Pocatello, ID

Weather Forecast Office

2017 Spring Flood Season

Overview

The winter of 2016-2017 produced historic snowfall across central and east Idaho. The season overachieved to the point that many communities exceeded their snow removal budgets. Several basins were over 150 percent of normal by March 15th and most upper level stations were reporting snowpack in the top 10 percent all time.

Abnormally cold temperatures in December and January combined with an active storm track created an above normal snowpack across the lower elevations. A major shift in the weather occurred in early February as temperatures rose and several systems brought rain to the lower elevations. Low land flooding occurred across the Magic Valley and quickly expanded into the Snake Plain as the resultant snowmelt was unable to seep into the frozen ground. Much of the Magic Valley and Snake Plain turned into a cluster of lakes for weeks until the ground thawed. Emergency channels were dug to allow the fields to drain. Homes, farm equipment, livestock were all threatened by the flooding and several roads were washed out by flood water. Several small rivers including the Raft River, Goose Creek and Trapper Creek experienced record or near-record levels.

As the calendar turned to March, the scenario witnessed in the Magic Valley and Snake Plain was replicated across the higher elevation communities of central and eastern Idaho. Fields turned into lakes threatening livelihoods with emergency canals dug to divert water until the ground thawed. The mid and upper slope snowpack began to melt and began to fill area reservoirs to capacity. By late March, Magic Reservoir filled so quickly that dam operators were not able to open flood gates because too much pressure was placed on them. Eventually, water went over the spillway and washed out a road that spanned the dam. Fortunately, most of the flood water from Magic Reservoir simply spilled into the lava fields north of Shoshone where it quickly found its way into the aquafer. A similar situation unfolded nearby at the Mackay Dam. The Big Lost quickly filled the reservoir. Fortunately, dam operators working with National Weather Service forecasters were able to meet area water needs of filling the reservoir while averting an uncontrolled release of water that would have threatened homes.

High flows and flooding along area streams and rivers were common. In many instances, lowland flooding was considerable but largely confined to agricultural land. Such was the case along the Bear River where lowland flooding lasted for a few months. However, there were several larger impacts as well. The Big Wood at Hailey set an all-time record stage height flooding several homes. Sandbagging efforts along the Big Wood in Blaine County began in early May and continued into July. In Challis, up to 10 homes were isolated when two bridges that spanned area creeks were threatened. High flows and minor flooding occurred along portions of the Snake River. The U.S. Army Corps of Engineers worked with officials from Jefferson and Madison counties to respond to bank erosion on levees that were protecting hundreds of acres of farmland and numerous homes.

Water pouring over the spillway at Magic Reservoir on April 1, 2017. Photo courtesy of Michael Flolo.

Spring Snowpack
February
March
April
May
June

Spring Snowpack


Snow Water Equivalent percentage of normal for March, April, and May 2017.				Snow Water Equivalent rankings for high-elevation reporting station. At the beginning of March, 2017, many stations were reporting historical snowpack (blue).


Accumulated snowfall at Stanley, Idaho for the winter of 2016-17 (blue) compared to normal (brown).	Accumulated snowfall at Picabo, Idaho for the winter of 2016-17 (blue) compared to normal (brown).	Accumulated snowfall at Aberdeen, Idaho for the winter of 2016-17 (blue) compared to normal (brown).

February


A sunset in Pocatello, Idaho in late January. Pocatello had a snow depth of around 15 inches going into February. For the month of January, the Pocatello Airport received 32" of snow in 2017, normal is 8.5".	An atmospheric river event occurred from February 4th to the 10th. This brought heavy snow to the mountains and highlands, but rain on snow in the lower elevations. Let the flooding commence!	Modeled snowmelt for the 3 day period from February 5th to the 7th.

Modeled snowmelt for the 3 day period from February 8th to the 10th. Snowmelt water equivalent for the entire 6 days was 2.50 to 6.00 inches across much of the Magic Valley and Snake Plain.	The worst flooding occurred in Cassia and Minidoka Counties on February 6th when snow melted in the fields and was unable to drain or seep into the frozen ground. Multiple homes were threatened and roads were submerged.	Crews working in the Mini-Cassia region to divert flood water on February 6th.

