Winter forecast predicts a triple La Niña may be good for snowpack in the West
Forecasting weather more than five days in advance is tricky, but winter predictions so far indicate a big snowfall coming to the Pacific Northwest and uncertain snowfall for the Wasatch Back.
Meteorologist Sam Collentine talked with KPCW about the weather and snow prediction service Open Snow. He said it uses past data and looks at existing storm details to predict where skiers and snowboarders can find the deepest powder.
"So, we have forecasts throughout the West, local forecasters that write daily snows every day throughout the winter," Collentine said. "But we also have the latest snow reports, webcams, five-to-10-day snow forecasts. So really everything you need as a skier, snowboarder, and especially a powder chaser throughout the West.”
Collentine said Pacific Ocean surface temperatures are cooler than average, which signals a La Niña phase. He said it would be the third La Niña in a row, and surface temperatures have stayed cold throughout the summer.
"It gives us kind of a confident signal that we're at least going to have a somewhat strong winter throughout the western United States because you're looking out months in advance but when we look back at previous winters it's a pretty decent signal for especially the Pacific Northwest, Western Canada," Collentine said. "It gets a little bit weaker of a signal when we get down to the central Rockies."
Collentine said there is no correlation between how warm it has been in Northern Utah this summer and how warm it will be this winter. Predicting snowfall this far out is imprecise, but meteorologists use past data to help forecast weather beyond 10 days out.
"When there's been this strong of La Niña in the summer months, six out of those seven winters since 1950, it's correlated to a very strong La Niña, Collentine said. "And like I said, it's mixed signals for a place like Utah."
National Oceanic Atmospheric Administration, or NOAA, temperature forecasts this winter will be warmer than average, especially in the desert southwest. He said NOAA uses the past 30 years when comparing average temperatures.
"Northern Utah [has] like equal chances of not really below or above average," Collentine said. "With climate change happening, we are seeing warmer temperatures. And so, when you look at even the past 10 or 15 years, you're really seeing a ramp up in the amount of record temperatures and warmer temperatures during the winter months throughout much of the West. And so, that really throws a wrench in those 30-year climate averages."
Collentine said the La Niña conditions make it impossible to predict precipitation in northern Utah because the weather can go either way based on historical models.
"Utah is right in that equal chances area, not really above, not really below," Collentine said. "And when we look back at those previous La Niña winters, there's been a couple of other strong La Niña winters where Utah has been 10% to 30% above average. There's been some that they're right at average, and some right below average. So again, there really isn't a clear signal for Utah."
Collentine said 'who knows?' when trying to predict weather farther than five to 10 days out.