310
FXUS63 KLSX 141945
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
245 PM CDT Sat Jun 14 2025

.KEY MESSAGES...

- There is a low risk (15%) of severe thunderstorms on Wednesday.

- A warming trend into next week will support some highs reaching
  90 degrees, threatening the long run of sub-90 temperatures.

&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 244 PM CDT Sat Jun 14 2025

Showers and isolated thunderstorms have formed this afternoon from
St. Louis and points east and south.  Regional RAP soundings are
showing uncapped narrow soundings on the back side of the upper low
currently seen on water vapor over the western Ohio Valley.  Expect
this activity to die out with the loss of daytime heating this
evening.  Until then, there could be pockets of brief downpours and
a report or two of cold air funnels.

Expect some clearing this evening into the overnight hours, so with
the absence of mixing today, there should be some redevelopment of
the fog tonight.  Confidence is not high in how widespread it will
be, so have just gone with patchy coverage for now.

Tomorrow looks like it will be mainly dry for now as we will be
between the exiting Ohio Valley upper low and another low over the
Plains.   There will be a return of showers and thunderstorms on
Sunday night, particularly across southeast Missouri into southwest
Illinois as a low level jet increases ahead of the approaching upper
low over the Plains.

Britt

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 244 PM CDT Sat Jun 14 2025

The LREF continues to show that the upper low currently over the
central Plains will be slowly migrate east across the Mississippi
Valley Monday into Tuesday. While there will be a chance for showers
and thunderstorms associated with this low, it appears they will be
primarily diurnally driven with the highest chances (30-40%) during
the afternoon.   While MLCAPES will climb into the 500-1500+ J/kg
range each afternoon, deep layer shear will be relative weak (15-25
knots) limiting the potential for severe thunderstorms.

A better chance for showers and thunderstorms will arrive by
Wednesday and Wednesday night when the next trough will move from
the Plains into the Midwest.  This system will have more forcing to
work with with the 50-70% of the LREF members producing rain
Wednesday and Wednesday evening.  While there are differences in
timing and strength in the trough seen in the deterministic models,
machine learning guidance continues to point to some low chance
(15%) for severe thunderstorms with this system.

Guidance continues to favor warming temperatures next week, with
highs mainly in the middle to upper 80s early next week. The NBM
50th percentile at STL reaches 90 degrees as soon as Tuesday and
over most of the CWA by late in the week as a large upper ridge
builds into the area.

Britt

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1235 PM CDT Sat Jun 14 2025

Isolated showers and thunderstorms are expected to remain mainly
east of the terminals this afternoon. I have added a PROB30 group
for showers for the first 2 hours at CPS as it will be the most
likely airport to see any shower activity. Otherwise I do expect
remaining ceilings to lift to VFR this afternoon. The clouds may
clear out of the area tonight and if they do, fog may redevelop
over the area between 09-13Z with MVFR, possible IFR visibilities.
I have included MVFR fog at all of the river locations and UIN
which had fog this morning. Winds will remain light through the
period.

Britt

&&

.CLIMATE...
Issued at 620 PM CDT Wed Jun 11 2025

St Louis still hasn`t reached 90 yet in 2025. This puts 2025 in
the Top 20 all time latest dates of the first 90 degree
temperature, and the latest in at least 30 years (Jun 19, 1995).
The all time latest first 90 degrees was July 4 in both 1961 and
1912. Records began in St Louis in 1874.

Columbia has also not yet seen a 90 degree reading in 2025. The
latest date of first 90 degrees on record was July 14, 1904.
Records began in Columbia in 1890.

Quincy reached 90 degrees on May 15 of this year.

Based on the current forecast, our next best chance to see 90
degrees is around June 17.

Kimble


&&

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

$$

WFO LSX