Alert archive / Illinois / Flash Flood Warnings in 2020

Flash Flood Warning 61, NWS St. Louis, MO

August 12, 2020Monroe County, Randolph County, Saint Clair County, Illinois

NWS St. Louis, MO issued this flash flood warning at Aug 12, 2020, 11:18 AM CDT for Monroe County, Randolph County, Saint Clair County, Illinois. It was in force for 3 hr. 4 reports 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
Aug 12, 2020, 11:18 AM CDT (16:18 UTC)
Expired
Aug 12, 2020, 2:46 PM CDT
In force
3 hr
Issued by
NWS St. Louis, MO
Area
Storm-based polygon
Flood severity
None

Counties Monroe County, IL, Randolph County, IL, Saint Clair County, IL

What was reported inside it

TimeReportWhereRemark
Aug 12, 12:00 PM CDTFLASH FLOODHecker, ILSTATE HIGHWAYS 156 AND 159 FLOODED IN SPOTS, 156 BETWEEN HECKER AND WATERLOO AND 159 BETWEEN HECKER AND BELLEVILLE.
Aug 12, 12:00 PM CDTFLASH FLOODSmithton, ILJUST SOUTH OF THE PARK IN SMITHTON, STATE HIGHWAY 159 NEAR THE CREEK WAS FLOODED.
Aug 12, 12:09 PM CDTFLOODWaterloo, ILMONROE COUNTY DEPUTIES ARE EN ROUTE TO WATERLOO TO INVESTIGATE FLOODED ROADS, BUT AT THE TIME OF THE CALL THE DISPATCHER WAS UNAWARE OF ANY ROAD CLOSURES IN MONROE COUNTY.
Aug 12, 12:50 PM CDTFLASH FLOODMaeystown, ILROADS AROUND MAEYSTOWN, INCLUDING MAEYSTOWN ROAD, HAVE DEBRIS LEFT ON THEM FROM THIS MORNINGS FLOODING.

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, 4.3 hours before the alert went out and 249 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 2020-08-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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 2020-08-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 14 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1132 m above ground
0-6 km bulk shear
3 kt
0-1 km storm-relative helicity
14 m²/s²
0-3 km storm-relative helicity
-3 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

552 
WGUS53 KLSX 121618
FFWLSX
ILC133-157-163-122215-
/O.NEW.KLSX.FF.W.0061.200812T1618Z-200812T2215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service St Louis MO
1118 AM CDT Wed Aug 12 2020

The National Weather Service in St Louis has issued a

* Flash Flood Warning for...
  Monroe County in southwestern Illinois...
  Northwestern Randolph County in southwestern Illinois...
  Southwestern St. Clair County in southwestern Illinois...

* Until 515 PM CDT.

* At 1117 AM CDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to two inches of rain have
  already fallen. Flash flooding is ongoing or expected to begin
  shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar indicated.

  IMPACT...Flooding of small creeks and streams, urban areas, 
           highways, streets and underpasses as well as other 
           drainage and low lying areas.

* Some locations that will experience flooding include...
  Belleville, Waterloo, Columbia, Freeburg, Millstadt, Red Bud,
  Oakville, Smithton, New Athens, Valmeyer, Evansville, Baldwin,
  Fountain, New Design, Preston, Prairie Du Rocher, Prairie, Hecker,
  Barr and Ruma.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3808 8986 3809 9021 3813 9026 3816 9028
      3818 9031 3822 9036 3832 9037 3839 9034
      3840 9032 3844 9029 3852 9026 3848 9021
      3845 8984

FLASH FLOOD...RADAR INDICATED

$$

MRM
3 follow-up statements
750 
WGUS73 KLSX 121720
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
1220 PM CDT Wed Aug 12 2020

ILC133-157-163-122215-
/O.CON.KLSX.FF.W.0061.000000T0000Z-200812T2215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Monroe IL-Randolph IL-St. Clair IL-
1220 PM CDT Wed Aug 12 2020

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 515 PM CDT FOR
MONROE...NORTHWESTERN RANDOLPH AND SOUTHWESTERN ST. CLAIR COUNTIES...

