Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

514
FXUS63 KLSX 111925
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
225 PM CDT Sun Oct 11 2026

.KEY MESSAGES...
- Near-record warmth for mid October is expected through Tuesday.

- A wobbling front will lead to multiple rounds of showers and
  thunderstorms Tuesday night through Thursday. Locally heavy
  rain is possible.

- A shift toward much cooler weather is expected this weekend.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 224 PM CDT Sun Oct 11 2026

Our weather locally continues to be dominated by a broad, warm ridge
of high pressure over the central to eastern US, punctuated only by
the remnants of former tropical cyclone Isaias now spinning through
the southern Appalachians. At the surface, high pressure over the
Gulf Coast extends its axis northward through the Mississippi Valley
leading to light winds and a clear sky locally. However, to our west
a large trough is developing over the Western US, with moisture from
tropical cyclone Rachel being absorbed into it. Some energy from
this trough will be pushing east through the Northern Plains over
the top of the ridge in the coming days, pushing a frontal boundary
toward our region. At the moment, this cold front is stretched from
northern Minnesota to western Nebraska. South of the front
widespread hot weather continues, with many locations near or over
90 degrees. North of it is actually some much colder air and even
snow in Montana, though this will be moderating in the coming days.
As this front approaches, we`ll see winds pick up out of the
southwest and the temperature climbing a couple degrees more for
high temperatures Monday and Tuesday. Moisture is a bit slow to
return, likely leading to elevated fire danger Monday afternoon.
Greater moisture (dewpoints near daily records near 70) on Tuesday
should temper the heating just a bit, but highs are still likely to
reach the low 90s.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 224 PM CDT Sun Oct 11 2026

The front finally drops into the region late on Tuesday, but it will
be slowing its progress as it arrives. Moisture pushing northward
toward the boundary will lead to the first of a few rounds of
showers and thunderstorms developing Tuesday night along and behind
the front. This round will favor northern portions of our forecast
area as guidance has slowed the progression of the front from prior
forecasts. Additional pockets of showers and thunderstorms continue
through the day Wednesday with the front slowly sinking southward.
Then finally one more focused round is expected Wednesday night into
Thursday as another more potent trough pushes eastward, briefly
lifting the front back north again before following it up with an
even stronger cold front Thursday night into Friday.

Although we couldn`t completely rule out any severe weather threat,
convection looks to be focused along and behind the front, and thus
elevated in nature. Wind shear is also modest but does increase as
Thursday`s trough moves through. The primary threat, though, will be
locally heavy rainfall. The moisture feeding into this system is
quite extreme for this time of year, with precipitable water values
approaching 2 inches. This will lead to the potential for heavy
rainfall rates in areas of convection, but the gradual progression
of the front southward should help to mitigate the threat for these
heavy rainfall rates to linger too long in one spot. If, however, we
do see multiple rounds of heavy rainfall, or storms training over
the same location, then the threat for flash flooding will increase.
Regarding amounts, ensemble guidance shows high confidence (near 100
percent) that all areas will receive at least some rainfall in the
Tuesday night through Thursday time period. Among the LREF, more
than 50 percent of members produce at least 1 inch of rain across
most of the area during this time frame, and up to 25 percent
produce at least 2 inches. A lower probability (10 percent) worst
case scenario could result in 3+ inches if storms line up and linger
in one spot.

Thursday night`s cold front ushers in a pattern change, shifting us
toward much cooler and drier conditions. Although guidance agrees on
the general timing, there remains considerable variance in the
intensity of the air mass behind this front. This all stems from how
to handle the interaction between a northern stream trough and the
trough over the western US. The northern stream trough is still over
eastern Asia at this time and still needs to round the Aleutian low
and skirt the western Canadian ridge before arriving in the central
US Thursday. The western trough has already cut itself off over
Oregon where it will wobble around over the next several days. The
disagreement comes with whether to absorb this trough with the
incoming northern stream wave or to keep some of this energy cut off
over the Southwest US. That depends both on how the north stream
wave tracks and also where the cut off low wobbles. These cut off
lows have been some of the more notoriously unpredictable features
of modern meteorology. Subtle wobbling of this low further east will
enable a more complete merging of the two waves, while wobbling
westward would make that merger more difficult.

Guidance sources which favor a full merging of these waves generate
a much deeper trough with more cold air behind it aimed directly at
the central US and our region. Guidance which favors only a partial
interaction track the northern trough further east, pointing the
cold air push toward New England leaving more modest cool
temperatures for our area. In the recent few days, the two camps
have been largely lining up with the parent model systems, with GEFS
members bringing a deeper trough and intense local cold air while
ENS members feature a lower amplitude trough and milder conditions
locally. With the 12Z run there has been a bit more merging of the
two camps, with about 25 percent of GEFS members now siding with the
warmer ENS solution and now 20 percent of ENS solutions favoring the
colder GEFS solution. The GEPS has been more evenly split, but
overall favoring the warmer ENS solution. What this all means for us
locally is a shift toward cooler temperatures is coming! On the
warmer end, we`ll be looking at highs near 70, much cooler than we
have been but near normal for this time of year. On the colder end,
we would be seeing highs closer to 50 with lows dropping near
freezing. The latest probabilistic NBM shows the likelihood of
freezing temperatures at 10 to 30 percent across the region this
weekend, though this blended guidance is usually a bit slow to react
to changes and emerging ensemble consensus.

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1213 PM CDT Sun Oct 11 2026

VFR conditions and light winds continue through tonight. Winds
will be a bit stronger tonight than the past several, so
confidence in fog in valley locations is considerably lower.
SSW winds pick up even more Monday morning, with gusts to
20-25KT likely at most sites by late morning.

&&

.CLIMATE...
Issued at 257 AM CDT Sun Oct 11 2026

Very warm temperatures are expected over the next several days.
This will challenge daily record highs and record warm lows on
multiple occasions. The daily records threatened are shown
below.

Record High Temperatures:

October 11:
KSTL: 94/1963
KCOU: 89/1962
KUIN: 88/1962

October 12:
KSTL: 89/1890
KCOU: 94/1899
KUIN: 90/2024

October 13:
KSTL: 90/1899
KCOU: 95/1899
KUIN: 87/1975

Record High Minimum Temperatures:

October 12:
KSTL: 70/1997
KCOU: 69/1928
KUIN: 70/1928

October 13:
KSTL: 69/2008
KCOU: 69/1899
KUIN: 65/1935

October 14:
KSTL: 70/1899
KCOU: 67/2017
KUIN: 67/1920

In addition, all time monthly record high temperatures are
within range of being broken. The following are the October
monthly high temperature records at each site:

October Record High:
KSTL: 94 most recently on Oct 1, 2019
KCOU: 96 on Oct 7, 1939
KUIN: 96 on Oct 7, 1939

&&

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

&&

$$

SHORT TERM...Kimble
LONG TERM...Kimble
AVIATION...Kimble
CLIMATE...Maples