Wet and Cool Weather Pattern to Linger This Week in Pacific Northwest

Posted: September 26, 2023 10:40 am

The Pacific Northwest received the signal this weekend that fall is here and winter is right around the corner. An unsettled weather pattern moved into the region over the last few days and is forecast to linger into the week. Here is what you need to know if you live in this corner of the U.S.

Powerful Area of Low Pressure to Trigger Rain to Start Week in Northwest

The arrival of wet weather in the Northwest has been a dramatic contrast to the dry conditions that have been in place since the start of the summer. The shift in the weather started last week when a storm system plunged down from Canada and brought the first snowflakes of the year to the higher elevations of the Cascade Mountains. While the lower elevations did not see any white stuff, rain showers and cooler temperatures signaled that a change was on the way.

More moisture is in store for the Northwest to start the work week, including significant amounts of rain for the major metropolitan areas of Seattle and Portland. The culprit will be a large area of low pressure moving down from the Gulf of Alaska. The region began to see these impacts over the weekend.

There is the chance that Seattle could see its wettest day of 2023 so far with this weather maker. The wettest day in the Emerald City thus far this year happened on May 5 when 0.70 of an inch of rain fell. The city could see rainfall of this magnitude on Monday as the storm picks up steam and moves onshore from the Pacific Ocean. According to the official records from the National Weather Service (NWS), there has never been a year since official records began in 1945 that Seattle has not seen at least one day of rain totaling over an inch or more.

Seattle has only recorded 1.06 inches of rain since the first day of the astronomical summer on June 21. Portland has only seen 0.65 of an inch of rain since this same date. These measurements translate to just 36% of the historical average for this timeframe for Seattle and only 28% of the norm for Portland. These figures speak to the exceptionally dry summers that both cities experienced.

More Rain in Store for Middle of Week

After Monday’s moisture moves through, another round of rain is on the horizon by the middle of the week. The week in total could bring a few inches of rain thanks to this constant parade of storms. The coastal areas will see the highest amounts of rain with less moisture falling farther inland and in areas on the other side of the Cascade Mountains. You can expect the rain to drop as far south as Northern California.
Monday’s storm may be followed by yet another push of moisture onshore around the middle part of the week.

The moisture will no doubt help to put a dent in the drought conditions that have been expanding throughout much of western Washington and Oregon over the last few months. Drought levels range from moderate to extreme since the end of June in many communities to the west of the Cascades.

The persistent rain will come at a cost. Motorists should expect travel delays along the Interstate 5 corridor from Seattle down into Medford, Oregon on Monday as the rain pushes inland from the coast. Roads may become slippery since there has been so little moisture as of late.

In addition, flooding may be an issue in parts of western Oregon and the northwestern corner of California in burn scar areas. Flooding is more common across burn scars because the soil is more vulnerable to mudslides and other weather hazards.

The good news with this forecast is that the rain will also impact the area just over the U.S. and Canada border, potentially ushering in much-needed moisture to parts of British Columbia and Alberta that are still dealing with wildfires.

Coastal Concerns Abound

The train of storms will also stir up the seas along the coastal areas of the Northwest. The high winds associated with the storms will create rough surf conditions and dangerous swells. Forecasters are also warning that the waves may unexpectedly wash up on the beaches farther than is typical, taking some people off guard. Boaters will also want to stay abreast of the likelihood of rough seas in the coming days.

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