Alert archive / Louisiana / Flash Flood Warnings in 2021

Flash Flood Warning 76, NWS New Orleans, LA

July 20, 2021Saint Tammany Parish, Louisiana

NWS New Orleans, LA issued this flash flood warning at Jul 20, 2021, 6:33 AM CDT for Saint Tammany Parish, Louisiana. It was in force for 4 hr. 10 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 20, 2021, 6:33 AM CDT (11:33 UTC)
Expired: Jul 20, 2021, 10:30 AM CDT
In force: 4 hr
Issued by: NWS New Orleans, LA
Area: Storm-based polygon
Flood severity: None

County Saint Tammany Parish, LA

What was reported inside it

Time	Report	Where	Remark
Jul 20, 6:46 AM CDT	FLASH FLOOD	2 N Mandeville, LA	FLOODING OUTSIDE CYPRESS LAKE APARTMENTS IN MANDEVILLE. ROADS COMPLETELY IMPASSABLE.
Jul 20, 6:46 AM CDT	FLASH FLOOD	3 Nw Mandeville, LA	SOCIAL MEDIA VIDEO SHOWS ANKLE DEEP FLOODING COVERING STREETS AND COMING INTO RESIDENTIAL YARDS.
Jul 20, 7:19 AM CDT	FLASH FLOOD	3 Sse Covington, LA	NWS EMPLOYED REPORTED HOLIDAY SQUARE BOULEVARD TO BE AN IMPASSABLE DUE TO HIGH WATER.
Jul 20, 7:46 AM CDT	FLASH FLOOD	1 Nne Madisonville, LA	SOCIAL MEDIA PICTURE SHOWING WATER INTRUSION AT THE ROUTE 22 GAS & BAIT STORE IN MADISONVILLE.
Jul 20, 8:15 AM CDT	FLASH FLOOD	3 N Mandeville, LA	TALL TIMBERS HAS MULTIPLE ROADS IMPASSABLE WATER AND ENCROACHING HOMES.
Jul 20, 9:03 AM CDT	FLASH FLOOD	2 Ese Mandeville, LA	ROADS ARE BEGINNING TO HOLD WATER IN MONTERREY AND STARTING TO APPROACHES HOUSES.
Jul 20, 9:59 AM CDT	FLASH FLOOD	1 Ese Mandeville, LA	SOCIAL MEDIA PHOTO SHOWS CAR WASH AND SURROUNDING ROAD FLOODED.
Jul 20, 9:59 AM CDT	FLASH FLOOD	1 Ese Mandeville, LA
Jul 20, 10:07 AM CDT	FLASH FLOOD	1 Ese Mandeville, LA	VEHICLES ARE PUSHING FLOODING WATER INTO BUILDINGS ON STREET INCLUDING THE FIRE STATION.
Jul 20, 10:31 AM CDT	FLASH FLOOD	1 Ese Mandeville, LA	HWY 190 IS CLOSED AT GIROD STREET DUE TO HIGH WATER.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 11.6 hours before the alert went out and 41 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: 866 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 872 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 56 m²/s²
0-3 km storm-relative helicity: 69 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.7

Open this sounding in Storm Lab

The text

As transmitted.

444 
WGUS54 KLIX 201133
FFWLIX
LAC103-201445-
/O.NEW.KLIX.FF.W.0076.210720T1133Z-210720T1445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service New Orleans LA
633 AM CDT Tue Jul 20 2021

The National Weather Service in New Orleans has issued a

* Flash Flood Warning for...
  West Central St. Tammany Parish in southeastern Louisiana...

* Until 945 AM CDT.

* At 633 AM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 4 and 6 inches of rain 
  have fallen. The expected rainfall rate is 2 to 4 inches in 1 
  hour. Additional rainfall amounts of 1 to 3 inches are possible in 
  the warned area. Flash flooding is ongoing or expected to begin 
  shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flash 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...
  Covington, Abita Springs and Madisonville.

This includes the following Interstates...
	Interstate 12 between mile markers 60 and 70.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 3040 9019 3050 9010 3043 8992 3032 9002
      3037 9009 3037 9011

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...2-4 INCHES IN 1 HOUR

$$

TE

3 follow-up statements

987 
WGUS74 KLIX 201237
FFSLIX

Flash Flood Statement
National Weather Service New Orleans LA
737 AM CDT Tue Jul 20 2021

LAC103-201445-
/O.CON.KLIX.FF.W.0076.000000T0000Z-210720T1445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
St. Tammany LA-
737 AM CDT Tue Jul 20 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 945 AM CDT THIS 
MORNING FOR WEST CENTRAL ST. TAMMANY PARISH...

