Severe Thunderstorm Warning 148, NWS St. Louis, MO

582 
WWUS53 KLSX 181128
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
628 AM CDT Mon May 18 2026

MOC007-181138-
/O.CAN.KLSX.SV.W.0148.000000T0000Z-260518T1200Z/
Audrain MO-
628 AM CDT Mon May 18 2026

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

The storm which prompted the warning has moved out of the area.
Therefore, the warning has been cancelled. To report severe weather,
contact your nearest law enforcement agency. They will send your
report to the National Weather Service office.

&&

LAT...LON 3941 9154 3957 9156 3985 9122 3951 9099
      3933 9150
TIME...MOT...LOC 1112Z 240DEG 34KT 3939 9160

$$


ILC001-149-MOC127-163-173-181200-
/O.CON.KLSX.SV.W.0148.000000T0000Z-260518T1200Z/
Adams IL-Pike IL-Marion MO-Pike MO-Ralls MO-
628 AM CDT Mon May 18 2026

...SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 7 AM CDT FOR
SOUTH CENTRAL ADAMS AND WESTERN PIKE COUNTIES IN WEST CENTRAL
ILLINOIS AND SOUTHEASTERN MARION, NORTHWESTERN PIKE AND CENTRAL RALLS
COUNTIES IN NORTHEASTERN MISSOURI...

At 628 AM CDT, a severe thunderstorm was located near Spencerburg, or
12 miles north of Vandalia, moving northeast at 45 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
  Center, Spencerburg, Frankford, New London, Ilasco, Hannibal,
  Saverton, Ashburn, Fall Creek, Seehorn, Hull, New Canton,
  Kinderhook, Payson, Rockport and Plainville.

This includes the following State Parks...
Fall Creek Scenic Overlook State Natural Area.

This includes Interstate 72 between exits 4 and 10.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 3941 9154 3957 9156 3985 9122 3951 9099
      3933 9150
TIME...MOT...LOC 1112Z 239DEG 37KT 3940 9159

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...0.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Britt

736 
WWUS53 KLSX 181204
SVSLSX

Severe Weather Statement
National Weather Service St Louis MO
704 AM CDT Mon May 18 2026

ILC001-149-MOC127-163-173-181214-
/O.EXP.KLSX.SV.W.0148.000000T0000Z-260518T1200Z/
Adams IL-Pike IL-Marion MO-Pike MO-Ralls MO-
704 AM CDT Mon May 18 2026

...SEVERE THUNDERSTORM WARNING HAS EXPIRED FOR SOUTH CENTRAL ADAMS
AND WESTERN PIKE COUNTIES IN WEST CENTRAL ILLINOIS AND SOUTHEASTERN
MARION, NORTHWESTERN PIKE AND CENTRAL RALLS COUNTIES IN NORTHEASTERN
MISSOURI...

The storm which prompted the warning has moved out of the area.
Therefore, the warning has been allowed to expire. To report severe
weather, contact your nearest law enforcement agency. They will send
your report to the National Weather Service office.

&&

LAT...LON 3941 9154 3957 9156 3985 9122 3951 9099
      3933 9150
TIME...MOT...LOC 1128Z 239DEG 37KT 3948 9141

$$

Pfahler

Area Forecast Discussion
National Weather Service Saint Louis MO
403 AM CDT Mon May 18 2026

.KEY MESSAGES...

- Widespread showers and thunderstorms are expected throughout the
  day with heavy rainfall in some locations potentially leading to
  flash flooding.

- A few strong to severe thunderstorms are possible this afternoon
  and evening with the main hazards being hail and damaging wind
  gusts.

- Additional thunderstorms are forecast late tonight and early
  Tuesday morning with another round possible along a cold front
  Tuesday afternoon/evening.

&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 402 AM CDT Mon May 18 2026

A complex of thunderstorms, that as of 09z, is currently positioned
near Quincy MO to Warrensburg MO. This activity initiated across
KS/NE on Sunday evening and has continued to push southeastward
early this morning, with arrival in central/northeast MO expect
around 09-10z. Within the last few hours, this complex has become
outflow dominant, which has led to a gradual weakening trend from
the severe wind gusts it was producing across northwestern MO around
midnight. Upstream observations indicate that the gust front has
been achieving winds gusts in the 30-50mph range. As a result, the
main severe hazard tied to these storms as they move into the area
are expected to be scattered wind gusts up to 50mph, along with
frequent lightning and heavy rain.

In fact, one of the main concerns regarding the short term is now
the threat for heavy rainfall and flash flooding, mainly across
central/south-central MO and points west. CAMs are in good consensus
that the southeastward progress of this thunderstorm complex will
continue to slow as it makes its way into the area this morning.
Additionally, there are signs that backbuilding of thunderstorms may
occur as the remnant outflow boundary/line of convection stall in a
west-east orientation, with strong low-level southerly warm/moist
advection overrunning this stationary boundary. Analysis of forecast
soundings unveils  a plentiful amount of uniform CAPE (around 1,500
J/kg) throughout the column, along with warm cloud temperatures with
freezing levels around 12-14kft AGL. In addition, PWATs are
currently in the 1.4-1.5" range, with the latest HREF indicating
values increasing to 1.7-1.9" today, which is near the 99th
percentile. Lastly, the HREF LPMM precipitation reveals the
potential for a west-east oriented swath of 2-4" with localized
pockets of 4-6" possible. Given all of the variables mentioned
above, the risk of heavy rainfall has prompted us to issue a Flash
Flood Watch for central/south-central MO and portions of east-
central MO that is in effect from 12z today through this evening.

