Ballwin, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

441
FXUS63 KLSX 290245
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
945 PM CDT Wed May 28 2025

.KEY MESSAGES...

- Widespread rain is forecast over much of the area on Thursday
  along with temperatures staying in the 60s.

- Warmer air will push temperatures into the 80s Saturday into
  next week.


&&

.SHORT TERM...  (Through Late Thursday Night)
Issued at 347 PM CDT Wed May 28 2025

A few sprinkles or very light rain showers are possible into the
evening given steep low-level lapse rates and a weak midlevel
impulse moving overhead. Otherwise, dry weather is forecast through
much of the overnight hours as temperatures drop back into the 50s.
Very late tonight, the probability of light rain increases into
central Missouri as widespread rain pushes eastward across the KS-MO
border. This area of widespread rain is aided by increasing low-
level moisture convergence, low/mid level frontogenesis, and the
approach of a midlevel shortwave trough. This definitely is more of
a cool season type of system, with a weak surface low passing to our
south and the aforementioned low/mid level frontogenesis. The
widespread rain should move east/southeast through the day,
providing about a 5-7 hour period of light to occasionally moderate
rain for most of the area. The exception could be parts of northeast
Missouri and west-central Illinois which just may miss this round of
rain to the south. There is some spread though on how far north the
steady rain will get, as the NAM spreads steady light rain all the
way to just north of the IA-MO border. This appears to be too far
north, and a consequence of the low-level jet (and associated
moisture convergence) being modeled too strong. This is a known bias
of the NAM.

Total rainfall amounts of 0.25-0.75" are expected, providing some
beneficial rain to parts of the area that missed out the past
several days. Cannot totally rule out a few spots to around 1" as
the LPMM on the HREF suggest, but this likely will be tough to come
by in the absence of any convection. CAMs suggest some convection
and higher rainfall rates may clip parts of southeast Missouri
centered around midday on Thursday. However, even in this scenario,
the longevity looks short so hard to see any widespread totals near
the 1" mark.

Another very cool day for late May standards is on tap given the
widespread rain, low stratus, and light northerly winds. Highs in
the 60s for the most part are expected, with readings staying in the
low 60s while it is raining steadily. These readings would be about
15 degrees below normal for the date, and more typical of early/mid
April than the conclusion of May.

Widespread, mostly stratiform, rain is expected to exit portions of
southeast Missouri and southwest Illinois by late Thursday evening.
There also should be some isolated-widely scattered shower activity
further to the northwest, aided by steep low-level lapse rates and
very cool temperatures aloft beneath the midlevel trough axis. These
showers will try and push southeast with time Thursday night, but
may tend to fade overnight as you lose the steep low-level lapse
rates. Mostly dry weather is then forecast for the remainder of the
night with some decreasing cloudiness from northwest to southeast.
Low temperatures in the 50s are forecast, with the coolest readings
in portions of northeast Missouri which should see at least some
partial clearing late.

Gosselin

&&

.LONG TERM...  (Friday through Next Wednesday)
Issued at 347 PM CDT Wed May 28 2025

(Friday - Friday Night)

Seasonably cool conditions are expected to end the work week as 850-
hPa temperatures stay at or below 10C (~10th percentile of
climatology). Cyclonic flow aloft and model soundings also suggest
quite a bit of cumulus/stratocumulus development, particularly
along/east of the Mississippi River. There may even be some isolated
shower activity in parts of Illinois. Highs are expected to be
mostly in the mid 70s, though some upper 70s may occur in northern
sections of the forecast area as some weak low-level warm air
advection begins. Lows in the  mid 50s to near 60 degrees are
forecast Friday night. Northwest wind speeds should stay up
along/east of the Mississippi River to keep temperatures a bit
warmer than areas further to the west.


(Saturday - Next Wednesday)

Ensemble guidance is in good agreement with the general weather
pattern across the CONUS this weekend, showing anomalous mid/upper
level troughing across the eastern US with strong ridging across the
intermountain west. Our area will be between these two features, but
with dry weather and temperatures closer to seasonal normals likely.
This moderating trend in temperatures will be aided by increasing
low-level warm air advection and rising mid/upper level heights. We
will have to keep an eye on the potential for a backdoor cold front
to move toward the area late Saturday into Sunday. This feature
could have some shower/weak thunderstorm activity along it during
the afternoon/evening hours. Behind it, some slightly cooler air
would also move in. However, there is low certainty that this
boundary will make it into the area at all. If it does, parts of
west central and south-central Illinois would have the best chance.
Highs in the mid 80s are expected each day, though some upper 70s
may be possible in the aforementioned areas if the front does manage
to make it far enough west.

There is high confidence in dry weather and above normal
temperatures early/mid next week as both the EPS/GEFS show good
continuity in the mid/upper level ridge axis moving into the
Mississippi Valley. There are signs that the ridge may begin to
break down and/or shift off more toward the Ohio Valley late in the
period. If this occurs, chances of showers and thunderstorms would
increase.

Gosselin

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 942 PM CDT Wed May 28 2025

A shield of rain is expected to enter central Missouri early
Thursday morning with most locations expected to see rain
throughout the day. MVFR to IFR ceilings will accompany the rain
and persist into Thursday night after the rain has exited. During
the bulk of the rain, MVFR visibilities are likely as well.
Otherwise, surface winds will remain at if not under 5 kts for
most of the TAF period with variable direction.

Jaja

&&

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

$$

WFO LSX