Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

138
FXUS63 KLSX 040505
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1105 PM CST Tue Mar 3 2026

.KEY MESSAGES...

- Showers and thunderstorms are forecast tonight through Wednesday
  night. A few storms may be strong to severe between 1 and 5 PM
  Wednesday in southeast Missouri and southwest Illinois.

- Additional rounds of showers and thunderstorms are forecast
  Thursday night and Friday night, providing additional rainfall
  and helping to alleviate the ongoing drought.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 222 PM CST Tue Mar 3 2026

Chances of showers and thunderstorms are expected to increase
north of a quasi-stationary front this evening as low-level
moisture convergence strengthens. Small hail will be possible in
the stronger storms, with an elevated supercell or two also
plausible. If any of these occur, a brief instance or two of
marginally severe hail may transpire. The favored region for
showers and thunderstorms will gradually shift southward out of
northeast Missouri/west central Illinois this evening southward
toward the I-70 corridor overnight as the low-level jet veers more
to the west. Similar to late last night into early this morning,
I would expect a gradual weakening trend with respect to ongoing
convection with lesser coverage as the low-level jet weakens.

Another round of widespread showers and thunderstorms is expected to
move in toward parts of central/southeast Missouri around noon ahead
of an approaching midlevel shortwave trough. This activity should
move eastward across much of the area (outside of northeast Missouri
and adjacent west-central Illinois) through the afternoon/early
evening hours. The convective mode looks to be mixed, comprised of
transient supercell structures as well as multicells. Damaging winds
look to be the main threat, followed by an isolated tornado or two
and then marginally severe hail (likely confined to any supercells).
Parts of southeast Missouri and southwest Illinois are the regions
of concern, mainly between 1 and 5 PM. There remains some
uncertainty as to how far north the boundary will be tomorrow, as
well as the amount of instability. The latest HREF shows
probabilities for >500 J/kg of SBCAPE in the 40-60%, but drop to 10-
30% for >1000 J/kg.

Another round of showers and thunderstorms may occur from late
evening into the early overnight hours as the nocturnal low-level
jet intensifies once again. I am not sure how far northwest this
activity will be able to get, as a cold pool may develop from the
antecedent round of convection detailed above. If that happens, it
may be more difficult for this activity to occur across our region.
But if it does, we may need to watch out for some localized
hydrological issues via flash flooding. Precipitable water values
look anomalously high (>1.25"; >98th percentile of climatology) and
there could be some training over areas that received heavier
rainfall in the afternoon/early evening. Given that this looks
highly conditional and soils/streams can take a lot of rain (and
need it), there remains no plans to issue a flash flood watch. There
could be some localized areas in southeast Missouri/southwest
Illinois that may see as much as 2-4" through Wednesday night,
which is supported by the LPMM of the 12Z HREF.


Gosselin

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 222 PM CST Tue Mar 3 2026

(Thursday - Friday Night)

A brief lull is expected most of the day on Thursday with mostly dry
weather favored during the day. A weak warm front is expected to
move north through the area Thursday afternoon/night. Increasing low-
level moisture convergence along with the passage of a midlevel
shortwave trough across the mid-Missouri Valley should yield another
round of showers and thunderstorms Thursday night, this time
centered across central/northeast Missouri.

Friday also looks mostly dry, but this time the bi-state area will
be fully in the warm sector. This should be a warm day for early
March, with highs well into the 70s and maybe near 80 degrees in
spots. While these readings should fall well short of daily records,
they would be about 25+ degrees above normal for the date.

Our attention then turns to an approaching cold front Friday night
as it moves across the Kansas-Missouri border. The current timing of
this front looks to pass through the region from 0600 to 1200 UTC
Saturday. This of course is not the most favorable time to sustain
severe convection. The current expectation is for strong to severe
thunderstorms in western Missouri Friday evening to weaken as they
head eastward given lesser amounts of instability in our region
later on Friday night. Probabilities for >500 J/kg of MUCAPE at 0600
UTC are in the 40-60% range, but drop to 30-50% by 1200 UTC. We will
have to keep an eye on the timing of the front itself over the next
couple of days, but also instability trends as sometimes guidance
dampens instability too fast after dark.


(Saturday - Next Tuesday)

Cooler air will infiltrate the mid-Mississippi early this weekend
behind Friday night`s cold front. The incoming air mass is not
particularly strong however, so we are still favoring seasonably
mild conditions (highs in 60s to near 70 degrees). There is still
some uncertainty with respect to highs however, especially on
Saturday. The spread between the 25th/75th percentiles of the NBM is
generally on the order of 10-15 degrees on Saturday behind the cold
front.

A warming trend should begin by early next week as mean 850-hPa
temperatures on the LREF climb back above +10C. While there is a lot
of spread with respect on the timing/track of a cutoff low departing
the desert southwest, an increasing threat for showers and
potentially some thunderstorms by next Tuesday.


Gosselin

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1059 PM CST Tue Mar 3 2026

IFR flight conditions are expected to prevail generally along and
north of I-70 in Missouri and along and north of I-65 in Illinois
through the period. IFR ceilings may build into the eastern
Ozarks late tonight and early Wednesday morning, but retreat back
to the north during the afternoon. Several rounds of showers with
occasional thunderstorms are also expected through the period. The
first across northeast Missouri and west central Illinois before
09Z, then another along the I-70 corridor from around 07Z through
12Z, a third from late morning into mid-late afternoon, and
finally another developing early Wednesday evening and continuing
through the end of the period.

Carney

&&

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

$$

WFO LSX