Alert archive / Illinois / Flash Flood Warnings in 2021

Flash Flood Warning 38, NWS St. Louis, MO

August 26, 2021Montgomery County, Illinois

NWS St. Louis, MO issued this flash flood warning at Aug 26, 2021, 2:45 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
Aug 26, 2021, 2:45 PM CDT (19:45 UTC)
Expired
Aug 26, 2021, 6:45 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), 105 km from the middle of the area, began a volume at 19:45 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, 7.8 hours before the alert went out and 133 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-pSkew-T log-p diagram, Lincoln, IL at 12:00Z on 2021-08-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1067 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lincoln, IL at 12:00Z on 2021-08-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 89 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
1067 J/kg
Mixed-layer CIN
-78 J/kg
Mixed-layer LCL
954 m above ground
0-6 km bulk shear
19 kt
0-1 km storm-relative helicity
89 m²/s²
0-3 km storm-relative helicity
118 m²/s²
Significant tornado parameter
0.0
Supercell composite
4.6

Open this sounding in Storm Lab

The text

As transmitted.

477 
WGUS53 KLSX 261945
FFWLSX
ILC135-262345-
/O.NEW.KLSX.FF.W.0038.210826T1945Z-210826T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service St Louis MO
245 PM CDT Thu Aug 26 2021

The National Weather Service in St Louis has issued a

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

* Until 645 PM CDT.

* At 245 PM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 3 inches of rain 
  have fallen. 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...
  Litchfield, Hillsboro, Taylor Springs, Butler and Honey Bend.

This includes the following State Parks...
	Lake Lou Yaeger.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3926 8963 3928 8960 3928 8956 3926 8948
      3912 8949 3910 8961 3921 8965

FLASH FLOOD...RADAR INDICATED

$$

Carney
2 follow-up statements
742 
WGUS73 KLSX 262118
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
418 PM CDT Thu Aug 26 2021

ILC135-262345-
/O.CON.KLSX.FF.W.0038.000000T0000Z-210826T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery IL-
418 PM CDT Thu Aug 26 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 645 PM CDT THIS 
EVENING FOR SOUTHWESTERN MONTGOMERY COUNTY IN SOUTH CENTRAL 
ILLINOIS...

At 418 PM CDT, Doppler radar indicated the thunderstorms had ended 
over the warned area.  However, up to 3 inches of rain have fallen, 
and flash flooding continues to be a threat as this heavy rainfall 
runs off.

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...
  Litchfield, Hillsboro, Taylor Springs, Butler and Honey Bend.

This includes the following State Parks...
	Lake Lou Yaeger.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3926 8963 3928 8960 3928 8956 3926 8948
      3912 8949 3910 8961 3921 8965

FLASH FLOOD...RADAR INDICATED

$$

Carney
993 
WGUS73 KLSX 262339
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
639 PM CDT Thu Aug 26 2021

ILC135-262349-
/O.EXP.KLSX.FF.W.0038.000000T0000Z-210826T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Montgomery IL-
639 PM CDT Thu Aug 26 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 645 PM CDT THIS EVENING FOR 
SOUTHWESTERN MONTGOMERY COUNTY IN SOUTH CENTRAL ILLINOIS...

Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

LAT...LON 3926 8963 3928 8960 3928 8956 3926 8948
      3912 8949 3910 8961 3921 8965

$$

Glass

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 26, 2:04 PM CDTSevere Thunderstorm WarningLSXMontgomery41 min
Aug 26, 4:38 PM CDTSevere Thunderstorm WarningLSXGreene52 min
Aug 26, 5:28 PM CDTSevere Thunderstorm WarningLSXAdams25 min
Aug 26, 5:57 PM CDTSevere Thunderstorm WarningLSXBond, Fayette48 min
Aug 26, 6:54 PM CDTAreal Flood AdvisoryLSXBond3 hr

Nearby

Flash Flood Warnings in Illinois, 2021Every 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.