Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

415
FXUS63 KLSX 091008
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
508 AM CDT Thu Apr 9 2026

.KEY MESSAGES...

- Low humidity, southwesterly winds, and dry vegetation will
  support Elevated Fire Danger this afternoon with erratic
  behavior of any fires.

- Above average temperatures will persist into next week aside
  from northern portions of the area behind a cold front Friday.

- Occasional opportunities for showers and thunderstorms are
  expected tonight through early next week with the highest/most
  confident chance (60 to 80 percent) tonight into Friday.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 343 AM CDT Thu Apr 9 2026

A weak cold front is expected to remain north of the CWA near the IA-
MO border through the daytime hours, leaving the CWA in the warm
sector and similar airmass to Wednesday. With strong insolation and
a warmer start to the day in the 50s and low-60s F, high
temperatures are expected to be approximately 5 F warmer and in the
mid-70s to low-80s F. Deep boundary-layer mixing (up to between 800
and 700 hPa), low-level southwesterly flow downsloped off the Ozark
Plateau, and limited moisture return support another day of Elevated
Fire Danger across most of the area with low RH and marginally
strong southwesterly winds (sustained 10 to 16 mph).

The vast majority of CAMs keep the CWA dry until the aforementioned
cold front finally advances southward through the CWA overnight
through Friday. Southeastward-moving showers and thunderstorms
along/behind the should be most numerous overnight across
northeastern, central MO and west-central IL as an upper-level
trough glances the Mid-Mississippi River Valley and a southwesterly
LLJ peaks in strength, but coverage is less confident on Friday as
the LLJ weakening and there are mixed signals for a weak MCV
tracking along the front during the morning or early afternoon.
Through the afternoon, most showers and thunderstorms are expected
to be across southeastern MO and southwestern IL as modest surface-
based instability develops along the front. That being said, severe
weather appears very unlikely due to HREF probabilities of SBCAPE 20
percent or less and deep-layer wind shear of around 20 kt. Given the
passage of the front, there will be a range of high temperatures on
Friday. Along/south of I-44 (MO) and I-70 (IL), the front will be
passing during the afternoon, allowing temperatures to reach the 70s
to near 80 F. However, north of/behind the front across the
remainder of the CWA, weak low-level CAA and considerable cloud
cover, including some stratus, will keep temperatures mainly in the
60s F.

Pfahler

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 343 AM CDT Thu Apr 9 2026

The cold front will be south of the CWA Friday night, but will lift
back northward as a warm front Saturday morning through afternoon in
response to surface cyclogenesis in the northern Front Range/High
Plains. Around 40 to 60 percent of ensemble model membership have
showers and a few thunderstorms at times in the vicinity of the
front, but a relative minimum in probabilities exists Saturday
afternoon into overnight along/east of the Mississippi River where
unfavorable, rising mid-level heights associated with a passing
ridge will be most pronounced. High temperatures on Saturday will be
generally warmer than Friday across most of the CWA with the lifting
warm front--in the 70s and low-80s in central, east-central, and
southeastern MO as well as southwestern IL; and in the mid-60s to
near 70 F in northeastern MO and west-central IL with later arrival
of the front.

Following the passage of the upper-level ridge, upper-level
southwesterly flow will become established across the central CONUS
as longwave troughing occurs over the Desert Southwest. This
configuration will lead to a warm, wet, and active pattern broadly
across the Central Plains and Mid-Mississippi River Valley, but the
details are still not entirely clear. Instability and wind shear
will be higher Sunday into early next week as rich Gulf of Mexico
moisture arrives and mid-level flow increases, with ensemble and
machine learning guidance signaling the potential for severe
thunderstorms regionally Monday, Tuesday, and to a lesser degree
Wednesday. However, the highest probabilities of their respective
memberships have shifted to the west of the CWA with weaker/less
discernible large-scale ascent and greater warm sector capping over
the CWA. Much of this shift has been a result of a later eastward
propagation of the primary trough and more amplified downstream
ridge. Conceptually, the greatest chance of severe weather would be
when this trough and associated cold front arrives, which ranges
from Tuesday night to Wednesday night, and whether or not that is in
phase with the diurnal maximum in instability. An important
disclaimer in this type of pattern is that model guidance often
struggles with the handling of upstream longwave troughs/cutoff
lows, exhibiting high variability and underdispersion that does
not truly capture all scenarios. So further forecast adjustments
can be expected in the coming days. What can be said with greater
confidence is that well-above temperatures will prevail Sunday
into early next week with the NBM high temperature distribution
focused on the 70s to near 90 F.

Pfahler

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 508 AM CDT Thu Apr 9 2026

Dry and VFR flight conditions will persist today with winds becoming
largely southwesterly late this morning and gusting 18 to 22 kt
through afternoon. A cold front will advance southward through the
region tonight into Friday, accompanied by showers and a few
thunderstorms and winds veering to westerly and then northerly.
Through the end of the TAF period, KUIN has the the highest chance
of impacts from thunderstorms including reduced visibilities. MVFR
ceilings are also likely behind the front, but are not expected to
arrive until around or just beyond the TAF period.

Pfahler

&&

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

$$

WFO LSX