Alert archive / Louisiana / Flash Flood Warnings in 2021

Flash Flood Warning 46, NWS New Orleans, LA

May 20, 20216 parishes in Louisiana

NWS New Orleans, LA issued this flash flood warning at May 20, 2021, 6:42 PM CDT for 6 parishes in Louisiana. It was in force for 4 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
May 20, 2021, 6:42 PM CDT (23:42 UTC)
Expired
May 20, 2021, 10:46 PM CDT
In force
4 hr
Issued by
NWS New Orleans, LA
Area
Storm-based polygon
Flood severity
None

Counties Ascension Parish, LA, East Baton Rouge Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Saint Helena Parish, LA, West Baton Rouge Parish, LA

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 11.7 hours before the alert went out and 135 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-pSkew-T log-p diagram, Slidell Radar S, LA at 12:00Z on 2021-05-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 622 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Slidell Radar S, LA at 12:00Z on 2021-05-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 152 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
622 J/kg
Mixed-layer CIN
-1 J/kg
Mixed-layer LCL
599 m above ground
0-6 km bulk shear
19 kt
0-1 km storm-relative helicity
152 m²/s²
0-3 km storm-relative helicity
227 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

506 
WGUS54 KLIX 202342
FFWLIX
LAC005-033-047-063-091-121-210445-
/O.NEW.KLIX.FF.W.0046.210520T2342Z-210521T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service New Orleans LA
642 PM CDT Thu May 20 2021

The National Weather Service in New Orleans has issued a

* Flash Flood Warning for...
  Northern Ascension Parish in southeastern Louisiana...
  East Baton Rouge Parish in southeastern Louisiana...
  East Central Iberville Parish in southeastern Louisiana...
  Western Livingston Parish in southeastern Louisiana...
  Southwestern St. Helena Parish in southeastern Louisiana...
  Eastern West Baton Rouge Parish in southeastern Louisiana...

* Until 1145 PM CDT.

* At 642 PM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 10 and 20 inches of 
  rain have fallen over the last few days. Flash flooding is ongoing 
  or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Doppler radar.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets and underpasses as well as other
           drainage and low lying areas.

* Some locations that will experience flash flooding include...
  Baton Rouge, Zachary, Baker, Denham Springs, Gonzales, Plaquemine, 
  Port Allen, Oak Hills Place, St. Gabriel, Walker, Addis, Brusly, 
  Sorrento, French Settlement, Slaughter, Port Vincent, Shenandoah, 
  Inniswold, Old Jefferson and Westminster.

This includes the following Interstates...
	Interstate 10 in Louisiana between mile markers 148 and 179.
	Interstate 12 between mile markers 1 and 20.
	Interstate 110 in Louisiana between mile markers 1 and 8.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 3063 9132 3065 9131 3066 9132 3065 9129
      3068 9128 3068 9127 3071 9125 3072 9085
      3073 9084 3073 9082 3054 9084 3022 9063
      3021 9063 3018 9080 3022 9112 3022 9118
      3025 9132

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 5 HOURS 

$$
1 follow-up statement
761 
WGUS74 KLIX 210346
FFSLIX

Flash Flood Statement
National Weather Service New Orleans LA
1046 PM CDT Thu May 20 2021

LAC005-033-047-063-091-121-210356-
/O.CAN.KLIX.FF.W.0046.000000T0000Z-210521T0445Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Ascension LA-East Baton Rouge LA-Iberville LA-Livingston LA-St.
Helena LA-West Baton Rouge LA-
1046 PM CDT Thu May 20 2021

...FLASH FLOOD WARNING IS CANCELLED FOR NORTHERN ASCENSION, EAST 
BATON ROUGE, EAST CENTRAL IBERVILLE, WESTERN LIVINGSTON, 
SOUTHWESTERN ST. HELENA AND EASTERN WEST BATON ROUGE PARISHES...

Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

A Flash Flood Watch remains in effect until 1200 PM CDT Friday for 
portions of southeast Louisiana and southern Mississippi.

