839
FXUS63 KLSX 302325
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
625 PM CDT Sat May 30 2026

.KEY MESSAGES...

- Additional rounds of showers and thunderstorms are forecast through
  Monday, but confidence is low on the specifics (timing, areas
  impacted) with respect to each round.

- Dry weather is forecast Tuesday through Thursday along with near
  normal temperatures.


&&

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 250 PM CDT Sat May 30 2026

Morning showers and thunderstorms that managed to stay tied to a
cold pool have propagated eastward through much of central
Missouri over the past few hours. Similar to yesterday, they have
been highly efficient rainfall producers with highly anomalous
precipitable water values (>1.7"; ~99th percentile), deep warm
cloud depths, and low echo centroids. Downstream, more diurnal
activity has begun as daytime instability climbs. This should be
mainly scattered in nature, though there may be pockets of more
widespread showers and thunderstorms across parts of east
central/northeast Missouri downstream of an MCV that was evident
on local radar reflectivity exiting central Missouri.

Similar to yesterday, the expectation is for activity to lessen in
coverage and strength through the evening hours as daytime
instability wanes. The late evening/early overnight hours are
largely expected to be dry, but we will be watching widespread
thunderstorms in east/northeast Kansas. This activity is forecast to
largely progress to the east/northeast with the mid/upper level
flow. However, the low-level jet does veer about 20-30 degrees late
tonight, which could help initiate additional thunderstorms further
to the south and west. The best chance (40-60%) of showers and
thunderstorms is across central Missouri northeast into west-central
Illinois from about daybreak through the mid morning hours. Similar
to today, I would expect activity to percolate through the morning
hours, with areas/segments that are able to stay closely tied to
their respective cold pools. Locally heavy rainfall may be a threat
once again, though the propensity for storms to have some forward
propagation and slightly less anomalous precipitable water values
suggest a lesser threat compared to the past couple of days.

Uncertainty increases for the afternoon hours in terms of whether or
not we see any additional convective initiation (CI). There is a lot
working against CI, with rising mid/upper level heights behind an
earlier midlevel shortwave trough and morning/ongoing activity
helping to lessen instability. There may be some surface convergence
somewhere in/near our western counties that could be just strong
enough to help develop a few thunderstorms, but this is a relatively
low probability (~20%). There will be more flow aloft Sunday
afternoon (30-35 knots) so IF we can get CI in the afternoon, there
would be a threat for a strong-severe thunderstorm or two. Hail up
to the size of quarters would be possible in any transient
supercell, with damaging winds possible as well.

Temperature wise, Sunday will be a challenge. While widespread low
to mid 80s are forecast, I have little doubt that some areas will
struggle to get into the upper 70s due to clouds/rain. Exactly where
(and how widespread) that will occur however even 24 hours out is
very difficult.


Gosselin

&&

.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 250 PM CDT Sat May 30 2026

(Sunday Night - Monday)

Another round of showers and thunderstorms is expected late Sunday
night into Monday morning on the nose of a 20-30 knot low-level jet
and downstream of a midlevel shortwave trough. Similar to late
tonight/Sunday morning`s round, there is uncertainty with the
track/timing of these storms. The general consensus though is for
storms to move east/southeast out of northeast/central Missouri
through at least portions of the area. This activity may weaken with
time as the low-level moisture convergence weakens. Additional
showers and thunderstorms seem unlikely to develop given rising
mid/upper level heights. There is enough midlevel flow though to
watch for the possibility of CI as there could be a couple of strong-
severe thunderstorms IF any storms that do develop. Subtle areas of
surface convergence (maybe remnant outflow?) look to be the only
potential forcing to help initiate storms, but sometimes that is
just enough.


(Monday Night - Next Saturday)

There remains high confidence in a dry period behind a backdoor cold
cold front Monday night through Thursday. The incoming air mass has
trended slightly stronger over the past 24-48 hours (i.e., cooler
and drier). The surface anticyclone on Wednesday across the Great
Lakes is forecast to be near 1026 hPa, or near the 99th percentile
of climatology. Temperatures at 850 hPa drop to near +10 to +14C
from east to west, or about 1-3C below normal. Another air mass
indication is surface dewpoints, and they are forecast to drop into
the upper 40s to mid 50s. These values would be roughly between the
10th and 25th percentile for early June. There also should not be
much in the way of clouds through midweek, so slightly below normal
lows and near normal highs are generally expected with light
easterly winds south of the aforementioned surface anticyclone.

Temperatures are expected to moderate late in the work week as low-
level flow turns out of the southwest. There are also signs that a
midlevel shortwave trough may approach the Great Lakes Friday into
next Saturday, which could bring a cold front along with a chance of
showers and thunderstorms back into our region.


Gosselin

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 618 PM CDT Sat May 30 2026

Showers and thunderstorms are rapidly diminishing across the
region, with mostly dry conditions expected through at least the
early overnight hours. Showers and thunderstorms currently over
central Kansas will eventually make their way into central
Missouri early to mid-morning, but confidence in their specific
timing is low. The current forecast at KCOU and KJEF is when
probabilities peak, but the window for impacts may be shifted a
couple of hours earlier or later. Confidence is then even lower
with how far eastward these showers and storms get; therefore,
impacts have been left out of the KUIN, KSUS, KSTL, and KCPS TAFs
for now. With all of the rainfall today, another round of fog
can`t be ruled out across portions of the area, but confidence is
currently low in its formation. Trends through this evening will
build confidence in this outcome, with a more confident yes/no
forecast expected by the 06z TAFs.

Elmore

&&

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

$$

WFO LSX