Mehlville, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

097
FXUS63 KLSX 261650
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1150 AM CDT Thu Mar 26 2026

.KEY MESSAGES...

-The potential continues for a few elevated severe thunderstorms
from 9PM-3AM, mainly across northeast Missouri and west-central
Illinois. These storms would be capable mainly of quarter-size hail.

-Elevated fire danger exists across central, east-central, and
southeast Missouri this afternoon.

-After record breaking temperatures today, temperatures will cool
Friday and Saturday before warming into next week.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 310 AM CDT Thu Mar 26 2026

As of 2 AM the mid-level ridge originally across the Desert
Southwest has started to broaden eastward into Texas, causing the
mid-level flow over the mid-Mississippi to flatten. Disturbances
within the quasi-zonal flow will move across the region this
evening, guiding the surface low currently over Colorado/Nebraska
eastward into the Ohio River Valley this afternoon and evening.
Showers and thunderstorms are still expected to form mainly behind
the associated cold front as it drops through the forecast area this
evening. Ahead of the front strong southwesterly low-level flow and
mixing to 850mb is still expected to push high temperatures near
monthly records, into the upper 80s to low 90s across the forecast
area. Confidence is high that daily high temperature records will be
broken, the NBM is indicating a 95% that the daily high temperature
record will be broken at KSTL. The tightening surface pressure
gradient and strong elevated winds will result in a hot and breezy
day across the region. The downsloping flow off the Ozarks will help
warm temperatures and dry dewpoints across central, southeast, and
east-central Missouri a few more degrees than operational guidance
suggested, resulting in elevated fire danger in this area during
the afternoon.

Very little has changed in our thinking with this system
and the severe potential surrounding it. The warm sector remains
very warm and unstable, but with a substantial cap unlikely to break
in the absence of significant mid to upper-level forcing. While
unlikely, if any storms break through the cap and initiate on the
boundary, all hazards are possible though quarter size hail and
damaging winds will be favored. Behind the front elevated
instability up to 2000 J/kg will linger, and the combination of the
frontogenesis and a weak mid-level disturbance are expected to be
enough to kick start convective initiation. A few supercells are
expected to form within the 40-60kts of 0-6 km shear and strong
updraft helicity. The resulting elevated hail threat (up to quarter
size) will exist from largely 9 PM to 3 AM across northwest Missouri
and west-central Illinois (within the Slight Risk). Individual
storms will be moving quickly in the strong easterly shear and are
expected to progress rapidly through the area once they have formed.

The low-level front is expected to weaken beyond 3 AM, bringing an
end to new convection, though any existing storms will be able to
persist. The remaining frontogenesis and mid-level disturbances have
the potential to keep showers and isolated sub-severe thunderstorms
going into Friday morning, though impacts will be relatively
minimal. A surface high will begin moving into the region Friday,
bringing cooler and drier air to the mid-Mississippi Valley. Cloud
cover and cooling behind the front will result in high temperatures
peaking in the 50s Friday, a nearly a 40 degree temperature drop
from today.

Delia

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 310 AM CDT Thu Mar 26 2026

The bulk of the cold air and the center of the surface high will
pass over the region Friday night into Saturday, resulting in the
coldest night of the week with a 40-70% chance of lows below
freezing. Warming will recommence Saturday as the high shifts
eastward and southwesterly low level returns, though the rebound
will be slow at the onset. 850 mb temperatures will return to
similar values as Friday and high temperatures will follow suit,
peaking in the 50s across most of the area.

The mid-level pattern will start to shift over the weekend, becoming
slightly more amplified with a trough over the eastern CONUS and a
ridge over the Intermountain West. Guidance diverges in how to
handle the evolution of these features beyond Sunday. Some sources
bring a weak mid-level trough onshore over the western CONUS as
early as Monday, pushing it east across the Central CONUS, while
other sources delay the onset of the trough a few days and produce a
more amplified pattern. The result is that while warming will
continue into next work week from the persistent southwesterly low
level flow, how warm we get beyond the mid-week period remains
uncertain. The interquartile spread for high temperatures increases
next work week from 8 degrees Monday/Tuesday to 15-20 degrees by the
second half of the week.

In addition to impacting our temperatures, this pattern has the
potential to produce multiple rounds of showers and thunderstorms
across the region, though the lack of consensus in the mid-level
pattern translates to uncertainty in timing and intensity of any
particular system.

Delia

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1141 AM CDT Thu Mar 26 2026

While VFR conditions will start the period, active weather is
expected with gusty southwest winds followed by a sharp cold front
and a round of showers, thunderstorms, and lowering ceilings.

First, breezy southwest winds have developed late this morning,
and this will continue through the afternoon. Beginning just prior
to sunset, a sharp cold front will push through the area, turning
winds very quickly to the north-northeast with increasing speeds
as well. Showers are also expected to begin along and behind the
front, with lowering ceilings. Current data suggests that MVFR
ceilings are increasingly likely in most areas, with lower
confidence at COU/JEF. Also, a few more robust thunderstorms are
also likely behind the front, with the greatest potential for
impacts at UIN, followed closely by St. Louis area terminals. This
potential also exists at COU/JEF, but with lower probabilities
overall.

Low clouds and precipitation are expected to clear early in the
morning, with VFR conditions expected. Wind speeds will also
reduce slightly, but will remain breezy.

BRC

&&

.CLIMATE...
Issued at 310 AM CDT Thu Mar 26 2026

Record Highs on March 26:
St Louis   87 in 1991
Columbia   86 in 1910
Quincy     82 in 1991

All Time March High Temperature Record:
St Louis   92 on March 24, 1929
Columbia   92 on March 21, 1907
Quincy     88 on March 21, 1907


&&

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

$$

WFO LSX