Alert archive / Illinois / Flash Flood Warnings in 2021

Flash Flood Warning 11, NWS Chicago, IL

August 25, 2021Cook County, Kankakee County, Will County, Illinois; Lake County, Porter County, Indiana

NWS Chicago, IL issued this flash flood warning at Aug 25, 2021, 9:15 PM CDT for Cook County, Kankakee County, Will County, Illinois; Lake County, Porter County, Indiana. It was in force for 4 hr. 9 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 25, 2021, 9:15 PM CDT (02:15 UTC)
Expired: Aug 26, 2021, 1:28 AM CDT
In force: 4 hr
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Flood severity: None

Counties Cook County, IL, Kankakee County, IL, Will County, IL, Lake County, IN, Porter County, IN

The radar

The Chicago radar (KLOT), 71 km from the middle of the area, began a volume at 02:19 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 25, 9:20 PM CDT	HEAVY RAIN 2.2	3 Sse St. John, IN	2.20 INCHES OF RAIN IN THE PAST HOUR WITH HEAVY RAIN STILL FALLING.
Aug 25, 9:28 PM CDT	FLOOD	South Haven, IN	GOVERNOR ROAD CLOSED WITH 2-3 INCHES OF WATER FLOWING OVER THE ROAD.
Aug 25, 9:30 PM CDT	HEAVY RAIN 3.52	3 Wnw Merrillville, IN	STATION ID KINMERRI14. RAINFALL SINCE 5:45 PM CDT.
Aug 25, 9:31 PM CDT	HEAVY RAIN 3.28	2 Se Schererville, IN	STATION ID KINCROWN79. RAINFALL SINCE 4:40 PM CDT.
Aug 25, 9:37 PM CDT	HEAVY RAIN 2.86	2 Nne Crown Point, IN	2.86 INCHES OF RAIN IN PAST 60 MINUTES, WITH MAJORITY FALLING IN 30 MINUTES.
Aug 25, 9:42 PM CDT	HEAVY RAIN 3.69	2 Ene Grant Park, IL	MESONET STATION ID KILGRANT13. RAINFALL SINCE 8:24 PM CDT.
Aug 25, 9:43 PM CDT	HEAVY RAIN 3.22	1 N Beecher, IL	MESONET STATION ID KILBEECH22. RAINFALL SINCE 7:45 PM CDT.
Aug 25, 9:44 PM CDT	HEAVY RAIN 3.76	4 Se Beecher, IL	MESONET STATION ID KILBEECH14. RAINFALL SINCE 8:24 PM CDT.
Aug 25, 10:19 PM CDT	FLOOD	2 W Merrillville, IN	INTERSECTION OF STATE ROUTE 30 AND TAFT STREET CLOSED DUE TO FLOODING. FLOODING ALSO REPORTED EAST ALONG STATE ROUTE 30 TO MISSISSIPPI STREET.

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, 2.3 hours before the alert went out and 180 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: 2295 J/kg
Mixed-layer CIN: -13 J/kg
Mixed-layer LCL: 1479 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 51 m²/s²
0-3 km storm-relative helicity: 40 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

209 
WGUS53 KLOT 260215
FFWLOT
ILC031-091-197-INC089-127-260815-
/O.NEW.KLOT.FF.W.0011.210826T0215Z-210826T0815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Chicago IL
915 PM CDT Wed Aug 25 2021

The National Weather Service in Chicago has issued a

* Flash Flood Warning for...
  Southeastern Cook County in northeastern Illinois...
  Northeastern Kankakee County in northeastern Illinois...
  Southeastern Will County in northeastern Illinois...
  Lake IN County in northwestern Indiana...
  Porter County in northwestern Indiana...

* Until 315 AM CDT.

* At 915 PM CDT, doppler radar and automated rain gauges 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.

