Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

782
FXUS63 KLSX 240912
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
412 AM CDT Tue Mar 24 2026

.KEY MESSAGES...

-Warming temperatures today through Thursday, then a cold front
brings a brief cool down for Friday.

-Showers and thunderstorms are expected along and behind
Thursday`s front, mainly Thursday evening through Friday morning.


&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 253 AM CDT Tue Mar 24 2026

Virga is eroding and edging out of the region, and the dry surface
layer has kept most of it from reaching the ground. Otherwise,
easterly surface flow associated with the departing surface high
will become southerly, and combined with the southwesterly low-
level flow, will result in warming temperatures today. Cloud cover
will stunt temperatures slightly, but we are still expected to
warm into the 60s across the forecast area.

Another subtle mid-level shortwave will traverse northwesterly mid-
level flow across the region this afternoon and evening, which will
generate another patch of virga within the mid-level cloud cover
this evening. Dry low-levels will prevent a majority of the rain
making it to the surface, though I can`t rule out a spare drop here
or there. Warm air advection will continue Wednesday as
southwesterly flow extends through the low-levels to the surface,
pulling high temperatures into the 70s to low 80s.

Delia

&&

.LONG TERM...  (Wednesday Night through Monday)
Issued at 253 AM CDT Tue Mar 24 2026

By Thursday the mid-level ridge that has been sitting over the
Desert Southwest will broaden across the southern US, while a mid-
level trough continues to churn over the Hudson Bay region. The
trough will drop it`s axis down through the mid-Mississippi Valley
Thursday into Friday, bringing a cold front through the forecast
area Thursday night. Ahead of the front, temperatures will warm
under continued strong warm air advection. 850 mb temperatures will
warm into the 18-20C range, at the climatological maximum for this
time of year. Efficient mixing to 850mb will allow these warm
temperatures to translate to highs in the upper 80s to low 90s
across much of the forecast area. As has been mentioned in previous
discussions, this is putting our daily and monthly high temperature
records in jeopardy at all our Climate sites (See Climate Section).

The front is currently forecast to enter central and northeast
Missouri and west-central Illinois during the early evening, and
progress through the forecast area into the overnight hours.
Instability will build ahead of the front in the warm and moist
environment, though a strong cap within the 700-800mb layer is also
expected to be present, limiting surface access to the instability.
In addition to the cap, weak forcing ahead of the front, including
surface flow largely parallel to the front, will inhibit warm sector
convective initiation during the afternoon. The best chance for
thunderstorm development will be along and behind the front where
frontogenesis and mid-level forcing will coincide. Here the
elevated cold front will begin to erode the 700-800mb cap,
allowing for the potential for surface based convection along/just
behind the front. How much cap erosion takes place remains
uncertain, and elevated convection remains most likely. Further
behind the front, and deeper into the evening, elevated convection
will dominate. From what convection does develop, a few
thunderstorms will be able to organize within the 40-60 kts or so
despite weakening lapse rates. Large hail is the main threat with
any storms that become strong to severe. Overall this event is
expected to behave very similarly to Sunday (3/22).

The front and the post-frontal precipitation will progress through
the region quickly overnight, exiting the forecast area Friday. In
the wake of the front and associated mid-level trough axis, the mid-
level trough will deepen into the eastern CONUS while a mid-level
ridge begins to build over the West Coast. Northwesterly mid-level
flow over the mid-Mississippi Valley will become amplified in the
process. Friday`s temperatures will take a tumble as cold air
advection surges into the region behind the front, dropping surface
temperatures back below normal. Cold air advection will continue
through the day and overnight as the coldest portion of the airmass
skims the region. An anomalously strong surface high above the
99.5th climatological percentile will pass through the region
overnight as well, allowing for very efficient radiational cooling
and dropping lows Friday night into the upper 20s to low 30s.

This cold air mass won`t linger long and by Sunday southwesterly low-
level flow will reestablish, kicking off warm air advection and our
next warming trend. Warm air advection will continue into next week
as well, and ensemble guidance shows steady warming continuing
through the end of the seven day forecast. Through the first half of
the work week the mid-level ridge over the West Coast will advance
eastward, with a few shortwaves embedded within the flow.
Differences in timing and strength of the shortwave results in
uncertainty in our next chance for precipitation next week. The mid-
level pattern becomes more amplified beyond the mid-week period,
increasing chances for precipitation and active weather.

Delia

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 410 AM CDT Tue Mar 24 2026

VFR and mostly dry conditions will prevail through the period. A
sprinkle or two is possible tonight with rain moving across the
region but most of it evaporating before hitting the ground. Winds
will become southerly this morning and persist largely from this
direction, at times becoming more southeasterly.

Delia

&&

.CLIMATE...
Issued at 245 PM CDT Mon Mar 23 2026

Record Highs on March 26:
St Louis   87 in 1991
Columbia   86 in 1910
Quincy     82 in 1991

All Time March High Temperature Record:
St Louis   92 on March 24, 1929
Columbia   92 on March 21, 1907
Quincy     88 on March 21, 1907


&&

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

$$

WFO LSX