LAT...LON 3063 9132 3065 9131 3066 9132 3065 9129
      3068 9128 3068 9127 3071 9125 3072 9085
      3073 9084 3073 9082 3054 9084 3022 9063
      3021 9063 3018 9080 3022 9112 3022 9118
      3025 9132

$$

The office that day

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

IssuedProductOfficeCountiesLasted
May 19, 7:03 PM CDTSpecial Weather StatementLIXSaint Tammany42 min
May 19, 7:24 PM CDTSpecial Marine WarningLIX81 min
May 19, 8:00 PM CDTSevere Thunderstorm WarningLIXSaint Charles, Saint John the Baptist25 min
May 19, 8:30 PM CDTSpecial Marine WarningLIX30 min
May 19, 9:19 PM CDTAreal Flood AdvisoryLIXAscension, East Baton Rouge, Iberville, Livingston116 min
May 20, 3:42 AM CDTSpecial Weather StatementLIXAscension, Assumption, Iberville, Jefferson, Plaquemines, Saint Charles and 3 more63 min
May 20, 4:05 AM CDTSpecial Marine WarningLIX55 min
May 20, 4:18 AM CDTSpecial Marine WarningLIX57 min
May 20, 5:03 AM CDTSpecial Marine WarningLIX57 min
May 20, 5:33 AM CDTSpecial Marine WarningLIX57 min
May 20, 7:00 AM CDTSpecial Weather StatementLIXAssumption, Jefferson, Lafourche, Saint Charles, Saint James60 min
May 20, 7:39 AM CDTTornado WarningLIXJefferson8 min
May 20, 7:42 AM CDTSpecial Marine WarningLIX33 min
May 20, 8:27 AM CDTSpecial Marine WarningLIX63 min
May 20, 8:37 AM CDTAreal Flood AdvisoryLIXAscension, Assumption, East Baton Rouge, Iberville, Lafourche, Livingston and 3 more52 min
May 20, 8:58 AM CDTTornado WarningLIXEast Feliciana13 min
May 20, 9:29 AM CDTFlash Flood WarningLIXAscension, East Baton Rouge, Iberville, Livingston, West Baton Rouge9 hr
May 20, 9:45 AM CDTFlash Flood WarningLIXEast Baton Rouge, East Feliciana, Saint Helena, West Feliciana11 hr
May 20, 10:04 AM CDTFlash Flood WarningLIXAscension, Assumption, Iberville, Lafourche, Livingston, Saint James and 1 more13 hr
May 20, 10:52 AM CDTSevere Thunderstorm WarningLIXSaint Charles, Saint John the Baptist19 min
May 20, 11:22 AM CDTSpecial Marine WarningLIX38 min
May 20, 11:26 AM CDTSevere Thunderstorm WarningLIXEast Baton Rouge, East Feliciana, Livingston, Saint Helena94 min
May 20, 2:16 PM CDTRiver Flood WarningLIXEast Baton Rouge, Livingston68 hr
May 20, 2:22 PM CDTRiver Flood WarningLIXAscension, Livingston4 days
May 20, 2:33 PM CDTSpecial Marine WarningLIX57 min
May 20, 2:40 PM CDTRiver Flood WarningLIXEast Baton Rouge61 hr
May 20, 3:29 PM CDTSpecial Marine WarningLIX61 min
May 20, 3:56 PM CDTGale WarningLIX19 hr
May 20, 3:56 PM CDTSmall Craft AdvisoryLIX60 hr
May 20, 3:56 PM CDTWind AdvisoryLIXOrleans, Saint Bernard, Saint John the Baptist, Saint Tammany27 hr
May 20, 4:30 PM CDTSpecial Marine WarningLIX90 min
May 20, 4:58 PM CDTSpecial Weather StatementLIXLafourche, Terrebonne47 min
May 20, 5:16 PM CDTAreal Flood AdvisoryLIXAssumption, Jefferson, Lafourche, Terrebonne3 hr

Nearby

Flash Flood Warnings in Louisiana, 2021Every 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; the sounding from the Mesonet's radiosonde archive.