New flood outlook: 50 percent chance of 50-foot crest in Grand Forks
The Red River Valley continues to be “at the mercy of March” as the risk for flooding keeps going higher in the area.
The National Weather Service has issued another flood outlook, and the predictions are bleak.
“The first half of March has been Merciless, adding significantly more snow into the spring snowmelt runoff mix,” the weather service said in its report.
A top 10 runoff year is now expected in most areas, though less likely in northeast North Dakota, based on snow already on the ground and normal conditions throughout the rest of the runoff period, meteorologist Greg Gust said.
“Significant snowmelt flooding is likely, with above- to much-above-average flood risks across the Red River and Devils Lake basins,” the weather service said.
Moderate to major flooding is “nearly guaranteed,” especially along and near the mainstem Red River. Significant overland and rural flooding is also likely, according to the weather service.
Gust said while the flood outlook has not improved since March 7, this week could have been much worse as regions south of Grand Forks and Fargo received tremendous rainfall and flooding this week.
Though the weather service says there is some good news, the next two weeks could bring temperatures slowly trending to near normal and a more favorable melt cycle, with precipitation near to slightly below normal.
However, there’s no guarantee that the end of March and beginning of April will cooperate, the weather service said. The beginning of April could bring a cold snap, and the chance for more moisture is uncertain.
Grand Forks has a 95 percent chance of moderate flooding, with the river potentially cresting around 45.8 feet. There is a 90 percent chance the river crests at 47.5 feet and a 50 percent chance the river reaches 50.6 feet.
Additionally, there is a 10 percent chance Grand Forks reaches 54.6 feet, above the record 1997 crest of 54.35 feet. The flood control system protects the city to a crest of 60 feet.
Gust said rising waters will likely shut down bridges in Grand Forks, including the Sorlie and the railroad bridge, which would affect traffic in the area. He added rural areas of the county will still likely be affected by runoff.
Crookston also has a chance of flooding with the Red Lake River. Crookston has a 75 percent chance of moderate flooding and a 50 percent chance of major flooding at 26.9 feet. There is also a 25 percent chance of a flood of record at 28.5 feet.
Gust said there is also a potential of ice jamming at the Red Lake River. Gust added the situation would need to be watched very carefully in case there is a need to evacuate part of the town.
Oslo, Minn., has a 95 percent chance of major flooding with the river potentially cresting at 37.2 feet and a 25 percent chance the river reaches 38 feet.
Gust said with the increased risk of flooding comes the increased chance of road closures to the west and east of Oslo. There is also a possibility the water could begin to approach the Interstate 29 corridor.
Pembina is likely to see major flooding at 51 feet with a 95 percent chance, according to the weather service.
There are several factors the weather service takes into account when putting together the flood outlook, including streamflow, soil moisture at freeze-up, frost depth, snowpack and total precipitation.
The weather service said that while the river is still frozen, base streamflow is near normal in the northern part of the basin and slightly above normal flow in the southern half of the basin. However, streamflows remain “much below” the record flood years of 1997, 2009, 2010 and 2011.
Soil moisture was below normal in the far northern part of the basin, near normal in the central basin and above normal in the south. Soil moisture is also much lower than it was in the record flood years of 1997, 2009, 2010 and 2011.
Frost depth is deeper than normal across the Red River Valley, in some areas the frost is 3 to 4 feet deep, with river ice and lake ice thicknesses above seasonal normal ranges.
Snowpack is also above normal. According to the weather service, since Dec. 1 snowfall has run from 100 to 200 percent of normal.
Total precipitation from Oct. 1 to March 15 is very high, the weather service said. Total precipitation ranges from 2 to 4 inches above the long-term normal for most of the central and southern Red River Basin.
— NWS Grand Forks (@NWSGrandForks) March 15, 2019