At 737 AM CDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 4 and 8 inches of rain have 
fallen. The expected rainfall rate is 2 to 4 inches in 1 hour. 
Additional rainfall amounts of 1 to 3 inches are possible in the 
warned area. Flash flooding is ongoing or expected to begin shortly.

HAZARD...Life threatening flash flooding. Thunderstorms producing
         flash flooding.

SOURCE...Radar.

IMPACT...Life threatening flash flooding of creeks and streams,
         urban areas, highways, streets and underpasses.

Some locations that will experience flash flooding include...
  Covington, Abita Springs and Madisonville.

This includes the following Interstates...
	Interstate 12 between mile markers 60 and 70.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 3040 9019 3050 9010 3043 8992 3032 9002
      3037 9009 3037 9011

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
EXPECTED RAINFALL...2-4 INCHES IN 1 HOUR

$$

TE

264 
WGUS54 KLIX 201427
FFWLIX
LAC103-201530-
/O.EXT.KLIX.FF.W.0076.000000T0000Z-210720T1530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service New Orleans LA
927 AM CDT Tue Jul 20 2021

The National Weather Service in New Orleans has extended the

* Flash Flood Warning for...
  West Central St. Tammany Parish in southeastern Louisiana...

* Until 1030 AM CDT.

* At 927 AM CDT, Broadcast media and public reported ongoing 
  flooding across the warned area. Between 4 and 11 inches of rain 
  have fallen since 11PM with some additional rainfall possible.

  HAZARD...Life threatening flash flooding.

  SOURCE...Broadcast media and public reported.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets and underpasses.

* Some locations that will experience flash flooding include...
  Covington, Abita Springs and Madisonville.

This includes the following Interstates...
	Interstate 12 between mile markers 60 and 70.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

Stay away or be swept away. River banks and culverts can become 
unstable and unsafe.

Please report observed flooding to local emergency services or law 
enforcement and request they pass this information to the National 
Weather Service when you can do so safely.

&&

LAT...LON 3040 9019 3050 9010 3043 8992 3032 9002
      3037 9009 3037 9011

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

KLG

259 
WGUS74 KLIX 201529
FFSLIX

Flash Flood Statement
National Weather Service New Orleans LA
1029 AM CDT Tue Jul 20 2021

LAC103-201539-
/O.EXP.KLIX.FF.W.0076.000000T0000Z-210720T1530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
St. Tammany LA-
1029 AM CDT Tue Jul 20 2021

...FLASH FLOOD WARNING AT 1030 AM CDT THIS MORNING FOR WEST CENTRAL 
ST. TAMMANY PARISH HAS BEEN REPLACED WITH A FLOOD WARNING...

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

LAT...LON 3040 9019 3050 9010 3043 8992 3032 9002
      3037 9009 3037 9011

$$

KLG

The office that day

Everything else NWS New Orleans, LA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 12:41 AM CDT	Areal Flood Advisory	LIX	Saint Tammany	17 min
Jul 20, 12:58 AM CDT	Flash Flood Warning Considerable damage threat	LIX	Saint Tammany	3 hr
Jul 20, 1:55 AM CDT	Areal Flood Advisory	LIX	Saint Tammany	3 hr
Jul 20, 4:02 AM CDT	Special Marine Warning	LIX		58 min
Jul 20, 5:24 AM CDT	Areal Flood Advisory	LIX	East Feliciana, Saint Helena, West Feliciana	3 hr
Jul 20, 5:44 AM CDT	Special Marine Warning	LIX		31 min
Jul 20, 6:23 AM CDT	Areal Flood Advisory	LIX	East Feliciana, Saint Helena, Tangipahoa, Washington	3 hr
Jul 20, 6:46 AM CDT	Flash Flood Warning	LIX	Saint Helena, Tangipahoa, Washington	3 hr
Jul 20, 6:55 AM CDT	Special Weather Statement	LIX	Saint Tammany	50 min
Jul 20, 8:28 AM CDT	Special Marine Warning	LIX		62 min
Jul 20, 9:19 AM CDT	Areal Flood Warning	LIX	Saint Tammany	3 hr
Jul 20, 10:29 AM CDT	Areal Flood Warning	LIX	Saint Tammany	2 hr
Jul 20, 2:50 PM CDT	River Flood Warning	LIX	Saint Tammany	43 hr

Nearby

Flash Flood Warnings in Louisiana, 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.