Severe Thunderstorm Warning 170, NWS St. Louis, MO

004 
WWUS53 KLSX 110126
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
826 PM CDT Wed Jun 10 2026

ILC001-110200-
/O.CON.KLSX.SV.W.0170.000000T0000Z-260611T0200Z/
Adams IL-
826 PM CDT Wed Jun 10 2026

...SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 9 PM CDT FOR
NORTHERN ADAMS COUNTY...

At 826 PM CDT, a severe thunderstorm was located 7 miles northwest of
Mendon, or 11 miles east of Canton, moving east at 40 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...
  Lima, Loraine, Woodville, Chatton, Golden and La Prairie.

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.

A Tornado Watch remains in effect until 1100 PM CDT Wednesday for a
portion of west central Illinois.

&&

LAT...LON 4011 9142 4020 9150 4019 9091 4011 9091
TIME...MOT...LOC 0057Z 259DEG 33KT 4013 9167

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

$$

Brown

906 
WWUS53 KLSX 110138
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
838 PM CDT Wed Jun 10 2026

ILC001-110200-
/O.CON.KLSX.SV.W.0170.000000T0000Z-260611T0200Z/
Adams IL-
838 PM CDT Wed Jun 10 2026

...SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 9 PM CDT FOR
NORTHEASTERN ADAMS COUNTY...

At 838 PM CDT, a severe thunderstorm was located 8 miles northeast of
Mendon, or 16 miles north of Quincy Regional Airport, moving east at
35 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...
  Loraine, Woodville, Chatton and La Prairie.

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.

A Tornado Watch remains in effect until 1100 PM CDT for a portion of
west central Illinois.

&&

LAT...LON 4014 9125 4020 9132 4019 9091 4013 9091
TIME...MOT...LOC 0126Z 266DEG 31KT 4018 9133

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

$$

Brown

402 
WWUS53 KLSX 110145
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
845 PM CDT Wed Jun 10 2026

ILC001-110155-
/O.CAN.KLSX.SV.W.0170.000000T0000Z-260611T0200Z/
Adams IL-
845 PM CDT Wed Jun 10 2026

...SEVERE THUNDERSTORM WARNING IS CANCELLED FOR NORTHEASTERN ADAMS
COUNTY...

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.

A Tornado Watch remains in effect until 1100 PM CDT for a portion of
west central Illinois.

&&

LAT...LON 4014 9125 4020 9132 4019 9091 4013 9091
TIME...MOT...LOC 0138Z 266DEG 31KT 4018 9120

$$

Brown

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
636 PM CDT Wed Jun 10 2026

.KEY MESSAGES...

- Showers and thunderstorms are expected this afternoon and
  evening, in northeast MO and west-central Illinois, posing a
  threat of flash flooding, damaging winds, and a few tornadoes.

- A cold front will drive another round of strong to severe
  thunderstorms through most of the area tomorrow evening and
  overnight, with damaging winds and tornadoes as the most likely
  hazards.

- Another round of similar early-season heat is expected tomorrow
  with heat index values of 95-105 degrees, although breezy winds
  will mitigate this slightly.

- Additional strong to severe thunderstorms are possible in some
  areas Saturday, but confidence in these storms is much lower.

&&

.SHORT TERM...  (Through Late Thursday Night)
Issued at 247 PM CDT Wed Jun 10 2026

An active 48 hours of weather is in store for the region, with
multiple opportunities for thunderstorms capable of damaging winds,
flash flooding, and even tornadoes. The first of these rounds of
storms is already ongoing in northeast Missouri thanks to a passing
shortwave, which triggered the development of early morning
elevated storms in northwest Missouri several hours ago. These
storms have steadily strengthened and moved east, and are now
slowly moving through northeast Missouri and west-central Illinois
as of 1:00 PM. For this initial round, the primary concern is
heavy rain, although the potential for damaging downburst winds
may also slowly increase as surface-based instability increases.
SPC mesoanalysis indicates that a corridor of 2-2.2 inches of
precipitable water has developed along the nose of a relatively
robust low level jet, and this is feeding directly into the
ongoing storms. While they are steadily moving east, they are not
doing so particularly quickly, and when combined with likely 1 to
2 inch per hour rain rates, localized flash flooding will be
possible. Fortunately these areas have not seen quite as much rain
as other areas over the past few days, but this is likely not
enough of a mitigating factor to eliminate this threat.