  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...
  Hammond, Gary, Tinley Park, Calumet City, Portage, Merrillville, 
  Valparaiso, Chicago Heights, East Chicago, Schererville, Hobart, 
  Lansing, Crown Point, Harvey, Highland, Munster, Park Forest, 
  Homewood, Matteson and Frankfort.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4164 8732 4164 8720 4166 8715 4171 8694
      4124 8693 4123 8698 4127 8706 4129 8713
      4119 8732 4115 8766 4123 8772 4155 8781

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

Borchardt

2 follow-up statements

936 
WGUS73 KLOT 260325
FFSLOT

Flash Flood Statement
National Weather Service Chicago IL
1025 PM CDT Wed Aug 25 2021

ILC031-091-197-INC089-127-260815-
/O.CON.KLOT.FF.W.0011.000000T0000Z-210826T0815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cook IL-Kankakee IL-Will IL-Lake IN IN-Porter IN-
1025 PM CDT Wed Aug 25 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 315 AM CDT THURSDAY 
FOR SOUTHEASTERN COOK, NORTHEASTERN KANKAKEE, SOUTHEASTERN WILL, 
LAKE IN AND PORTER COUNTIES...

At 1025 PM CDT, trained weather spotters and local 911 dispatch 
centers reported flooded roadways including along state highway 30 
near Merrillville and along residential streets in South Haven. 
Additionally, flooding of residential streets was reported in Grant 
Park. Doppler radar and automated rain gauges indicate that 1 to 
locally 4 inches of rain fell in the warned area in less then two 
hours. The heaviest rain has ended, and water will continue receding.

HAZARD...Flash flooding.

SOURCE...Radar and automated gauges.

IMPACT...Continued 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...
  Hammond, Gary, Tinley Park, Calumet City, Portage, Merrillville, 
  Valparaiso, Chicago Heights, East Chicago, Schererville, Hobart, 
  Lansing, Crown Point, Harvey, Highland, Munster, Park Forest, 
  Homewood, Matteson and Frankfort.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 4164 8732 4164 8720 4166 8715 4171 8694
      4124 8693 4123 8698 4127 8706 4129 8713
      4119 8732 4115 8766 4123 8772 4155 8781

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

Borchardt

767 
WGUS73 KLOT 260628
FFSLOT

Flash Flood Statement
National Weather Service Chicago IL
128 AM CDT Thu Aug 26 2021

ILC031-091-197-INC089-127-260638-
/O.CAN.KLOT.FF.W.0011.000000T0000Z-210826T0815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cook IL-Kankakee IL-Will IL-Lake IN IN-Porter IN-
128 AM CDT Thu Aug 26 2021

...FLASH FLOOD WARNING FOR SOUTHEASTERN COOK, NORTHEASTERN KANKAKEE, 
SOUTHEASTERN WILL, LAKE IN AND PORTER COUNTIES HAS BEEN REPLACED 
WITH A FLOOD ADVISORY...

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

LAT...LON 4164 8732 4164 8720 4166 8715 4171 8694
      4124 8693 4123 8698 4127 8706 4129 8713
      4119 8732 4115 8766 4123 8772 4155 8781

$$

Carlaw

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 25, 7:21 PM CDT	Flash Flood Warning	LOT	Cook, DuPage	3 hr
Aug 25, 7:33 PM CDT	Special Marine Warning	LOT		117 min
Aug 25, 8:34 PM CDT	Areal Flood Advisory	LOT	Cook, Kankakee, Will	3 hr
Aug 25, 8:43 PM CDT	Special Weather Statement	LOT	Kankakee	47 min
Aug 25, 8:54 PM CDT	Areal Flood Advisory	LOT	DuPage, Kane, Kendall, Will	17 min
Aug 25, 9:06 PM CDT	Flash Flood Warning	LOT	DuPage, Kane, Kendall, Will	5 hr
Aug 26, 1:38 AM CDT	Areal Flood Advisory	LOT	Kane, Kendall	2 hr
Aug 26, 5:30 PM CDT	Special Weather Statement	LOT	Cook	30 min
Aug 25, 8:46 PM CDT	Special Weather Statement	LOT	Porter	44 min
Aug 26, 1:28 AM CDT	Areal Flood Advisory	LOT	Lake, Porter	2 hr

Nearby

Flash Flood Warnings in Illinois, 2021 Flash Flood Warnings in Indiana, 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.