Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

180
FXUS63 KLSX 250655
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
155 AM CDT Fri Sep 25 2026

.KEY MESSAGES...

- Cloudy and cool weather will prevail through the weekend.
  Those who see rain will experience the coolest conditions.

- The greatest chance for rain (60-80%) this weekend will be in
  northeast MO and west-central IL early Saturday morning. The
  potential for widespread beneficial rainfall during the middle
  of next week is increasing.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 154 AM CDT Fri Sep 25 2026

Low-level high pressure continues to swirl over eastern
Ontario/western Quebec this morning. Well to the southwest, a mid-
level ridge centered over the Southern Plains is extending through
the Mid-Mississippi Valley, bringing with it weak shortwave impulses
and a tongue of rich mid-level moisture. This combination has been
enough to produce showers and a storm or two in northwestern
Missouri this morning. What falls in northeast Missouri and west-
central Illinois through today, though, is expected to be much
lighter in nature as the primary forcing and moisture remain to our
north and west and MUCAPE values fail to reach even 50 J/kg. The
aforementioned Canadian high pressure will also drive low-level dry
air into the region from the east today which will slowly undercut
showers and make it harder for rain to reach the ground. The
associated low-level cloud cover will keep temperatures in affected
areas dampened today with highs likely struggling to reach 70
degrees. Elsewhere, especially where clouds break more frequently,
highs are forecast to climb well into the 70s. Portions of far
southeast Missouri even have a chance (10-20%) of reaching 80
degrees this afternoon.

Light rain is likely (60-80% chance) early Saturday morning as the
eroding southern ridge brings mid-level moisture further south and
into our CWA. The arrival of more vorticity lobes and low-level warm
air advection will support scattered showers. A lucky few may even
hear a rumble of thunder as MUCAPE increases to 100-200 J/kg. The
greatest chance for this to occur will be in central Missouri,
northeast Missouri, and west-central Illinois. Again, rain chances
decrease with southern and eastern extent due to 1) proximity to
moisture and forcing and 2) low-level dry air. Highs Saturday will
struggle to reach 70 degrees for locations that see rain. This time,
that area encapsulates most of central and Missouri north of I-70 as
well as portions of west-central Illinois. Elsewhere, generally low
to mid-70s are expected.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 154 AM CDT Fri Sep 25 2026

Aside from the chance (20-40%) of light showers continuing into
Sunday morning, next week will start off dry. By Tuesday, a longwave
trough is forecast to be swinging through the Intermountain West.
Discrepancies in guidance begin to build at this point in time, such
as the amount of vorticity lobes that are ejected out ahead of the
system and into the Mid-Mississippi Valley as well as the timing and
strength of warm air and moisture advection associated with it.
Despite this, ensembles are very optimistic regarding our rainfall
chances. Both the NBM and LREF 24 hr probabilities for measurable
precipitation between Tuesday and Wednesday reach 90% in portions of
the area. Although this is washed out given the previously discussed
discrepancies and low model resolution, it does increase confidence
in widespread rain falling during the middle of next week.

Otherwise, the temperature forecast appears to be fairly steady
through next week as warm air advection and cloud cover negate each
other. Highs in the low 70s to low 80s are forecast each day with a
north-south gradient.

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 1222 AM CDT Fri Sep 25 2026

Low ceilings remain the most pressing concern during the 06Z TAF
period. While ceilings lifted to VFR levels at STL/UIN/SUS/CPS this
evening, a shield of MVFR level stratus continues to linger around
COU/JEF. Some brief clearing is possible at the start of the period
at these terminals as well, but overnight and early this morning
MVFR ceilings are expected to move back into local terminals. Skies
should gradually lift to VFR levels by sometime early tomorrow
afternoon, but once again low clouds may linger into evening in some
areas, and confidence in the timing is relatively low.

Otherwise, precipitation chances remain low during this period, but
light showers are expected at COU/JEF just beyond 06Z Saturday.

&&

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

&&

$$

SHORT TERM...Jaja
LONG TERM...Jaja
AVIATION...19