Alert archive / Louisiana / Flash Flood Watches in 2020

Flash Flood Watch 8, NWS New Orleans, LA

September 12, 202011 parishes in Louisiana; 4 counties in Mississippi

NWS New Orleans, LA issued this flash flood watch at Sep 12, 2020, 4:36 PM CDT for 11 parishes in Louisiana; 4 counties in Mississippi. It took effect at Sep 13, 2020, 7:00 PM CDT. It was in force for 60 hr.

The area

The counties it named.

The facts

Issued
Sep 12, 2020, 4:36 PM CDT (21:36 UTC)
In effect from
Sep 13, 2020, 7:00 PM CDT
Expired
Sep 16, 2020, 7:06 AM CDT
In force
60 hr
Issued by
NWS New Orleans, LA
Flood severity
None

Counties Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Saint Bernard Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, Amite County, MS, Pearl River County, MS, Pike County, MS, Walthall County, MS

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 9.6 hours before the alert went out and 94 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 2020-09-12Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1403 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 12:00Z on 2020-09-12The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 38 square meters per square second.1939Sfc1 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
1403 J/kg
Mixed-layer CIN
-36 J/kg
Mixed-layer LCL
697 m above ground
0-6 km bulk shear
12 kt
0-1 km storm-relative helicity
38 m²/s²
0-3 km storm-relative helicity
33 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 12, 12:16 PM CDTSpecial Weather StatementLIXOrleans59 min
Sep 12, 12:40 PM CDTSpecial Marine WarningLIX19 min
Sep 12, 1:16 PM CDTSpecial Weather StatementLIXSaint Charles, Saint James, Saint John the Baptist29 min
Sep 12, 3:29 PM CDTSpecial Weather StatementLIXPointe Coupee, West Feliciana61 min
Sep 12, 4:13 PM CDTHurricane WatchLIXAssumption, Saint Bernard, Saint James, Saint John the Baptist, Washington30 hr
Sep 12, 4:13 PM CDTStorm Surge WatchLIXSaint Bernard, Saint John the Baptist12 hr
Sep 12, 4:13 PM CDTTropical Storm WatchLIXSaint Helena, Tangipahoa12 hr
Sep 12, 2:48 PM CDTSpecial Weather StatementLIXPearl River57 min

Nearby

Flash Flood Watches in Louisiana, 2020Flash Flood Watches in Mississippi, 2020Every flash flood watch in 2020

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.