Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

377
FXUS63 KLSX 151126
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
626 AM CDT Thu Oct 15 2026

.KEY MESSAGES...

- Widespread showers and thunderstorms are expected through the
first half of the day, becoming isolated to scattered this afternoon
and evening. There is a low potential for isolated damaging winds,
and lower potential for a brief, week tornado.

- A strong cold front brings much cooler and drier conditions Friday
through Sunday morning. A gradual warming trend begin Sunday and
continues into next week.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 259 AM CDT Thu Oct 15 2026

Showers and thunderstorms approach the area early this morning out
of the southwest and continue advancing northeast over the CWA
through early this afternoon. A strong cold front then quickly moves
west to east with much cooler air spilling into the area overnight
into Friday.

The area being monitored for the next round of showers and
thunderstorms is currently over sections of eastern OK. This
activity is being driven by a shortwave trough and corresponding
surface low in advance of the upper level low over CO. The surface
low parallels I-44 on its northeast track with broad scale ascent,
lifting the stationary boundary northward through the area through
the morning. A broad area of showers and embedded thunderstorms
accompany the warm front with HRRR/NAMNest indicating a few strong
cells in close proximity to the warm front and surface low. HREF
ensembles show mean CAPE values of 1000-1500 J/kg with around 40
knots of shear and backed surface winds near the boundary resulting
in curved hodographs. These indicators would normally raise some
concern, but in this case, showers and embedded thunderstorms enter
the southwest CWA between 10-12z and near the MS River around 15z.
RAP model soundings show a capping inversion just below 850mb, CAPE
below 500 J/kg, and mid-level lapse rates below 6C. The system and
front moves relatively quickly, placing the warm front north of I-70
around 18-19z. The issue then, is to monitor the warm sector over
southeast MO and southwest IL, where HREF shows roughly 20-40
percent probabilities for cloud cover of great than 50 percent. This
leaves much to be desired with respect to severe potential with low
confidence that severe weather will materialize. Instability will
have a very short window of 3-4 hours (2-6PM) for recovery at a time
of year with lower sun angle and earlier sunset, considering that
enough clearing occurs quickly enough. Therefore, while we are
messaging the marginal risk, the threat for severe weather looks
very low and isolated at best. Damaging winds would be the primary
threat. The low tornado potential is also limited in aerial coverage
(along and north of I-70 and east of I-55).

A strong cold front trails the system and races west to east late
this evening and overnight as the system moves into the the Great
Lakes and is wrapped into a vigorous northern stream Canadian upper
trough. Scattered showers and an isolated thunderstorm are possible
along the front as upper ascent evacuates to the northeast. There is
not much concern for severe potential along the front itself as much
of the atmosphere is work over and we enter the diurnal downward
trend. The front should be east of the CWA around or just after
midnight with a surface ridging beginning to build in from the
northwest. Strong cold air advection drops temperatures overnight
with cold air continuing to advect in through the day Friday. The
surface high remain departed enough to the west that the upper
trough exhibits more influence in terms of moisture. Though we may
briefly see partial clearing early Friday, higher RH advects
southeastward with the amplified upper trough overhead and surface
ridge to the west. Clouds will build back in Friday in conjunction
with continuing cold air advection. It is expected to be the coolest
day of the fall so far.

Highs today will range from the 70s over northern sections of the
CWA to the mid-80s over southeast MO and southwest IL. Lows tonight
drop into the 40s behind the cold front. Highs Friday will be in the
50s, even struggling reach 60 degrees across far southeast MO.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 259 AM CDT Thu Oct 15 2026

The fall chill will continue into Saturday before temperatures begin
to moderate Sunday into next week. A long stretch of dry weather is
expected through much of next week.

The amplified trough shifts east of the area Friday night into
Saturday with a longwave upper ridge over the western 2/3rds of the
CONUS. Northwesterly flow continues aloft as the surface ridge moves
southeastward and its orientation varies between RAP/NAM and long
range suites. These vary from a slanted ridge axis to a more
formidable, consolidated surface high. Though minor, range solutions
may be the difference between a decent frost and cold, morning dew
on the lawn. The orientation, placement of the ridge, and resulting
surface flow suggest that while temperatures will be the coolest of
the season, so far, NBM is likely too cool, leaning at or just below
the 25th percentile of the IQR. LREF guidance has not only tightened
in its IQR range (3-4 degrees), it has consistently shown morning
lows in the upper 30s to low-40s with locally cooler temperatures in
the well-known microclimates (e.g. Freedom, and Rose Bud, MO). The
scenario is slightly different for Sunday as the high positions
overhead and winds become light and variable. Sunday looks like the
cooler of the two, barring how quickly the high moves east and
return flow commences. General speaking, morning lows in the low in
the upper 30s to low-40s will represent a large majority of the
area. Locally cooler temperatures will support better frost
potential with mid-30s.

Upper ridging moves eastward and envelops the region Sunday into
next week. The pattern look void of any formidable systems and
drives the northern stream track into the northern CONUS/southern
Canada. Another surface ridges moves west to east near the Canadian
border with dry easterly flow through the midweek period. NBM has
suggested high temperatures in the upper 70s to near 80 degrees
through the midweek stretch, but has since come down to more
reasonable levels (low to mid-70s). Morning lows will follow suit
with temperatures doing a daily stair step from the upper 30s/40s
early in the week to 50s by Friday.

&&

.AVIATION /12Z TAFS THROUGH 18Z FRIDAY/...
Issued at 626 AM CDT Thu Oct 15 2026

A warm front will lift northeast over the terminals this morning
through early afternoon. The front includes a broken line of
heavier showers resulting in vsby restrictions locally as low
as 1 3/4SM. Lightning has been limited/isolated due to lower
instability this morning though thunder potential increases this
afternoon. By that time, the warm front lifts north of the
metro terminals to near KUIN. Rain chances lower slightly after
the first round of showers move northward along and north of
the warm front.

This afternoon brings the concern for isolated strong to severe
thunderstorms with a very short window of opportunity, mainly
around metro terminals. The system initially approaches
KCOU/KJEF by early afternoon and before instability returns.
The system quickly moves northeast, affecting the metro sites in
the later half of the day. -TSRA was included in PROB30 groups
with some uncertainty in how well instability recovers behind
this morning`s initial wave. Thunderstorms that develop should
move east of the metro terminals this evening. Isolated showers
remain possible until the front clears from west to east.
Evening SHRA potential was not included at this time given the
limited coverage. A mix of MVFR/IFR covers much of the period
with gradual improvement overnight, though northwesterly winds
are expected to gust on occasion.

&&

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

&&

$$

SHORT TERM...Maples
LONG TERM...Maples
AVIATION...Maples