Ian Morrison skiing on Whistler Mountain
Ian Morrison skiing on Whistler Mountain

Want to Predict Snowfall in the Pacific Northwest?

What you need to know before planning a last-minute trip to Whistler, Stevens Pass, or Mount Baker

Marquee Image: Ian Morrison. Blackcomb, British Columbia. PHOTO: Paul Morrison

Days before the men's mogul competition kicked off the 2010 Vancouver Olympics, the venue on Cypress Mountain was green. Organizers had to truck in snow from the interior of BC. Meanwhile, less than 100 miles to the north, Whistler-Blackcomb had winter snow into the village, well below Cypress's elevation at 2,953 feet. Such is the fickle nature of skiing in the Pacific North West.

Sitting so close to the Pacific Ocean and at elevations that sound more Adirondack than Western, the ski conditions at places like Whistler-Blackcomb, Mount Baker, Mount Washington, Steven's Pass, and Vancouver's North Shore sometimes swing through all four seasons in a week. And just as likely it can dump in constant and prodigious quantities for days. Sometimes all season. There's a reason the deepest snowpacks in the world are often in the Pacific Northwest. Long-range predictions suggest this winter should be a good one in the PNW. But even when the odds are good the key to scoring is knowing the weather patterns that bless the slopes. Then, you want to have the flexibility to drop everything and go. We can't help with the latter, but as for what to watch for we talked to experts across the PNW. Here's what you need to know.

Freezing Levels

Disregard the El Nino Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Arctic Oscillation (AO), and other cycles and phases, says Larry Schick, the Northwest meteorologist for ski weather forecasting site OpenSnow.com. For Schick and others, it's all about the freezing level. "The sweet spot for snow levels in the Northwest is 1,000 to 3,000 feet, even up to 4,000 feet," he says.

Higher freezing levels tend to bring wet snow or rain and lower ones suck moisture out of the air reducing snowfall totals.

Jet Streams
A simpler, but duller, gauge is to look at jet streams, the rivers of air that steer weather and temperature across the continent.

"There are two weather patterns that give us the best snow quality," says Anton Horvath, Whistler-Blackcomb's senior avalanche forecaster. These are a westerly flow for quantity, and a northwesterly storm track for quality.

The westerly is more common. On a jet stream map, look for storms lining up, like planes waiting to land, off the Washington or BC coast. "This is when we gets lots and lots of snow," says Horvath. "Sometimes the storms stack up one right after the other for a week or more."

A northwesterly jet stream flow carries storms down from the Alaska Panhandle, across coastal BC and down into Washington and Oregon. Because the temperatures tend to be colder, the storms are usually drier, but the snow quality is at its best.

The weather pattern to avoid is the Pineapple Express, rivers of moisture coming from the southwest. Sometimes these sopping wet storm cycles look like a conveyor belt of clouds extending all the way to Hawaii, hence the name. These systems bring high freezing levels and tons of moisture, which mostly falls as rain. Avoid them with one caveat.

"Often right after they move through snow can improve dramatically, as freezing levels lower," notes Schick.

The tricky part of all this is that the weather is mostly coming from the open ocean where there are few observation points and weather changes fast. Don't trust forecasts more than three days out. "In general, the long-range forecasts aren't worth the paper they're printed on," says Horvath. Each forecast is based on different computer models. "Frequently they contradict each other," he continues. "When they do, it's a coin toss."

The opposite holds true, too: When they all agree, even weeklong forecast tends to be pretty reliable. Schick and Horvath think the best forecasts come from the University of Washington. The information is technical and requires some interpretation to hone in on what it means for each ski area, but the discussions help make sense of it all. Regardless, start watching the weather now and keep an eye on it through the early part of the winter. The more you watch the more it will make sense and the better you'll be at knowing when the time is right to go all in on a vintage PNW storm cycle.