Alert archive / Illinois / Flash Flood Warnings in 2012

Flash Flood Warning 3, NWS Chicago, IL

May 4, 2012LaSalle County, Livingston County, Illinois

NWS Chicago, IL issued this flash flood warning at May 4, 2012, 12:46 AM CDT for LaSalle County, Livingston County, Illinois. It was in force for 6 hr. 1 report 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: May 4, 2012, 12:46 AM CDT (05:46 UTC)
Expired: May 4, 2012, 6:30 AM CDT
In force: 6 hr
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Flood severity: None

Counties LaSalle County, IL, Livingston County, IL

The radar

The Chicago radar (KLOT), 83 km from the middle of the area, began a volume at 05:49 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
May 4, 1:00 AM CDT	FLASH FLOOD	4 Sse La Salle, IL	STATE POLICE RECIEVED SEVERAL REPORTS OF WATER OVER ROADS...INCLUDING INTERSTATE 39 NEAR MILE MARKER 54 WEST OF OGLESBY.

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, 5.8 hours before the alert went out and 123 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: 1905 J/kg
Mixed-layer CIN: -30 J/kg
Mixed-layer LCL: 1071 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 12 m²/s²
0-3 km storm-relative helicity: 96 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

397 
WGUS53 KLOT 040546
FFWLOT
ILC099-105-041130-
/O.NEW.KLOT.FF.W.0003.120504T0546Z-120504T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 AM CDT FRI MAY 4 2012

THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  LA SALLE COUNTY IN NORTH CENTRAL ILLINOIS...
  NORTHWESTERN LIVINGSTON COUNTY IN CENTRAL ILLINOIS...

* UNTIL 630 AM CDT

* AT 1241 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  SLOW MOVING THUNDERSTORMS WITH VERY HEAVY RAINFALL ACROSS THE
  WARNED AREA. RADAR ESTIMATED RAINFALL TOTALS ARE BETWEEN ONE AND   
  TWO INCHES SO FAR...AND ADDITIONAL HEAVY RAIN IS EXPECTED.

* RUNOFF FROM THIS EXCESSIVE RAINFALL WILL CAUSE FLASH FLOODING TO
  OCCUR. THE LOCATIONS MOST LIKELY TO EXPERIENCE FLOODING IN THE     
  IMMEDIATE NEAR TERM INCLUDE...LA SALLE...OGLESBY...CEDAR           
  POINT...AND UTICA.  NORTHWEST LIVINGSTON COUNTY LIKELY IS NOT      
  EXPERIENCING FLOODING AT THIS TIME BUT IS IN LINE FOR VERY HEAVY   
  RAINFALL OVER THE NEXT 2 OR 3 HOURS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. DO
NOT ENTER THE WATER. TURN AROUND AND MOVE UP TO HIGHER GROUND TO
ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS SUBJECT TO FLOODING WHEN
WATER BEGINS RISING.

&&

LAT...LON 4163 8917 4163 8861 4111 8859 4110 8857
      4093 8893 4093 8905 4110 8905 4110 8916
      4112 8917

$$

LENNING

4 follow-up statements

972 
WGUS73 KLOT 040723
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
223 AM CDT FRI MAY 4 2012

ILC099-105-041130-
/O.CON.KLOT.FF.W.0003.000000T0000Z-120504T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
LA SALLE IL-LIVINGSTON IL-
223 AM CDT FRI MAY 4 2012

...FLASH FLOOD WARNING REMAINS IN EFFECT FOR NORTHWESTERN LIVINGSTON
AND LA SALLE COUNTIES UNTIL 630 AM CDT...

AT 219 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO 
INDICATE THUNDERSTORMS ACROSS THE WARNED AREA.

RUNOFF FROM THIS EXCESSIVE RAINFALL HAS CAUSED FLASH FLOODING TO
OCCUR. SOME LOCATIONS THAT ARE MOST LIKELY TO EXPERIENCE FLOODING 
INCLUDE...LA SALLE...OGLESBY...PERU...SENECA...GRAND 
RIDGE...SHERIDAN...TONICA AND UTICA.

STATE POLICE HAVE RECEIVED REPORTS OF WATER OVER SEVERAL ROADS IN 
THE AREA...INCLUDING INTERSTATE 39 NEAR MILE MARKER 54.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY.

&&

LAT...LON 4163 8917 4163 8861 4111 8859 4110 8857
      4093 8893 4093 8905 4110 8905 4110 8916
      4112 8917

$$

LENNING

186 
WGUS73 KLOT 040831
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
331 AM CDT FRI MAY 4 2012

ILC099-105-041130-
/O.CON.KLOT.FF.W.0003.000000T0000Z-120504T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
LA SALLE IL-LIVINGSTON IL-
331 AM CDT FRI MAY 4 2012

...FLASH FLOOD WARNING REMAINS IN EFFECT FOR NORTHWESTERN LIVINGSTON
AND LA SALLE COUNTIES UNTIL 630 AM CDT...

AT 326 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED THAT
RAIN HAD MOSTLY ENDED OVER THE WARNED AREA...BUT ADDITIONAL 
THUNDERSTORMS WERE NEARBY AND MAY AGAIN AFFECT THE LOCATIONS WHERE 
HEAVY RAIN FELL EARLIER TONIGHT.  