At 1218 PM CDT, law enforcement reported heavy rain from 
thunderstorms causing flooding along I-59 in Smithton. Up to two 
inches of rain have already fallen. Flash flooding is ongoing or 
expected to begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Law enforcement.

IMPACT...Flooding of small creeks and streams, urban areas, 
         highways, streets and underpasses as well as other drainage 
         and low lying areas.

Some locations that will experience flooding include...
Belleville, Waterloo, Columbia, Freeburg, Millstadt, Red Bud,
Oakville, Smithton, New Athens, Valmeyer, Evansville, Baldwin,
Fountain, New Design, Preston, Prairie Du Rocher, Prairie, Hecker,
Barr and Ruma.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3808 8986 3809 9021 3813 9026 3816 9028
      3818 9031 3822 9036 3832 9037 3839 9034
      3840 9032 3844 9029 3852 9026 3848 9021
      3845 8984

FLASH FLOOD...OBSERVED

$$

MRM
572 
WGUS73 KLSX 121747
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
1247 PM CDT Wed Aug 12 2020

ILC133-157-163-122215-
/O.CON.KLSX.FF.W.0061.000000T0000Z-200812T2215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Monroe IL-Randolph IL-St. Clair IL-
1247 PM CDT Wed Aug 12 2020

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 515 PM CDT FOR
MONROE...NORTHWESTERN RANDOLPH AND SOUTHWESTERN ST. CLAIR COUNTIES...

At 1246 PM CDT, trained weather spotters reported heavy rain from 
thunderstorms flooding several highways in Waterloo, Hecker, and 
Smithton. Up to two inches of rain have already fallen. Flash 
flooding is ongoing or expected to begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Trained weather spotters.

IMPACT...Flooding of small creeks and streams, urban areas, 
         highways, streets and underpasses as well as other drainage 
         and low lying areas.

Some locations that will experience flooding include...
Belleville, Waterloo, Columbia, Freeburg, Millstadt, Red Bud,
Oakville, Smithton, New Athens, Valmeyer, Evansville, Baldwin,
Fountain, New Design, Preston, Prairie Du Rocher, Prairie, Hecker,
Barr and Ruma.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3808 8986 3809 9021 3813 9026 3816 9028
      3818 9031 3822 9036 3832 9037 3839 9034
      3840 9032 3844 9029 3852 9026 3848 9021
      3845 8984

FLASH FLOOD...OBSERVED

$$

MRM
257 
WGUS73 KLSX 121946
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
246 PM CDT Wed Aug 12 2020

ILC133-157-163-121956-
/O.CAN.KLSX.FF.W.0061.000000T0000Z-200812T2215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Monroe IL-Randolph IL-St. Clair IL-
246 PM CDT Wed Aug 12 2020

...THE FLASH FLOOD WARNING FOR MONROE...NORTHWESTERN RANDOLPH AND
SOUTHWESTERN ST. CLAIR COUNTIES IS CANCELLED...

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

LAT...LON 3808 8986 3809 9021 3813 9026 3816 9028
      3818 9031 3822 9036 3832 9037 3839 9034
      3840 9032 3844 9029 3852 9026 3848 9021
      3845 8984

$$

MRM

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 12, 9:41 AM CDTFlash Flood WarningLSXMadison, Saint Clair5 hr
Aug 12, 10:19 AM CDTFlash Flood WarningLSXMadison, Saint Clair4 hr
Aug 12, 11:47 AM CDTFlash Flood WarningLSXClinton, Randolph, Saint Clair, Washington6 hr
Aug 12, 2:57 PM CDTAreal Flood WarningLSXSaint Clair3 hr

Nearby

Flash Flood Warnings in Illinois, 2020Every flash flood warning in 2020

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.