A weaken frontal boundary along the Interstate 10 corridor in southeast Louisiana and south Mississippi along with local land-lake/sea breeze interaction aided in the development of thunderstorms producing heavy rain along this corridor on all 3 days. Reports of flash flooding were received from the New Orleans area on the 4th and 5th, and the Gulfport-Biloxi area on the 6th.
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The episode as NWS LIX wrote it up.
A weaken frontal boundary along the Interstate 10 corridor in southeast Louisiana and south Mississippi along with local land-lake/sea breeze interaction aided in the development of thunderstorms producing heavy rain along this corridor on all 3 days. Reports of flash flooding were received from the New Orleans area on the 4th and 5th, and the Gulfport-Biloxi area on the 6th.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS New Orleans, LA wrote its last area forecast discussion before the first event at Aug 6, 2:51 AM CST, 6 hours 9 minutes earlier.
Area Forecast Discussion National Weather Service New Orleans LA 351 AM CDT Sun Aug 6 2017 .SHORT TERM... Once again, sh/ts will develop starting before sunrise. And once again, these will be backbuilding like they have been for several days now. Although, very high rainfall amounts will not be widespread, any one isolated location could receive very high amounts from 3 to as much as 6 inches of rainfall. This is normally not an issue if it is spread through a long period of time but unfortunately, this amount of rainfall could again fall within a short duration for any particular area. This scenario is not expected to change today or Monday as rainfall rates of 2 to 3 inches per hour can be expected with a few of these sh/ts. But the area of focus will start to change today and Monday. Today, the area will lay along, north and west of a line from Thibodaux to New Orleans to Picayune. Monday, this focus will lay along, north and west of a line from Pierre Part to Picayune. Monday may show an even more focused event from metro Baton Rouge to areas northeast. The reason for the rain leaving most south shore locations is due to dry air moving into the area in the mid levels from the south. The Bermuda Ridge will be the responsible party as it begins to edge northward over the southern half of the area. The weakness will not altogether leave the area as it should remain over the northwestern half of the area. The next thing that will help out is the tropical system that looks to move across the Yucatan Pen. The outer envelope of any tropical cyclone is comprised of a relatively subsident dry area. This subsident drying looks to move into the area Monday night and Tuesday. This should help by reducing the amount of sh/ts over the area, although the numbers will not be eliminated. .LONG TERM... The system currently over the Caribbean is forecast to stay well south of the area which would help keep some dry air filtering through the mid levels causing sh/ts numbers to remain reduced, and the word reduced is used conservatively. This should remain the case Tuesday through Friday. The 850mb trough will then once again move back into the area providing this troughiness(weakness) by Saturday. This trough may be enhanced quite a bit via two distinct easterly waves that interact with it by providing an abundance of deep moisture. The first, and weaker of the two, moves through the northern gulf possibly as early as Sunday of next week. The second looks to affect the area by Tuesday. This would cause a very similar situation which we are currently under with a better possibility of being a more widespread event. Ofcourse this is well in the future and we will simply remain attentive to it through the next several days. && .AVIATION... A weak low level inversion has developed this morning due to the rain cooled airmass in place. This has allowed for some IFR visibility and ceiling restrictions to develop at KMCB. These IFR conditions should persist through around 12z before improving. After 12z, the inversion will quickly mix out and ceilings should rise along with the lifted condensation level. Expect to see prevailing MVFR ceilings ranging from 2000 to 3000 feet in place at all the terminals by 15z. These ceilings should persist through around 00z. After 00z, ceilings should rise into VFR range as the cloud development near the LCL becomes more scattered. Of course, scattered daytime convection will also develop today, and have VCTS wording in place to reflect this risk. 32 && .MARINE... No significant changes in thinking concerning the marine forecast this morning. Overall, a prevailing onshore flow regime averaging around 10 knots will be in place through the entire forecast period. Significant wave heights should generally range from 1 to 2 feet in the lakes and sounds to 2 to 4 feet in the open Gulf waters. However, one caveat to the seas forecast will be the potential development of a tropical system in the southwest Gulf or Bay of Campeche Tuesday into Wednesday. If this system forms, a swell train could move