Severe Thunderstorm Warning 254, NWS St. Louis, MO

551 
WWUS53 KLSX 160111
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
811 PM CDT Tue Sep 15 2026

MOC137-160145-
/O.CON.KLSX.SV.W.0254.000000T0000Z-260916T0145Z/
Monroe MO-
811 PM CDT Tue Sep 15 2026

...SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 845 PM CDT FOR
NORTH CENTRAL MONROE COUNTY IN NORTHEASTERN MISSOURI...

At 811 PM CDT, a severe thunderstorm was located over Granville, or 6
miles north of Paris, moving east at 25 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to
         roofs, siding, and trees.

Locations impacted include...
  Granville and Stoutsville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter inside a well-built structure and stay away from
windows. This storm is capable of producing damaging winds and large
hail.

&&

LAT...LON 3952 9213 3963 9213 3966 9187 3966 9186
      3949 9186
TIME...MOT...LOC 0054Z 270DEG 20KT 3956 9218

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Pfahler

791 
WWUS53 KLSX 160121
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
821 PM CDT Tue Sep 15 2026

MOC137-160131-
/O.CAN.KLSX.SV.W.0254.000000T0000Z-260916T0145Z/
Monroe MO-
821 PM CDT Tue Sep 15 2026

...SEVERE THUNDERSTORM WARNING IS CANCELLED FOR NORTH CENTRAL MONROE
COUNTY IN NORTHEASTERN MISSOURI...

The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been cancelled.

&&

LAT...LON 3952 9213 3963 9213 3966 9187 3966 9186
      3949 9186
TIME...MOT...LOC 0111Z 270DEG 20KT 3956 9205

$$

Pfahler

Area Forecast Discussion
National Weather Service St Louis MO
653 PM CDT Tue Sep 15 2026

.KEY MESSAGES...

- A late season heat wave with peak heat index values of
  100-105F+ will continue through at least Friday along/south
  of I-70.

- Widespread showers and thunderstorms are forecast tonight,
  mainly across northeast Missouri and west-central Illinois
  where locally heavy rainfall is possible. A few may also be
  strong to severe with damaging winds the main threat through
  this evening.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 240 PM CDT Tue Sep 15 2026

Regional radar imagery shows an outflow boundary from morning
convection oriented from southwest to northeast across central
Missouri into west-central Illinois. This boundary is moving
southeast, and extrapolation would put it near a Jefferson City
to Carlinville line around 2100 UTC. This area may be where
storms initiate later this afternoon, though CAMs also suggest
additional development within the broad warm sector to the
southeast too. Given building cumulus on GOES-19 visible
satellite imagery, this has merit and have isolated thunderstorm
wording to the southeast, with scattered thunderstorms more
likely near the aforementioned outflow boundary. Additional
storms are also forecast to develop late this afternoon into
early this evening along/behind the synoptic cold front. This
boundary is currently located near a KMCI>>KIRK line and is also
slowly moving to the southeast. There is better shear near the
actual cold front (30+ knots), and this is where the risk for
severe weather is primarily located this evening (northeast
Missouri into west-central Illinois). Damaging winds gusts are
the primary threat in multicellular clusters/mini bowing
segments, though marginally severe hail may be possible in any
transient supercells. Further to the southeast this
afternoon/early evening, much weaker effective shear (<20 knots)
strongly suggests pulse convection. Most storms will long last
long as rain-cooled downdrafts quickly extinguish parent
updrafts. However, the latest SPC mesoanalysis does show steep
low-level lapse rates and high DCAPE values, so a microburst or
two with gusts as high as 60 mph are possible.

The coverage of showers and thunderstorms should increase late this
evening into the early overnight hours as the low-level jet
strengthens. Widespread showers and thunderstorms are forecast
across northeast Missouri and west-central Illinois north of the
frontal boundary through early to mid morning on Wednesday. While
the severe threat should diminish by late this evening, there is a
threat for locally heavy rainfall given anomalous precipitable water
values (~1.9", >95th percentile of climatology), deep warm cloud
depths, and the possibility of training. The signal for the heaviest
rainfall (2-4+") is across northwest Missouri, which is also where
the strongest low-level moisture convergence is forecast overnight.
However, some streaks of 2-3+" may occur in our area given the
chance of training in a favorable environment for efficient rainfall
processes.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 240 PM CDT Tue Sep 15 2026

