Alert archive / Illinois / Flash Flood Warnings in 2021

Flash Flood Warning 28, NWS St. Louis, MO

July 12, 2021Montgomery County, Illinois

NWS St. Louis, MO issued this flash flood warning at Jul 12, 2021, 6:50 PM CDT for Montgomery County, Illinois. It was in force for 4 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 12, 2021, 6:50 PM CDT (23:50 UTC)
Expired: Jul 12, 2021, 11:00 PM CDT
In force: 4 hr
Issued by: NWS St. Louis, MO
Area: Storm-based polygon
Flood severity: None

County Montgomery County, IL

The radar

The Lincoln radar (KILX), 103 km from the middle of the area, began a volume at 23:50 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.

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 11.8 hours before the alert went out and 118 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: 653 J/kg
Mixed-layer CIN: -21 J/kg
Mixed-layer LCL: 548 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 80 m²/s²
0-3 km storm-relative helicity: 102 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

492 
WGUS53 KLSX 122350
FFWLSX
ILC135-130400-
/O.NEW.KLSX.FF.W.0028.210712T2350Z-210713T0400Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service St Louis MO
650 PM CDT Mon Jul 12 2021

The National Weather Service in St Louis has issued a

* Flash Flood Warning for...
  East Central Montgomery County in south central Illinois...

* Until 1100 PM CDT.

* At 650 PM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Up to 2 inches of rain have 
  fallen. Additional rainfall amounts up to 1 inch are possible in 
  the warned area. Flash flooding is ongoing or expected to begin 
  shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  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...
  Nokomis, Witt, Irving, Coalton, Ohlman and Wenonah.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3922 8914 3922 8925 3915 8925 3912 8931
      3912 8941 3926 8941 3935 8931 3935 8914

FLASH FLOOD...RADAR INDICATED

$$

Britt

2 follow-up statements

368 
WGUS73 KLSX 130257
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
957 PM CDT Mon Jul 12 2021

ILC135-130400-
/O.CON.KLSX.FF.W.0028.000000T0000Z-210713T0400Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery IL-
957 PM CDT Mon Jul 12 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 11 PM CDT THIS 
EVENING FOR EAST CENTRAL MONTGOMERY COUNTY IN SOUTH CENTRAL 
ILLINOIS...

At 957 PM CDT, Doppler radar indicated that earlier thunderstorms 
have produced between 1 and 3 inches of rain in some locations in 
the warned area.  Flash flooding is ongoing or expected to begin 
shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar.

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

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3922 8914 3922 8925 3915 8925 3912 8931
      3912 8941 3926 8941 3935 8931 3935 8914

FLASH FLOOD...RADAR INDICATED

$$

Britt

899 
WGUS73 KLSX 130356
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
1056 PM CDT Mon Jul 12 2021

ILC135-130406-
/O.EXP.KLSX.FF.W.0028.000000T0000Z-210713T0400Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery IL-
1056 PM CDT Mon Jul 12 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 11 PM CDT THIS EVENING FOR 
EAST CENTRAL MONTGOMERY COUNTY IN SOUTH CENTRAL ILLINOIS...

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

LAT...LON 3922 8914 3922 8925 3915 8925 3912 8931
      3912 8941 3926 8941 3935 8931 3935 8914

$$

Britt

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 11, 7:50 PM CDT	Areal Flood Advisory	LSX	Monroe, Randolph, Saint Clair	3 hr
Jul 11, 10:43 PM CDT	Areal Flood Advisory	LSX	Macoupin	3 hr
Jul 12, 12:17 AM CDT	Areal Flood Advisory	LSX	Montgomery	3 hr
Jul 12, 6:27 PM CDT	Areal Flood Advisory	LSX	Pike	3 hr

Nearby

Flash Flood Warnings in Illinois, 2021 Every flash flood warning in 2021

Sources

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