832
FXUS63 KLSX 140350
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1050 PM CDT Fri Jun 13 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms will last into the early
  evening. Locally heavy rainfall could result in an isolated
  instance of flash flooding. Coverage of showers and
  thunderstorms will be lower over the weekend.

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


&&

.SHORT TERM...  (Through Late Saturday Night)
Issued at 143 PM CDT Fri Jun 13 2025

The long advertised cutoff low has finally made it into Missouri and
has resulted in ample cloud coverage, seasonably cool daytime
temperatures, very high humidity, and pockets of showers and a few
thunderstorms across the Mid Mississippi Valley. The most focused
wing of widespread showers moved northward through the region
this morning along a lobe a vorticity on the northeast side of the
low, but now we`re left with more scattered weak convection
closer to the center of the low. This continued support for ascent
coupled with the deep moisture, characterized by precipitable
water values approaching 2 inches, will keep showers in the region
into the evening. We`ll also likely (> 80% chance) see at least a
few thunderstorms this afternoon as modest instability (roughly
1000 J/kg MUCAPE per the HREF) builds into the region. These
storms are not expected to be organized given very weak wind
shear. That said, slow storm motion, very rich moisture, and warm
cloud depths nearing 10kft may still support isolated instances
of heavy rainfall or perhaps flash flooding, but limited storm
organization should also curtail this threat.

Shower and storm coverage will diminish this evening as instability
wanes, though at least isolated showers will linger through the
night due to the modest forcing associated with the low and
persistent rich moisture. The low will be just east of the region
tomorrow, allowing isolated showers and perhaps a thunderstorm or
two linger through tomorrow afternoon, especially across IL and
SE MO as the low slowly departs the area.

BSH

&&

.LONG TERM...  (Sunday through Next Friday)
Issued at 143 PM CDT Fri Jun 13 2025

On Sunday, a shortwave will drop southeastward through the Lower
Missouri River Valley, slowly tracking toward the Lower Ohio River
Valley on Monday. There will be a dearth of moisture between this
shortwave and the departing cutoff low, meaning that we should
actually have a relatively nice summer day on Sunday. Precipitation
chances will pick up on Sunday evening and Monday as the shortwave
skirts to the south of the region, and it`s beginning to look like
Monday might be another dreary day with temperatures a bit below
normal.

Beginning Tuesday and Wednesday, the subtropical jet will drop south
out of Canada, placing the storm track a bit closer to our neck of
the woods. There is a general consensus that another shortwave will
push through the region sometime on Wednesday, bringing yet another
round of precipitation. We`ll have plenty of instability, as is
typical in the summer, but with the jet in the vicinity of the
forecast area, we`ll see modest deep layer wind shear. This
combination of lift, instability, and shear at least opens the
door to a potential for severe weather, highlighted by the day 6
convective outlook from SPC. All that being said, any severe
potential will most certainly hinge on a number of factors that
are unresolvable this far out (e.g., boundary locations, short
wave timing), so we will not be messaging severe weather outside
of this discussion.


BSH

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1048 PM CDT Fri Jun 13 2025

Main issue for the TAFs overnight will be the potential
redevelopment of more widespread IFR ceilings. Most guidance says
this will occur, although I think this is most likely near the
slow moving surface low which will be tracking northeast through
the St Louis metro overnight. Areas that see some clearing will be
more likely to fog in. This scenario is more likely in central
Missouri. Conditions should improve area wide through the day on
Saturday. Some scattered showers and thunderstorms are expected
again during the afternoon, but should for the most part stay east
of the TAF sites.

Kimble

&&

.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