Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

924
FXUS63 KLSX 101127
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
627 AM CDT Wed Jun 10 2026

.KEY MESSAGES...

- Hot and humid conditions are expected through Thursday.

- Strong to severe thunderstorms are expected this evening, with
  the main threats being damaging wind gusts and large hail.

- Another round of strong to severe thunderstorms will occur
  along a cold front Thursday afternoon and evening. These storms
  will be capable of damaging wind gusts, large hail, and
  tornadoes.


&&

.SHORT TERM... (Through Thursday Night)
Issued at 223 AM CDT Wed Jun 10 2026

Water vapor imagery shows an upper-level trough broadening across
the Northern and Central Plains this morning. This trough will mute
the upper-level ridge over the Middle Mississippi Valley today, with
guidance consensus showing 850 mb temperatures cooling by a degree
or two compared to yesterday. While this favors slightly cooler
temperatures at the surface, southwesterly surface flow will provide
a boost to temperatures via downsloping and adiabatic warming off
the Ozarks. This will produce air temperatures a degree or two
warmer than yesterday; however, the same process will also lower dew
points. In the end, this will result in heat index values similar to
if not a few degrees below what was experienced yesterday and below
Heat Advisory criteria.

Another heat-mitigating factor is the potential for convection prior
to and during peak heating. As the trough draws closer to the CWA, a
subtle disturbance within the southwesterly flow aloft will move
northeastward across Missouri into northern Illinois from mid
morning into the afternoon. Despite this being prior to peak heating
and when instability will be maximized, there will be at least 2,500
J/kg of SBCAPE per guidance consensus. Deep layer shear is expected
to be around 30 kts, but updrafts may be slightly elevated with
lower effective shear. The instability will be sufficient for at
least small hail production in the strongest cores, and if the
degree of forecasted shear is realized, there will be a threat for
isolated large hail and damaging wind gusts across northeastern
Missouri and west-central Illinois. Convective debris and/or outflow
from this convection will reduce temperatures across this part of
the area.

The main concern for strong to severe storms will come later this
evening as a cold front sinks south-southeastward into the region.
There is some concern that the early-day convection may reduce
instability and the atmosphere not be able to fully recover prior to
late afternoon/early evening CI; however, there is a strong
consensus among guidance that recovery will not be an issue and the
environment will be plenty unstable. Around 4pm when CI is expected
roughly across north-central Missouri and southern Iowa, 3,000-4,000
J/kg of SBCAPE is forecast within the warm sector among 30-35 kts of
deep-layer shear. The shear vectors will be nearly parallel to the
front, leading to quick upscale growth as storms move into the CWA
this evening. Clusters of multi-cells with embedded supercells will
pose mainly a damaging wind and large hail threat. Low-level shear
will be sufficient for tornadoes, though storm interactions and any
supercells being short-lived limit this threat to bowing segments
that can develop mesovortices. The area most favorable for these
threats is northeastern Missouri and west-central Illinois along and
north of Highway 36 and I-72. Convection is expected to drift east
of the CWA by around midnight as the low-level jet veers, with a
relative lull in activity then expected through Thursday morning.

The aforementioned cold front will not make much progress south until
a shortwave induces cyclogenesis along the boundary over the Central
Plains during the day Thursday; swinging it through the Middle
Mississippi Valley during the late afternoon and evening. With that
frontal timing, there is a low to medium chance for dangerous heat
across portions of the CWA, with potential cloud cover and
uncertainty in FROPA specifics leading these confidence levels.
Nevertheless, upwards of 3,000 J/kg of SBCAPE is expected ahead of
the front with deep-layer shear once again being around 30kts. An
inversion/capping around 700mb within the warm sector is expected to
keep convection tied to the front, with the deep-layer shear vectors
becoming increasingly parallel to the boundary as proximity to it
increases. Both factors will favor clusters and/or a linear storm
mode, with steep low-level lapse rates and DCAPE over 1,000 J/kg
supporting primarily a damaging wind threat. Low-level shear of 20-
30 kts is favorable for a tornado threat, but a limiting factor may
be slightly elevated LCLs. Convection will gradually weaken with
southeastward extent as instability and shear decrease through the
evening, with the front clearing the CWA as early as late evening to
just after midnight.

Elmore

&&

.LONG TERM... (Friday through Tuesday)
Issued at 223 AM CDT Wed Jun 10 2026

The consensus among guidance continues to be that zonal flow will
persist over the Middle Mississippi Valley in the wake of Thursday`s
front. This flow and a weekend FROPA will keep temperatures at or
below climatological normals through this portion of the period.
This cold front will drift southward through the region Saturday
into Sunday and serve as the focus for periodic rounds of rain
through the weekend. Guidance diverges on how far south it makes it
relative to the CWA before a shortwave enhances rain chances along
it early next week. If the front is further south from the CWA,
little to no rain can be expected. If it stalls just south of the
CWA, rain chances will continue into early next week.

Elmore

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 622 AM CDT Wed Jun 10 2026

Concern for impacts will be primarily confined to KUIN this TAF
period, as multiple rounds of thunderstorms pass near and over the
terminal. For the first round late this morning into the early
afternoon, shower and thunderstorm coverage will be isolated to
scattered, with any impacts being brief. There is a very low
chance that these same showers and thunderstorms impact KCOU
and/or KJEF from mid to late morning. This evening, another more
potent round of showers and thunderstorms is expected to impact
KUIN. This round will be more persistently impactful than the
first, but uncertainty over timing and placement of the worst of
the storms has confidence low in specifics relative to KUIN. For
this round, there is a low chance that showers, thunderstorms,
and/or outflow impact KSUS, KSTL, and KCPS.

Elmore

&&

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

$$

WFO LSX