Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

083
FXUS63 KLSX 230344
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1044 PM CDT Wed Apr 22 2026

.KEY MESSAGES...

- Above average temperatures (5-15 degrees) along with breezy
  south winds are expected on Thursday with temperatures remaining
  near or slightly above average into early next week.

- Confidence remains high (80-90%) in widespread rainfall Thursday
  night lingering into Friday with a 40-50% chance of
  thunderstorms. A few storms may pose a threat for damaging winds
  with a lesser threat for tornadoes.

- Additional chances (70-80%) for rainfall continue to increase
  beginning Sunday night through Monday.


&&

.SHORT TERM... (Through Late Thursday)
Issued at 321 PM CDT Wed Apr 22 2026

An area of stratus advected into locations across central/northeast
MO earlier this morning within low-level southerly moisture
advection and weak isentropic ascent. The higher late-April sun
angle, providing ample solar insolation, halted further
northeastward progression of this stratus field late in the morning
and has worked to erode it along the northern/eastern edges
throughout the afternoon. Locations that avoided the stratus today,
generally east of a line from Pittsfield, IL to Sullivan, MO, have
jumped into the mid/upper 70s this afternoon. While areas west of
that line are in the mid/upper 60s, where a majority of the day was
spent under the stratus. A mid/upper level ridge is centered across
the Midwest this afternoon with has led to height rises aloft today
as the ridge axis approaches the area. Subsidence has also worked to
erode the stratus and has led to mostly sunny conditions this
afternoon, aside from locations across central MO, where the stratus
has been more persistent.

Southwesterly surface winds have been lighter today, sustained 7-
12mph with intermittent gusts near 20mph, thanks to a slackened
surface pressure gradient across the area. Tonight will feature calm
conditions with surface winds forecast to be light as they gradually
become more southerly with Thursday morning lows in the upper 50s
across most the area with lower 60s in the St. Louis metro. By
Thursday, the ridge aloft will have progressed east across the area
with a broad mid/upper-level longwave trough across the
Intermountain West, placing the area under deep southwesterly flow.
A mid-level shortwave, within the broadened longwave, swings around
the base of the trough on Thursday and ejects into the Great Plains
Thursday night, sparking low-level cyclogenesis across the Northern
Plains. All of this leads to a tightening surface pressure gradient
tomorrow that will enhance low-level flow, resulting in winds that
are 10-15mph stronger than today (sustained and gusts). With mid-
level ridging still nearby and the shortwave progged to eject
Thursday night, Thursday will remain dry across the area with highs
in the upper 70s/lower 80s by the afternoon. Shower and thunderstorm
chances ramp up Thursday night from west-east and will be analyzed
further in the long-term that follows.

Peine

&&

.LONG TERM... (Thursday Night through Next Wednesday)
Issued at 321 PM CDT Wed Apr 22 2026

By Thursday night, surface cyclogenesis across the Northern Plains
will be well underway with a north-south cold front stretching
southward into the Southern Plains. As the mid-level shortwave
continues to eject northeastward, the surface reflection follows
suite, dragging a cold front east into the area. Ahead of this
front, increased low-level southerly flow leads to ample moisture
return from the Gulf that boosts PWATs Thursday night into Friday
morning to the 1.2-1.3" range (according to the LREF), which is near
the 90-95th climatological percentile. Across the Great Plains,
robust frontogenetical forcing colliding with ample instability, is
forecast to result in convective initiation Thursday evening growing
upscale into a line or broken line of thunderstorms along the front.
For our area, the arrival time of showers and thunderstorms progged
by model guidance still varies greatly. In general, most CAMs reveal
a north-northeast to south-southwest oriented line of showers and
thunderstorms approaching central/northeast MO sometime between 03-
07Z on Friday morning. Instability will be continuously waning as
the cold front and showers/thunderstorms march southeastward, with
LREF mean MUCAPE remaining <1,000 J/kg all throughout Thursday
night. With conditions more conducive for strong to severe
thunderstorms to the west, the setup across our area favors
weakening thunderstorms with eastward extent. Currently, the
greatest hazard Thursday night into Friday morning with strong and
severe thunderstorms will be the potential for damaging winds with a
lesser threat for tornadoes, both related to any line segments that
maintain strength into the area.

Numerical model guidance continues to show this cold front slowing
down while it pivots clockwise, with most guidance now progressing
the front out of our area into southern MO/IL by Friday afternoon.
The location of this front will be key in determining where the
greatest chance for lingering showers and additional chances for
strong to severe thunderstorms will be Friday evening. Along and
south of this boundary, instability will consistently be near 1,000
J/kg, indicating there is continued potential for additional
thunderstorms in the open warm sector. Confidence has increased in a
more progressive front, placing our area north of the front and the
greatest probabilities for showers and thunderstorms south of the
area. Lastly, it is important to note that there is still concern
for localized heavy rainfall since the mean flow will be nearly
parallel to the passing cold front, which is conducive for training
convection. Currently, the greatest concern for heavy rainfall is
across central MO and points further south and west, as this is
where recent heavier rainfall has saturated area soils and where
model guidance reveals higher amounts could be with this round of
showers/storms. Here, the NBM 90th percentile for 72hr accumulated
precipitation reveals rainfall amounts over 2" in localized pockets.
Amounts like this could certainly be realized given the convective
element at play and the higher PWATs that will be in place.

Quasi-zonal mid/upper-level flow settles into the region as the mid-
level shortwave continues to swing cyclonically around the longwave
trough with both lifting into southern Canada by Saturday.
Confidence has continued to increase that Saturday will be dry for
the entire area as the LREF 6hr probabilities for measurable
precipitation stay below 10%. The southern stream becomes more
active with a mid-level shortwave traversing the Four Corners Region
on Sunday leading to a steady increase in rain chances from the west
on Sunday, with the LREF indicating up to a 50% chance for rainfall
across central MO by late Sunday evening. Regardless, most of the
area is forecast to remain dry on Sunday also, with temperatures
each day this weekend expected to be in the 70s areawide. The
southern stream mid-level shortwave ejects into the Great Plains
sometime Sunday night into Monday, bringing with it additional 70-
90% chances for showers and thunderstorms to the area on Monday.
Analysis of LREF temperature IQRs reveals that temperatures look to
remain near or slightly above average for the entire extended, with
the exception of next Wednesday. This is when long-range
deterministic guidance is in fairly good agreement that the longwave
trough to our north pushes far enough east where is opens to the
area up to west-northwesterly flow. LREF temperature IQRs for next
Wednesday stay spread around 5 degrees but lower to values centered
5-10 degrees below average, hinting that cooler conditions are
possible by the middle of next week.

Peine

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1039 PM CDT Wed Apr 22 2026

VFR flight conditions are anticipated to continue through a
majority of the TAF period at all local terminals. A decaying line
of thunderstorms will be moving into the region near the end of
the TAF period Thursday night, with possible impacts to KCOU,
KJEF, and KUIN around or just after midnight.

Elmore

&&

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

$$

WFO LSX