By: Erik Burgess, INFORUM
FARGO – City officials here say they plan on significantly dialing back flood protection plans after weather service forecasters told them Tuesday the Red River could crest lower than 39 feet.
“We’re looking at deployment of fewer sandbags. We’re looking at using the students less. We’re looking at fewer neighborhoods that we have to get into,” City Administrator Pat Zavoral said.
Weather service forecasters told city officials in a conference call late Tuesday afternoon that if a gentle melt and below-average precipitation continues, the crest could be in the 38- to 40-foot range, said City Engineer Mark Bittner, who participated in the conference call.
Zavoral said he is confident the city will only need to protect against a 38-foot flood, which requires significantly less effort than earlier worst-case projections of 41 feet or higher.
National Weather Service officials said the range given to Fargo officials was not an official deterministic crest forecast, though a crest forecast is likely to be issued today. They said Tuesday that because of a variety of factors, it’s too soon to tell if the flood will top out around 38 feet – a historically severe but largely manageable crest.
“We’re not ready to pick that (crest) range and draw that line for Fargo,” said Greg Gust, a warning coordination meteorologist with the weather service. “We’re trying to get there.”
Building defenses to 43 feet takes around 1.8 million sandbags, while the city is now looking at throwing less than 400,000 bags to build protection up to 40 feet, Zavoral said.
He said the city is still technically waiting for the weather service to issue an official deterministic crest forecast before ratcheting down protection plans.
“But we’ve already alerted the school district that there’s going to be some changes,” he said late Tuesday afternoon.
The city was originally planning on enlisting the help of more than 1,000 students to build sandbag dikes Thursday.
More decisions on how to react to new the prediction will be made today, Zavoral said. A public meeting on flood preparations that was scheduled for 8 a.m. was moved to 5 p.m., to allow for more time to adapt to what city officials hope will be an official crest forecast.
Cass County officials also said they were encouraged by flood predictions issued on Tuesday.
The conference call took place Tuesday afternoon between weather forecasters and Fargo officials. In the call, Bittner said he and other city staff were told there were three possible crest ranges.
A seven-day forecast considering better-than-normal weather, melt and runoff would have the Red River in Fargo cresting somewhere between 38.7 and about 40 feet. If weather and melt is just normal, the river level range was between 40 to 41 feet, and if weather is severe in the next week, the flood could be above 41 feet.
Weather forecasters said in the conference call that while an official deterministic forecast is yet to be made, Fargo can start using 38 to 40 feet as a closer guideline, Bittner said.
“They’re saying we’re expecting the crest to be at the lower end of the previous curves that we had seen … in the 38-foot range,” Bittner said. “But they won’t know for sure until they actually run the deterministic. They don’t think that we’re going to reach those higher levels that they were talking about in the 41, 42 foot range.”
Crews worked Tuesday to stage 300,000 sandbags in Fargo’s north side, preparing to build levees to 43 feet, which would defend against a 41-foot flood with 2 feet of freeboard.
In a probability-based forecast last week, weather service forecasters said the Red River in Fargo had a 95 percent chance of hitting 39.3 feet, a 90 percent chance of 39.4 feet, a 75 percent chance of 39.8 feet, a 50 percent chance of 40.3 feet, a 25 percent chance of 41.3 feet, a 10 percent chance of 42.1 feet and a 5 percent chance at 42.4 feet.
A 40.84-foot crest in 2009 is the largest Fargo flood in recorded history.
Updated outlook issued
The conference call came after the weather service issued an updated flood outlook Tuesday morning, predicting the Red River in Fargo would hit 35.4 feet next Tuesday. The same forecast called for the Red to reach 31.6 feet by Monday.
The river in Fargo was at 16.9 feet just after 5 p.m. on Tuesday.
Based on forecast temperatures, the crest is expected next week and was expected beyond the seven-day forecast issued Tuesday, Gust said. It’s a “fairly strong maybe” that a forecast that includes an apparent crest could come out today, he said.
