Pattern change to usher moisture-laden storms into Pacific Northwest
AccuWeather forecasters say storms early next week will bring appreciable precipitation to a large swath of the region, and may result in the wettest day of the year so far in one city.
A surge of moisture will deliver much-needed rain across the drought-stricken Northwest this week.
Unusually dry weather has gripped the Pacific Northwest since the official start of summer in late June, but AccuWeather meteorologists say a big change in the weather pattern will arrive right on cue with the first days of fall.
Part of the Northwest was already beginning to feel a turn toward stormier weather around the middle of this past week as a storm system dropped southward with showers, high-elevation snow and chilly air.
AccuWeather forecasters say storms early this week will bring appreciable precipitation to a larger swath of the region and may result in the wettest day of the year so far for one city in particular.
Seattle, Portland among cities in line for a soaking
"A powerful area of low pressure set to dive south from the Gulf of Alaska will usher some much-needed rain into the Pacific Northwest into early week," AccuWeather Meteorologist Brandon Buckingham said.
Seattle's wettest day thus far in 2023 occurred on May 5 when 0.70 of an inch of rain was recorded. The Emerald City could pick up this amount of rain or more on Monday alone as a moisture-laden storm charges in from the Pacific Ocean. Since record-keeping began at Seattle-Tacoma International Airport in 1945, there has never been a year without a daily rain amount of an inch or more, according to the National Weather Service.
Since the first day of summer on June 21, Seattle has picked up 1.06 inches of rain, or 36% of the historical average for that timeframe. Farther south, Portland, Oregon, has experienced even less wet weather, recording only 0.65 of an inch of rain since June 21, or 28% of the historical average.
Monday's storm may be followed by yet another push of moisture onshore around the middle part of the week.
AccuWeather meteorologists say there is the potential for at least a couple of inches of rain, if not more, as storm systems return during the first half of the week. Higher amounts of rain are likely to fall along the coast and areas just inland with lesser amounts to the east of the Cascades. Some of the rain with the storms can reach as far south as Northern California.
Wet weather to bring hazards but also help to ease drought
"A majority of western Washington and Oregon have experienced expanding drought conditions in recent months, so the rain will be welcomed by many," Buckingham said.
The latest outlook from the United States Drought Monitor, released on Sept. 21, shows areas from the coast to the Cascades in Washington and Oregon enduring drought conditions ranging in severity from moderate to extreme, a jump of two categories or more on the scale since the latter part of June.
The U.S. Drought Monitor from Thursday, Sept. 21, 2023.
Although the rain is expected to be largely beneficial for the region, AccuWeather meteorologists say that enough rain travel headaches and other hazards are likely as the pattern changes.
The stretch of wet weather can also cause some travel disruptions especially along the Interstate 5 corridor from Medford, Oregon, to Portland and Seattle. Driving along this stretch of highway could be slow on Monday as the wet weather arrives in time for the morning commute. In areas where there has been an extended stretch without rainfall, oil buildup on the roadways can combine with the rain to create slippery conditions.
"Rain in some burn scar areas of western Oregon and far northwestern California could tally up enough rain to create localized flooding concerns early next week. With soil integrity compromised due to the wildfire activity, heavy rain of this nature could lead to mudslides," Buckingham said.
Across the United States-Canada border, portions of British Columbia and western Alberta can receive welcome rain where ongoing firefighting efforts continue.
Storms to stir up rough waters along the coast
Coastal concerns are likely to increase as the storm train commences and strong winds churn up the sea.
AccuWeather forecasters warn that the pattern early next week could increase the risk of sneaker waves, which can take unsuspecting beachgoers by surprise as water rushes farther up the beach than expected. Boaters are also urged to exercise caution in the rough waters.
AccuWeather Meteorologist Elizabeth Danco contributed to this story.
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