Severe Thunderstorm Warning 173, NWS St. Louis, MO

078 
WWUS53 KLSX 112129
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
429 PM CDT Thu Jun 11 2026

MOC103-205-112200-
/O.CON.KLSX.SV.W.0173.000000T0000Z-260611T2200Z/
Knox MO-Shelby MO-
429 PM CDT Thu Jun 11 2026

...SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 5 PM CDT FOR
SOUTHERN KNOX AND NORTHERN SHELBY COUNTIES...

At 429 PM CDT, severe thunderstorms were located along a line from
near Knox City to 9 miles northwest of Clarence, or along a line from
8 miles southeast of Edina to 21 miles northwest of Shelbina, moving
east at 35 mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

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

Locations impacted include...
  Novelty, Clarence, Leonard, Plevna, Newark, Bethel and Shelbyville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter inside a well-built structure and stay away from
windows. These storms are capable of producing damaging winds and
large hail.

Tornadoes can develop quickly from severe thunderstorms. Seek shelter
immediately in an interior room on the lowest floor of a well-built
structure.

A Tornado Watch remains in effect until 900 PM CDT Thursday for a
portion of northeast Missouri.

&&

LAT...LON 4003 9234 4005 9195 3995 9195 3974 9193
      3973 9230 3995 9229 3995 9234
TIME...MOT...LOC 2102Z 249DEG 28KT 4003 9232 3991 9245 3974 9265

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.25 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Brown

Area Forecast Discussion
National Weather Service Saint Louis MO
243 PM CDT Thu Jun 11 2026

.KEY MESSAGES...

- Another round of strong to severe storms is expected in most of
  our area between late this afternoon and evening. Damaging
  straight line winds and tornadoes are the most likely hazards,
  with a more limited potential for large hail.

- Seasonable and dry conditions are expected tomorrow, but showers
  and thunderstorms will again be possible at various times
  between late tomorrow night and early Sunday. Some strong to
  severe storms are possible, but forecast confidence is low.

&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 238 PM CDT Thu Jun 11 2026

After an early round of thunderstorms moved through portions of
northeast Missouri and west-central Illinois this morning, the
forecast remains on track for a more widespread round of strong to
severe thunderstorms this afternoon and evening. Damaging straight
line winds and tornadoes will be the most probable hazards
associated with these storms, with a more limited hail threat and
also the potential to worsen ongoing flooding mainly in northeast
Missouri.

While early morning storms have exited the area, allowing us to
cancel the previous Tornado Watch early, satellite and radar
observations indicate that the atmosphere is destabilizing quickly
behind it and ahead of an advancing cold front in northwest
Missouri. According to SPC mesoanalysis, as much as 3000-3500 J/kg
of largely uncapped MLCAPE is already in place, thanks to very rich
low level moisture featuring low to mid 70s dewpoints. As such, new
updrafts are already beginning to develop along the cold front in
northwest Missouri, and these storms are expected to continue to
expand and strengthen as the front overturns this extremely unstable
airmass.

Meanwhile, effective shear parameters across especially the
northern third of Missouri are more than sufficient to support
organized updrafts, ranging from 40 to 50 kt. Low level shear is
also relatively abundant (0-3km of 30-40kt, 0-1km of 20-30kt)
thanks again to a strong southwesterly low level jet. In spite of
the southwesterly surface winds, there is still at least some
clockwise curvature in the hodographs, although perhaps not as
enlarged as those further northwest. Finally, there appears to be
some semblance of an outflow boundary remnant from this morning's
round of storms, which may also add some additional low level
helicity if storms can manage to interact with it at the right
orientation.

All of this is to say that organized severe storms are very likely
this afternoon and evening, with all hazards on the table. Large
hail and tornadoes will be most likely with any supercells that
develop initially, although these storm modes are likely to occur
primarily to our west. Eventually, supercells are expected to grow
upscale into an expansive linear complex with embedded bowing
segments, possibly very quickly due to the strong forcing along the
front. Given the above parameters and a high probability of linear
storm modes, damaging straight line winds and QLCS tornadoes appear
the be the highest probability hazards. The latter threat appears
to be maximized across northern Missouri and west-central
Illinois where shear parameters are most favorable. Large hail in
the 1-2 inch range will also be possible, particularly with
isolated cells, but this potential will become more limited as
storms transition into a line. Finally, while these storms will be
progressive, we do expect brief heavy rain rates to occur given
the very rich moisture in place, and this may exacerbate ongoing
flooding issues in northeast Missouri and west-central Illinois.
Even an hour or two of heavy rain may be enough to cause flooding
in these areas, and considering that we had another round of rain
this morning, a Flash Flood Watch has also been issued through 7
PM to account for this.

Storms will steadily move southeast through the evening, and
eventually exit the area to the southeast sometime between 11 pm and
1 am. Severe storms will be possible at any time between roughly 4
PM and then, but will likely be maximized before roughly 10 pm when
instability is expected to be highest...which also places the
greatest threat area along and north of I-44.

