings our next
  chance of thunderstorms, followed by a cooldown and possibly
  more chances for rain later in the week.


&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 219 PM CDT Sat Mar 28 2026

After a chilly morning that saw widespread freezing temperatures,
another warmup is in store over the next several days as southerly
winds become re-established. We will also see the return of
shower/thunderstorm chances Tuesday onward as we enter a more
unsettled pattern.

In the near-term, the focus continues to be on some lingering fire
weather potential thanks to the presence of an exceptionally dry
airmass. Precipitable water values are currently below 0.2 inches
area-wide with surface dewpoints in the teens and 20s, all thanks to
an expansive area of surface high pressure that moved into the area
yesterday and overnight. Already relative humidity has plunged into
the 20s across the Ozarks central/NE MO, and may drop below 20% by
peak heating. With such low humidity in place you don`t need quite
as much wind to support erratic fire behavior if fine-dead fuels are
dry enough, and even after the recent rain, 10-hour dead fuels are
on pace to reach 7-8% by the middle of the afternoon. That being
considered, sustained winds of 5-10 mph with gusts in the 15-20 mph
range will be enough to be worthy of extra caution with outdoor
burns this afternoon. Otherwise, temperatures are near or slightly
warmer than they were yesterday at this time, and we can expect
highs generally in the 50s.

Between tonight and tomorrow, broad lee-troughing and associated
pressure falls across the central and northern Plains will drive
steadily increasing south-southwest surface winds across the area.
This will kick off another substantial warming trend that will
continue through Tuesday, and temperatures Sunday are expected to
jump roughly 10-15 degrees from today`s values in response,
generally in the upper 60s to low 70s (not to mention putting an end
to the threat of a repeat freeze). In addition to the rapid warming,
moisture advection will also drive a steady increase in dewpoints
beginning tomorrow, but since we are starting so dry and will be
warming quickly at the same time, relative humidity may still bottom
out in the low 30s or even upper 20s over a fairly broad footprint.
When coupled with an increase in surface winds, this will likely
maintain elevated fire weather conditions at least one more day.

BRC

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 219 PM CDT Sat Mar 28 2026

The peak of the warmth arrives Monday and Tuesday, as a broad, but
low-amplitude ridge nudges eastward and steady warm/moist advection
continues on both days. Since there have been few changes since the
previous forecast, there is little else to elaborate on, except to
say that ensemble guidance continues to project very high
temperature anomalies during this period, and likewise forecast
confidence remains high that we will once again climb well into the
80s. Ensemble mean 850 mb temperatures reach 97th-99th percentile
values, with an ECMWF Extreme Forecast Index values of 0.8 - 0.95
(a.k.a...very high confidence) which all support a very warm couple
of days. While some timing uncertainty exists with the approach of a
cold front Tuesday that is resulting in slightly wider temperature
spreads, most areas are still likely to remain south of it (and very
warm) before peak heating ends Tuesday.

However, confidence remains relatively high that a cold front will
push through the area at some point Tuesday through early Wednesday,
with improving but still somewhat variable timing/strength
agreement among ensemble members. This will almost certainty put
an end to our significant warming trend by Wednesday, although
exactly how cold it will be, and how long this cooldown will last,
is less certain due to the aforementioned uncertainty. This is
evident in the increasing temperature spreads Wednesday onward,
and has a lot to do with member-to-member differences in the
depiction of a passing shortwave and the aforementioned cold
front.

This also has significant implications for shower/thunderstorm
chances, which continue to increase albeit with some continued
timing uncertainty. LREF cluster analysis still maintains non-
trivial differences in the timing of the front as it arrives,
perhaps by as much as 6 hours or so, but it should also be noted
that this gap has narrowed, and eventually it does move through our
area. Meanwhile, PWAT values climb to at least the 95th percentile
in each of these clusters regardless of the timing, and likewise,
chances for precipitation at some point Tuesday continue to climb
(80-90+% for any rain, 60-70% for 1/2 inch or more). Part of the
issue with this initial front is that it may be far removed from
its surface low as it arrives, which slowing its progression and
allowing it to weaken as it moves further south. This will impact
how far south it goes before returning northward, and also how
much convergence/lift it will provide for precipitation. We`ll
also continue to watch the potential for thunderstorms, as
ensemble guidance continues to project modest (but sufficient)
instability and wind shear to support convection, and at least a
low-end chance for a few stronger storms.

Wednesday onward, the day-to-day details become much less clear, but
latest trends suggest that an active/wet pattern will likely
continue as another more substantial trough (or possibly two)
follows with additional chances for showers/thunderstorms late in
the week.

BRC

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1026 PM CDT Sat Mar 28 2026

All TAF sites are VFR with light southeast winds. On Sunday, VFR
cumulus will make a return with some wind gusts up to 25 kt.

BAH

&&

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

$$

WFO LSX