Worst Boise winter in years? Blame La Niña, experts say

Boise got slammed with 6 1/2 inches of snow on Wednesday — the 15th-highest one-day total since 1892. The 15 inches of snow on the ground that day was the most since that statistic was first recorded in 1940.

“The valley locations have as much snow as we’ve seen,” said Jay Breidenbach, a meteorologist with the National Weather Service in Boise.

If that wasn’t enough, Friday morning’s temperature of 8 degrees below zero was the coldest since Jan. 5, 1991, when it was 12 below. That came a day after Boise Mayor Dave Bieter declared a state of emergency. On Friday afternoon, Ada County and the city of Meridian issued emergency declarations of their own.

Schools were shut down, sports games canceled and some residents couldn’t drive out of neighborhoods that hadn’t been plowed.

Think it will get better? The National Weather Service forecast for Sunday calls for a mixture of snow, sleet and possibly freezing rain. Oh, and it could warm up and the snow could start to melt, raising concerns about blocked storm drains and standing water on roadways.

“It’s a mess right now,” said Nicole DuBois, spokeswoman for the Ada County Highway District.

The wacky weather comes thanks to La Niña, a weather phenomena that typically brings cooler, wetter weather to the Pacific Northwest and warmer, drier weather to Southern California and areas farther east.

“We think the cold is going to continue through January,” said Bob Smerbeck, senior meteorologist with Accuweather.com.

Temperatures are expected to remain 2 to 3 degrees below normal for the rest of January and 1 degree cooler in February. But the good news is the recent overly frigid temperatures should be a thing of the past.

“We don’t see any more Arctic air coming in like you have now,” Smerbeck said.

La Niña episodes bring below-average surface temperatures along the sea at the equator in the eastern and central Pacific, according to the National Ocean Service. Resulting changes in the jet stream bring cooler, moister air to the Pacific Northwest.

An opposite phase, El Niño, brings warmer water temperatures along the same area of the ocean.

La Niña and El Niño episodes typically last nine to 12 months.

Even all this snowfall doesn’t mean much waterwise, Breidenbach said. The 15 inches present on Wednesday — later sagging to 14 — would have only yielded 1.6 inches of water when melted, he said.

Still, he said, the trend is for continuing snow in the mountains, raising the snowpack, which is good news for irrigators later in the season.

So far, snowpacks look good throughout Idaho, said Ron Abramovich, a water supply specialist with the U.S. Natural Resources Conservation Service.

Officials will keep a close eye on temperatures over the next week to monitor how quickly the snow melts, he said.

Floods on New Year’s Day 1997 caused $65 million in damage in the Weiser, Payette and Salmon river drainages. Warm temperatures combined with rainfall levels four to six times normal amounts triggered floods, mudslides and avalanches.

This winter, the Mores Creek area near Idaho City received 18 inches of precipitation in 15 days, Abramovich said. It started out as snow and then turned to rain as temperatures rose.

“So it will be better that any precipitation in the next few days falls as snow and not rain” to mitigate flooding risk, he said.

The Idaho Office of Emergency Management is monitoring conditions statewide. There is a potential for flooding from ice jams on the Snake, Salmon, Lemhi and Big Wood rivers and tributaries, spokeswoman Elizabeth Duncan said.

There are also concerns for increased avalanche dangers in mountain areas and possible power outages.

Treasure Valley agencies prep for melting, flooding

Here in the Valley, the potential for flooding damage is less. But agencies are still concerned.

ACHD has 22 vacuum sweepers and trucks lined up to suck up water. The cities of Boise, Meridian and Garden City have pledged the use of five additional vacuum trucks if needed.

In addition, there are 37 plows to open snow berms and a number of backhoes that can be used to dig out clogged storm drains.

The highway district is asking for the public’s help in clearing blocked storm drains.

“Help us help you. A little more shovel work can keep your property dry and help the overall effort,” Tim Morgan, the highway district’s deputy director of maintenance, said in a written release.

A map showing locations of drains in your neighborhood is available online at www.achdidaho.org.

Resident can alert authorities to areas where a large amount of water covers a roadway. The dispatch center at the Ada County Sheriff’s Office, 208-377-6790, will pass along messages to the highway district.

The city of Boise expects only localized “nuisance flooding,” spokesman Mike Journee said.

He reiterated clearing snow and ice from storm drains and catch basins. He also asked residents to clear snow away from fire hydrants to give fire crews easy access in case of an emergency.

In Nampa, city officials do not anticipate widespread flooding. Still, the city assigned public works crews weekend duty to ensure that critical storm drain lines and catch basins remain open.

Officials thanked residents for their cooperation.

“Whether people have been shoveling snow off their sidewalks or keeping storm drain openings clear, we appreciate the extra help,” Public Works Director Michael Fuss said.

Gem County Commissioner Bill Butticci said city of Emmett public works officials will monitor the level of the Payette River which passes along the north end of town. He said he doesn’t anticipate problems since winter river levels are down.

“Right now, we don’t have any concerns,” Butticci said.

Bruce Evans, public works superintendent in Emmett, said his crews have been working to clear snow from all roadways in the city. He said they move to clearing slush and water if the temperatures rise and the snow melts.

“I am OK with the weather warming up but if it could do this slowly, it would be better. That way, the snow would melt slowly too,” Evans said.

Crews with Canyon Highway District No. 4, which maintains 323 miles of rural roads north of Nampa and west of Caldwell, have been working to clear snow from main roads and resulting snowpacks.

“When the snow starts to melt, the barrow ditches will contain that water coming off the roads,” said Chainey Rhodes, the district’s maintenance manager.

Rhodes says he does not anticipate any problems with flooding, as the district does not have the storm drains that can get covered over in cities and cause problems with trapped water.

He urged motorists to continue to slow down and exercise caution.

“We’re doing everything we can to keep people safe, but we’re still seeing people run off the road because they’re driving too fast,” Rhodes said.

This story was originally published January 6, 2017 at 7:43 PM with the headline "Worst Boise winter in years? Blame La Niña, experts say."