Severe Thunderstorm Warning 69, NWS St. Louis, MO

835 
WWUS53 KLSX 180129
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
829 PM CDT Fri Apr 17 2026

ILC009-149-180139-
/O.CAN.KLSX.SV.W.0069.000000T0000Z-260418T0145Z/
Brown IL-Pike IL-
829 PM CDT Fri Apr 17 2026

...SEVERE THUNDERSTORM WARNING IS CANCELLED FOR SOUTHEASTERN BROWN
AND NORTHEASTERN PIKE COUNTIES IN WEST CENTRAL ILLINOIS...

The storms which prompted the warning have weakened below severe
limits, and no longer pose an immediate threat to life or property.
Therefore, the warning has been cancelled. However, gusty winds and
heavy rain are still possible with these thunderstorms.

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

&&

LAT...LON 3963 9111 3976 9093 3976 9092 3977 9092
      3998 9061 3998 9051 3997 9051 3995 9053
      3992 9054 3990 9055 3989 9057 3988 9058
      3985 9058 3983 9057 3979 9060 3976 9061
      3970 9065 3964 9061 3957 9058
TIME...MOT...LOC 0112Z 267DEG 36KT 3998 9030 3982 9054 3962 9088

$$

BRC

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
647 PM CDT Fri Apr 17 2026

.KEY MESSAGES...

- Strong/severe thunderstorms are expected from late afternoon
  into the evening, mainly in central/northeast Missouri and west-
  central Illinois. Damaging wind gusts are the most likely
  hazard, followed by brief tornadoes. Occasional large hail and
  localized flash flooding are secondary threats.

- Weather hazards are minimal Saturday through mid week, but a
  modest potential (30-50%) for patchy frost exists Sunday
  morning.

&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 247 AM CDT Fri Apr 17 2026

With yesterday's showers and thunderstorms concluded, attention
turns squarely onto the potential for severe thunderstorms late this
afternoon through the early overnight hours, which remains on track
for a substantial portion of the area. Strong to severe
thunderstorms continue to be expected in portions of
northeast/central Missouri and west-central Illinois at a minimum,
with damaging straight line-winds the primary threat, followed by a
more limited potential for large hail and tornadoes.

As we approach sunrise, dry but relatively humid conditions have
developed throughout the area after a round of scattered
thunderstorms across the Ozarks yesterday. As the day progresses
though, strengthening southerly low level flow will transport
increasingly rich moisture (surface dewpoints in the mid-upper
60s) northward into much of Missouri ahead of an advancing cold
front, and underneath a plume of steepening mid-level lapse rates
(7-8C). By mid afternoon, the combination of these factors along
with afternoon heating is expected to generate a broad corridor of
substantial instability, with high confidence in 3000-4000 J/kg
of mixed-layer CAPE just ahead of the advancing front by mid-
afternoon. The strongest instability is expected to initially be
located just to our east across northwest and north-central
Missouri, but still- impressive values of 2000-3000 J/kg are also
projected to extend farther east into much of northeast/central MO
and west-central IL. Meanwhile, guidance continues to project
around 30-40kt of 0-6km bulk shear, with long straight-line
hodographs and perhaps some slight curvature in the low levels.
To put it more succinctly, this environment will have more than
enough of the baseline parameters to set the stage for severe
thunderstorms across a broad area.

Exactly what materializes in our portion of this event will depend
on a few more subtle factors. High resolution guidance continues to
suggest that rapid overturning and widespread convective
initiation will occur along and just ahead of the cold front
during the mid- late afternoon period, thanks to both the front
and cooling aloft/increasing divergence from an approaching
shortwave trough. However, exactly where this occurs will depend
largely on the timing, as earlier initiation would likely keep
the vast majority of initial storms to our west. Meanwhile, CAMS
continue to depict a few open warm-sector storms developing in our
area earlier in the day in our area, mainly central/NE MO, but
without an obvious forcing mechanism, along with recent failures
of such activity to materialize during other recent events,
confidence is low that this will occur. However, confidence
remains high that strong/severe storms will reach our area at some
point in the late afternoon/early evening given the ample
instability present, along with a steadily increasing low level
jet during this period.

