The Big Wood River at Hailey is predicted surge to 7 feet on May 23, according to the May 13 forecast from the National Oceanic and Atmospheric Administration’s Northwest River Forecast Center.
That's about half way between NOAA's threshold for "moderate" and "major" flooding, and just six inches below the record high for that date.
The forecast shows the Big Wood River gauge at Ketchum reaching 7.8 feet on May 23, below the flood stage of 8 feet. However, the chart indicates a continued rise.
As of 2:45 p.m. on Saturday, May 13, the river measured a depth of 4.39 feet at the Bullion Street gauge in Hailey. On May 4, it reached a level of 5.4 feet before receding with cooler temperatures.
The forecast shows the river reaching flood stage—5 feet—on Sunday, May 15, and reaching 6 feet around Friday or Saturday, May 19 or 20.
Current forecasts show the air temperatures heating up to 79 degrees on May 21, before cooling somewhat, and dropping to around 69 degrees on May 28.
The relatively steep and prolonged warm up is precisely the wrong mix for flood risk—resulting in a large quantity of quickly-melting snow.
The conditions in the high country will also likely increase the risk for avalanches, especially on north-facing slopes at the highest elevations in the Sawtooth and Smoky mountain ranges.
As temperatures are forecast to climb into the 70s next week, the Big Wood River will likely again rise above flood stage around the morning of May 16, according to an update given Tuesday to the Blaine County Commissioners by Disaster Services Coordinator Chris Corwin.
And, with temperatures predicted to reach the 80s by next Friday, the National Oceanic and Atmospheric Administration’s Northwest River Forecast Center predicts the river swelling to over 6 feet at the Bullion Street gauge in Hailey on May 20, and climbing further from there. Flood stage on that stretch of the Big Wood is 5 feet. This year’s highest measured level was 5.34 feet on May 4 before it began to drop.
Compared to past years—particularly 2017 and 2006—Corwin said he didn’t anticipate reaching any record levels of flooding, or high stage flooding.
“But,” he said, “it is something that definitely will cause some issues with some properties.”
Corwin estimated water levels won’t likely hit their crest until around the week of May 22.
“We’re not out of the woods,” Corwin said. “There’s a lot of time left. And if it continues to get hot and stay hot, we are going to see a lot of water come down.”
As of press time on Thursday, the Big Wood River in Blaine County is under a National Weather Service flood advisory until further notice.
At 6.0 feet, the Weather Service stated that “moderate” flooding will occur along Cedar, War Eagle, and Della Vista drives in the lower subdivisions in Hailey, which may be inaccessible. Residents should also expect flooding in the Riverview Drive area of Bellevue, and Draper Preserve will be inaccessible.
“Water may be over some secondary roads in West Ketchum,” the Weather Service stated. “Gimlet subdivision will have some residents with flooding issues.”
On Thursday morning on War Eagle Drive, water still pooled around some houses. Walls of sandbags and water bladders remained in place from last week’s flooding.
“I guess I’m as ready as I can be,” said Cindy Theobald, who lives nearby on Red Elephant Drive. Theobald recalled the 2017 flood, when “I lived on an island.” For three months, she and her family were exiled to “couch-surfing around town” and using a rowboat to access their house from the road.
Theobald said there’s been some debate among her neighbors about what is going to happen—or not happen—this year. She said she was hoping the recent cold weather would keep things at bay, but she’s preparing for high water.
“In anticipation, I’ve lifted everything in the garage off the floor and purchased 20-foot-long bladders to put in front of the garage,” she said. “I have three pumps in the crawl space, and I have a generator.”
The recent cool down “saved us,” Corwin said, but it also brought additional snow to higher elevations.
From May 4 through May 10, it snowed about 14 inches on Galena Summit, about 12 inches on Trail Creek Summit, and about 2 feet on Dollarhide Summit, reported Ethan Davis, an avalanche specialist with the Sawtooth Avalanche Center.
The amount of rain in the valley over that same time period was relatively negligible in terms of adding much to river height, Corwin said.
As the river rises again into next week, “it’s important to maintain situational awareness with the river,” Corwin advised. “Be aware of things like logs and debris continuing to move down the water, trees being eroded into the water, and be diligent about watching the banks.”
Corwin also encouraged residents to report any damage or concerns related to the rising water to himself or to the flood plain manager. “It’s always good to know what people are seeing, because we can’t be everywhere.”
And while there remains significant snow at higher elevations, Corwin noted those snowpack levels are also well below the record-setting levels in 2006 and 2017.
“At the same time,” he said, “if it got hot really fast or stayed hot for a long time, it could bring a lot of moisture down in a short amount of time.” Corwin noted that possibility—a steep rise in water levels, a short peak, and a quick drop off—could follow a pattern similar to 2006.
The longer-term forecasts suggest temperatures climbing to the mid to upper 70s and potentially to 80 around the weekend of May 20.
Avalanche Center: Spring transition delayed, danger remains
High above the valley floors, Davis said there are still areas with significant avalanche risk, particularly in the Sawtooth and Smoky Mountain Ranges and their north-facing slopes.
In terms of assessing that risk, Davis said the key to remember is that “when the dry, cold snow gets warm for the first time, it is likely to produce avalanches.” Much of the snow there still needs to undergo that initial spring transition, he said, and this year the transition has been significantly delayed.
The process often spans months, Davis said, as when snow in the lower elevations warmed or got rain for the first time of the season, and the avalanches hit rivers and the valley floor in April.
“The shadiest, coldest, and highest elevations have still not gotten through the transition to a more stable springtime snowpack that we might expect this time of year already.”
Once the water gets through the snow, he explained, it stabilizes and becomes that “holy grail” of spring snow sought by skiers and snowmobilers.
And while there are no longer avalanche forecasts being issued, Davis encouraged people who are venturing to higher elevations to check the Sawtooth Avalanche Center’s website to get the latest information and read observations made by the public. “People still going out and then telling others what they have found has become super valuable because we don’t put out an active forecast every day.”
In the Pioneers, there have been “dozens and dozens of avalanches since forecasting stopped,” Davis said. At the end of April there were some large avalanches in the Pioneer and Boulder Mountains, he said, which are expected during long, prolonged warmups.
If over the next 10 days temperatures on Galena stay above freezing, Davis said, “that will likely push water into places that haven’t seen water, which will likely produce some large avalanches.”
Davis said he estimated as many as 40 slides on Trail Creek Pass over the winter, which remains closed.
A spokesperson from the Blaine County Road and Bridge Department said there are not currently any changes to the existing resolution governing the opening of Trail Creek Road into Custer County. Per the resolution, Trail Creek will open to vehicles on the Friday before Memorial Day “unless snow or other conditions require a later opening, as determined by the Blaine County Road and Bridge Manager in consultation with the Board [of County Commissioners].”
Flat Top Road north of Carey remains closed by floodwaters, and crews will wait until the water dissipates before fixing the road, Corwin said.
Both Corwin and Davis noted the numerous variables involved when it comes to forecasting avalanches, snowmelt and flooding. But the primary question right now, Corwin said, remains: “How fast will it get hot, and how hot will it get?” ￼
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