Florissant, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

502
FXUS63 KLSX 120839
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
339 AM CDT Thu Jun 12 2025

.KEY MESSAGES...

- Increased humidity marks the return of showers and a few
  thunderstorms later today that persist through the middle of
  next week. Even in southeast Missouri and southwest Illinois,
  where rain chances are highest, the weekend won`t be a washout.

- After a dip in temperatures this weekend, more seasonable
  warmth returns next week.

&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 339 AM CDT Thu Jun 12 2025

A shield of cirrus clouds continue to stream north into the Mid-
Mississippi Valley per the latest GOES-East Nighttime Microphysics
output, riding weak but persistent moisture transport and
isentropic ascent from the Gulf. Aloft, a sluggish cutoff wave is
evident on GOES-East Mid-Level Water Vapor imagery meandering
north and east from the southern Plains. Along its leading edge,
the southerly flow is further promoting weak moisture and warm air
advection poleward. Cloud cover will only increase through the
day today, sufficiently stunting insolation and keeping
temperatures a few degrees cooler than yesterday. High-resolution
guidance is keying in on a local minimum in low-level moisture lee
of the Ozarks across east-central Missouri into parts of
southwest Illinois today. Along with limited surface heating
today, that will severely hamper instability (and convection)
across most of the region. The highest HREF/REFS probabilities of
at least 500J/kg of SBCAPE are consistently across northeast
Missouri and west-central Illinois, where the highest PoPs
generally are today. Elsewhere, while the southwest flow aloft may
help stimulate a few weak showers, expect plenty of dry time.

Moisture advection continues through the night as the trough
approaches the bi-state, establishing precipitable water values near
the 90th climatological percentile areawide by Friday. Model
soundings continue to depict a favorable thermodynamic environment
for localized downpours, but the kinematics surrounding this system
remain unimpressive to support stronger convection or a more
tangible heavy rain threat. The best threat for locally-heavy rain
tomorrow will exist coincident with a corridor of stronger
integrated water vapor transport in far southeast Missouri and
southwest Illinois, where LPMM output suggests up to 1.50" may fall
locally by late Friday night. Further north and west of here, while
heavy rain won`t be too much of a threat, a weak surface low may
form to stimulate more stratiform rain or weak showers during the
day. I doubt Friday will be a washout, but the chances for more
widespread rain are certainly higher than today.

MRB

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 339 AM CDT Thu Jun 12 2025

Upper-level low and its surface reflection will still influence our
sensible weather to start the weekend. Save for areas in northeast
Missouri, isolated to scattered showers and a few thunderstorms will
result primarily in the afternoon coincident with the diurnal
instability peak. The best chances for rain are once again in our
southeast Missouri and southwest Illinois counties where the
"best" mid-level ascent will reside. That said, the system will be
exiting through the afternoon to the east, and most will see more
dry time than rain with temperatures in the mid-80s. Sadly, it`ll
be one of the muggier days of the year so far with dewpoints
jumping into the low 70s.

Most of the ensemble envelope and deterministic guidance concur that
Sunday will be largely dry with the surface low departing and
heights rising aloft. However, by this point another shortwave takes
aim at the region to threaten additional scattered showers and a few
thunderstorms to start the next work week. This feature will not be
working with as noteworthy moisture as the wave over the weekend,
which will generally limit convective intensity and coverage. This
starts daily chances for scattered showers and thunderstorms, with
the chances peaking in the afternoon along with the diurnal
instability maxima. Deep-layer shear stays largely unimpressive with
the subtropical jet relegated to the northern CONUS, keeping the
threat for stronger thunderstorms very low (5-10%). Temperatures
will be on the rise, however, and currently look to peak on
Wednesday when 850mb temperatures approach the 90th climatological
percentile. This will be our next chance of reaching 90 degrees in
St. Louis and Columbia, MO. It is exceedingly uncommon to not warm
to that temperature this far into a calendar year, but the chances
of ending that streak are fairly high (70-80%).

MRB

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1047 PM CDT Wed Jun 11 2025

VFR conditions continue tonight and into tomorrow. High level
clouds gradually thicken and lower through the day tomorrow. A
stray shower or thunderstorm is possible mainly in central MO on
Thursday, but chances are too low to mention in the TAF at this
point. Clouds may lower to MVFR by late Thursday into Friday
morning from southwest to northeast as moisture continues to
stream into the region.

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