755
FXUS63 KLSX 242304
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
604 PM CDT Fri Apr 24 2026

.KEY MESSAGES...

- The next round of thunderstorms, some of which may be severe,
  comes on Monday.

- Warm spring weather continues through Monday with a cool down
  coming for the rest of next week.


&&

.SHORT TERM...  (Through Late Saturday Night)
Issued at 215 PM CDT Fri Apr 24 2026

Yesterday`s trough has pushed off to the northeast while the remnant
convection has moved southeast into the Midsouth. A weak cold front
has lagged behind the morning thunderstorm complex and is currently
making its way through our forecast area. Winds ahead of the front
are largely southwesterly while behind it they shift to the NNW.
Extensive cloud cover this morning delayed surface heating. There is
some concern that additional showers or thunderstorms may develop
ahead of the front as it continues southeast this afternoon, as some
high resolution guidance suggests. However, the delayed heating may
limit the instability and lack of strong forcing on the front
further limits confidence that this will occur. We`ll maintain some
20 percent POPs for this threat through sunset, but most areas will
remain dry.

Looking upstream we see widespread dewpoints in the 40s across Iowa
and spilling into Missouri. So the air mass behind this front is
considerably drier. Plenty of sun on Saturday will allow the
temperature to warm back into the mid to upper 70s, but the incoming
dry air ensures we get a break from the storms locally... at least
until that moisture returns.

Kimble

&&

.LONG TERM...  (Sunday through Next Friday)
Issued at 215 PM CDT Fri Apr 24 2026

Looking at the bigger picture, a large trough is spinning over the
Canadian Prairies with embedded shortwave troughs rotating around it
like spokes on of wheel. The most recent of these moved off into the
Great Lakes and slid a cold front through our area today. That`s
shutting Gulf moisture down for a time, but as the main forcing is
so far removed from that front it will be slowing and stalling to
our south tonight into Saturday. Westerly flow across the Rockies
establishes lee troughing in the southern High Plains which in turn
triggers southerly return flow to its east. This begins to push the
former cold front back north as a warm front initially over Oklahoma
on Saturday, then further north and east over the coming few days.
So eventually we will see the moisture returning to our region and
along with it the chance for thunderstorms.

The next more potent shortwave trough moves into the Central Rockies
on Sunday, with moisture return across the Plains triggering another
round of afternoon and evening thunderstorms. The focus for this
round will be across Kansas and Nebraska where moisture return with
the warm front occurs beneath the approaching mid level trough.
These storms may form a convective complex which attempts to push
eastward overnight, but storms will be running out of instability as
they outrun the moisture return. Thus the threat for our area is
very limited and focused in the overnight hours. The Day3 outlook
from SPC rightly places the focus to our west with the threat
trailing off as storms push east overnight.

However, as the mid level trough moves east on Sunday it will push
the focus for the next round of thunderstorms more firmly over our
region. Moisture return along the advancing warm front overnight may
trigger an initial round of elevated thunderstorms in the early
morning hours, with some uncertainty as to how long this lingers
into the day. However, The moisture return is quite robust and even
some lingering cloud cover won`t completely eliminate the return of
instability to the region. Among the GEFS and GEPS members, 75
percent produce at least 1000 SBCAPE as far north as St Louis Monday
afternoon, with 60 percent even as far north as Quincy. That`s
plenty of fuel for the next round of storms. With the trough moving
through during peak heating we expect thunderstorm initiation ahead
of an approaching cold front, likely within our forecast area during
the afternoon. With the proximity of the trough aloft there will be
plenty of deep layer shear (40 to 50KT) for storms to organize into
supercells with large hail and damaging winds. Strong low level
shear also suggests tornadoes will be a concern. Some storms forming
into clusters may enhance the damaging wind threat and reduce the
hail threat, but the tornado threat will remain with QLCS features.

While there are plenty of variables to look at to try to decipher
where the GREATEST threat might be Monday afternoon (proximity of
the fronts, locally backing surface winds, orientation of shear to
the boundary, morning convection`s impact on instability, strength
of the eroding cap, etc.), it has become clear that our area will be
at the center of a broad severe weather threat. So while some
details may focus threats locally in spots, overall confidence has
increased for this time frame being the greatest severe weather
threat we`ve seen locally so far this year. The extended SPC outlook
features a 30 percent risk area bullseye over our region, and while
that may not sound like much it`s actually fairly unusual to see
such a high risk so far out in the outlook. While those percentages
are in reference to a 25 mile radius from a point, our confidence in
seeing severe weather in our forecast area is considerably higher
than that.

Monday`s cold front ushers in a trend toward cooler weather that
lasts through the end of the week. That big trough over the Canadian
Prairies expands its influence across the center of the continent to
include our area. There are some embedded waves rotating around the
base of the trough that may bring periodic chances for rain, but
confidence is low on the timing or location of those at this range.
Confidence is higher on the trend toward cooler weather, actually
below normal temperatures headed into the first part of May. How far
below normal is more uncertain as it will depend on how the upper
trough wobbles and the character of the air masses it sends our way.
At the moment, dewpoint forecasts in the 40s suggest lows will stay
above freezing even on the coldest nights.

Kimble

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 602 PM CDT Fri Apr 24 2026

Dry and VFR conditions will prevail through the TAF period.

Jaja

&&

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

$$

WFO LSX