Ballwin, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

814
FXUS63 KLSX 141951
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
251 PM CDT Sun Jun 14 2026

.KEY MESSAGES...

- Seasonably cool and dry conditions will continue through Monday
  night.

- Chances of showers and thunderstorms return to the area on
  Tuesday, with the best chances Wednesday - Thursday.


&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 246 PM CDT Sun Jun 14 2026

Cooler and less humid air continues to move into the region from
the northwest behind the cold front from early this morning. The
strong (~1020 hPa; >90th percentile) surface ridge axis is
currently moving toward the Missouri Valley and will continue to
slide eastward through Monday. Plenty of clear skies, light winds,
and continued dry/seasonably cool weather will continue as a
result. Lows tonight are forecast to be in the 50s, with coolest
locations potentially flirting with the 50 degree mark. Favored
river valleys across central, east central, and southeast Missouri
would be the spots to potentially see these lows. For Monday
afternoon, highs are expected to reach into the mid to upper 70s,
or about 10 degrees below normal for the date.


Gosselin

&&

.LONG TERM...  (Monday Night through Next Sunday)
Issued at 246 PM CDT Sun Jun 14 2026

(Monday Night - Thursday)

Return flow will begin late Monday night as the surface ridge moves
into the Ohio Valley. The combination of light southerly surface
winds and increasing mid/high clouds should lead to a bit of a
milder night with lows closer to 60 degrees.

A midlevel disturbance is expected to quickly move across the Upper
Midwest early Tuesday, with a surface low to its east and an
attendant cold front draped to its southwest. This boundary will
move across the mid-Mississippi Valley during the day, but we are
not expecting too much in the way of impacts. Some scattered showers
and a few rumbles of thunder are possible, mainly in west central
and south-central Illinois where the surface convergence will be
slightly stronger.

The main focus continues to be on the second system Wednesday into
Thursday. There is still considerable spread with respect to several
aspects of this system, including the surface low track. The GEFS
has a low track through eastern Iowa late Wednesday whereas the
EPS mean is about 150-200 miles farther north across western
Wisconsin. Those latitudinal differences do not show up with
respect to the midlevel impulse however, and given the track of
that feature on both the GEFS/EPS through the Upper Midwest, it
would seem to favor the EPS surface low track more than the GEFS.
The surface low track is important (especially for our northern
counties) as a track farther south (north) likely would mean more
backed (veered) surface winds and more (less) low-level cyclonic
hodograph curvature. In other words, the tornado threat would be
higher in northeast Missouri/west central Illinois if the GEFS
surface low track ends up being correct compared to the EPS.
Surface moisture return and midlevel lapse rates also vary
substantially among ensemble membership. The inter-quartile range
for SBCAPE 0Z Thursday is still near or just above 1500 J/kg in
northeast Missouri/west central Illinois on the GEFS/GEPS. Yet
another thing to watch (as almost always) is nocturnal convection
late Tuesday night into Wednesday morning. Model guidance is
suggesting widespread convection/possible MCS somewhere near the
Missouri-Iowa border. These storms should tend to move
east/southeast close to the forward-propagating Corfidi vectors
and could impact parts of northeast Missouri/west central
Illinois. These storms should tend to be elevated through early
Wednesday morning, with marginally severe hail possible. With
time, storms should become more surface based and may tend to
strengthen as diurnal instability climbs. The threat for damaging
winds should in turn ramp up, though this is more likely to focus
across eastern Illinois as it looks right now. The timing and
track of these storms may impact things during the afternoon, but
any impacts this far out are highly uncertain. The low-level jet
does not weaken at all, so there is the possibility at least of
continued renewed convective initiation on the nose of the
southwesterly low-level jet. In that scenario, renewed convection
could really limit instability later in the afternoon/evening.
However, there is the other extreme as well. Early morning
convection could depart and leave an outflow boundary draped
across northeast Missouri/west central Illinois, which would
increase the risk of tornadoes. Speaking of threats, it does seem
probable that supercells would be favored to develop along/near
the trailing cold front during the afternoon/early evening hours.
Where this occurs initially and the coverage is usually dictated
by where the surface convergence is strongest. One area is likely
to be near/just east of the track of the surface low. Even in the
GEFS solution which is further south, most of these supercells
should stay to our north and east. A second favored area may be
eastern Kansas/far western Missouri. Similar to last week`s
systems, that could lead mean our area is between two regions
where CI is most favored. That doesn`t necessarily mean the threat
for severe weather is low by any means, but could mean that there
could be more focused areas of severe weather which may miss us.
With any supercell thunderstorms that do develop during the
afternoon/early evening hours, large hail and tornadoes would be
the main threats. Unlike the past couple of events, the deep-layer
shear vector though is more parallel to the orientation of the
cold front. Therefore, upscale growth (especially considering the
strong mid/upper level forcing) should be pretty rapid. Damaging
winds would be the main threat later on in the evening as storms
head southeast. QLCS mesovortex tornadoes may also be possible,
but less so late evening onward as the 0-3 km shear magnitudes
decrease with vectors likely parallel to the boundary.
Thunderstorms may tend to weaken quickly toward midnight as
diurnal instability wanes and storms enter a region with less
effective shear.


(Thursday Night - Next Sunday)

Cooler temperatures will move back in behind Wednesday
night/Thursday`s cold front. Readings should drop back to near or
slightly below normal values for the middle of June. Dry weather is
also favored for the most part through Saturday, but chances of
showers and thunderstorms do return to end next weekend as another
midlevel disturbance comes across the Upper Midwest embedded within
northwest flow aloft.


Gosselin

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1221 PM CDT Sun Jun 14 2026

Dry/VFR conditions are expected with northwest winds through the
day. These winds should slacken by evening before becoming
light/variable tonight.

Gosselin

&&

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

$$

WFO LSX