National Weather Service: Red River flooding less likely this spring

After three consecutive years of major floods, the Red River Valley could get a reprieve next spring.

The National Weather Service indicates just a 3 percent chance that Grand Forks and East Grand Forks will experience major flooding, which occurs when the river reaches a level of 46 feet.

The weather service's first 120-day hydrologic outlook for the season, released Friday, indicates the chance of minor flooding at Grand Forks at 48 percent, and moderate flooding at 14 percent. Minor flood stage is Grand Forks is 28 feet, while moderate flood stage is 40 feet.

That's a significant change from the early forecast in August when the weather service said the valley could face an "unprecedented fourth consecutive major spring flood threat."

Continuous wet conditions carrying into the summer caused forecasters to worry that even normal precipitation over the fall and winter could exacerbate flood risks. Instead, this fall has been exceptionally dry.

The next forecast will be issued Jan. 24. Forecasters said several factors could change the outlook, which extends to April 30.

Precipitation

The latest outlook from the weather service's Climate Prediction Center indicates equal chances of normal, above normal or below normal temperatures and precipitation over the next 120 days.

In April and May, the CPC forecasts an enhanced risk of above-normal precipitation and a slightly enhanced risk of below normal temperatures over the northern Red River Basin.

The flood of record in Grand Forks was in 1997, when the river hit 54.35 feet.

Four of the city's Top 10 floods have occurred since then, including this past spring, when the 49.87-foot crest marked the third highest flood on record. In 2009, it reached 49.33 feet, to rank fourth. In 2010, it hit 46.09 feet, which ranks eighth, while the 2006 crest of 47.93 feet is 7th.

Key factors

The weather service indicates that several factors could alter the original spring outlook, including:

• How much snow pack builds up in the basin before the spring thaw.

• How much water is in the snow pack going into the thaw.

• How fast the snow melts during the thaw.

• How high the rivers are at the start of the thaw.

• Soil conditions, including soil moisture and frost depth, at the time of the thaw.

• Whether significant rain or snow occurs during the thaw or at peak flood time in the basin.

Opposing forces

The dry, mild fall we experienced this year is only indirectly related to the positive spring flood outlook, according to Mark Ewens, climate forecaster with the weather service in Grand Forks.

It is more directly related to a weakening La Niña weather pattern and Arctic conditions, he said.

Typically, La Niña brings colder, snowier winters, but they weaken in their second year, and this is the second year, according to Ewens. At the same time, the Arctic air mass has oscillated toward a period of high pressure when colder air is more likely to be trapped in the northern regions instead of spreading south.

"In this case, the Arctic oscillation became so strong that it overcame the influences of the El Niño and La Niña," he said.

Red River

Below are weather service forecasts for the Red River, followed by forecasts for its tributaries.

• Wahpeton, N.D.: Minor flooding (10 ft.) 33 percent; moderate (12 ft.) 11 percent; major (14 ft.) 6 percent.

• Fargo: Minor (18) 69 percent; moderate (25) 19 percent; major (30) 11 percent.

• Halstad, Minn.: Minor (26) 17 percent; moderate (32) 6 percent; major (37.5) 3 percent.

• Grand Forks: Minor (28) 48 percent; moderate (40) 14 percent; major (46) 3 percent.

• Oslo, Minn.: Minor (26) 54 percent; moderate (30) 38 percent; major (36) 6 percent.

• Drayton, N.D.: Minor (32) 37 percent; moderate (38) 21 percent; major (42) 9 percent.

• Pembina, N.D.: Minor (39) 45 percent; moderate (44) 30 percent; major (49) 9 percent.

Minnesota tributaries

• Hendrum (Wild Rice): Minor (20) 35 percent; moderate (28) 6 percent; major (32) 1 percent.

• Shelly (Marsh): Minor (14) 9 percent; moderate (20) 3 percent; major (23) less than 1 percent.

• Climax (Sand Hill): Minor (20) 9 percent; moderate (25) 3 percent; major (30) 1 percent.

• Crookston (Red Lake): Minor (15) 28 percent; moderate (23) 1 percent; major (25) less than 1 percent.

• Alvarado (Snake): Minor (106) 11 percent; moderate (108) 4 percent; major (110) 1 percent.

• Hallock (Two Rivers): Minor (802) 46 percent; moderate (806) 25 percent; major (810) less than 1 percent.

• Roseau (Roseau): Minor (16) 24 percent; moderate (18) 12 percent; major (19) 9 percent.

North Dakota tributaries

• Valley City (Sheyenne): Minor (15 ft.) 9 percent; moderate (16 ft.) 8 percent; major (17 ft.) 6 percent.

• West Fargo (Sheyenne): Minor (18) 17 percent; moderate (20) 12 percent; major (21) 4 percent.

• Hillsboro (Goose): Minor (10) 8 percent; moderate (13) 4 percent; major (16) 1 percent.

• Minto (Forest): Minor (6) 25 percent; moderate (8) 9 percent; major (16) less than 1 percent.

• Grafton (Park): Minor (12) 17 percent; moderate (13.5) 8 percent; major (14.5) 4 percent.

• Walhalla (Pembina): Minor (11) 19 percent; moderate (16) and major (18) less than 1 percent.

• Neche (Pembina): Minor (18) 28 percent; moderate (19) 25 percent; major (21.5) 19 percent.

Reach Bonham at (701) 780-1110; (800) 477-6572, ext. 110; or send email to kbonham@gfherald.com .