LOCAL LAW ENFORCEMENT WAS NOT AWARE OF ANY ONGOING ISSUES...BUT 
FLOODING IS OFTEN UNDER REPORTED AT NIGHT.  BY MORNING THERE MAY BE 
ADDITIONAL REPORTS OF FLOODED ROADWAYS FROM THE OVERNIGHT RAINFALL.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLOODING IS OBSERVED...ACT QUICKLY. DO NOT
ENTER THE WATER. TURN AROUND AND MOVE UP TO HIGHER GROUND. DO NOT
STAY IN AREAS SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

&&

LAT...LON 4163 8917 4163 8861 4111 8859 4110 8857
      4093 8893 4093 8905 4110 8905 4110 8916
      4112 8917

$$

LENNING

739 
WGUS73 KLOT 041007
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
507 AM CDT FRI MAY 4 2012

ILC099-105-041130-
/O.CON.KLOT.FF.W.0003.000000T0000Z-120504T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
LA SALLE IL-LIVINGSTON IL-
507 AM CDT FRI MAY 4 2012

...FLASH FLOOD WARNING REMAINS IN EFFECT FOR NORTHWESTERN LIVINGSTON
AND LA SALLE COUNTIES UNTIL 630 AM CDT...

AT 502 AM CDT...RAINFALL HAD MOSTLY ENDED ACROSS THE WARNED AREA.  
RUNOFF FROM EARLIER RAINFALL HAD CAUSED FLASH FLOODING TO
OCCUR IN SOME LOCATIONS OVERNIGHT...BUT FLOOD PROBLEMS AT THIS POINT 
SHOULD BE MINIMAL.  ADDITIONAL THUNDERSTORMS THAT DEVELOPED 
OVERNIGHT STAYED GENERALLY SOUTH OF THE WARNED AREA...SO THE WARNING 
LIKELY WILL BE ALLOWED TO EXPIRE ON TIME.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLOODING IS OBSERVED...ACT QUICKLY. DO NOT
ENTER THE WATER. TURN AROUND AND MOVE UP TO HIGHER GROUND. DO NOT
STAY IN AREAS SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

&&

LAT...LON 4163 8917 4163 8861 4111 8859 4110 8857
      4093 8893 4093 8905 4110 8905 4110 8916
      4112 8917

$$

868 
WGUS73 KLOT 041126
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
626 AM CDT FRI MAY 4 2012

ILC099-105-041139-
/O.EXP.KLOT.FF.W.0003.000000T0000Z-120504T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
LA SALLE IL-LIVINGSTON IL-
626 AM CDT FRI MAY 4 2012

...THE FLASH FLOOD WARNING THAT WAS IN EFFECT FOR NORTHWESTERN
LIVINGSTON AND LA SALLE COUNTIES WILL BE ALLOWED TO EXPIRE AT 630 AM
CDT...

NO ADDITIONAL REPORTS OF FLOODING HAVE BEEN RECEIVED BUT LIGHT TO 
MODERATE RAIN WILL BE POSSIBLE THIS MORNING. ADDITIONAL 
THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON. 

EXCESS RUNOFF FROM HEAVY RAIN HAS ENDED OVER THE WARNED AREA. STREAMS
AND CREEKS IN THE WARNED AREA HAVE RECEDED OR WERE BEGINNING TO
RECEDE...ENDING THE FLOOD THREAT. IF FLOODING HAS BEEN OBSERVED...
PLEASE REPORT IT TO YOUR LOCAL LAW ENFORCEMENT AGENCY.

LAT...LON 4163 8917 4163 8861 4111 8859 4110 8857
      4093 8893 4093 8905 4110 8905 4110 8916
      4112 8917

$$

The office that day

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

Issued	Product	Office	Counties	Lasted
May 3, 7:08 PM CDT	Severe Thunderstorm Warning	LOT	Cook	67 min
May 3, 7:23 PM CDT	Flash Flood Warning	LOT	Cook, DuPage	4 hr
May 3, 8:00 PM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage	75 min
May 3, 8:07 PM CDT	Severe Thunderstorm Warning	LOT	LaSalle, Livingston	68 min
May 3, 8:12 PM CDT	Special Marine Warning	LOT		2 hr
May 3, 8:43 PM CDT	Flash Flood Watch	LOT	DuPage, Grundy, Kankakee, Kendall, LaSalle, Livingston	7 hr
May 3, 9:19 PM CDT	Special Marine Warning	LOT		116 min
May 3, 9:29 PM CDT	Special Weather Statement	LOT	Will	31 min
May 3, 9:50 PM CDT	Severe Thunderstorm Warning	LOT	Cook, Will	55 min
May 3, 10:10 PM CDT	Flash Flood Warning	LOT	Cook	5 hr
May 3, 10:47 PM CDT	Special Weather Statement	LOT	Cook	28 min
May 4, 12:34 AM CDT	Severe Thunderstorm Warning	LOT	Grundy, LaSalle, Livingston	71 min
May 4, 1:26 AM CDT	Severe Thunderstorm Warning	LOT	Ford, Grundy, Iroquois, Kankakee, Livingston	63 min
May 4, 3:07 AM CDT	Marine Dense Fog Advisory	LOT		18 hr

Nearby

Flash Flood Warnings in Illinois, 2012 Every flash flood warning in 2012

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.