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Barry continues to weaken but significant flood risk remains for lower Mississippi Valley

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Barry prompts new mandatory evacuation orders as floodwaters overtop multiple levees in Louisiana

While Barry is no longer a hurricane, the risk for major flooding will remain as up to two feet of rain is expected to inundate parts of the lower Mississippi Valley into Monday.

Officials performed swift water rescues on Saturday as storm surge flooding inundated the Louisiana coastline. Just east of where Barry made landfall, a tide gauge at Amerada Pass measured a storm surge of nearly 7 feet on Saturday afternoon.

Power outages are also mounting as strong winds howl, with more than 120,000 customers in Louisiana without power as of 4:30 p.m. CDT Saturday, according to PowerOutage.us. A gust of 66 mph whipped Dulac, which is located along the southeastern Louisiana coast, at midday Saturday.

Barry graphic Sat 4:30 p.m.

The risks for storm surge flooding will gradually wane and wind damage will become more sporadic as Barry loses wind strength through the rest of the weekend. Barry is expected to become a tropical depression on Sunday, then a tropical rainstorm by Monday.

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Regardless of the official designation on the Saffir-Simpson scale, AccuWeather declared Barry a level 2 storm on its RealImpact™ Scale for Hurricanes. The scale ranges from “Less than 1” to a 5, with 5 having the most severe impact.

“Our greatest concern is for torrential rain that would result in life-threatening flooding,” AccuWeather Hurricane Expert Dan Kottlowski said.

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Lives and property will continue to be threatened as Barry unloads a swath of 8-18 inches of rain across eastern Louisiana, western and southern Mississippi and eastern Arkansas into Monday.

Rainfall rates can be as high as 2-4 inches per hour in some areas with an AccuWeather Local StormMax™ of 24 inches.

Surge July 13

Isolated tornadoes and waterspouts can be produced east of Barry’s track through the weekend. Some of these may be wrapped in rain and difficult to see until they are already in the neighborhood.

These dangers may occur well away from the center of Barry, as was evident by the thunderstorms that were capable of producing tornadoes in southwestern Alabama on Saturday afternoon.

Gusts July 13

Streets, highways and low-lying areas are the first to take on water as torrential rain pours down. However, flooding will progress and expand as the storm moves slowly inland.

Residents in low-lying and flood-prone areas should be prepared to evacuate at a moment’s notice as waters may rapidly rise. More roads may become submerged and impassable, which may trap residents in these flood-prone areas.

Barry is soaking New Orleans after 6-10 inches of rain deluged the city, which is below sea level, and caused a flash flood emergency Wednesday. The pumps and elaborate drainage system could not keep up with rainfall rates of 2-3 inches per hour, resulting in serious street flooding and numerous high-water rescues.

Barry Impact 7.13 AM

With this storm, the amount of rain can overwhelm any city’s drainage system, let alone that of New Orleans.

Significant rises on the secondary rivers in the region are likely with the risk of major river flooding including the Pearl, Black, Tickfaw, Comite, Amite and Tchefuncte.

The Comite River near Baton Rouge, Louisiana, is expected to crest near record-high levels early next week.

Some secondary rivers, such as the Atchafalaya, generally do not contribute to the flow on the Mississippi in the delta region, but rather take water away from the main stem.

New rain July 13

However, as heavy rain falls immediately over the lower part of the main stem of the Mississippi, a rise of a few feet can occur on that waterway.

The Mississippi River may crest one or two more times in the days and even weeks after Barry as the torrential rain falling during the storm will be followed by all the runoff draining downstream.

It is possible that the lower Mississippi River may not recede below flood stage until the end of the summer, further prolonging what is already the longest flood event on record at Baton Rouge, Louisiana.

Barry Sat night July 13

The river rose above flood stage on Jan. 6 and has not dropped below that mark since.

Water levels on the lower Mississippi River remain high from spring flooding that was still flowing downstream from the middle and upper part of the basin.

In comparison, the level on the Mississippi River prior to the arrival of Hurricane Katrina was 2 feet. On Thursday morning, the river level was just above 16 feet. Flooding in New Orleans during Katrina occurred primarily as levees failed as a storm surge caused waters to rise in Lake Pontchartrain.

Barry Sunday July 13

With Barry, heavy rain that falls directly on New Orleans poses the greatest threat for flooding in the city than the threat for levee breaches.

Earlier Friday, NWS hydrologists expected the Mississippi River at New Orleans to surge to near 19 feet. However, in a stroke of good news for locals, by Friday evening, they revised that forecast and now believe the Mississippi River will crest around 17 feet. Earlier in the week, hydrologists called for a 20-foot crest.

Miss river July 13

Levees in New Orleans are between 20 and 25 feet high at different points along the river, according to what Ricky Boyett, the spokesman for the Army Corps of Engineers in the New Orleans District, told The New York Times.

J. David Rogers, the lead author of a definitive 2015 study on the canal wall failures and catastrophic flooding of New Orleans following Hurricane Katrina in 2005, told AccuWeather in an interview that new levees installed in 2011 will provide the city with much better protection from major flooding.

“It’s a much more robust defense system that they have today with probably a 100-fold better site characterization than they had going into Katrina,” Rogers said. “You can’t even compare pre-Katrina to post-Katrina; it’s like comparing a biplane to a 747.”

Worst of July 13 pm

The heavy rain will gradually ease across the lower Mississippi Valley Monday into Tuesday as Barry focuses on the Ohio Valley.

While there can be an isolated shower or thunderstorm that briefly forces those working outdoors to seek shelter, drier weather will be welcome along the central Gulf Coast next week, starting on Tuesday.

However, humid and seasonably hot weather will put those engaging in storm cleanup operations or without power at risk for heat-related illnesses. It may take days or even weeks for power to be fully restored across the region.

July 13 Mon

AccuWeather RealFeel® Temperatures can approach or exceed 100 F daily next week during the midday and afternoon hours. There will be little relief at night when these values may not drop below the 80s.

Download the free AccuWeather app to stay alert to any tropical advisories, watches, and warnings. Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.


Source: https://www.accuweather.com/en/weather-news/tropical-storm-barry-strengthens-set-to-unload-feet-of-flooding-rain-along-the-gulf-coast/70008788

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