Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

702
FXUS63 KLSX 292318
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
618 PM CDT Sun Mar 29 2026

.KEY MESSAGES...

- Near-record warm temperatures are expected tomorrow and
  Tuesday, with temperatures climbing back into the 80s both days.

- Multiple rounds of rain are expected (80-90+%) between Tuesday
  night and the end of the weekend, with a few chances for
  thunderstorms.


&&

.SHORT TERM... (Through Tuesday Afternoon)
Issued at 224 PM CDT Sun Mar 29 2026

The most pressing item to address in the short term period is the
development of critical fire weather conditions across parts of
southwest Illinois and southeast Missouri, prompting a Red Flag
Warning for the rest of the afternoon today. While cloud cover has
kept temperatures, and likewise humidity, in check across a large
portion of Missouri, this has not been the case in southeast
Missouri and southwest Illinois. Meanwhile, moisture advection has
also lagged slightly, and the combination of these factors is
leading to RH values near 25% as early as 12-1 PM in those areas.
Meanwhile, sustained 15-20 mph winds have also been observed,
with gusts to 25, and as such, we expect a few hours of critical
fire weather conditions to occur through the remainder of the
afternoon. Meanwhile, fine-dead fuels (1-10hr) are very dry
throughout the area after a full day of breezy winds and poor
overnight humidity recovery, and this is in tandem with dry fuels
of larger sizes as well (100,1000 hr). Given those factors, we
felt it was worth issuing a short-fused Red Flag Warning through 7
PM for these areas.

Winds are expected to weaken slightly but will remain somewhat
breezy through the night thanks to a relatively tight pressure
gradient. However, increasing dewpoints will lead to much improved
humidity recovery than the night before, which should mitigate the
overnight threat.

Tomorrow and Tuesday, the big story will be another round of very
warm temperatures, as we can expect to climb well into the 80s on
both days. The forecast for these two days (at least until a cold
front arrives later Tuesday) has been rather consistent, featuring
ensemble mean 850 mb temperatures in the 97th-99th percentile of
climatology, and a robust signal for "extreme" temperatures
(relative to the time of year) in the ECMWF Extreme Forecast Index
product. Meanwhile, ensemble spreads remain very narrow during this
period, although we suspect that we will end up near the upper end
of these ranges due to the downslope warming effect of the Ozarks
and perhaps compressional warming along an advancing cold front
Tuesday.

BRC

&&

.LONG TERM...  (Late Tuesday through Next Sunday)
Issued at 224 PM CDT Sun Mar 29 2026

By late Tuesday, a back-door cold front is expected to gradually
sink into the area, far removed from its originating low pressure
system in the Great Lakes and Ontario. Recent trends of a slower,
weaker front that stalls somewhere near or just south of our area
have continued in the most recent ensemble model data, and
cluster analysis appears to be converging on timing later Tuesday
night or even Wednesday morning. Not only this, but another trough
and surface low is likely to start pulling this front back
northward as a warm front by Wednesday, followed by perhaps
another later in the week. This is leading to huge temperature
spreads among ensemble guidance in the mid-late week period, as
day to day temperatures Wednesday onward will depend a lot on the
position of this front. Still, we do still expect that we will
see an overall cooling trend at least briefly, considering that
we are also expecting multiple rounds of rain and we do lose the
previously mentioned significant 850mb temperature anomalies.

Meanwhile, Tuesday night`s cold front will also bring the first of
what is expected to be multiple rounds of rainfall to the area.
While this front will be weakening as it arrives, there will
nonetheless be plenty of moisture available for precipitation, with
PWAT values nearly certain to climb above 1 inch and reasonably
(50%) above the 90th percentile of climatology. Ensemble members
are nearly unanimous in predicting a round of showers along and
behind the front, which would slowly move through the area
sometime late Tuesday through early Wednesday. While there is
still some timing uncertainty, like in previous forecasts, the
chance of precipitation is very high over a 24 hour period
(80-90%+). Meanwhile, models continue to depict some marginal
SBCAPE ahead of the front and some elevated MUCAPE behind it, but
as noted previously the warm sector appears to be largely capped,
with most activity remaining behind the front itself. Meanwhile,
wind shear is also somewhat limited given that there is not much
in the way of upper level forcing. While we can`t completely rule
out a stronger storm or two, the ceiling for severe storms appears
rather low at this time.

Beyond Tuesday night/Wednesday, ensemble guidance maintains a very
active pattern thanks to our position within a southwesterly flow
regime and directly in the path of multiple shortwave troughs. This
is expected to keep the previously mentioned front/baroclinic zone
oscillating back and forth across our area, with concentrated bursts
of upper forcing and associated precipitation as shortwaves move
through the area. At this point it is very difficult to precisely
time each of these waves of showers, but overall, confidence is
increasing that substantial rainfall will occur throughout the
course of the week, and potentially into the weekend as well. While
it`s a bit too early to pinpoint amounts, especially with rain
spread out across the next 7 days, ensemble probabilities of at
least 2 inches of rain in both the NBM and LREF have now climbed
above 50% in many areas over the next week, which appears very
reasonable considering the pattern. We`re also starting to see an
increasing ECMWF EFI signal for heavy rain Wednesday and Thursday,
although this signal is not quite as robust (.6-.7) as the signal
for temperatures (.8-95) Monday and Tuesday.

There are still plenty of failure modes, as each round of rain will
likely depend on how the prior round materializes, which decreases
confidence with each successive round. However, there will be plenty
to monitor over the next week thanks to this active pattern.

BRC

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 614 PM CDT Sun Mar 29 2026

VFR conditions continue overnight tonight and through the day
tomorrow. However, wind flow is getting a bit stronger, especially
aloft overnight. This introduces the potential for low level wind
shear especially in areas where winds drop off and lose their
gusts. If winds stay stronger and gustier at ground level, then
wind shear won`t exist. Winds aloft peak at about 45KT from 230
degrees during the early morning hours. Shortly after sunrise any
wind shear disappears as surface winds pick up and get gusty while
winds aloft taper off.

Kimble

&&

.CLIMATE...
Issued at 238 AM CDT Sun Mar 29 2026

Record Maximum Temperatures at Regional Long-Term Climate Sites

             March 30th   March 31st

St. Louis:   86F (1986)   87F (1981)
Columbia:    84F (1967)   86F (1940)
Quincy:      82F (1943)   81F (2010)

Record High Minimum Temperatures at Regional Long-Term Climate Sites

St. Louis:   67F (1998)   63F (1917)
Columbia:    65F (1967)   59F (1967)
Quincy:      61F (1998)   58F (2010)


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Red Flag Warning until 7 PM CDT this evening for Madison MO-
     Saint Francois MO-Sainte Genevieve MO.

IL...Red Flag Warning until 7 PM CDT this evening for Bond IL-Clinton
     IL-Fayette IL-Madison IL-Marion IL-Monroe IL-Randolph IL-
     Saint Clair IL-Washington IL.

&&

$$

WFO LSX