Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

330
FXUS63 KLSX 220158
AFDLSX

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
858 PM CDT Sun Jun 21 2026

.KEY MESSAGES...

- Damaging winds and tornadoes are possible through this evening
  across east central and southeast Missouri into southwest Illinois.

- Locally heavy rainfall is also possible through early tonight.

- Seasonably cool conditions are forecast this work week.


&&

.SHORT TERM... (Through Late Tonight)
Issued at 9 PM CDT Sun Jun 21 2026

The tornado watch has been canceled for all of Missouri and west
central Illinois.

There are currently two lines of showers and thunderstorms across
the area. The first line being north of St. Louis and the second
being across a Crawford to Washington to Randolph County line. The
northern line is in association with a surface cold front, while
the southern line is in association with a much weaker frontal
zone. The northern line is expected to remain rather weak and
lightning deficient, while the southern line of storms is
forecast to be stronger. This is due to the northern line being
directly upstream of the departing MCV (weak upper level
subsidence), and less overall instability. The southern line has
less surface convergence, but storms have much more instability to
work with (upwards of 2000 J/kg of MLCAPE in places). The primary
threats for the southern storms will be large hail, damaging wind
gusts, and a tornado or two.

The surface cold front will sweep through central Missouri and
west-central Illinois tonight with temperatures and dewpoints
falling. Skies will remain overcast to broken though with
ceilings lowering to less than 1000 ft by early Monday morning.
Expect low temperatures in the lower 60s.

BAH

&&

.LONG TERM...  (Monday through Next Sunday)
Issued at 324 PM CDT Sun Jun 21 2026

(Monday - Monday Night)

Cooler weather along with northerly winds and clouds are
expected on Monday. High temperatures are only expected to reach
into the mid 70s, or about 10 degrees below normal for the date.
Lows Monday night are forecast to drop into the mid 50s to near the
60 degree mark.


(Tuesday - Next Sunday)

Not much has changed with respect to the work week forecast with
broad northwest flow aloft across the Mississippi Valley. There is
high confidence in seasonally cool temperatures with mostly dry
weather expected outside of a cold frontal passage
Wednesday/Wednesday night.

Moderating temperatures are forecast heading into next weekend with
flow aloft becoming more zonal. That means increasing
moisture/instability as well and increasing chances of showers and
thunderstorms.


Gosselin

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 632 PM CDT Sun Jun 21 2026

There currently are two surface cold fronts across the region. The
first cold front is located southeast of KUIN and northwest of
KSTL. Showers and thunderstorms have generally struggled to
maintain themselves with this northern front, with not much
lightning being observed. This is likely due to the more limited
instability and weak subsidence upstream of the MCV. The secondary
cold front, is located near a Crawford to Randolph County line
and is where more robust and even severe thunderstorms exist.

The surface cold front to the northwest is what will affect the
STL terminals overnight. However, have not included the mention of
thunder in the STL terminals given the waning instability. Behind
the cold front, winds will veer around from the northwest at about
10 kts with some gusts possible. The other impact to the terminals
will be the rapidly decreasing CIGS as IFR filters in from the
northwest. Forecast soundings show all terminals going IFR
overnight into the Monday morning hours. A slow recovery to VFR
is expected in the afternoon hours from northwest to southeast.

BAH

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch until 7 AM CDT Monday for Iron MO-Madison MO-
     Reynolds MO-Saint Francois MO-Sainte Genevieve MO.

IL...Flood Watch until 1 AM CDT Monday for Bond IL-Fayette IL-
     Montgomery IL.

     Flood Watch until 7 AM CDT Monday for Clinton IL-Marion IL-
     Randolph IL-Washington IL.

&&

$$

WFO LSX