I-86 was reopened a couple days later even though some water was still flowing over the highway. Traffic through the region was attempting to bypass the highway by taking local roads which were in many cases were compromised. Highway Patrol closely monitored this stretch, ensuring vehicles slowed down and did not have problems.	Homes in the Malta and Almo areas using haystacks to beat back flood waters. This picture was taken on February 8th.	Flooding began to move further into east Idaho by the 9th. This photo shows the onset of sheet flooding near Ammon. Photo courtesy of East Idaho News.

Hydrograph of the Raft River showing record crest.	Aerial photo of Cassia County on February 10th. This pictures shows a portion of the sheet flooding in the Mini-Cassia region. Courtesy of KMVT.	Aerial photo of home surrounded by sheet flooding in Cassia County on February 10th. Courtesy of KMVT.

Preston business surrounded by sheet flooding around February 10th. Photo courtesy of Derrick Hughes via Idaho State Journal.	Sheet flooding threatening business near Idaho Falls around February 10th. Photo courtesy of KIFI.	Aerial photo of Minidoka County looking north. In the foreground, sheet flooding is occurring. In the distance, heavy snowpack still to melt out. Generally, water ran from north to south. Photo courtesy of Kevin Gebhart via Times News

.Marsh Creek south of Pocatello on February 14th. Photo courtesy of Jordan Beesley via Idaho State Journal.	Minidoka County on February 14th.	Washed out road in Minidoka County around February 19th.

Goose Creek area on February 21st. Photo courtesy of Capitol Press.	Blackfoot area on February 21st. Video by Shantel Morgan.	Washed out road in Jefferson County around February 21st. Photo courtesy of Dave Walrath.

Washed out road in Jefferson County on February 22nd. Photo courtesy of Rebecca Squires.	Map showing areas of concern north of Rupert on February 23rd.	Topographical map showing areas of concern north of Rupert on February 23rd. The direction that snowmelt would flow was of great interest.

Weather turned colder on February 23rd. Multiple slideoffs across central and east Idaho occurred.	The colder air brought a cease fire to the snowmelt as seen in this hydrograph for the Portneuf River at Pocatello.	Damage estimates from the snow and flood across east Idaho topped $22 million dollars for just the month of February. One might think with all this flooding there should be a good dent in the snowpack. But, no. There's a LOT more to come.

March


Flooding in the Magic Valley had unveiled a new problem by early March. Flood water from the agricultural areas was beginning to taint the water supply. Emergency management officials working with the U.S. Army Corps of Engineers made plans to deal with this new problem by pumping the water away from Rupert.	The first half of March began cold as evident by this picture from Pocatello taken on March 5th. Emergency managers working with the National Weather Service spent a lot of this time planning for the next round of snowmelt.	Warmer weather gradually returned around March 10th. This hydrograph for the Portneuf River at Pocatello shows a strong rise over the next couple of days with this particular gauge reaching minor flood stage by March 12th.

Sheet flooding near Taber on March 16th. Photo by Edward Andersen.	Evidence of road damage from sheet flooding near Taber. Photo taken on March 16th by Edward Andersen.	Sheet flooding near Ovid on March 20th.

Combination of sheet and river flooding near Pegram on March 20th.	Snow in the process of transforming to sheet flooding near Wayan. Photo by Eric Hobson.	High flows on Rapid Creek in Inkom on March 22nd.

Flooding along the Bear River near Dingle on March 26th. Photo by Devin Skinner.	Flooding along the Bear River along Highway 30 near the Wyoming border on March 27th. The green object in the center of the picture is a river gauge. When not in flood, the bank of the river is just to the right of the gauge in this photo.	Flooding along the Bear River near Dingle on March 27th. Video courtesy of Kevin Smith.

Home surrounded by flood waters near the Bear River near Dingle on March 27th.	By March 30th, Magic Reservoir reached capacity and began to overflow the spillway. This video shows the water pouring over the spillway. As a point of reference, the dam appears in this video at the 6 second mark.	This washed out road goes across the spillway at Magic Reservoir before continuing on across the dam.

The area downstream of Magic Reservoir is largely rural, but there were a few homes that were threatened by the flood water.

April


Road washed out from March floods about 5 miles northwest of Preston. Repair work began in early April. Picture by Necia Seamons via Preston Citizen.	Another home still threatened by flood waters from the Big Wood River downstream of Magic Reservoir on April 5th.		Big Wood River near Highway 75 about 15 miles north of Shoshone on April 5th. The Big Wood is often a dry river bed at this location.

