085
FXUS63 KLSX 080740
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
240 AM CDT Fri May 8 2026

.KEY MESSAGES...

- Widespread showers and scattered thunderstorms are expected this afternoon
  and evening. A few stronger storms may produce small hail
  and/or gusty winds.

- After a warmer Saturday, a cold front brings another chance (20-
  40%) of rain along with a return to cooler weather behind the
  front.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 239 AM CDT Fri May 8 2026

A weak Pacific "cool" front is currently located from
west/southwest to east/northeast across the mid-Missouri into the
Upper Mississippi Valleys early this morning. This boundary is
expected to continue to slowly progress equatorward during the day
today, reaching into northern sections of the CWA by late
morning. Chances of showers will increase in the vicinity of this
boundary as low-level moisture convergence strengthens and a
midlevel trough axis approaches from the west. With time, the
shower activity should become more widespread as large scale
forcing for ascent maximizes across the bi- state region.
Thunderstorm chances also increase diurnally, with scattered
thunderstorms forecast for the afternoon/very early evening hours.
Strong west/northwesterly flow aloft is expected to yield plenty
of deep-layer shear, but weak midlevel lapse rates and relatively
dry air at the surface (dewpoints in the 50s) both portend to
weaker overall instability. Model soundings back this assertion
up, with mainly tall/thin CAPE profiles with a vast majority of
the CAPE below the hail-growth zone. The latest HREF also
highlights this limited instability, with probabilities for >750
J/kg of SBCAPE only in the 20-50% range centered on central
Missouri. Therefore, the chances for any semblance of organized
severe weather continues to look quite low. A stronger
thunderstorm or two may be possible in/near central Missouri. If
any stronger storms do manage to form, small hail and gusty winds
would be the main threats between roughly 3 and 8 PM.

Rain chances cease closer to midnight across parts of southeast
Missouri and southwest Illinois as the midlevel shortwave trough
pushes east into the Ohio Valley. A decrease in cloudiness is
expected overnight, allowing for at least partial clearing. Light
winds along with this partial clearing should allow for temperatures
to drop back into the upper 40s to low 50s, or right near normal for
early/mid May.

Saturday should be at least slightly warmer than this afternoon, as
low-level winds veer back to the west/southwest. High temperatures
should flirt with or just break the 80 degree. For many locations,
Saturday`s highs will be the warmest day so far this month.


Gosselin

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 239 AM CDT Fri May 8 2026

(Saturday Night - Sunday)

Another cold front is forecast to approach northeast Missouri and
west-central Illinois early Saturday evening. Unlike its
predecessor, this is certainly not a Pacific front, but one with a
real air mass change in its wake. A chance (20-40%) of showers (and
possibly a rumble or two of thunder) will accompany this front
Saturday night into Sunday morning from north to south. However,
this front looks more like an anafront, where most if not all of the
precipitation is post frontal. Lingering rain shower activity behind
the front is also supported by low-mid level frontogenesis.

Much cooler temperatures are in store areawide for Sunday, but
exactly how much cooler is the question mark. As always deep into
the warm season, how cool usually depends on clouds and rain. Model
guidance differs in how fast the lower clouds and rain exits from
north to south. In the slower scenario, some parts of the CWA may
struggle to get much above 60 degrees. Whereas in the faster
scenario where lower clouds exit earlier in the day, highs in the
low 70s are possible. At this time, the official forecast blends
these 2 scenarios with highs mostly in the 60s. The LREF would
support at least slightly cooler highs than forecast, depicting
probabilities for highs below 70 degrees at or above 90% along/north
of I-44 in Missouri and I-70 in Illinois. Chances for highs below 65
degrees are also pretty respectable, with a maximum of 40-60% just
north of the I-70 corridor. Given all of this, I would not be
surprised to see forecast highs tick down a couple of degrees or so
over the next 24-36 hours.


(Sunday Night - Monday Night)

A period of dry and seasonably cool weather is expected into early
next week as a strong (1022+ hPa; >90th percentile of climatology)
surface high moves across the mid-Mississippi Valley. Sunday
night/Monday morning should be the cooler of the two nights due to
the timing of the aforementioned surface high. Lows in the low to
mid 40s are expected, and I would not be surprised to see some
typical cool spots in the upper 30s given dewpoints in the mid 30s.
Monday`s highs are forecast to range from the mid 60s to low 70s
from east to west, or about 2-5 degrees below normal for the date.


(Tuesday - Thursday)

A warming trend is expected on Tuesday ahead of an approaching
midlevel shortwave trough and an associated cold front. There have
been noticeable changes with respect to this trough and the air mass
behind its cold front. Notably, the midlevel trough has trended
deeper and further west, moreso over the Upper Midwest instead of
the Great Lakes. That in turn has led to a substantial shift toward
a return to below normal temperatures Wednesday into Thursday. Mean
temperatures at 850 hPa from the LREF have cooled 6+C over the past
48 hours. This trend has been consistent across both the GEFS/EPS,
though the EPS remains quite a bit cooler than the GEFS for this
period. If the cooler trends continue though, both high and low
temperatures may need to come down several degrees from currently
forecast. For reference, the current highs from the NBM both
Wednesday and Thursday are warmer than nearly every other model
blend and individual deterministic models.


Gosselin

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1020 PM CDT Thu May 7 2026

Mainly dry and VFR conditions are expected through 12Z. Then there
will be an increasing (40-60%) chance of showers over northeast
Missouri and west central Illinois by late Friday morning
including at UIN where I have included a TEMPO group between
17-21Z. A better (70-90%) chance for showers and a few
thunderstorms will affect central Missouri including at COU/JEF
where I have included a FM group starting at 19Z with a PROB30
group for TS. Farther east the showers and thunderstorms won`t
move into the St. Louis area terminals until mid to late afternoon
when I have stared the FM/PROB30 groups for showers and
thunderstorms. Any of the heavier showers and thunderstorms will
be capable of producing MVFR/possible IFR ceilings and
visibilities in heavy downpours with best chance for any hail or
wind gusts over 35 knots on Friday afternoon and evening at
COU/JEF. Improving conditions are expected on Friday evening when
dry and VFR conditions are expected.


Britt

&&

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

$$

WFO LSX