As for storm mode, initial storms are likely to feature a mix of
modes, with supercells and multicells favored initially. However,
given the strong forcing along the front, numerous updrafts/cold
pools interacting with each other, and bulk shear vectors largely
parallel to the front, we expect that storms will develop upscale
into one or more QLCS' before they arrive or shortly afterward.
As such, damaging straight line wind continues to be the primary
hazard with this event, with perhaps some more significant
straight line winds approaching 70 mph (or more). The potential
for QLCS tornadoes will also exist, particularly along bowing
segments during the early evening that can become more favorably
oriented with 0-3km shear vectors. This will be most favored
during a window in the early evening when strong instability is
still present ahead of a strengthening low level jet and low level
shear/SRH, and LCLS can lower slightly, and while the advancing
line is still strong. Shear parameters are not particularly strong
(0-3km of 30-40kt), but with the right orientation there is
enough there to support a couple of brief tornadoes.

As the evening progresses into the overnight hours, model guidance
continued to suggest that instability will quickly wane, which
should limit the overall severe threat with southeastward extent.
Exactly when and where this occurs, though, is somewhat uncertain.
While we do expect at least some strong/severe storms in our area
during this event, the full geographic coverage is less certain this
far east than it is for our western and northern neighbors. Still,
there is a reasonable potential for severe storms as far southeast
as the I-44 corridor until roughly midnight or so, with quickly
decreasing confidence later and farther southeast. For the remainder
of the event, a weakening convective line with widespread stratiform
rain will be more likely, albeit with lingering lightning and a
limited potential for rogue strong/severe gusts throughout the
night.

Finally, while the advancing line of storms should have enough
forward motion to limit the potential for training and flooding in
most areas, the large parallel component of the wind shear with the
evolving line will maintain at least a limited potential for this,
particularly along the southwestern flank of the line in central
Missouri where forward motion may be a bit slower. LPMM output does
paint around 1.5-2.5 inches of rain in this area, and there are a
few locations around here and closer to I-44 that have already seen
1-3 inches of rain over the past couple of days. While there isn't a
high probability for widespread flash flooding, we can't rule out
some localized issues if storms can orient themselves favorably in
these areas late in the evening and overnight.

As lingering showers and thunderstorms move southeast late tonight
through early tomorrow morning, the cold front will filter in behind
with breezy northwest winds and quickly dropping temperatures, to
the tune of 30 to 45 degrees colder from this afternoon to tomorrow
morning. Persistent northwest winds will maintain these chilly
temperatures through the day, with highs in the mid 50s to mid 60s
Saturday afternoon (about 10 degrees below average). Most areas are
also likely to remain dry throughout the day, but a few showers may
linger across our far southeastern border into the afternoon.

BRC

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 247 AM CDT Fri Apr 17 2026

After today's thunderstorms and tonight's cold front, a relatively
quiet period of weather is expected through mid-week as northwest
flow aloft slowly transitions into a building ridge. This will lead
to a gradual warming trend through mid-week and mostly dry weather,
with perhaps a return to more active weather late in the period.

Before we get to our warming trend, though, we will need to monitor
the potential for patchy frost Sunday morning, as surface high
pressure finally allows winds to weaken. Current temperature
forecasts suggest morning lows may dip into the mid 30s in some
areas, and thus may not be fully capturing protected valleys where
cool air drainage could lead to some low 30s in a few spots. This
may also be true Monday morning as well, but more likely in our
eastern areas.

Otherwise, the main story through Wednesday will be steadily
increasing temperatures as southerly and southwesterly low level
flow resumes, and an upper ridge reasserts itself. Ensemble guidance
suggests that temperatures will likely climb back to near seasonal
averages by Monday afternoon and slightly above Tuesday and
Wednesday, with relatively narrow ensemble spreads. Meanwhile,
precipitation chances remain low throughout this period, with only a
few hints of isolated showers by mid-week. Until southerly flow can
become more firmly established, moisture return will be quite
limited, thus keeping precipitation chances relatively low through
this period.

However, this may change over the latter half of the week, as
southerly flow continues to bring increasing moisture northward, and
some variation of an upper trough approaches from the west. While
the upper flow pattern becomes more amplified in the extended as
this trough approaches, the timing and strength of this trough
remain highly variable among ensemble members and clusters. Still,
precipitation probabilities do increase substantially Thursday
onward, signaling perhaps a return to a more active period.

