Alert archive / Illinois / Flash Flood Warnings in 2021

Flash Flood Warning 8, NWS Chicago, IL

August 24, 2021Cook County, DuPage County, Lake County, Illinois

NWS Chicago, IL issued this flash flood warning at Aug 24, 2021, 6:36 PM CDT for Cook County, DuPage County, Lake County, Illinois. It was in force for 3 hr. 5 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 24, 2021, 6:36 PM CDT (23:36 UTC)
Expired: Aug 24, 2021, 9:15 PM CDT
In force: 3 hr
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Flood severity: None

Counties Cook County, IL, DuPage County, IL, Lake County, IL

The radar

The Chicago radar (KLOT), 46 km from the middle of the area, began a volume at 23:35 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
Aug 24, 7:09 PM CDT	FLOOD	Edgewater - Chicago, IL	PHOTO SHARED VIA SOCIAL MEDIA SHOWS SEVERAL INCHES OF STANDING WATER ON RESIDENTIAL STREET IN ANDERSONVILLE, CHICAGO.
Aug 24, 7:22 PM CDT	FLOOD	1 Ne North Center - Chi, IL	VIDEOS SHARED TO SOCIAL MEDIA SHOW SEVERAL INCHES OF WATER AT IRVING PARK ROAD UNDERPASS AT RAVENSWOOD AVENUE.
Aug 24, 7:30 PM CDT	FLOOD	2 Wnw Chicago Loop, IL	DELAYED REPORT. REPORT OF A STALLED CAR AT UNDERPASS NEAR ASHLAND AVENUE AND KINZIE STREET. TIME ESTIMATED.
Aug 24, 8:14 PM CDT	HEAVY RAIN 2.74	1 Ene Lincoln Square -, IL	STORM TOTAL. 2.27 INCHES FELL OVER A ONE HOUR PERIOD BETWEEN 5:49 AND 6:49 PM. PERSONAL WEATHER STATION KILCHICA440.
Aug 24, 8:20 PM CDT	FLASH FLOOD	1 E North Lawndale - Ch, IL	DELAYED REPORT. REPORT OF CARS STALLED IN WATER NEAR OGDEN AVENUE AND WESTERN AVENUE. TIME ESTIMATED.

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, 11.6 hours before the alert went out and 212 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: 1513 J/kg
Mixed-layer CIN: -147 J/kg
Mixed-layer LCL: 1124 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 59 m²/s²
0-3 km storm-relative helicity: 65 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

255 
WGUS53 KLOT 242336
FFWLOT
ILC031-043-097-250215-
/O.NEW.KLOT.FF.W.0008.210824T2336Z-210825T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Chicago IL
636 PM CDT Tue Aug 24 2021

The National Weather Service in Chicago has issued a

* Flash Flood Warning for...
  Northern Cook County in northeastern Illinois...
  Northeastern DuPage County in northeastern Illinois...
  Southeastern Lake IL County in northeastern Illinois...

* Until 915 PM CDT.

* At 636 PM CDT, doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  1 and 2 inches of rain have fallen. Slow-moving thunderstorms 
  continue to develop over the same areas, producing rainfall rates 
  of 1 to 2 inches per hour. Additional rainfall amounts of 1 to 2 
  inches are possible in the warned area.

  HAZARD...Flash flooding.

  SOURCE...Radar and automated gauges.

  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...
  Chicago, Cicero, Arlington Heights, Evanston, Schaumburg, Skokie, 
  Des Plaines, Berwyn, Mount Prospect, Wheaton, Hoffman Estates, Oak 
  Park, Glenview, Elmhurst, Lombard, Bartlett, Ohare Airport, 
  Streamwood, Carol Stream and Hanover Park.

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, canals, and storm sewers, as 
well roadways, underpasses, and other poor drainage areas.