By mid April, much of central and east Idaho were experiencing high flows on area rivers. This picture was taken along the Snake River at Lorenzo on April 12th.	Many of the area reservoirs were releasing water. This picture shows the impressive flows coming out of American Falls Reservoir on April 12th.		Blackfoot River southwest of Blackfoot on April 19th had high flows resulting in minor flooding in some areas.

Flooding along the Portneuf River west of Inkom on April 19th.	Flooding along the Snake River near Heise on April 19th.		High flows along the Snake River near Firth on April 19th.

Bear River flooding along highway 30 near Dingle on April 25th.		High flows along the Snake River in Burley on April 25th.

May


On May 6th, the Big Wood overflowed its banks at Hailey and caused serious problems for area residents.	Flood waters from the Big Wood River surround this home in Hailey on May 6th. Photo taken by Jorge Pulleiro via Idaho Mountain Express.		Flooding in the Warm Springs area near Ketchum on May 6th. Photo by Tom Drougas via Idaho Mountain Express.

Video of flooding in Hailey from the Big Wood River on May 6th courtesy of Idaho Mountain Express.	Flooding in Hailey from the Big Wood River on May 6th. Photo courtesy of Idaho Mountain Express.		Valley Creek in Stanley flooding on May 7th.

Sandbagging efforts along Valley Creek in Stanley on May 7th.	Aerial view of the Big Wood River flooding in Hailey on May 8th. Sadly, a fatality occurred just north of Ketchum 2 days later when a man drowned in a spare unlit basement room of a home. Rescuers found that the room had about 6 feet of water in it.		Home surrounded by flood water in Hailey on May 8th. Photo courtesy of KTVB.

Video from Hailey on May 8th of flooding from the Big Wood River. Courtesy of Mark Oliver.	Road partially washed out along Morgan Creek about 8 miles northeast of Challis. Photo taken around May 8th by Mike Clements.		Flooding from Morgan Creek about 8 miles northeast of Challis. Photo taken around May 8th by Mike Clements.

Road partially flooded from Antelope Creek 5 to 10 miles southwest of Darlington on May 11th.	Antelope Creek flooding about 5 to 10 miles southwest of Darlington on May 12th.		Flooding from Morgan Creek about 8 miles northeast of Challis. Photo taken around May 8th by Mike Clements.

Vehicle in flood waters from the Big Wood River in Hailey on May 15th. Photo courtesy of City of Hailey.	Hydrograph of the Big Wood River at Hailey showing the peak of the flooding in May.		Aerial photo of Big Wood River taken by Willy Cook via Idaho Mountain Express on May 19th.

Big Wood River washing out roads in Hailey on May 22nd. Photo courtesy of City of Hailey.		Video of continued flooding in Hailey from the Big Wood River on May 25th. Video courtesy of City of Hailey.

June


Another peak of high flood water occurred in early June on the Big Wood at Hailey.	The Big Lost above Mackay Reservoir had high flows in early June.	Mackay Reservoir was filling very quickly in early June.

Aerial photo of the Della Vista subdivision in Hailey which suffered the brunt of the flood waters from the Big Wood River. Photo taken on June 1st courtesy of Idaho Mountain Express.	Valley Creek near Stanley washed out part of Highway 21 on June 5th. Photo courtesy of Idaho Transportation Department.	Antelope Creek near Darlington flooding road on June 5th. Photo by KJ Babcock.

By June 7th, the Teton River near Driggs overflowed its banks. This picture was taken about 4 miles west of Driggs courtesy of Teton Valley Weather Facebook Page.	Flooding along the Big Lost River just upstream from Mackay Reservoir on June 7th. Photo by Vicki Dunn.	Flooding along Garden Creek near Challis on June 8th. Photo by Todd Adams via Challis Messenger.

Flooding along the Big Lost River about 2 miles north of Darlington on June 8th. Photo by Scott Hoenshell.	Flooding from the Snake River at the boat docks near Roberts on June 15th. Photo by Latausha Vanleuven via KIFI.	Flooding along the Snake River near Menan Butte on June 16th.

Flooding along the Snake River near Menan Butte on June 16th. Photo looking south from near the top of Menan Butte.	Flooding along the Big Wood River near Gimlet on June 21st. Photo by Willy Cook via Idaho Mountain Express.	Flooding along the Teton River West of Driggs on June 23rd.

Flooding in Hailey from the Big Wood River on July 7th. Photo by Craig Aberbach. Flooding across all of central and east Idaho finally subsided by July 14th.