BRC

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 637 PM CDT Fri Apr 17 2026

A line of thunderstorms will continue to move east, affecting UIN
between 00-02Z, JEF/COU between 01-03Z, and the St. Louis metro
terminals between 03-06Z. The strongest storms will be capable of
producing IFR ceilings and visibilities, wind gusts between 35-50
knots, hail, and IFR ceilings and visibilities in brief heavy
downpours. This line will move east of the area this evening and
with showers lingering for around 3 hours afterwards and MVFR
ceilings continuing at UIN/COU/JEF through 08-09Z and the St.
Louis area terminals through 12Z. Then mainly dry and VFR
conditions are expected on Saturday with northwest winds gusting
to 25 knots.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch until 4 AM CDT Saturday for Audrain MO-Boone MO-
     Callaway MO-Cole MO-Knox MO-Lewis MO-Lincoln MO-Marion MO-
     Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike MO-Ralls
     MO-Shelby MO.

IL...Flood Watch until 4 AM CDT Saturday for Adams IL-Brown IL-
     Calhoun IL-Greene IL-Jersey IL-Macoupin IL-Montgomery IL-
     Pike IL.

&&

WFO LSX

Hazardous Weather Outlook
National Weather Service St Louis MO
233 PM CDT Fri Apr 17 2026

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-181945-
Greene IL-Macoupin IL-Montgomery IL-Bond IL-Fayette IL-Clinton IL-
Marion IL-Washington IL-Randolph IL-Adams IL-Brown IL-Pike IL-
Calhoun IL-Jersey IL-Madison IL-Saint Clair IL-Monroe IL-Knox MO-
Lewis MO-Shelby MO-Marion MO-Monroe MO-Ralls MO-Pike MO-Boone MO-
Audrain MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-
Lincoln MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO-
Saint Louis MO-Saint Louis City MO-Jefferson MO-Crawford MO-
Washington MO-Saint Francois MO-Sainte Genevieve MO-Iron MO-
Madison MO-Reynolds MO-
233 PM CDT Fri Apr 17 2026

This Hazardous Weather Outlook is for portions of eastern and
central Missouri as well as west central and southwest Illinois.

.DAY ONE...Tonight.

Widespread thunderstorms are forecast through this evening. Several
of these thunderstorms may become severe.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Jaja

Preliminary Local Storm Report
National Weather Service St Louis MO
715 PM CDT Fri Apr 17 2026

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

0335 PM     Tstm Wnd Dmg     3 W Winfield            39.01N 90.79W
04/17/2026                   Lincoln            MO   Public

            Report of multiple smaller limbs snapped off
            large trees.

&&

CP

Preliminary Local Storm Report
National Weather Service St Louis MO
716 PM CDT Fri Apr 17 2026

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

0349 PM     Hail             1 NE Harvester          38.76N 90.57W
04/17/2026  E1.00 Inch       St. Charles        MO   Public

            Report from mPING: Quarter (1.00 in.).

&&

CP

Preliminary Local Storm Report
National Weather Service St Louis MO
717 PM CDT Fri Apr 17 2026

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

0403 PM     Hail             1 W Mexico              39.17N 91.89W
04/17/2026  E1.00 Inch       Audrain            MO   Public

            Report from mPING: Quarter (1.00 in.).

&&

CP

Preliminary Local Storm Report
National Weather Service St Louis MO
718 PM CDT Fri Apr 17 2026

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

0405 PM     Hail             2 SW Saint Charles      38.77N 90.53W
04/17/2026  E1.00 Inch       St. Charles        MO   Public

            Report from mPING: Quarter (1.00 in.).

&&

CP

Preliminary Local Storm Report
National Weather Service St Louis MO
740 PM CDT Fri Apr 17 2026

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

0735 PM     Tstm Wnd Gst     4 NE Burton             39.94N 91.20W
04/17/2026  M62 MPH          Adams              IL   ASOS

            Quincy Regional.

&&

JPG

Preliminary Local Storm Report
National Weather Service St Louis MO
752 PM CDT Fri Apr 17 2026

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

0325 PM     Tstm Wnd Dmg     2 NW Flint Hill         38.87N 90.90W
04/17/2026                   St. Charles        MO   Public

            Report of trees down and limbs snapped off.

&&

CP