Alert archive / Illinois / Flash Flood Warnings in 2021

Flash Flood Warning 5, NWS Chicago, IL

July 12, 2021Grundy County, Livingston County, Will County, Illinois

NWS Chicago, IL issued this flash flood warning at Jul 12, 2021, 11:56 PM CDT for Grundy County, Livingston County, Will County, Illinois. It was in force for 4 hr. 2 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: Jul 12, 2021, 11:56 PM CDT (04:56 UTC)
Expired: Jul 13, 2021, 3:45 AM CDT
In force: 4 hr
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Flood severity: None

Counties Grundy County, IL, Livingston County, IL, Will County, IL

The radar

The Chicago radar (KLOT), 53 km from the middle of the area, began a volume at 04:55 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
Jul 13, 12:15 AM CDT	FLOOD	Braceville, IL	6 TO 8 INCHES OF STANDING WATER IN YARDS ON THE NORTH SIDE OF BRACEVILLE.
Jul 13, 12:30 AM CDT	HEAVY RAIN 1.57	1 Ssw Coal City, IL	MOST OF THIS FELL BETWEEN 10:30 PM AND 12:30 AM.

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 00:00Z, 4.9 hours before the alert went out and 115 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: 235 J/kg
Mixed-layer CIN: -19 J/kg
Mixed-layer LCL: 949 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 16 m²/s²
0-3 km storm-relative helicity: 37 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted.

407 
WGUS53 KLOT 130456
FFWLOT
ILC063-105-197-130845-
/O.NEW.KLOT.FF.W.0005.210713T0456Z-210713T0845Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Chicago IL
1156 PM CDT Mon Jul 12 2021

The National Weather Service in Chicago has issued a

* Flash Flood Warning for...
  Northeastern Livingston County in central Illinois...
  Southeastern Grundy County in northeastern Illinois...
  Southwestern Will County in northeastern Illinois...

* Until 345 AM CDT.

* At 1156 PM CDT, doppler radar indicated showers training over the 
  warned area producing heavy rain. Between 1 and 3 inches of rain 
  have fallen. Additional rainfall amounts of 1 to 2 inches are 
  possible in the warned area. Flash flooding is expected to begin 
  shortly.

  HAZARD...Flash flooding.

  SOURCE...Radar.

  IMPACT...Rapid-onset 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...
  Braidwood, Coal City, Dwight, Diamond, Gardner, Braceville, South 
  Wilmington, Godley, Carbon Hill and East Brooklyn.

This includes the following highways...
	I-55 between mile markers 220 and 236.

The heavy rain will also produce very low visibility, including 
along I-55.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Warning means rapid-onset flooding is imminent or may 
already be occurring. Persons along creeks, drainage ditches, and 
other waterways should take immediate precautions to protect life 
and property.

Expect flooding of creeks, ditches, farmland, roadways, and and 
other low lying areas.

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

&&

LAT...LON 4111 8843 4132 8834 4138 8822 4120 8821
      4120 8824 4119 8824 4114 8824 4113 8824
      4111 8824 4111 8825 4101 8838 4102 8842

FLASH FLOOD...RADAR INDICATED

$$

Friedlein

2 follow-up statements

479 
WGUS73 KLOT 130637
FFSLOT

Flash Flood Statement
National Weather Service Chicago IL
137 AM CDT Tue Jul 13 2021

ILC063-105-197-130845-
/O.CON.KLOT.FF.W.0005.000000T0000Z-210713T0845Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grundy IL-Livingston IL-Will IL-
137 AM CDT Tue Jul 13 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 345 AM CDT EARLY THIS 
MORNING FOR NORTHEASTERN LIVINGSTON, SOUTHEASTERN GRUNDY AND 
SOUTHWESTERN WILL COUNTIES...

At 137 AM CDT, doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 1.5 and 3.5 inches of rain have 
fallen across much of the warned area. Additional rainfall amounts 
up to 1 inch are possible in the warned area through daybreak. Flash 
flooding is likely ongoing or expected to begin shortly in parts of 
the area.

HAZARD...Flash flooding.

SOURCE...Radar.

IMPACT...Rapid-onset 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...
  Braidwood, Coal City, Dwight, Diamond, Gardner, Braceville, South 
  Wilmington, Godley and East Brooklyn.

This includes the following highways...
	I-55 between mile markers 221 and 236.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Warning means rapid-onset flooding is imminent or may 
already be occurring. Persons along creeks, drainage ditches, and 
other waterways should take immediate precautions to protect life 
and property.

Expect flooding of creeks, ditches, farmland, roadways, and and 
other low lying areas.

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

&&

LAT...LON 4111 8841 4125 8835 4129 8830 4130 8822
      4120 8822 4120 8824 4119 8824 4114 8824
      4113 8824 4111 8824 4111 8825 4101 8838
      4102 8842 4109 8842

FLASH FLOOD...RADAR INDICATED

$$

Friedlein

407 
WGUS73 KLOT 130846
FFSLOT

Flash Flood Statement
National Weather Service Chicago IL
346 AM CDT Tue Jul 13 2021

ILC063-105-197-130856-
/O.EXP.KLOT.FF.W.0005.000000T0000Z-210713T0845Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grundy IL-Livingston IL-Will IL-
346 AM CDT Tue Jul 13 2021

...FLASH FLOOD WARNING HAS EXPIRED FOR NORTHEASTERN LIVINGSTON, 
SOUTHEASTERN GRUNDY AND SOUTHWESTERN WILL COUNTIES...

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

LAT...LON 4111 8841 4125 8835 4129 8830 4130 8822
      4120 8822 4120 8824 4119 8824 4114 8824
      4113 8824 4111 8824 4111 8825 4101 8838
      4102 8842 4109 8842

$$

Donofrio

The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 12, 8:14 PM CDT	Areal Flood Advisory	LOT	Grundy, LaSalle, Livingston	4 hr
Jul 12, 8:42 PM CDT	Flash Flood Warning	LOT	Grundy, LaSalle	5 hr
Jul 12, 10:33 PM CDT	Areal Flood Advisory	LOT	Grundy	4 hr
Jul 13, 1:29 AM CDT	Areal Flood Warning	LOT	Grundy, LaSalle	9 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.