Alert archive / Missouri / Flash Flood Warnings in 2026

Flash Flood Warning 21, NWS St. Louis, MO

May 18, 2026Saint Charles County, Saint Louis County, City of Saint Louis, Missouri

NWS St. Louis, MO issued this flash flood warning at May 18, 2026, 5:12 PM CDT for Saint Charles County, Saint Louis County, City of Saint Louis, Missouri. It was in force for 3 hr. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: May 18, 2026, 5:12 PM CDT (22:12 UTC)
Expired: May 18, 2026, 8:15 PM CDT
In force: 3 hr
Issued by: NWS St. Louis, MO
Area: Storm-based polygon
Flood severity: None

Counties City of Saint Louis, MO, Saint Charles County, MO, Saint Louis County, MO

The radar

The St Louis radar (KLSX), 10 km from the middle of the area, began a volume at 22:14 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
May 18, 6:52 PM CDT	RAIN 2.38	3 Nw Clarkson Valley, MO	Courtesy of KTVI-TV.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 10.2 hours before the alert went out and 237 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 850 J/kg
Mixed-layer CIN: -80 J/kg
Mixed-layer LCL: 966 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 301 m²/s²
0-3 km storm-relative helicity: 331 m²/s²
Significant tornado parameter: 0.8
Supercell composite: 8.8

Open this sounding in Storm Lab

The text

As transmitted.

929 
WGUS53 KLSX 182212
FFWLSX
MOC183-189-510-190115-
/O.NEW.KLSX.FF.W.0021.260518T2212Z-260519T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service St Louis MO
512 PM CDT Mon May 18 2026

The National Weather Service in St Louis has issued a

* Flash Flood Warning for...
  Saint Charles County in east central Missouri...
  Saint Louis County in east central Missouri...
  Saint Louis City in east central Missouri...

* Until 815 PM CDT.

* At 512 PM CDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Between 1 and 2 inches of rain
  have fallen. Additional rainfall amounts of 0.5 to 2 inches are
  possible in the warned area. Flash flooding is ongoing or expected
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar indicated.

  IMPACT...Flash flooding of small creeks and streams, urban areas,
           highways, streets and underpasses as well as other poor
           drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  St. Louis, O'Fallon, St. Charles, St. Peters, Florissant,
  Chesterfield, Wildwood, University City, Ballwin, Wentzville,
  Kirkwood, Maryland Heights, Hazelwood, Webster Groves, Ferguson,
  Manchester, Creve Coeur and Overland.

This includes the following State Parks...
Babler Memorial State Park, Scott Joplin Historic Site, Route 66
State Park, Castlewood State Park, Confluence State Park and First
Missouri State Capitol Historic Site.

This includes the following highways...
Interstate 70 in Missouri between exits 203 and 231. Interstate 44 in
Missouri between exits 261 and 277.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

&&

LAT...LON 3864 9073 3854 9090 3855 9096 3889 9096
      3888 9082 3892 9079 3893 9067 3887 9056
      3897 9044 3884 9011 3872 9021 3861 9018
      3839 9034 3845 9034 3848 9042 3850 9041
      3845 9068 3847 9074

FLASH FLOOD...RADAR INDICATED

$$

Walsh

1 follow-up statement

341 
WGUS73 KLSX 190107
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
807 PM CDT Mon May 18 2026

MOC183-189-510-190117-
/O.EXP.KLSX.FF.W.0021.000000T0000Z-260519T0115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Saint Charles MO-Saint Louis MO-Saint Louis City MO-
807 PM CDT Mon May 18 2026

...FLASH FLOOD WARNING WILL EXPIRE AT 815 PM CDT THIS EVENING FOR
SAINT CHARLES AND SAINT LOUIS COUNTIES AND THE SAINT LOUIS CITY...

The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed remaining road closures.

A Flood Watch remains in effect until 100 PM CDT Tuesday for portions
of southwest Illinois and east central Missouri.

A Flood Watch remains in effect until 100 PM CDT Tuesday for portions
of southwest Illinois and Missouri.

A Flood Watch remains in effect until 100 PM CDT Tuesday for portions
of central and east central Missouri.

&&

LAT...LON 3864 9073 3854 9090 3855 9096 3889 9096
      3888 9082 3892 9079 3893 9067 3887 9056
      3897 9044 3884 9011 3872 9021 3861 9018
      3839 9034 3845 9034 3848 9042 3850 9041
      3845 9068 3847 9074

$$

Maples

The office that day

Everything else NWS St. Louis, MO issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 18, 1:12 AM CDT	Flood Watch	LSX	Audrain, Boone, Callaway, Cole, Crawford, Franklin and 14 more	35 hr
May 18, 6:12 AM CDT	Severe Thunderstorm Warning	LSX	Audrain, Marion, Pike, Ralls	48 min
May 18, 6:18 AM CDT	Severe Thunderstorm Warning Considerable damage threat	LSX	Audrain, Boone, Callaway	42 min
May 18, 6:41 AM CDT	Tornado Warning	LSX	Pike, Ralls	28 min
May 18, 7:21 AM CDT	Severe Thunderstorm Warning	LSX	Lincoln, Pike	39 min
May 18, 10:56 AM CDT	Areal Flood Advisory	LSX	Franklin, Gasconade	4 hr
May 18, 12:39 PM CDT	Areal Flood Advisory	LSX	Crawford, Franklin, Washington	7 hr
May 18, 1:22 PM CDT	Areal Flood Advisory	LSX	Saint Louis, City of Saint Louis	6 hr
May 18, 2:40 PM CDT	Areal Flood Advisory	LSX	Boone, Callaway, Cole, Moniteau	4 hr
May 18, 3:05 PM CDT	Flash Flood Warning	LSX	Crawford, Franklin, Gasconade, Warren	6 hr
May 18, 5:01 PM CDT	Flash Flood Warning	LSX	Franklin, Gasconade, Warren	3 hr
May 18, 5:06 PM CDT	Flash Flood Warning	LSX	Jefferson, Saint Louis, City of Saint Louis	4 hr

Nearby

Flash Flood Warnings in Missouri, 2026 Every flash flood warning in 2026

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.