This initial round is likely to last another couple of hours, and
move east of the area by roughly 3 to 4 PM. Even if we manage to
escape widespread flash flooding issues with this initial round
though, it likely will act to saturate some areas in advance of the
next round of thunderstorms later this evening. While these storms
are acting to stabilize the lower levels in the immediate vicinity,
satellite imagery reveals plenty of clearing behind this round, and
mesoanalysis also indicates that a very unstable airmass
(3000-3500 J/kg MLCAPE) is being quickly reinforced just to the
west across northwest Missouri. This is likely due to the presence
of the aforementioned low level jet, which is drawing warm and
humid air quickly in to replace the shallow cold pool behind these
storms. Not to mention, 2+ inch PWAT values also extend well to
the west and even into far northeast Kansas, so there will be
plenty of fuel for more heavy rain with the next round. As storms
arrive from the west, confidence is growing that a line of storms
will slowly pivot into our area and become oriented almost
parallel to the mean flow, potentially leading to training cells
with very heavy rain rates. This also may occur over the same
areas that are seeing heavy rain now, exacerbating the threat. All
told, totals of 3 to 6 inches of rain will be possible between
this afternoon and early tomorrow morning, primarily across
northeast Missouri and west-central Illinois. A Flash Flood Watch
has been issued in these areas until 6 AM tomorrow to account for
this.

Not only this, but there is also amble effective bulk shear
collocated with all of this instability (40-50kt), which will also
support organized convection capable of severe thunderstorm hazards.
Current shear parameters and initially clockwise-turning hodographs
suggest that while supercells may develop to our west, as discussed
previously these storms are very likely to grow upscale into a
linear complex of storms. As such, damaging straight line winds (60-
75mph) will be the most likely (non-water) hazard in our area,
although considering the 30-35kt 0-3km shear and likely presence of
a lingering outflow boundary, QLCS tornadoes will be possible as
well. Hail does not appear to be a significant hazard, unless a
stray supercell manages to remain isolated long enough to reach our
area. The most significant hazards for the second round are most
likely locally between about 7 PM and 11 PM, with a gradual
weakening as storms move east-southeast through the night. Storms
are expected to exit the area or diminish prior to sunrise, laying
down an outflow boundary somewhere across our area in the morning.
This will set the stage for tomorrow's threat, which will be
discussed in more detail in the Long Term discussion below.

BRC

&&

.LONG TERM...  (Friday through Next Wednesday)
Issued at 247 PM CDT Wed Jun 10 2026

In the wake of tonight's storms, persistent south-southwest return
flow is likely to maintain a hot and humid airmass across our area,
although the distribution of greatest instability may be impacted
by outflow from morning activity if it persists later than
currently expected. In the afternoon and evening, a shortwave will
drive a sharp cold front southeast through Missouri and
eventually Illinois, which is expected to overturn this unstable
airmass and produce another round of strong to severe
thunderstorms across much of the area.

While most of the early part of the day should be dry, temperatures
in the low to mid 90s coupled with low to mid 70s dewpoints should
yield 3000-4000+ J/kg of surface-based CAPE by mid to late
afternoon. Initial storms are expected to develop along the boundary
to our west in northwest Missouri during the early to mid afternoon,
grow upscale into another line, and steadily move through our area
during the evening hours. As it does so, damaging straight line
winds appear to be the most likely hazard with these storms,
followed closely by QLCS tornadoes thanks to continued southwesterly
30-40kt 0-3km shear and perhaps the presence of another lingering
outflow boundary. What separates tomorrow's severe threat from
tonight's is most coverage, as stronger storms are likely to spread
further southeast and impact a larger portion of the forecast area.
These storms likely will also feature heavy rain rates but will be
more progressive than tonight's storms, which should mitigate the
threat of another round of flash flooding. The most likely window
for severe hazards will be between 6 to 11 pm, although this may
linger a little bit later into the night. Thunderstorms, severe or
not, should exit the area to the southeast prior to sunrise.

