Big Picture Weather Pattern

We have two low pressure areas (denoted by the red L's) over Western North America right now. The first low over the Southwest is contributing to showers and thunderstorms over New Mexico and Southern Colorado on Thursday, though this will exit to the east by Friday.

A second stronger low pressure system is located over British Columbia and will work its way into the Northwest U.S. this weekend, resulting in rain and high elevation snow for the Cascades and Northern Rockies.

Pacific Northwest Rainfall

The Pacific Northwest saw a stretch of dry weather along with well-above-average temperatures last week, but this region is heading back into a cooler and wetter pattern now. 

Rainfall through Tuesday, May 21 will favor the Northern Cascades in Washington with even higher amounts further north in Canada. 

Snow will also fall across the higher elevations, with snow levels dropping as low as 4,000-5,000 feet this weekend in the Cascades.

Let's check out a couple of our forecasts in Washington...

Tiger Mountain, in the foothills on the west side of the Cascades, will see light rain showers on Thursday and Friday, followed by more widespread rain on Saturday and again around the middle of next week.

Only minimal rainfall is expected for the San Juan Islands this weekend, including Friday Harbor, but gusty winds will result in chilly conditions, especially near the water. 

West-Wide Forecast for Thu (May 16) to Fri (May 17)

Showers and thunderstorms will continue across New Mexico and Southern Colorado on Thursday and Thursday night with locally heavy rain possible. Most of the Southwest will dry out on Friday, but isolated afternoon showers are possible across the High Sierra and higher peaks of the Colorado Rockies.

Across the Northwest, rain and high-elevation snow will overspread the Washington Cascades and Northern Rockies on Thursday and Friday, with heavier precipitation north of the border in BC and Alberta. Heavy snow is expected for the eastern ranges of BC and the Canadian Rockies. 

Forecast for Sat (May 18) to Sun (May 19)

Another round of showers will move across the Cascades and Northern Rockies this weekend. The Cascades and Pacific Northwest will see most of its precipitation on Saturday, and the Northern Rockies will be favored on Sunday.

To the south, a weaker area of low pressure will move into California and the Southwest, resulting in lighter rain showers from the Sierra Nevada Range to the Colorado Rockies. 

Forecast for Mon (May 20) to Tue (May 21)

The Northwest will see a break in the action on Monday, while the Northern and Central Rockies will have a better chance of showers, with some models hinting at significant precipitation for the Colorado Front Range, though confidence is low.

The next storm system will move into the Pacific Northwest on Tuesday with moderate to heavy rain possible for the Cascades, Olympics, and BC Coast Range.

Total Precipitation (May 16-21)

The wettest areas will be across the Pacific Northwest, Northern Rockies, and to a lesser extent near and east of the Continental Divide across the Central and Southern Rockies.

Total Snowfall (May 16-21)

Heavy snow will fall across BC and Alberta in this pattern, with the Canadian Rockies (Banff, Lake Louise, Jasper) seeing some of the deepest totals. The Cascades and Northern U.S. Rockies will pick up some lighter snow as well. Snow levels will dip as low as 4,000-5,000 feet at times.

Outlook for Wed (May 22) to Sun (May 26)

More of the same is expected late next week and into Memorial Day weekend with cool and wet conditions across the Pacific Northwest and Northern Rockies. The Central Rockies (Utah and Colorado) could see showers at times though less moisture is expected to reach these areas. 

Temperatures are expected to be below-average for most of the West during this pattern, except for the Four Corners region where temperatures should be close to average. 

Thanks so much for reading and have a great weekend! Next update on Monday (May 20).

Alan Smith