University City, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

107
FXUS63 KLSX 271720
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1220 PM CDT Fri Jun 27 2025

.KEY MESSAGES...

- Multiple rounds of showers and thunderstorms are expected through
  Monday.

- Showers and thunderstorms are expected to take a slight edge
  off the heat through the weekend, with more seasonable
  temperatures expected starting Monday through much of the
  upcoming workweek.


&&

.SHORT TERM... (Through Sunday Night)
Issued at 317 AM CDT Fri Jun 27 2025

The axis of the upper-level ridge responsible for our recent heat
continues to shift eastward as a weak shortwave moves through the
Upper Midwest per recent water vapor imagery. These features have
the Middle Mississippi Valley beneath southwesterly flow aloft
with embedded disturbances rippling overhead. Such disturbances
are responsible for convection stretching from central Missouri
northeastward into west-central Illinois, which is being fed by a
weak low-level jet. As the jet and main thrust of the shortwave
move northeastward through the remainder of the morning, shower
and thunderstorm chances will gradually diminish.

While a lull in convection is expected later this morning into the
early afternoon, outflow from this morning`s convection will serve
as a focus for another round of scattered showers and thunderstorms
this afternoon and early evening roughly along and south of I-70.
Then, temperatures warming to around 90 degrees and and dew points
in the low 70s will elide SBCAPE of 2,000-2,500 J/kg across
southern portions of the CWA per the 00z HREF mean, leading to
robust updraft potential. However, deep layer shear of
approximately 20 kts will limit updraft strength and organization.
For taller updrafts, there will be a low chance for downbursts as
the updrafts collapse given PWATs around 1.9" and inverted V
soundings. Convective coverage and intensity will diminish during
the evening as instability wanes with the setting sun.

While this afternoon will once again be hot and muggy, the outflow
and convective debris is still expected to take the edge off the
heat relative to the past week. Portions of southeastern Missouri
and southwestern Illinois have the greatest potential of being
unimpacted by the outflow and convective debris prior to peak
heating, and it is here where heat index values have a low chance of
reaching 100 degrees this afternoon.

Saturday through Sunday, the upper-level ridge remains relatively
subdued as additional disturbances pass through the central Midwest,
leading to daily chances of scattered convection. The potential for
convection and associated cloud cover, paired with slightly cooler
mid-level temperatures, keeps confidence in Heat Advisory criteria
heat index values low through Sunday. Sunday evening into the
overnight hours, guidance consensus is that a cold front will drop
southward into the Middle Mississippi Valley ahead of a digging
trough. This front will serve as the greatest chance (60-70%) for
showers and thunderstorms for the weekend, and these chances will
likely rise and become increasingly temporally confined once
there is a better consensus on frontal timing. Regardless of the
exact timing, this front will mark the end of this prolonged
stretch of heat that we`ve been experiencing lately.

Elmore

&&

.LONG TERM... (Monday through Thursday)
Issued at 317 AM CDT Fri Jun 27 2025

At the start of the workweek on Monday, guidance consensus is that
an upper-level trough will be digging into the Midwest, pushing
Sunday night`s cold front somewhere across southeastern Missouri and
southwestern Illinois or perhaps even further southward. The
front will serve as the focus for additional convection on Monday
as the trough pivots east-southeastward, though with the
uncertainty in frontal positioning, where this focus for
convection is remains uncertain. Currently, southeastern Missouri
and southwestern Illinois have the best probabilities (60-70%) of
seeing showers and thunderstorms.

In the wake upper-level trough, northwesterly flow will set up over
the Middle Mississippi Valley Tuesday, pushing the cold front
southward away from the region. In the front`s wake, a more
seasonable airmass will settle into the area for much of the
upcoming workweek, with ensemble means clustering around highs in
the upper 80s to around 90 degrees and lows in the mid to upper 60s.
How long this period of seasonable temperatures last through the end
of the week into the holiday weekend is uncertain, as guidance shows
varying phasing of an upper-level ridge building into the Midwest.
Ensemble low-level temperatures respond by increasing in spread: The
25th percentile of ensemble guidance keeps temperatures similar to a
couple degrees warmer than values forecast for the week, while the
75th percentile supports temperatures returning to the low to mid
90s. The current forecast/NBM favors the warmer side of the spread,
which seems reasonable given a majority of ensemble guidance
favoring some degree of ridging building into the region Friday
onward.

Elmore

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1220 PM CDT Fri Jun 27 2025

Main concern for the TAFs is the potential for thunderstorms in
the near term. This threat is greatest in the St Louis metro and
central Missouri locations over the next 4 hours or so. These
storms are diurnally generated, so they will dissipate fairly
quickly this evening. Additional storms are expected to develop on
Saturday, but the axis of development is expected to be further
south, with a much less chance of affecting any TAF location.

Kimble

&&

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

$$

WFO LSX