New Series of Storms to Bring Massive Moisture to the Northwest

While the central and eastern U.S. has been stealing all the weather headlines this week with the winter weather and dangerously cold temperatures, Mother Nature is also starting to get to work in the West. A series of storms is forecast to move across the Pacific Northwest in the days ahead, bringing rain and snow to the region. Here is what you need to know about this active weather pattern.

New Train of Storms Chugging Into the Pacific Northwest

The Pacific Northwest is going to be under the gun for heavy snow and rain beginning at the end of the work week and lingering for days. The storms are brewing in the Pacific Ocean and are set to track through the Northwest and the southern edge of British Columbia, Canada well into next week. While each storm on its own may not deliver significant impacts, the cumulative effects of all of the rain and snow will add up over time.

Several waves of moisture will come ashore every one to two days with the impacts ranging from heavy rain in the lower elevations to measurable snow accumulation in the mountains. The first storm of the bunch fired up on Thursday, bringing along the coldest air of the train. Heavy snow is in the forecast for the Cascade Mountains in Washington state and Oregon.

The snow levels will drop to pass level, making travel difficult to impossible. The forecast is calling for widespread snowfall accumulations of 6 to 12 inches at terrains over 2,000 feet across this mountain range in Washington and down to 3,000 feet in Oregon.

The heavily traveled Snoqualmie Pass along Interstate 90 in Washington is forecast to see a mix of rain and snow through Friday with the moisture switching over to all rain on Saturday. Highs will hover in upper 30s on Friday before rising into the 40s for the weekend.

Warmer air coming in after the first storm will send the snow levels higher by the weekend. For instance, snow levels will climb to almost 8,000 feet by Saturday in the Cascades. Although rain is less disruptive for travel across the mountain passes, the heavy rain hitting the fresh batch of snow will create worrisome runoff issues.

Forecasters are warning that small streams and rivers coming down from the mountains will be at risk of flooding as water levels swell. In addition to the rain hitting the snow and accelerating the melting, the warmer temperatures moving into the region will also work to speed up this process. The steep terrain of the Cascades will also see a heightened risk of rock slides and other types of debris flows.

Other Impacts of Weekend Storm

The weekend storm event will also usher in the strongest winds of the parade with gale conditions likely for the Washington and Oregon coasts. The winds will be powerful enough to raise the risk of power outages across the region.

The latest forecast models indicate that 2 to 4 inches of rain is expected in the lower terrains of the Northwest, including up and down the Interstate 5 corridor connecting Seattle to Portland. Rainfall of this magnitude will inevitably slow down travel along the busy roadway.

The heaviest rain bands will set up over the western slopes of the Coast Ranges and across the west-facing slopes of the Cascades. These areas should prepare for 6 to 12 inches of rain by the time the inclement conditions clear out by next week.

The action of the rain falling on top of the recent snow in the higher elevations will also pose a danger from avalanches. Snowfall of 5 to 10 feet is possible in the highest peaks of the Cascade and the Olympics throughout the duration of the storms.

Rainfall Expectations for Biggest Metro Areas in the Northwest

It has been a dry start to the year for many of the biggest cities in the Northwest. This is typically the gray and rainy time of the year for this corner of the country.

For instance, rainfall in Seattle is hovering at about one-third of the usual amount received by the middle of February. The Emerald City has seen a bit over 3 inches thus far this year, compared to the historical norm of 8.30 inches.

The weekend forecast is likely to add to the rain totals in Seattle. The moisture machine will ramp up late Friday across the metro area. Saturday's forecast is calling for rainfall of about a half of an inch. Another quarter of an inch will fall overnight and into Sunday. The weekend will wrap up with about an additional half of an inch of rain.

Temperatures will remain comfortable in Seattle with highs in the mid 50s and lows that bottom out at the 40-degree mark. However, winds out of the south at 10 to 20 mph throughout the weekend will add to the misery brought by the heavy rain.

It has only been slightly rainier up the road in Vancouver, British Columbia. The Canadian city has picked up just under 40% of its historical average.

Moving in the other direction, Portland has measured about 60% of its historical average through the middle of February. Despite being in the middle of the latest storm train, the college town of Eugene, Oregon is now sitting at 70% of its historical average of rainfall dating back to the beginning of the year.

Locations to the east of the Cascades have seen more typical precipitation amounts this winter. For example, the city of Spokane in the northeastern corner of Washington is now at almost 90% of its historical average for the year thus far.