Atmospheric River for the Northwest

A deep plume of subtropical moisture from the South Pacific known as an atmospheric river will take aim at the Northwest early this week, resulting in heavy precipitation, mild temperatures, and rising snow levels across the Cascades, Coast Range, and even the Northern Rockies. Casually speaking, this pattern is sometimes referred to by skiers as a "pineapple express" since moisture often originates near Hawaii.

This pattern will result in a change-over to rain for some ski areas on Tuesday especially in the Cascades, but higher elevation areas that remain above the rain/snow line such as Whistler-Blackcomb, Whitewater, Revelstoke, Lake Louise, and Banff Sunshine will see heavy (and relatively wet) snow.

Our Northwest Snow Forecast, Larry Schick, wrote an excellent article explaining atmospheric rivers and what they mean for the Northwest.

Forecast for Mon, Jan 11 – Tue, Jan 12

Snow and rain will fall across British Columbia and Washington on Monday and into Tuesday with rising snow levels expected through Tuesday afternoon. Idaho, Northwest Montana, Interior BC, and Alberta will pick up most of their snow on Tuesday, but even some of these areas (especially south of the border) could experience rain issues. The Northeast will also see light snow showers on Monday and Tuesday as a weak disturbance moves across the area.

Forecast for Wed, Jan 13 – Thu, Jan 14

Another storm will move across the Northwest on Wednesday with colder temperatures and falling snow levels, and snow will spread a bit farther south into Idaho, Montana, and Wyoming as well. An unsettled pattern over the Northeast could result in additional snow showers on Wednesday and Thursday, but only light amounts are expected.

Forecast for Fri, Jan 15 – Sat, Jan 16

Another warm storm will reach the Northwest on Friday with rain and snow expected across Southern BC and Washington depending on elevation while Northern BC and Alaska will pick up heavy snow. The Upper Midwest will also see some much-needed snow on Friday, but then confidence decreases regarding the storm track for the East later Friday and into Saturday due to poor model agreement. Snow, rain, or a combination of both are all possibilities at this time for New England and the Mid-Atlantic. 

Outlook for Sun, Jan 17 – Thu, Jan 21

The Northeast and Mid-Atlantic will be favored during this period as a trough of low pressure becomes established as the dominant pattern across the Eastern U.S. with colder than average temperatures also expected. In the West, high pressure will gradually start to weaken and shift farther west during this period, opening the door to better storm potential across the Cascades/British Columbia initially, and eventually extending into the Northern and Central Rockies.

Thanks so much for reading! Check back for my next post on Wednesday, January 13th.

ALAN SMITH

NEW: Wind Gust Map Layer

In addition to the Estimated Snow Depth, Current & Forecast Radar, Temperature Forecast, and Avalanche Forecast maps, we now have a Wind Gust map layer on OpenSnow!

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