Analysis: La Niña doesn’t guarantee a super-snowy winter
SPOKANE, Wash. — Data from the National Weather Service confirms that while it’s the most likely scenario, a La Niña winter doesn’t always guarantee towering drifts of snow in the Inland Northwest. Eastern Washington and North Idaho do average more snowfall during La Niña events over the past 120 years. Average is the keyword, however.
The winter of 2021-2022 will be a “double-dip” La Niña, the second of two La Niña winter seasons in a row. We showed you previously on KXLY.com that this double-dip year is more likely to have more snow than the first year. It’s happened in six out of ten double-dip La Niñas on record for Spokane. However, that doesn’t mean that every one of these years trapped Spokane in towering snowdrifts. Most winters were actually very close to the average range, 40 to 50 inches.
In just the last 15 years, Spokane had three double-dip La Niña winters with three different outcomes. It’s clear that La Niña isn’t the only factor in play with the winter forecast. Weekly and monthly patterns play a role too with where and how long the jet stream winds set up over certain areas. These rivers of wind in the upper atmosphere are what La Niña impacts in order to give us greater odds of a cold, snowy winter.
These jets don’t fly over one place all the time, otherwise, the weather would never change! Instead, they move around, but sometimes keep going back over the same spots through the winter. If the jet stream sets up a little further north of our area, we could still see a wetter winter, but cold enough for a snowier one. That’s what happened during the winter of 2020-21. If the jet sets up further south more often, then we end up colder but get less moisture too.
The bottom line is that seasonal forecasting is complicated! Snowfall in Spokane this winter is most likely to be around average to a little ways above, 40 to 59 inches, with the odds of going over that range more likely than going under. It’s not a precise prediction, but how precise can you be when you can expect snow at least five months of the year?
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