&&

LAT...LON 4199 8816 4215 8784 4216 8771 4206 8761
      4189 8754 4186 8755 4184 8761 4185 8792
      4189 8812

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 1 HOUR

$$

WSL

2 follow-up statements

257 
WGUS73 KLOT 250130
FFSLOT

Flash Flood Statement
National Weather Service Chicago IL
830 PM CDT Tue Aug 24 2021

ILC031-043-097-250215-
/O.CON.KLOT.FF.W.0008.000000T0000Z-210825T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cook IL-DuPage IL-Lake IL IL-
830 PM CDT Tue Aug 24 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 915 PM CDT THIS 
EVENING FOR NORTHERN COOK, NORTHEASTERN DUPAGE AND SOUTHEASTERN LAKE 
IL COUNTIES...

At 830 PM CDT, doppler radar indicated thunderstorms had moved east 
out of the warned area. Between 2 and 4 inches of rain have fallen, 
with little to no additional rainfall expected. Flooding will 
continue across the area, but will begin to recede soon.

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...
  Chicago, Cicero, Arlington Heights, Evanston, Schaumburg, Skokie, 
  Des Plaines, Berwyn, Mount Prospect, Wheaton, Hoffman Estates, Oak 
  Park, Glenview, Elmhurst, Lombard, Bartlett, Ohare Airport, 
  Streamwood, Carol Stream and Hanover Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Expect flooding of creeks, ditches, canals, and storm sewers, as 
well roadways, underpasses, and other poor drainage areas.

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

&&

LAT...LON 4199 8816 4215 8784 4216 8771 4206 8761
      4189 8754 4186 8755 4184 8761 4185 8792
      4189 8812

FLASH FLOOD...RADAR INDICATED

$$

WSL

143 
WGUS73 KLOT 250207
FFSLOT

Flash Flood Statement
National Weather Service Chicago IL
907 PM CDT Tue Aug 24 2021

ILC031-043-097-250217-
/O.EXP.KLOT.FF.W.0008.000000T0000Z-210825T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cook IL-DuPage IL-Lake IL IL-
907 PM CDT Tue Aug 24 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 915 PM CDT THIS EVENING FOR 
NORTHERN COOK, NORTHEASTERN DUPAGE AND SOUTHEASTERN LAKE IL 
COUNTIES...

The heavy rain has ended. Any remaining standing water will continue 
to recede and flooding is no longer expected to pose a threat. If 
you encounter a flooded roadway, find a different route!

LAT...LON 4199 8816 4215 8784 4216 8771 4206 8761
      4189 8754 4186 8755 4184 8761 4185 8792
      4189 8812

$$

WSL

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 24, 3:19 AM CDT	Heat Advisory	LOT	Cook, DeKalb, Ford, Grundy, Iroquois, Kankakee and 6 more	17 hr
Aug 24, 3:30 PM CDT	Special Marine Warning	LOT		60 min
Aug 24, 4:21 PM CDT	Special Weather Statement	LOT	Boone	24 min
Aug 24, 4:33 PM CDT	Heat Advisory	LOT	Ford, Grundy, Iroquois, Kankakee, LaSalle, Livingston and 1 more	26 hr
Aug 24, 4:58 PM CDT	Areal Flood Advisory	LOT	Boone, Lake, McHenry	3 hr
Aug 24, 5:13 PM CDT	Special Weather Statement	LOT	DuPage	32 min
Aug 24, 5:26 PM CDT	Severe Thunderstorm Warning	LOT	Boone, Lee, Ogle, Winnebago	64 min
Aug 24, 5:28 PM CDT	Special Marine Warning	LOT		92 min
Aug 24, 5:40 PM CDT	Flash Flood Warning	LOT	Boone, McHenry	4 hr
Aug 24, 6:09 PM CDT	Severe Thunderstorm Warning	LOT	Boone, DeKalb, Kane, Lee, McHenry, Ogle	66 min
Aug 24, 6:13 PM CDT	Beach Hazards Statement	LOT	Cook, Lake	4 hr
Aug 24, 6:19 PM CDT	Areal Flood Advisory	LOT	Cook, DuPage, Lake	17 min
Aug 24, 6:54 PM CDT	Special Weather Statement	LOT	Kendall, LaSalle	51 min

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.