Lastly, tomorrow is also expected to be the third day in a row
featuring early season heat, with heat index values ranging from
generally 95 to 105 degrees (highest in the St. Louis metro area).
This still falls just a bit short of Heat Advisory levels, but may
cause problems for those sensitive to heat or otherwise unprepared
for these conditions this early in the season.

While Friday will feature largely dry conditions and milder
temperatures in the wake of the passing cold front, an active, quasi-
zonal flow regime will maintain an active pattern over the weekend
and potentially into next week. In particular, Saturday may see
another round of strong to severe thunderstorms, although with
multiple rounds of strong to severe storms just over the next 24-36
hours, most forecast attention was given to the shorter-term
hazards for this forecast package.

BRC

&&

.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 620 PM CDT Wed Jun 10 2026

Showers and thunderstorms, some strong to severe, will move toward
UIN through 03Z bringing MVFR/IFR ceilings and visibilities in
heavy downpours along with the potential for hail and wind gusts
over 35 knots. These storms will move south affecting COU/JEF
between 04-08Z and the St. Louis area terminals between 05-08Z,
though they are expected to lose some of their intensity as they
move to the southeast. Additional thunderstorms are expected to
develop on Thursday afternoon and evening along a cold front which
will affect UIN/COU/JEF during the afternoon, and the St. Louis
area terminals after 00Z. These storms will likely also have the
potential to produce MVFR or possible IFR ceilings and
visibilities in heavy downpours in addition to hail and strong
wind gusts. Winds will gust into the 25 to 30 knot range on
Thursday afternoon outside of thunderstorms.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch through Thursday morning for Knox MO-Lewis MO-Marion
     MO-Shelby MO.

IL...Flood Watch through Thursday morning for Adams IL-Brown IL-Pike
     IL.

&&

WFO LSX

Preliminary Local Storm Report
National Weather Service St Louis MO
203 PM CDT Wed Jun 10 2026

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

0145 PM     Flash Flood      1 NE Clarence           39.76N 92.24W
06/10/2026                   Shelby             MO   Emergency Mngr

            CR 305 flooded with 2ft of water.

&&

MRB

Preliminary Local Storm Report
National Weather Service St Louis MO
225 PM CDT Wed Jun 10 2026

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

0225 PM     Flash Flood      3 E Clarence            39.74N 92.20W
06/10/2026                   Shelby             MO   Emergency Mngr

            The westbound lanes of US-36 are flooded
            with 2ft of water.

&&

MRB

Preliminary Local Storm Report
National Weather Service St Louis MO
256 PM CDT Wed Jun 10 2026

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

0231 PM     Flash Flood      Clarence                39.74N 92.26W
06/10/2026                   Shelby             MO   Public

            Report from mPING: Street/road flooding;
            Street/road closed.

&&

MRB

Preliminary Local Storm Report
National Weather Service St Louis MO
412 PM CDT Wed Jun 10 2026

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

0349 PM     Hail             Paris                   39.48N 92.00W
06/10/2026  M1.75 Inch       Monroe             MO   Fire Dept/Rescue

            Paris MO Fire reported golf ball size hail.

&&

Maples

Preliminary Local Storm Report
National Weather Service St Louis MO
609 PM CDT Wed Jun 10 2026

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

0503 PM     Tstm Wnd Dmg     2 ESE Harvel            39.35N 89.52W
06/10/2026                   Montgomery         IL   Emergency Mngr

            8-12in diameter tree limbs snapped.

&&

MRB

Preliminary Local Storm Report
National Weather Service St Louis MO
610 PM CDT Wed Jun 10 2026

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

0503 PM     Hail             2 ESE Harvel            39.35N 89.52W
06/10/2026  E1.25 Inch       Montgomery         IL   Emergency Mngr

            Corrects previous hail report from 2 ESE
            Harvel. Size estimated from picture.

&&

MRB