(Wednesday - Monday)

There is still some uncertainty with the exact location of the front
on Wednesday morning, but the most likely location is near the I-
44/I-55 corridors in Missouri and Illinois respectively. Widespread
showers and thunderstorms should continue to percolate during the
morning hours along/poleward of this boundary. A gradual decrease in
coverage is expected as the low-level jet and associated moisture
convergence slowly wanes with time. There will be a pretty sharp
temperature difference across the front Wednesday afternoon. North
of the boundary across parts of northeast Missouri and west-central
Illinois, low clouds and lingering rain will really hamper
temperatures. Highs may not get much higher than the mid 70s to near
80 degrees. To the southeast on the warm side of the front,
widespread mid 90s are forecast though this may be a bit too warm if
outflow and/or clouds linger. Regardless, dewpoints pooling near the
front should result in 100F+ heat index values within the advisory
area on Wednesday so the heat advisory was extended in time all the
way through Friday. The chances for outflow or thicker clouds are
less across that area later this week as the front moves back to the
north as a warm front. There is now pretty high confidence that near-
record highs will continue at least through Saturday. Once the
boundary does retreat northward, dewpoints should come down each day
Thursday through Saturday. In other words, a bit of a transition to
a "drier" heat. Heat index values on Saturday may not even be much,
if at all, above the ambient air temperature. That is the reason the
heat advisory was not extended all the way through Saturday. If
dewpoints are a bit higher than forecast, more widespread ~100F heat
index values would occur so it is possible that another day could be
required.

In the more bad news if you don't like heat department, there has
been a pretty substantial change for late this weekend into early
next week. The mid/upper level trough on both the GEFS/EPS has
trended more cutoff and slower as it moves across the northern
Plains/Upper Midwest. That means a shift toward a slower cold
frontal passage. Sunday looks most likely to be a continuation of
this very late season heat wave with another day topping out in the
90s for most locations. This more prolonged period of anomalous
warmth should equate to one of the warmest first 20 days of
September at all 3 of our climate stations, and probably THE warmest
at KSTL. Monday is the day with the most uncertainty now, and high
temperatures will depend on the exact timing of the front. If the
front is delayed further, you can likely book another day of
anomalous warmth with highs in the 90s. If the front does make it
through, highs closer to normal (70s/80s) would be expected.

(Monday Night - Next Tuesday)

There is still a strong signal that the cold front will finally make
it through by Tuesday, though the closed mid/upper level low and
overall "blockiness" of the pattern does shred at least some minor
doubts. There still remains differences on the strength of the air
mass behind the front early/mid next week, with the EPS still quite
a bit cooler than the GEFS. A safe bet is for temperatures to
finally get back closer to normal, though whether it ends up a bit
below or slightly above normal is still uncertain.

&&

.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 653 PM CDT Tue Sep 15 2026

A cold front moving through the area is sparking some convection
along and ahead of the front as it moves southeast before stalling
out near the St. Louis metro this evening. The highest chance of
showers and thunderstorms associated with the front is in
northeastern MO and west-central IL, with UIN being the most
impacted through Wednesday morning. MVFR flight conditions are
expected behind the front due to lowered ceilings primarily at UIN,
COU, and JEF. There remains some uncertainty on the exact location
to which the front will stall, and if the St. Louis metro terminals
will be impacted by MVFR ceilings. To highlight the possibility of
lower ceilings, a SCT015 was included to the metro TAFs.

&&

.CLIMATE...
Issued at 231 PM CDT Mon Sep 14 2026

Daily record high temperatures may be threatened for both St. Louis
(KSTL) and Columbia (KCOU) this week. NOTE: Records at Quincy (KUIN)
are not shown below due to cooler temperatures forecast:

          9/15        9/16        9/17        9/18        9/19
KSTL   101/1939     98/1954     97/1931     97/1925     96/1955
KCOU   101/1893     99/1954     98/1895     98/1893     98/2022

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 8 PM CDT Friday for MOZ047>049-059>065-
     072>075-084-085-099.
IL...Heat Advisory until 8 PM CDT Friday for ILZ064-069-070-074-079-
     100>102.

&&

SHORT TERM...Gosselin
LONG TERM...Gosselin
AVIATION...Asel/Carney
CLIMATE...Gosselin