Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

422
FXUS63 KLSX 082354
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
654 PM CDT Fri May 8 2026

.KEY MESSAGES...

- Showers and a few thunderstorms will move through the area this
  afternoon and evening, and weaken overnight. While a few
  stronger thunderstorms may product gusty winds and small hail in
  central/southeast Missouri, these will be very isolated.

- A cold front will bring a few showers Saturday night followed by
  a brief cooldown Sunday and Monday. However, a slow, but long-
  term warming trend is expected to follow Tuesday onward.


&&

.SHORT TERM... (Through Sunday)
Issued at 241 PM CDT Fri May 8 2026

The main focus of this forecast package continues to be in the near
term as we watch for the development of scattered thunderstorms
later this afternoon and evening. While there remains a limited
potential for a stronger core capable of brief strong winds and
small hail, the potential for severe thunderstorms remains low.

Driving this potential is a mid/upper level shortwave currently
approaching the area from the west, along with a slowly moving and
diffuse cold front. Over the course of the morning and early
afternoon, a steady stream of mid and high level cloud cover has
persisted across the mid-Mississippi River Valley, which has slowed
our warming and limited our destabilization locally. While we are
finally beginning to see some indications of slowly increasing CAPE,
including a few weak elevated cores already producing a few strikes
of lightning here and there, the ceiling of instability appears to
be rather limited. In addition to the weak heating, mid-level lapse
rates are generally modest (6-7C/km) aside from some steepness in
the lowest part of that layer. Model forecast and ACARS soundings
also support this, and as a result, only about 500-1000 J/kg of ML
CAPE can be reasonably expected by roughly 3 to 4 pm, spread out
across a long, skinny profile, and this will likely require some
advection of steeper lapse rate air from the southwest in order to
materialize. Meanwhile, the persistent cloud cover is also expected
to limit low level lapse rates, and further limit our severe wind
potential.

However, as the shortwave arrives we do expect an increase in mid
level winds and likewise will see a boost in effective bulk shear,
perhaps to 35-45 kt per most available model guidance. In spite of
the rather marginal thermodynamic profiles detailed above, all of
these parameters still suggest that organized updrafts remain
possible once deep convection can become established. In spite of
the slow heating, recent CAMS continue to suggest that more
substantial and potentially surface-based convective initiation will
begin sometime between 3 and 5 PM along the cold front, extending
from Central Missouri eastward into southwest Illinois. Out of this
activity we may see a few cores capable of producing mainly small
hail and sporadic wind gusts to 40-50 mph, with the highest
probabilities of either occurring in central Missouri where
instability is projected to be highest. Severe hail appears to be
rather unlikely, although we can`t rule out a few 1 inch hailstones
here and there. While we do note just enough low level shear to
support tornadoes, LCLs appear to be prohibitively high, and we do
not expect this to be a significant threat.

This line of showers and a few weak thunderstorms is expected to
progress slowly southeast through the late afternoon and early
evening, and gradually lose strength near and after sunset. The
remnants of this activity are expected to clear the area completely
after midnight, leaving behind some low clouds and little else.

While technically a cold front will move through our area this
afternoon and evening, this front is very weak and does not carry
with it a significant push of colder air. In fact this boundary is
expected to completely diminish, and warm air advection will resume
quickly in its wake. As a result, tomorrow`s temperatures are
actually expected to be noticeably warmer than today, with highs
reaching into the upper 70s to low 80s. However, moisture content
will remain rather limited, and this should lead to a mostly dry
day.

Later in the evening and overnight, another cold front will sink
into the area, and by mid-day is expected to already reach near the
MO/AR state line. Along and behind this front, another round of
showers is expected to move into the area, although this second
round continues to be de-emphasised by model guidance. Considering
that these showers are likely to be post-frontal, with only modest
MUCAPE to work with overnight, we remain skeptical that
thunderstorms will be able to materialize. Instead, expect one or
two rounds of showers between Saturday night and Sunday morning, and
even then many areas are likely to miss out completely.

Temperatures Sunday are also expected to be much lower, as this
second cold front will be driven south by a more expansive area of
cooler air. While not exceptionally cold by any means, afternoon
temperatures Sunday are expected to be about 10 degrees below
seasonal averages, followed by a crisp morning in the low 40s
Monday.

BRC

&&

.LONG TERM... (Monday through Next Friday)
Issued at 241 PM CDT Fri May 8 2026

For most of the work week, very little in the way of hazards can
be expected as we will remain within a persistent pattern of
northwest flow aloft and generally dry airmasses. Aside from a few
marginal opportunities for showers here and there, dry conditions
can be expected, with seasonable temperatures that will warm
toward the end of the week.

After a chilly Monday morning, temperatures are expected to rebound
nicely into the low 70s during the day, and will be followed up by
another slight increase in temperatures Tuesday thanks to the
resumption of breezy southwest winds and warm air advection. This
will take place ahead of another advancing cold front, which is
expected to move through the area sometime between Tuesday night and
Wednesday morning. While we can`t rule out some showers with this
feature, the combination of another nocturnal frontal passage along
with rather meager moisture advection (thanks to the previous front
cutting off the Gulf) will significantly limit our potential for
significant rain and thunderstorms. This will also likely stunt our
warming trend, albeit only briefly.

Late in the work week, ensemble guidance continues to suggest that a
longwave ridge will slide east into the Central Plains and
Mississippi River Valley, and more expansive southerly return flow
will resume as well. This will very likely drive another warming
trend, although current ensemble mean 850 mb temperature anomalies
remain rather subdued through Friday (below the 90th percentile),
although we do note increasing spread. This trend does continue
beyond the workweek and into the weekend/early next week, though,
and there are some early indications that more significant warmth
will be possible in the extended period.

BRC

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 654 PM CDT Fri May 8 2026

A swath of showers with embedded weak thunderstorms, generally along
the I-70 corridor, continues to slide east-southeastward and has
cleared KUIN within the last few hours. Both KCOU/KJEF will have the
best chance to be impacted by a scattered weak thunderstorm within
the next hour or two before the threat ends by 03z. This activity
will continue to push eastward into the St. Louis metro terminals at
the start of the TAF before pushing out later this evening (04-05z).
With the more intense thunderstorms, which are expected to be very
isolated, brief IFR cigs/vis are possible along with small hail and
stronger wind gusts. Overnight, some model guidance is hinting that
a narrow swath of IFR/MVFR ceilings moves across the central MO and
St. Louis metro terminals. Confidence in this is low, but will
continue to be monitored throughout the evening. Light and variable
surface winds persist this evening and overnight with southwesterly
winds increasing in strength after sunrise of Saturday.

Peine

&&

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

$$

WFO LSX