In the morning hours on July 20th, 2021, slow moving thunderstorms developed overnight ,one specific cluster formed over the Northshore that led to significant flooding, with areas of flooding elsewhere from developing clusters of thunderstorms through the morning hours. These storms formed within a rich Gulf, unstable airmass out ahead of an approaching outflow boundary and slow moving cold front from the west.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 01:19:00 to 20-JUL-21 01:19:00 (CST-6)
Location: CHINCHUBA
Flood cause: Heavy Rain
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water entering several homes. many roads impassable and barricaded.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 02:15:00 to 20-JUL-21 02:15:00 (CST-6)
Location: CHINCHUBA
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Public

A social media video showed at least a dozen flooded cars in an apartment complex in Mandeville.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 02:30:00 to 20-JUL-21 02:30:00 (CST-6)
Location: CHINCHUBA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported service road was impassable in Mandeville due to high water.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 05:46:00 to 20-JUL-21 05:46:00 (CST-6)
Location: CHINCHUBA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Flooding outside Cypress Lake apartments in Mandeville. Roads completely impassable.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 05:50:00 to 20-JUL-21 05:50:00 (CST-6)
Location: COVINGTON
Flood cause: Heavy Rain
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Public

Public reports ankle deep water entering their apartment.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 06:19:00 to 20-JUL-21 06:19:00 (CST-6)
Location: CLAIBORNE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS employed reported Holiday Square Boulevard to be an impassable due to high water.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 06:46:00 to 20-JUL-21 06:46:00 (CST-6)
Location: HOULTONVILLE
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Social media picture showing water entering gas station.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 07:15:00 to 20-JUL-21 07:15:00 (CST-6)
Location: CHINCHUBA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Tall Timbers has multiple roads impassable water and encroaching on homes.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 08:03:00 to 20-JUL-21 08:03:00 (CST-6)
Location: MANDEVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Roads are beginning to hold water in Monterrey and starting to approaches houses.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 08:59:00 to 20-JUL-21 08:59:00 (CST-6)
Location: MANDEVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Social media photo shows car wash and surrounding road flooded.

Flash Flood in ST. TAMMANY, LOUISIANA
From 20-JUL-21 09:07:00 to 20-JUL-21 09:07:00 (CST-6)
Location: MANDEVILLE
Flood cause: Heavy Rain
Property damage: 45.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Vehicles are pushing flooding water into buildings on street including the fire station.