831
FXUS63 KLSX 300348
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1048 PM CDT Fri May 29 2026

.KEY MESSAGES...

- Chances of showers and thunderstorms (30-60%) continue through
  Monday, mainly across central and southeast Missouri.

- Dry weather is favored for the rest of next week along with near
  normal temperatures.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 226 PM CDT Fri May 29 2026

Scattered showers and thunderstorms have continued through much
of the day across portions of central/southeast Missouri. This is
in an area of modest instability (~500 J/kg SBCAPE per SPC
mesoanalysis) ahead of a weak midlevel impulse. This activity has
been mainly along/west of an old backdoor "cold" front that
manifests itself now moreso in a dewpoint/instability gradient.
The main impact from these storms is high rainfall rates and
intermittent lightning. Hourly rainfall rates of 1 to as much as
2"/hr have been observed, with instantaneous rates as high as
4+"/hr. The atmosphere is definitely conducive to efficient
rainfall rates, with observed precipitable water values near 1.8"
(>99th percentile) and deep warm cloud depths. As instability
decreases this evening, the coverage of showers and thunderstorms
should take a downturn. Weak low-level moisture convergence
however does keep the threat for isolated to widely scattered
showers (and possibly a rumble of thunder) overnight tonight.
Similar to this afternoon, most if not all of these showers should
be confined to central/southeast Missouri with dry weather
favored farther to the northeast.

There is very little change in the overall weather pattern
heading into the weekend with light easterly flow at the surface
and a east/northeast to west/southwest dewpoint/instability
gradient. Scattered showers and thunderstorms are once again
expected on Saturday, mainly in central/southeast Missouri with
the highest coverage peaking in the afternoon hours when diurnal
instability is maximized. While there are no major differences
when looking at tomorrow compared to today, there are some subtle
changes. There is not a midlevel impulse moving through the
region, so there should be lesser coverage of showers/storms
compared to today. In addition, there are slightly lower
precipitable water values expected. This combination portends to a
lesser threat for locally heavy rainfall.


Gosselin

&&

.LONG TERM...  (Saturday Night through Next Friday)
Issued at 226 PM CDT Fri May 29 2026

(Saturday Night - Monday)

Forecast uncertainty increases Saturday night into Sunday.
Deterministic guidance depicts another midlevel shortwave trough
moving through the mid-Mississippi Valley, but vary with the
timing/track of this feature. Chances of showers and thunderstorms
should increase ahead of the aforementioned trough sometime between
Saturday night and Sunday afternoon. The timing of this feature is
also key because there will be 25-30+ knots of flow ahead/to the
southeast of this feature. That is enough deep-layer shear to
potentially help yield some multicell clusters capable of damaging
winds and/or hail up to the size of 1" IF it comes through during
the afternoon hours.

Chances of showers and thunderstorms continue through Monday, with
the best chances (30-60%) west of the Mississippi River. This is
where higher surface dewpoints/instability will reside, with
locations further east feeling more influence from the relative dry
easterly flow (coming across the Great Lakes).


(Monday Night - Next Friday)

Ensemble guidance is in good agreement showing an overall
amplification of the upper air pattern across the CONUS early next
week. As deeper troughing carves out across the Great Lakes/eastern
US, more substantial drier (and probably slightly cooler) air
should advect in from east to west and overspread the entire
region. There is high confidence in a drier pattern with
seasonably low dewpoints (~25th percentile), though how much
cooler is still uncertain. Two of the four clusters (53% of LREF
members) of the 500-hPa pattern show a deeper midlevel trough
located further southwest. In that solution, slightly cooler
highs than forecast may occur. If the weaker/further east solution
verifies, temperatures would tend to be at or even a bit above
normal for early June. Regardless, the expectation is for lows at
least back closer to normal, if not slightly below normal, due to
less cloud cover and the aforementioned lower dewpoints.


Gosselin

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1038 PM CDT Fri May 29 2026

KCOU and KJEF have the greatest chance of seeing impacts through
the TAF period. Ample low-level moisture thanks to repeated rounds
of showers and thunderstorms across central Missouri on Friday has
increased the potential for fog. Confidence is low on where the
worst of the fog will form, and there is a low chance for IFR
visibilities at KCOU and KJEF. Any fog that develops will
dissipate after sunrise, but our attention then turns to the
potential for showers and thunderstorms at KCOU and KJEF. Direct
impacts are uncertain, and while the current forecast calls for
afternoon timing, showers and thunderstorms could move over these
terminals during the late morning and/or early evening.

As for KUIN, KSUS, KSTL, and KCPS, confidence is high that VFR
flight conditions will prevail through a majority of the TAF
period. There is a very low chance that showers impact KSUS, KSTL
and/or KCPS during the afternoon, and whether or not they do so
won`t be clear until mid to late morning.

Elmore

&&

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

$$

WFO LSX