Is a 'Snowmageddon' repeat in store for the Treasure Valley?

Brian Holmes answers the question that's on the minds of many: Will this winter will be as extreme as what we experienced last winter?

BOISE - As summer came to a close about a month ago, many people across southern Idaho were already looking two seasons ahead, and at KTVB we've heard the same question a lot:

Will this winter look anything like last winter?

All the indicators have stacked up to put us on a path to a similar winter season. but the short answer is: Not likely, especially considering the historic conditions we saw last winter.

We all remember last winter: The snow, the shoveling, the frigid temperatures. Nearly 40 inches of snow fell in Boise from December through April - the fourth most since 1950.

In fact, some place along the greenbelt are still - two seasons later - dealing with the effects of last winter's historic conditions.

The damage done in the Valley was due to the near-record snowfall in the mountains. Totals from monthly snow surveys in the Boise Mountains added up to the eighth-highest snow total in the Boise Basin since 1961 - and it kept coming in February.

"Storm after storm came and the precip in the Boise Basin was 2.5 times normal," says Ron Abramovich, a water supply specialist with the Natural Resources Conservation Service. "The Big Wood Basin received 5 times normal precipitation in February."

The abundance of snow  last winter was brought to us by what was considered a weak La Niña - the same scenario that is supposed to happen this season.

But what is that exactly?

El Niño and La Niña are opposite phases of what is known as the El Niño Southern Oscillation - which is a fancy way to describe the fluctuation in temperatures between the ocean and atmosphere in the eastern Pacific along the equator.

In normal seasons atmospheric pressure pulls trade winds westward toward East Asia. During El Niño seasons the trade winds weaken, allowing the warmer water to shift east and taking the potential for strong tropical storms with it.

Typically, La Niña will follow an El Niño event - almost like a course correction.

La Niña will show ocean temperatures in the eastern Pacific that are cooler than average. What does that do to the weather in the northern hemisphere? It allows a ridge of high pressure to settle along the West Coast of the United States, pushing the polar jet stream further north and pulling the pacific jet stream - and all that moisture -along with it.

So what does that mean when it comes to the winter weather forecast across the country, and more specifically, here in the Northwest and southern Idaho? La Niña years usually translate into cooler-than-average temperatures across portions of the upper half of the United States. Southern Idaho falls outside that realm of cooler-than-average temperatures and we should expect average temperatures for this winter.

When it comes to precipitation, southwestern Idaho lands just on the fringe of a forecast where we could see a wetter than average winter. However, the rest of Idaho and the Northern Rockies could see another winter with abundant rain and snowfall.

But even with expectations from the National Oceanic and Atmospheric Administration Climate Prediction Center, experts give no guarantees about the storms heading our way

"Are they going to hit Oregon, Washington, the Cascades or are they going to come through California again and nail southern Idaho?" asks Abramovich.

That's an unknown that doesn't sit so well with those who remember last winter in the Treasure Valley.

But if history can give us some indication, we typically see the effects of La Niña losing more of its energy the further out we are from the last El Niño event. That was a rather strong one in 2015-2016. And most forecast models predict ocean temperatures will return to normal after the first of the year, thus ending La Niña before winter 2018 is over.

So the likelihood of seeing a carbon copy of last winter remains on the low side.

 

 

 

 

 

© 2017 KTVB-TV


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