Midweek storm to quench parched Pacific Northwest

After an abnormally dry first half of the month, April showers, rain and snow will bring much-needed precipitation to the Pacific Northwest this week, while the Southwest can expect a substantial warmup.

So far this April, the general track of storms for the West has shifted southward and taken aim at California, resulting in an abnormally wet stretch of weather across the area. However, that pattern is due for a shake-up this week.

“Into midweek, the storm pattern will shift northward and bring back wet weather across the Pacific Northwest,” AccuWeather Meteorologist Brandon Buckingham said.

The general storm track in the West is heavily influenced by the position of the jet stream. The jet stream will shift northward and take aim at the Pacific Northwest by early Wednesday morning. An increased amount of Pacific moisture will be allowed to funnel into the region, enabling a series of storms to march through the area every few days, at least through the end of April.

On Wednesday, the first of these storms will come ashore along the Washington and Oregon border and will bring beneficial coastal rain and mountain snow back into the region.

“The extended dry stretch of weather has led to expanding drought conditions across much of the Pacific Northwest,” Buckingham said.

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Conditions along the West coast range from abnormally dry in western Washington, to severe drought in western Oregon and northwestern California, according to the United States Drought Monitor.

As of April 18, the cities of Seattle and Portland, Oregon, have only recorded 2 percent and 10 percent of their monthly rainfall, respectively. In contrast, as of April 19, cities influenced by the southerly storm track such as Los Angeles and Palm Springs, California, have recorded 465 percent and 1,565 percent of their monthly rainfall, respectively.

"As the storm system comes ashore, many coastal communities in Washington and Oregon can expect beneficial wet weather to arrive by daybreak on Wednesday,” Buckingham said.

A majority of the coastal rain will fall Wednesday morning into Wednesday evening, while showery weather spreads farther inland throughout the day. As beneficial rain quenches the coastal Pacific Northwest, higher-elevation snow will ramp up over the Cascades.

Throughout the day, as colder air filters into the area, snow levels may fall low enough to bring some accumulating snow and slushy travel conditions to area passes on Wednesday night and Thursday, according to Buckingham.

Slushy and slick road conditions can make traveling tricky for essential workers and those hauling much-needed supplies around interstates 5, 84 and 90.

The center of this storm will shift east into the northern Rockies early Thursday, bringing periods of snow to the higher elevations and rain showers down to some valley locations across Idaho, Montana and Utah.

Rain and snow will wind down over the Pacific Northwest and northern Rockies late on Thursday night as the storm system ejects out of the area.

The return of much-needed rain to the Pacific Northwest is not the only major pattern change made possible in the West by a northward shift in the general storm track this week.

While many cities across central and Southern California have run about average temperature-wise in April, this pattern change will usher in the first major warmup so far this spring for many locations.

The northward shift in the jet stream that will allow California and much of the Desert Southwest to warm up through a majority of the week and this weekend is expected to keep the general storm track aimed at the Pacific Northwest.

Another storm system may take aim at places like Seattle and Portland this weekend, brining along additional beneficial moisture to the region.

Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.

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