into the open Gulf waters for mid-week resulting in higher overall seas. 32 && DSS code: Green. Deployed: None. Activation: None. Activities: None. Decision Support Services (DSS) Code Legend Green = No weather impacts that require action. Blue = Long-fused watch, warning, or advisory in effect or high visibility event. Yellow = Heightened impacts with short-fused watch, warning or advisory issuances; radar support. Orange = High Impacts; Slight to Moderate risk severe; nearby tropical events; HazMat or other large episodes. Red = Full engagement for Moderate risk of severe and/or direct tropical threats; Events of National Significance. && .PRELIMINARY POINT TEMPS/POPS... MCB 87 72 89 73 / 80 20 70 40 BTR 89 75 90 74 / 80 20 70 40 ASD 88 74 91 75 / 70 20 50 30 MSY 88 76 90 76 / 60 20 40 30 GPT 86 76 88 76 / 50 20 40 30 PQL 87 74 89 74 / 50 30 30 30 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. &&
Hazardous Weather Outlook...CORRECTED National Weather Service New Orleans LA 523 AM CDT Sun Aug 6 2017 GMZ530-532-534-536-538-550-552-555-557-570-572-575-577-LAZ034>037- 039-040-046>050-056>072-MSZ068>071-077-080>082-062045- Lake Pontchartrain and Lake Maurepas-Mississippi Sound- Lake Borgne-Chandeleur Sound-Breton Sound- Coastal Waters from Port Fourchon LA to Lower Atchafalaya River LA out 20 nm- Coastal waters from the Southwest Pass of the Mississippi River to Port Fourchon Louisiana out 20 NM- Coastal Waters from Boothville LA to Southwest Pass of the Mississippi River out 20 nm- Coastal waters from Pascagoula Mississippi to Stake Island out 20 NM- Coastal waters from Port Fourchon Louisiana to Lower Atchafalaya River LA from 20 to 60 NM- Coastal waters from Southwest Pass of the Mississippi River to Port Fourchon Louisiana from 20 to 60 NM- Coastal Waters from Stake Island LA to Southwest Pass of the Mississippi River from 20 to 60 nm- Coastal waters from Pascagoula Mississippi to Stake Island Louisiana out 20 to 60 NM-Pointe Coupee-West Feliciana- East Feliciana-St. Helena-Washington-St. Tammany-Iberville- West Baton Rouge-East Baton Rouge-Ascension-Livingston-Assumption- St. James-St. John The Baptist-Upper Lafourche-St. Charles- Upper Jefferson-Orleans-Upper Plaquemines-Upper St. Bernard- Upper Terrebonne-Lower Terrebonne-Lower Lafourche-Lower Jefferson- Lower Plaquemines-Lower St. Bernard-Northern Tangipahoa- Southern Tangipahoa-Wilkinson-Amite-Pike-Walthall-Pearl River- Hancock-Harrison-Jackson- 523 AM CDT Sun Aug 6 2017 This Hazardous Weather Outlook is for portions of Southeast Louisiana...South Mississippi and the adjacent coastal waters. .DAY ONE...Today and Tonight Scattered to numerous showers and thunderstorms are expected to develop today. A few of these thunderstorms could become strong and produce frequent lightning strikes, gusty winds, and locally heavy rainfall. There is a marginal risk of flooding rainfall over the northwest half of the area today. .DAYS TWO THROUGH SEVEN...Monday through Saturday Scattered to numerous showers and thunderstorms are expected each during the period. A few of these storms could become strong and produce gusty winds, frequent lightning and locally heavy rainfall that could produce localized street flooding. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated. 32
Special Weather Statement
National Weather Service New Orleans LA
928 AM CDT SUN AUG 6 2017
LAZ061-062-061515-
Orleans LA-Upper Jefferson LA-
928 AM CDT SUN AUG 6 2017
...THUNDERSTORMS WITH LOCALLY HEAVY RAIN AFFECTING ORLEANS PARISH
AND UPPER JEFFERSON PARISH...
At 925 AM CDT, National Weather Service meteorologists were watching
a few strong thunderstorms across upper Jefferson and Orleans
Parishes, moving northeast at 20 mph.
These storms could produce 1 to 2 inches of rain in a relatively
short period, resulting in localized street flooding.
Locations impacted include...
New Orleans, Metairie, East New Orleans, Avondale, Jefferson, Gretna,
Harahan, Westwego, Bridge City, Elmwood, Arabi and Lakefront Airport.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Heavy rainfall is occurring with these storms, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
Occasional cloud to ground lightning is also occurring with these
storms. Lightning can strike 10 miles away from a thunderstorm. Seek
a safe shelter inside a building.
&&
LAT...LON 3002 9018 3003 9004 3005 9003 3004 9001
3007 8995 3015 8988 3011 8985 3005 8977
3004 8982 2999 8988 3000 8991 2998 8994
2999 8997 2999 8999 2995 9001 2994 9006
2992 9008 2991 9019
TIME...MOT...LOC 1425Z 227DEG 16KT 2996 9012
95/DMThe Mobile radar (KMOB), 83 km away, was scanning. The volume nearest the first event began at 14:58 UTC.
1 flash flood. Local standard time, as filed.
Broadus Road and Clark Road were reported washed out by flash flooding. The county Emergency Manager measured 5.78 inches of rain nearby. Time of flooding was estimated.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Mississippi in 2017Every state in 2017This day in weather historyWarnings in Mississippi, August 2017
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 713245.