BRC

&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 238 PM CDT Thu Jun 11 2026

Overnight tonight, a cold front will move through the area, which
will usher in a more seasonable and mild airmass for early summer.
Clearing skies and light winds may also allow for some river valley
fog overnight as well, particularly in central/northeast Missouri
where skies will clear faster, and also in areas that have more
lingering surface moisture. Expect near average temperatures
tomorrow, with mostly clear skies and more comfortable humidity
levels.

While we will have Friday to provide a bit of a lull in our active
pattern, additional rounds of showers and thunderstorms are expected
Saturday and again Sunday as we enter a zonal flow pattern aloft.
Saturday in particular has a lot of moving pieces, including the
potential for early morning convection along the nose of a
strengthening low level jet, followed by possibly additional showers
and storms later in the day and again overnight/Sunday morning. Much
will depend on how each round evolves, and also on the passage of
subtle shortwaves through the day and overnight. While very little
confidence exists in the coverage or timing of strong or severe
storms, bulk parameters support the potential for this to occur at
some point during this window, and this threat will be evaluated
more closely in subsequent forecast packages. Beyond Sunday,
confidence is increasing that we will enter a relatively cool
pattern as a trough digs into the central U.S., although there may
be a few opportunities for showers periodically.

BRC

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1218 PM CDT Thu Jun 11 2026

VFR conditions are in place early this afternoon, but widespread
MVFR cumulus clouds exist throughout the area and will remain so
until a round of showers and thunderstorms sweeps through late
this afternoon and evening. This round of storms will be brief,
but is expected to impact all local terminals at some point
between 21 and 02Z, first at COU/JEF/UIN, and later at
STL/SUS/CPS. Strong surface winds and brief heavy rain can be
expected with these storms, with a more limited potential for
hail. Brief visibility and ceiling reductions are both expected
as storms impact terminals.

Skies will clear behind these storms and a cold front will switch
breezy south-southwest winds to the northwest. Winds will weaken
overnight, and patchy fog is likely in some river valleys. This
has been included at the SUS and JEF TAFs as these sites are fog
prone in these conditions.

BRC

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch until 7 PM CDT this evening for Knox MO-Lewis MO-
     Marion MO-Shelby MO.

IL...Flood Watch until 7 PM CDT this evening for Adams IL-Brown IL.

&&

WFO LSX

Preliminary Local Storm Report
National Weather Service St Louis MO
1048 AM CDT Thu Jun 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1035 AM     Flood            2 WNW Palmyra           39.81N 91.56W
06/11/2026                   Marion             MO   Trained Spotter

            The North River is out of its banks and
            impacting several roads in the county.
            Spotter stated that County Road 324 is under
            a few inches of water. County road 230 is
            likely impassable. The water level on the
            river is just under the MO 168 bridge west
            of Palmyra.

&&

Maples

Preliminary Local Storm Report
National Weather Service St Louis MO
1130 AM CDT Thu Jun 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1130 PM     Flash Flood      3 N Leonard             39.94N 92.18W
06/10/2026                   Shelby             MO   Dept of Highways

            As of 11AM 6/11 Shelby Co. Commission Office
            stated that the county road department
            continues to address road closures due to
            flooding. Flooding initially began impacting
            roads late last night and river rises are
            extending impacts. MO 151 is closed north of
            Leonard and around Hagers Grove. Initial
            time of impact is estimated by radar trends
            and flash products.

&&

Maples

Preliminary Local Storm Report
National Weather Service St Louis MO
1134 AM CDT Thu Jun 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1130 PM     Flash Flood      5 ENE Bethel            39.90N 91.92W
06/10/2026                   Shelby             MO   Dept of Highways

            MO J and MO W are closed due to flooding.
            Flooding initially began late last evening
            with several small rivers and tributaries
            extending flooding due to river rises. Time
            of initial impact estimated by radar trends
            and flash products.

&&

Maples

Preliminary Local Storm Report
National Weather Service St Louis MO
1232 PM CDT Thu Jun 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1130 PM     Flash Flood      3 WSW Ewing             40.00N 91.77W
06/10/2026                   Lewis              MO   Emergency Mngr

            State Emergency Management Agency and Lewis
            County reported continuing impacts to
            several roads throughout the county.
            Flooding initial began late Wednesday
            evening with ongoing flooding due to river
            rises. 156 remains closed west of Ewing.
            Time of flooding impacts estimated by radar
            trends and flash products.

&&

Maples

Preliminary Local Storm Report
National Weather Service St Louis MO
1245 PM CDT Thu Jun 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0831 AM     Flood            6 SE Philadelphia       39.79N 91.65W
06/11/2026                   Marion             MO   Emergency Mngr

            State Emergency Management Agency reported a
            motorist was stranded in their vehicle near
            County Road 281 and 234 between the North
            River and Big Branch River. The water was
            approximately knee deep. The individual was
            unharmed.

&&

Maples

Preliminary Local Storm Report
National Weather Service St Louis MO
1252 PM CDT Thu Jun 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0504 PM     Hail             1 SE Raymond            39.31N 89.56W
06/10/2026  M1.00 Inch       Montgomery         IL   Emergency Mngr

            Delayed Report - County EM submitted a
            report from yesterdays severe thunderstorm
            that impacted the northwest portion of the
            county just southeast of Raymond IL.

&&

Maples