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Heidi Shaffer, Published September 25 2010

Will our wet fall lead to spring flood?

Fargo-Moorhead’s fall is off to a record-breaking wet start.

A record 1.6 inches of rain fell Thursday, surpassing the previous Sept. 23 high mark set 90 years ago and bringing this month’s precipitation total to 5.31 inches, 3.62 inches more than normal.

Thursday’s rain was the second time this month Fargo-Moorhead has seen a daily record rainfall, according to the National Weather Service in Grand Forks. A record 1.99 inches soaked the city Sept. 6.

While it’s still too early to predict when or how high the Red River will crest next spring, the past two wet falls preceded record-setting spring floods.

Vince Godon, a meteorologist at the National Weather Service in Grand Forks, said fall precipitation is just one factor that can lead to spring flooding.

Frost depths, winter precipitation, spring melt-off and rainfall will also play into whether spring flooding occurs, Godon said.

“Judging from the last couple of years, the wet fall has been there,” he said. “It’s one condition. I wouldn’t say it’s significant, but it definitely factors in.”

Heavy fall rain leads to ground saturation. A high soil saturation means the spring melt will run off rather than soaking into the ground and increase flooding.

In 2008, fall rain totals topped the monthly normal each month during the fall. In September 2008, 5.08 inches of rain fell, followed by another 4.46 inches in October and 1.13 inches in November.

The next spring, on March 28, 2009, the Red River hit its high crest of record: 40.84 feet.

In the fall of 2009, September’s rainfall hit 2.05 inches, 0.36 inches more than normal. A wet October followed, with 5.44 inches of precipitation, 3.47 inches more than normal.

But the soggy trend did not continue into November of 2009. That month 0.41 inches fell, 0.65 inches below normal.

In the winters preceding record flooding in 2009 and 2010, snowfall varied.

During winter of 2008-09, snow totals hit 79.7 inches, almost double the normal amount, Godon said.

Last winter brought 46.6 inches of snow and preceded the sixth highest Red River crest of 36.95 on March 21.

So far this year, every month since December has seen higher than normal precipitation. Fargo has received 24.58 inches of precipitation since Jan. 1, 7.48 inches above normal.

On Friday, the weather service said another storm system will pass over the region and last into today, bringing another quarter to half inch of rain.

The Red River sat fairly steady at 15.5 feet for most of the summer but hit minor flood stage of 18 feet last week.

Godon said it takes only an inch or two of rain to push the Red River to Fargo’s minor flood stage.

The weather service won’t begin spring flood predictions until early next year.

Fargo Mayor Dennis Walaker said it’s still too early to start worrying about another flood.

“(Fall rain) probably is one of the indicators of having problems in the spring, but we have to wait to find out exactly where we stand,” Walaker said.

“Right now is not the time to lose any sleep over it,” Walaker said.

Readers can reach Forum reporter Heidi Shaffer at (701) 241-5511