Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

185
FXUS63 KLSX 200834
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
334 AM CDT Wed May 20 2026

.KEY MESSAGES...

- Cooler temperatures are expected through Friday.

- There will be several chances for showers and thunderstorms over
  the upcoming Memorial Day weekend.

&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 332 AM CDT Wed May 20 2026

Temperatures have dropped into the 50s early this morning behind the
cold front that has now moved south of Missouri and Illinois.  There
are scattered showers that continue to form to the north of the
front by low level frontogenesis that will gradually move south of
the CWA through mid-late morning. The HREF is then showing a
short wave ridge building over the Midwest later today into
tonight which will keep the forecast dry into early Thursday. At
the same time a large surface high will slowly move east across
the Great Lakes causing the surface winds to slowly shift from
northerly to easterly by tomorrow. Model guidance is showing that
we will likely stay mainly cloudy through tomorrow, with lower
ceilings in the southern half of the CWA today which favors cooler
temperatures. Highs will likely stay in the 60s today and range
from the mid 60s to mid 70s on Thursday.

Britt

&&

.LONG TERM...  (Thursday Night through Tuesday)
Issued at 332 AM CDT Wed May 20 2026

After the brief dry period on Wednesday night and Thursday, the
chances for showers and thunderstorms increases over the Memorial
Day weekend into next week as the LREF is showing southwesterly
upper flow over Missouri and Illinois.  Model guidance is consistent
with a trough moving across the area late Thursday night into Friday
which is when the LREF has 60-90% of its members are producing rain
over the area. This is also the period when PWATS will be the
highest (near 2.0") and WPC has highlighted the southern half of the
CWA in a marginal risk of excessive rainfall.   There are lower
chances on Friday night, but two or three more shortwaves will move
across the area over the weekend bringing additional chances for
showers and thunderstorms the rest of the weekend. At this point,
the LREF/NBM members are keeping the better chances (40-60%) over
southeast Missouri into southwest Illinois which is closer to
where a surface front will be during the extended weekend.

Temperatures will start to warm back up over the weekend, though
as pointed out by the previous discussion, the NBM is on the
warmest side of guidance. While upper heights will be building
over the area which favors the warmer temperatures, they will be
tempered by the clouds and rain chances which should keep highs in
the 70s.

Britt

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1043 PM CDT Tue May 19 2026

MVFR ceilings are locked in across sections of southeast Missouri
through southern and west-central Illinois late this evening.
Fortunately, drier air has eaten into the northwest periphery of
the lower ceiling with quicker improvement over sections of
central Missouri through northeast Missouri and west-central
Illinois. MVFR is likely to hold over the metro terminals through
much of Wednesday as the front linger to the south and low
pressure pivots into the Ohio Valley. Meanwhile, dry air will
slowly erode MVFR ceilings through Wednesday with all site
improving to VFR through the end of the 24 hour period.

While a few showers could pop up overnight, direct impacts to
terminals would be minor, if affected. Chances are low enough that
they were not included in prevailing groups at the time.

Maples

&&

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

$$

WFO LSX