The weather service has not officially given a crest range in Fargo because there are some unknown factors that could change the outlook, Gust said.
The Wild Rice River, which feeds into the Red, is not yet moving, and it’s unknown exactly how much snowmelt is soaking into the soil in southern Cass County and northern Richland and Wilkin counties, Gust said.
Temperatures are expected to rise starting Friday into the weekend, with highs in the lower 60s. Morning lows are expected to be above freezing, resulting in “significant snowmelt runoff,” the outlook said. Precipitation over the next seven days should be below normal, which is a good sign, Gust said.
The updated 7-day forecast projects a rising river through Tuesday, but the rise of the river seems to slow down and curl at that time, appearing to create the beginning of a top of a bell curve in the river level prediction hydrograph.
Gust said the hydrograph is “hypothetical,” and that it’s too soon to tell when the river will crest and at what stage.
“That’s so far in the future,” he said. “That curl (in the hydrograph) is just way too hypothetical at this point to attach much (meaning) to.”
But city and county officials noticed the bend in the graph, and they’re taking it as a sign of good things to come.
“We’re cautiously optimistic,” said Keith Berndt, county administrator in Cass County, where about 300 homes would be impacted by a 39-foot flood. “We still haven’t seen an official crest projection, neither date nor height, but we can kinda read into things a little bit.”
Jeremy Gorden, a Fargo traffic engineer, said the hydrograph released on Monday had flood levels shooting “straight up,” but the graph released Tuesday appears to be trending toward a lower river crest.
“(It) looks like it’s starting to bend at the end meaning hopefully a 43-foot flood is out of the realm of possibility,” Gorden said.
Crest a ‘moving target’
There is the potential for significant summer-like rainfall to occur next week, which could disrupt any crest prediction, said Steve Buan, a service coordination hydrologist for the National Weather Service office in Chanhassen, Minn.
While Buan was not on the conference call with Fargo officials, he confirmed that it took place and said that based on the “benign” weather forecast for the next seven days, a 38- to 40-foot flood prediction was probably given by forecasters to Fargo officials as “guidance.”
But Buan said outside of that seven-day forecast, there is the potential for severe rainfall, which is why he said he was uncomfortable and unable to provide an official river level range.
“It’s going to be a moving target here for the next several days,” Buan said of the crest prediction.
Buan said the possibility for a summer-like rain was raised by a new model that came in after the late afternoon conference call with Fargo city officials.
“I don’t think they (Fargo officials) were given a range. They were given guidance on picking their own range and again, that’s at this moment in time,” Buan said. “There’s nothing set in stone.”
Zavoral said if heavy rain did bring a higher flood, the city would be ready. He said it would take two days to increase protections from 40 feet to 42 feet level, the difference between 400,000 bags and 1.1 million.
“We’ll have more than enough sandbags in the neighborhoods,” he said.
The weather service has already issued a crest prediction for the Red River in Wahpeton.
In the outlook released Tuesday, forecasters said that the Red River in Wahpeton will likely crest at 16.5 feet on Monday, April 29. The forecast crest range in Wahpeton is between 16 and 18 feet.
That’s half a foot lower than an earlier weather service crest prediction there, Gust said, and also well below the record 19.42-foot crest set in 1997. It’s also lower than the 2009 crest in Wahpeton, when the Red River hit 17.5 feet.
Gust said that’s because the weather service has a better understanding of the snowmelt infiltration in southern Wilkin County and how the Rabbit River and other tributaries are melting and feeding into the Bois de Sioux River, which joins the Ottertail River to form the headwaters of the Red River in Wahpeton.
Tuesday’s updated flood outlook predicted the Red River in Hickson, N.D. to hit 37.5 feet on Tuesday, which would be the third highest flood on record. The prediction hydrograph appears to begin to taper off at that point. The record flood there was in 2009 at 39.04 feet, and major flood stage is 38 feet.
Gust also said overland flooding started to take shape Tuesday in northern Wilkin County, northeastern Richland County and in parts of Cass and Clay counties, but Berndt said it’s not yet a major concern in Cass County.