University City, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

471
FXUS63 KLSX 101032
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
532 AM CDT Tue Jun 10 2025

.KEY MESSAGES...

- Other than a gradual warming trend through the week, which may
  bring parts of the area to 90 degrees for the first time this
  year, our sensible weather remains welcomingly tranquil through
  at least early Thursday.

- Unsettled, showery conditions return late Thursday through the
  weekend, with confidence still fairly low on timing and exact
  amounts. That said, there is little pointing to any noteworthy
  hazards beyond thunderstorms.

&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 348 AM CDT Tue Jun 10 2025

In the wake of a dry cold frontal passage yesterday, something not
often seen in this area in June, weak and nebulous high surface
pressure is settled over the bi-state region. Weak but present
northwest flow aloft is promoting a dry, seasonably cool airmass
that will make for fairly comfortable mid-June weather today. The
only fly in the ointment will be some high-level smoke from ongoing
Canadian wildfires, but they won`t do much more than make the sky
just a tad hazy aloft. Otherwise, temperatures will top out in the
upper 70s to low 80s today with comfortable humidity.

Winds gradually back this evening and become more southerly as the
surface ridge shifts east, drawing warm, moist air poleward. The
resultant increased, albeit weak, warm air advection will bolster
overnight lows 5-10 degrees warmer than last night`s. The warmup
continues into the day on Wednesday, but most deterministic guidance
shows a weakening in the warm advection with the approach of a broad
mid-level wave during the late morning/early afternoon. That, plus
the approach of high cirrus during this same time, throws doubt on
whether St. Louis sees its first 90 degree day this year (see the
Climate section at the bottom of this discussion). Regardless, it`ll
be a more summerlike day across the region Wednesday, kicking off
several days of near to above-normal temperatures. Between weakened
WAA and nebulous forcing/lift, Wednesday will almost certainly stay
dry.

MRB

&&

.LONG TERM...  (Wednesday Night through Monday)
Issued at 348 AM CDT Tue Jun 10 2025

Amidst broader, longwave ridging aloft spanning the CONUS, the
aforementioned mid-level closed low meanders into the Mid-
Mississippi Valley Thursday morning. The speed, position, and
structure of this feature still vary among the ensemble guidance
membership, which will impact the coverage and timing of showers and
a few thunderstorms late Thursday into Friday. Regardless, this
amplification in the flow will further promote increased Gulf
moisture advection into the region, with NAEFS guidance showing
precipitable water values approaching the 90th climatological
percentile. With the increased moisture and trough aloft, diurnally-
driven maxima in instability is likely to result in disorganized
waves of showers and thunderstorms in the region through the
weekend.

Fortunately, the subtropical jet relegated to the northern tier of
the CONUS on the periphery of the longwave ridge, and winds
throughout the column struggle to exceed 20-30kts in all available
guidance. As a result, organized strong to severe convection is very
unlikely. While I can`t rule out pulse convection resulting in a
localized damaging wind threat in this setup, that is a worst-case
scenario. What is more likely to occur is pockets of locally-heavy
rain, especially in the absence of any appreciable steering flow.
Finally, with respect to temperatures, the low aloft and resultant
clouds/convection will work to very marginally subdue temperatures.
This trend is evident in the NBM maximum temperature distribution,
which dips a bit on Friday and through the weekend. That said, most
of the ensemble envelope is at least near-normal, so showing that
this system`s effect on temperatures is likely to be minimal.

There is as much uncertainty surrounding this wave`s exit than there
is its arrival, but a preponderance of guidance passes the trough
axis through the region by Sunday evening. While this ends the more
sporadic showery activity associated with the sluggish upper-level
low, the flow appears to turn quasi-zonal and remains somewhat
unsettled as a result. The NBM holds onto persistent, low chances
for showers and thunderstorms through early next week which matches
the large-scale setup. A few deterministic models do show more
amplified shortwaves glancing the northern fringes of the Lower
Midwest, which would promote a threat for stronger convection, but
none really stand out as threatening to us locally.

MRB

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 531 AM CDT Tue Jun 10 2025

Dry VFR conditions will prevail amidst light, generally westerly
winds through the valid TAF period.

MRB

&&

.CLIMATE...
Issued at 348 AM CDT Tue Jun 10 2025

St Louis has still not seen 90 degrees yet in 2025. The average
first 90 degree reading is May 20. The most recent late 90-degree
start was June 10, 2021. With 90 degrees being highly unlikely
today (June 10), this is the latest first 90 degree day since at
least 1995 (June 19). The latest date of first 90 degrees on
record was July 4 in both 1961 and 1912.

Columbia has also not yet seen a 90 degree reading in 2025, however
the average first date is much later (May 31). The latest date of
first 90 degrees on record was July 14, 1904.

Quincy reached 90 degrees on May 15 of this year, about 3 weeks
earlier than their average first 90 degrees (June 2).

Kimble/MRB


&&

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

$$

WFO LSX