FARGO, N.D. — The National Weather Service on Thursday dramatically bumped up the chances of major flooding on the Red River near Fargo, but city officials say it should have minimal impact on residents if the numbers hold true.

Weather service officials say the chance of major flooding in North Dakota’s largest city has increased from 6 percent a month ago to 79 percent, based mainly on water content in the snowpack. Major flood stage in Fargo is listed at 30 feet, but the city has built up its defenses to handle 37 feet without breaking out many sandbags.

The new flood outlook shows there’s a 50 percent chance the Red River will reach 33.2 feet, a 25 percent chance it will hit 35.1 feet and a 5 percent chance of reaching 37.8 feet.

Mark Bittner, Fargo city engineer, said if those figures hold up, the city would likely have to build a temporary dike in a low-lying area in front of city hall, creating little more than a traffic nuisance.

“Beyond that, 37 feet brings a few residential properties into it, but not a lot,” Bittner said.

Dave Rogness, Cass County emergency manager, said the worst-case scenario is “still generally very manageable,” but county officials will be closely monitoring weather service reports.

“It went from nothing is going to happen and we can sleep at night to now we need to pay attention,” Rogness said.

Residents in the Fargo and Moorhead area battled three straight years of flooding, beginning with a record crest of 40.84 feet in 2009. The cities have since reduced their vulnerability by buying out homes in flood-prone areas and building up permanent dikes.

Greg Gust, weather service meteorologist, said the heaviest snowpack is in the southern Red River Valley, where snow-water measurements show “pretty high numbers.”

He listed high topsoil moisture and heavy frost depth as “cautionary” factors to spring flooding, but said low stream flows in the basin are favorable.

Michael Redlinger, Moorhead city manager, said the report wasn’t a surprise because of a large snowstorm in early February.

“It really is our spring ritual. We start in February monitoring these forecasts,” Redlinger said. “With this much time on the clock until we start melting and rivers start to open up, we’ll continue to monitor it. But there are no alarm bells at this point.”

The wild card will be the spring thaw cycle and precipitation, Gust said. The climate outlook calls for a cool, wet spring.

Gust said the Devils Lake basin in northeastern North Dakota has a 50 percent chance of increasing by as much as 2 feet, although the lake has dropped 3 feet from its record level in 2011. That would likely not affect area residents, who have been dealing with the high water for 20 years.

The best news in the report, Gust said, is that drought impacts are lessening from 2011.

The next flood outlook will be released March 7.