I’m a firm believer that it’s important to pick up a winter sport if you live in the Pacific Northwest. It could be snowshoeing. Or perhaps heli-skiing is your cup of tea. It doesn’t matter the sport – all that matters is that it requires mountain snow.
Why do I hold such a strong belief? Well, in the dark, dreary, drizzly days of our seemingly incessant winter, it’s important to be excited about a weather pattern that would otherwise be miserable for life here in the lowlands. A pattern highly conducive to snow in the mountains.
And thankfully, that’s exactly what we will see over the next week! We’ll have a classic mountain snow pattern, with a strong ridge in the northern pacific, a deep trough in the Gulf of Alaska, and a parade of cool, showery systems arriving from the northwest, bringing bouts of rain to the lowlands and heavy snow above 3,000 feet.
The current upper-level pattern shows exactly that; an upper-level ridge in the Northern Pacific and a deep trough in the Gulf of Alaska, resulting in cool, unstable, showery onshore flow that becomes orographically enhanced as it encounters the Olympics and Cascades. Technically, you’d like to have the pattern moved just a little bit further to the east, so that the upper-level flow into the Pacific NW arrives from the WNW or NW (it currently is arriving from the WSW), but that will happen as the week progresses.
Decent mtn snow pattern with ridge over N Pacific and trough in Gulf of Alaska. Ideally, you’d want everything ~1000 miles further E so the Pacific NW saw NW flow and with it (1) a cooler airmass, (2) more favorable orographics, and (3) stronger winds aloft. Will happen by Tue! pic.twitter.com/Z9exDMX4Ip
— Charlie Phillips (@GeoduckChuck) November 6, 2021
So, how much snow will we end up seeing out of this? The heaviest snow should be over the North Cascades and BC Coast range, which could see 2-4′ of snow. The rest of the Washington and Oregon Cascades above 3,000 feet (north) and 4,500 feet (south) should also get clobbered, with 6″ – 24″ possible depending on elevation, and several inches of snow are also expected for the inland NW. Even the Sierras should see moderate snow over the next few days!
Credit: University of Washington
Regarding the timing of individual systems… expect showers on Sunday, mostly cloudy skies for most of Monday, rain Monday night into Tuesday morning, and frequent showers persisting through Tuesday and Wednesday. The heaviest mountain snow should occur between Monday night and Wednesday morning. A wetter and warmer system arrives Friday and Saturday, lifting the snow level above the passes and resulting in sharp rises on rivers across Western Washington. No flooding is expected at this time.
After the cooler systems this week, a weak “atmospheric river” will arrive Friday & Saturday, bringing sharp river rises and lifting snow levels to 6000-8000 feet. Widespread flooding is not forecast – rainfall amounts with this AR are not that impressive. pic.twitter.com/a5GS2MNtwH
— Charlie Phillips (@GeoduckChuck) November 7, 2021
Unfortunately, warmer and drier-than-average weather is expected for the Western US as weak ridging builds over the West. However, this ridge is what meteorologists like to call a “dirty ridge,” meaning that it is expected to be weak enough to have systems come over the top of it and bring periods of light rain and higher elevation snow to the Pacific Northwest. This is contrasted with the feared “death ridge,” which sends the jet stream way up into Alaska and gives us an extended period of low clouds and fog at the surface while snow levels skyrocket up to over 10,000 feet.
Extended forecast calls for warmer/drier-than-average weather across the West next week as weak ridging sets in, but systems riding over the top of this ridge should still bring some higher-elevation mtn snow to the PacNW. pic.twitter.com/GWVG2lhapT
— Charlie Phillips (@GeoduckChuck) November 7, 2021
In the meantime, enjoy the mountain snow over the next several days! Hopefully it is just a taste of what is to come during our La Nina winter.
