Into the first half of the upcoming week, an active weather pattern will continue across much of the Northwest U.S. From Sunday to Monday, a plume of moisture will surge into parts of Washington, Oregon and far Northern California.
A northward bulge in the jet stream over much of California, Nevada, Utah and southern Idaho will help to keep much of the Southwest dry into at least midweek.
“While a majority of the West will experience a trend towards drier conditions this upcoming week, that will not be the case across the Pacific Northwest. Multiple waves of moisture taking aim at the region will likely keep wet weather in the forecast into midweek next week,” explained AccuWeather Meteorologist Brandon Buckingham.
A zone of low pressure will advance into the far southeast flank of Alaska and the coast of British Columbia by the late weekend, spreading rain and snow across the region. The storm’s associated frontal boundary will swing into the Pacific Northwest into Monday night and become the driving factor for the swath of rain and mountain snow into the start of the week.
During the second half of the week, storm activity along the Northwest coast is expected to decline gradually. Although nearby areas of low pressure can bring intervals of rain or snow to the region from Wednesday to Friday, these events are likely to be weak compared to the river of moisture approaching for the early week.
Even though the stream of rain forecast to move into the Northwest early week may bring pockets of localized flooding, rockslides and rises on select streams and creeks, the rain may also prove beneficial for western Washington.
Many observation sites in western Washington, including Seattle, Olympia and Tacoma, Washington, recorded lower rainfall totals throughout January, February and March. From January to March, all three locations recorded roughly 54% of the historical average rainfall for each site. However, April showers have helped to keep rainfall amounts on track for the most part for those locations in Washington so far this month at least.
So far in April, temperatures across the Seattle and Portland areas have trended on the cooler side compared to what is typically observed this time of year. AccuWeather meteorologists say that monthly values are generally running between 4-5 degrees F below the historical average for early April, and this trend is forecast to continue through the upcoming week.
Daytime high temperatures in Seattle this week are forecast to dip into the upper 40s F, with intervals of rain expected across the metro area at least through Wednesday. A damp outlook is in store for any residents looking to hold outdoor Easter egg hunts on Sunday or Passover celebrations.
Cooler conditions will largely be confined to areas west of the Rocky Mountains during the first half of the week, while locations from the Intermountain West into the Plains will be experiencing quite the warm surge throughout the week.
Even places in Utah, such as Salt Lake City, will see much milder conditions by early week, climbing roughly 14-18 degrees F above the historical average to the upper 70s F. This surge of warmth will be quite noticeable compared to high temperatures recorded around Salt Lake City at the start of the previous week when the city only climbed to the 30s F and totaled nearly 15 inches of snow from Sunday to Wednesday.
Due to the climbing temperatures, forecasters are monitoring the threat of flooding from area snowmelt across parts of the western and central states.
“Across the interior Northwest, valley rain and mountain snow will be much more sparse in coverage over the coming days, but even though largely dry weather is in store, the flooding threat is expected to increase. This will occur as a result of climbing temperatures that will begin to melt off some of the deep snowpack across the mountains,” stated Buckingham.
Ice jams will elevate the flood from eastern Oregon to the Great Lakes region through Tuesday. Snowmelt along the foothills of the mountain regions can quickly cause rises in area rivers and streams, including portions of the Missouri River. If possible, residents are encouraged to clear any snow or ice from flow paths and culverts to allow for runoff to be transported away from roadways and structures.
Produced in association with AccuWeather
