Alert archive / Louisiana / Flash Flood Warnings in 2021

Flash Flood Warning 29, NWS New Orleans, LA

May 11, 20214 parishes in Louisiana

NWS New Orleans, LA issued this flash flood warning at May 11, 2021, 10:38 PM CDT for 4 parishes in Louisiana. It was in force for 3 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 11, 2021, 10:38 PM CDT (03:38 UTC)
Expired
May 12, 2021, 1:45 AM CDT
In force
3 hr
Issued by
NWS New Orleans, LA
Area
Storm-based polygon
Flood severity
None

Counties Ascension Parish, LA, Assumption Parish, LA, Iberville Parish, LA, Saint James Parish, LA

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 3.6 hours before the alert went out and 121 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 00:00Z on 2021-05-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 618 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Slidell Radar S, LA at 00:00Z on 2021-05-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 135 square meters per square second.19395878Sfc1 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
618 J/kg
Mixed-layer CIN
-59 J/kg
Mixed-layer LCL
924 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
135 m²/s²
0-3 km storm-relative helicity
212 m²/s²
Significant tornado parameter
0.3
Supercell composite
4.7

Open this sounding in Storm Lab

The text

As transmitted.

127 
WGUS54 KLIX 120338
FFWLIX
LAC005-007-047-093-120645-
/O.NEW.KLIX.FF.W.0029.210512T0338Z-210512T0645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service New Orleans LA
1038 PM CDT Tue May 11 2021

The National Weather Service in New Orleans has issued a

* Flash Flood Warning for...
  Ascension Parish in southeastern Louisiana...
  Northern Assumption Parish in southeastern Louisiana...
  Southeastern Iberville Parish in southeastern Louisiana...
  Northern St. James Parish in southeastern Louisiana...

* Until 145 AM CDT.

* At 1038 PM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 3 inches of rain 
  have fallen. Flash flooding is 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...
  Gonzales, Donaldsonville, Napoleonville, St. Gabriel, Lutcher, 
  White Castle, Sorrento, Port Vincent, Belle Rose, Geismar, 
  Paincourtville, Convent and Prairieville.

This includes the following Interstates...
	Interstate 10 in Louisiana between mile markers 170 and 196.

Additional rainfall amounts of 1 to 3 inches are possible in the 
warned area.

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 3004 9125 3034 9099 3034 9086 3032 9083
      3028 9081 3028 9079 3026 9079 3024 9074
      3019 9072 3018 9070 3023 9066 3023 9064
      3012 9065 2991 9103 2987 9120 2995 9125
      3000 9125 3000 9123 3004 9122 3003 9124

FLASH FLOOD...RADAR INDICATED

$$

CAB
1 follow-up statement
707 
WGUS74 KLIX 120432
FFSLIX

Flash Flood Statement
National Weather Service New Orleans LA
1132 PM CDT Tue May 11 2021

LAC005-007-047-093-120645-
/O.CON.KLIX.FF.W.0029.000000T0000Z-210512T0645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Ascension LA-Assumption LA-Iberville LA-St. James LA-
1132 PM CDT Tue May 11 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 145 AM CDT WEDNESDAY 
FOR ASCENSION, NORTHERN ASSUMPTION, SOUTHEASTERN IBERVILLE AND 
NORTHERN ST. JAMES PARISHES...

At 1132 PM CDT, Doppler radar indicated thunderstorms produced heavy 
rain across the warned area. Between 1 and 3 inches of rain have 
fallen. Additional storms are anticipated to move back into the area 
shortly. 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...
  Gonzales, Donaldsonville, Napoleonville, St. Gabriel, Lutcher, 
  White Castle, Sorrento, Port Vincent, Belle Rose, Geismar, 
  Paincourtville, Convent and Prairieville.

This includes the following Interstates...
	Interstate 10 in Louisiana between mile markers 170 and 196.

Additional rainfall amounts of 1 to 2 inches are possible in the 
warned area.

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 3004 9125 3034 9099 3034 9086 3032 9083
      3028 9081 3028 9079 3026 9079 3024 9074
      3019 9072 3018 9070 3023 9066 3023 9064
      3012 9065 2991 9103 2987 9120 2995 9125
      3000 9125 3000 9123 3004 9122 3003 9124

FLASH FLOOD...RADAR INDICATED

$$

CAB

The office that day

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

IssuedProductOfficeCountiesLasted
May 11, 8:49 PM CDTRiver Flood WarningLIXSaint Tammany14 hr
May 11, 9:24 PM CDTSpecial Weather StatementLIXAssumption51 min
May 11, 10:15 PM CDTSpecial Weather StatementLIXAscension30 min
May 11, 10:35 PM CDTSpecial Weather StatementLIXAscension, Assumption, Saint James40 min
May 11, 10:37 PM CDTSevere Thunderstorm WarningLIXAscension, Assumption, Iberville, Saint James30 min
May 11, 11:05 PM CDTSevere Thunderstorm WarningLIXAscension, Assumption, Lafourche, Saint James, Saint John the Baptist40 min
May 11, 11:41 PM CDTSevere Thunderstorm WarningLIXAscension, Assumption, Lafourche, Saint Charles, Saint James, Saint John the Baptist64 min
May 12, 12:18 AM CDTSpecial Weather StatementLIXAssumption27 min
May 12, 12:31 AM CDTAreal Flood AdvisoryLIXAssumption, Jefferson, Lafourche, Saint Charles, Saint James, Saint John the Baptist2 hr
May 12, 12:33 AM CDTSpecial Weather StatementLIXSaint Charles42 min
May 12, 12:48 AM CDTSpecial Weather StatementLIXLafourche57 min
May 12, 1:12 AM CDTSpecial Weather StatementLIXSaint Charles33 min
May 12, 1:41 AM CDTSpecial Weather StatementLIXLafourche, Orleans, Saint Charles, Saint Tammany49 min
May 12, 1:46 AM CDTSpecial Marine WarningLIX44 min
May 12, 1:58 AM CDTAreal Flood AdvisoryLIXJefferson, Orleans, Plaquemines, Saint Bernard, Saint Charles81 min
May 12, 1:58 AM CDTSevere Thunderstorm WarningLIXJefferson, Orleans, Plaquemines, Saint Bernard, Saint Charles32 min
May 12, 2:08 AM CDTTornado WarningLIXJefferson, Orleans, Plaquemines, Saint Bernard12 min
May 12, 2:30 AM CDTSpecial Marine WarningLIX46 min
May 12, 2:47 AM CDTSpecial Marine WarningLIX43 min
May 12, 3:14 AM CDTSpecial Marine WarningLIX108 min
May 12, 4:25 AM CDTSpecial Marine WarningLIX65 min

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.