Regarding the severe weather potential throughout the day, the
threat remains for an isolated thunderstorm becoming strong/severe
with hazards being hail along with damaging winds. This potential
appears to be lower due to the lingering showers and thunderstorms
across a large portion of the area, inhibiting solar insolation, and
thus, robust destabilization this afternoon. Regardless, given the
warm/moist summerlike airmass in place and the continuation of
steepened mid-level lapse rates, maintaining sufficient instability,
the threat for an isolated severe storm remains. A few locations may
be able to clear by this afternoon, allowing the environment to
recover and destabilize, and potentially the threat for strong to
severe thunderstorms to increase in localized areas. With
uncertainty regarding the evolution/coverage of lingering
showers/storms, confidence is low regarding the extent of severe
weather that may be realized across the area this afternoon and
evening.

By tonight, the large-scale pattern features a broad mid/upper level
trough to the west, with an embedded shortwave ejecting
northeastward into the Great Plains. This mid-level feature triggers
lee-side surface cyclogenesis across the Central Plains/Midwest near
a quasi-stationary baroclinic zone. Convection is modeled by high
resolution guidance to initiate along this boundary in KS/NE, with
quick upscale growth ensuing with eastward progression. The surface
low is modeled to lift northeast into the Midwest on Tuesday, which
begins to slowly shift the quasi-stationary baroclinic zone
southeastward as a cold front. However, this convection is progged
by guidance to outrun this slowly advancing cold front out west, and
gradually weaken as it approaches the area. This weakening trend
appears reasonable since the best deep-layer shear remains displaced
to the north and west of the area and forcing for ascent will be
limited without convection tied to the boundary. Regardless, this
threat for severe weather late Monday night into early Tuesday
morning will include the potential for large hail and damaging wind
gusts. Additionally, if surges or bowing segments occur, then
severe outflow gusts or embedded circulations leading to brief
tornadoes may also be possible.

Guidance is in fairly good agreement that the cold front will
approach northeast MO/west-central IL Tuesday morning with it
exiting to the southeast late Tuesday evening. Locations that remain
pre-frontal for a majority of the day on Tuesday will have the
greatest severe weather threat. The big question that remains is,
how quickly will the atmosphere recover from the early Tuesday
morning convection by the time the front is working its way through
the area. As of now, it appears the severe weather threat will be
greatest from east-central MO and points southeastward, as these
locations will have the best chance to destabilize in the early
afternoon on before the arrival of the front. Regardless,
instability and mid-level flow are still forecast to be sufficient
enough to support organized storms with potential for large hail,
damaging winds, and tornadoes. Any lingering outflow boundaries from
morning convection may serve as areas of focus for thunderstorm
development in the afternoon ahead of the cold front.

Peine

&&

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 402 AM CDT Mon May 18 2026

Low-level cold air advection within the post-frontal airmass will
lead to much cooler conditions for Wednesday, with highs forecast to
be around 10-15 degrees below average. Quasi-zonal flow aloft
encompasses the region through the end of the week, which should
allow for a period of dry conditions until Friday. By the end of the
week, the general trend of LREF temperature IQRs is a gradual warmup
to temperatures right around climatological normals.

Peine

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1022 PM CDT Sun May 17 2026

Showers and thunderstorms line up from Minnesota through Kansas
late this evening. This activity is expected to be the primary
source for thunderstorm potential heading into Monday with the
main impacts being MVFR visibilities, locally heavy rain, and
gusty winds. However, the intensity of this line is in question as
it moves southeast through Missouri and into Illinois early Monday
morning. Another disturbance drive northeast out of the southern
Plains, which could lead to a few showers and isolated
thunderstorm ahead of the approaching line.

The isolated nature of what develops ahead of the line makes it
difficult to pinpoint direct impact to any one terminal and
therefore is not mentioned in the TAF at this time. The strategy
was to focus on TSRA along the main line and target best potential
for TSRA impacts. KUIN has the greatest chances (70-80%). KCOU/KJEF
lie at the southern end of the line, where thunderstorms are
likely to weaken, but maintain a broad spread of showers with
embedded thunder potential. It remains uncertain whether
thunderstorms will maintain enough intensity through the metro
terminals, justifying the continuation of PROB30 groups to account
for TSRA.

One trend that will need to be monitored is where outflow stalls
Monday. A second, weaker surface low ejects from the Plains along
the boundary, which could support showers and isolated
thunderstorms over central MO/metro sites through much of the day.
It would be reasonable to extend the -SHRA mention with PROB30s
for TSRA, if trends continue in this direction. Otherwise,
conditions largely vary between MVFR/VFR through the period with
MVFR concentrated on relatively more intense SHRA/TSRA.

Maples

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch through this evening for Boone MO-Callaway MO-Cole
     MO-Crawford MO-Franklin MO-Gasconade MO-Moniteau MO-
     Montgomery MO-Osage MO-Warren MO-Washington MO.

IL...None.
&&

WFO LSX

Hazardous Weather Outlook
National Weather Service St Louis MO
600 AM CDT Mon May 18 2026

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-191100-
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-
600 AM CDT Mon May 18 2026

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

.DAYS ONE THROUGH SEVEN...Today through Sunday.

More detailed information can be accessed at:
https://www.weather.gov/media/lsx/DssPacket.pdf

The Area Forecast Discussion is available at:
https://forecast.weather.gov/
product.php?issuedby=LSX&product=AFD&site=lsx

.KEY MESSAGES...

- Widespread showers and thunderstorms are expected throughout the
  day with heavy rainfall in some locations potentially leading to
  flash flooding.

- A few strong to severe thunderstorms are possible this afternoon
  and evening with the main hazards being hail and damaging wind
  gusts.

- Additional thunderstorms are forecast late tonight and early
  Tuesday morning with another round possible along a cold front
  Tuesday afternoon/evening.

NOTE: Starting May 29, 2026, this outlook product will be
discontinued. Please see the above products for more detailed
forecast information.

WFO LSX