Pacific storm train poised to bring big cooldown, snow to the West

Multiple storms will move through the Northwest through the end of the month, bringing rain, strong winds and high-elevation snow while also providing welcome relief from summerlike heat farther south.

"Storms will roll into the Northwest from the Pacific Ocean every couple of days," AccuWeather Lead Long-Range Expert Paul Pastelok said.

The lead car of the storm train spread rain across western Washington and Oregon through Saturday night, and then gained forward momentum and expanded precipitation into the northern Rockies through Sunday.

Showers and thunderstorms are expected along the coastline of northwestern Oregon and Washington through Monday.

"There can be localized flooding, mainly in low-lying and poor drainage areas," AccuWeather Meteorologist Alyssa Glenny said.

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October is the month that historical average precipitation rises significantly in the Pacific Northwest following the typical drop in wet weather during the summer months.

The rain and snow showers will also bring benefits to places where numerous wildfires have occurred.

"Fires across Oregon and Idaho will slowly be contained in this pattern," Pastelok said.

A plunge of chilly air behind the storm will cause snow levels to fall in the Cascades and northern Rockies early this week. Travel along I-90's Snoqualmie Pass may become slippery for a time as temperatures fall to near freezing with some snow expected on Monday morning.

Glenny warned that less-traveled secondary roads may be at a greater risk of slick spots.

By Monday and Tuesday, cold air will plunge across the interior West, and accumulating snow will take aim at the high terrain of Utah, Wyoming and Colorado. There is the potential for snow accumulations of half a foot or more across the central Rockies, resulting in slippery and slow travel through the mountains.

"Ski areas will start to build their snowpack," Pastelok said.

Residents of the Desert Southwest who have been sweltering all month in temperatures more typical of summertime will be pleased to hear that the cooler air will arrive by Tuesday. In Phoenix, where temperature departures so far this month have been around 8 degrees above the historical average, highs in the 70s are projected Tuesday and Wednesday. Following days in the 80s, Las Vegas will cool into the 60s.

"This will be a cooler pattern compared to early and mid-October," Pastelok said.

Another storm is poised to dive into the Northwest during the middle and latter part of this week, around the time of Halloween. This storm may bring a more substantial hit of snow for the Cascades and northern Rockies.

AccuWeather's long-range experts expect the storm train to keep rolling right into the first week of November.

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