Puget Sound's long dry streak, which began in late July, is expected to come to a dramatic halt on Friday. Rain, heavy at times, is in the forecast well into next week.

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The sky will darken. Little dots will appear on your windshield, and on the sidewalk.

Water, as if by magic, will fall from above.

All this could happen in time for Friday morning’s commute, as our long-lost companion, rain, brings a soggy conclusion to one of the driest stretches Seattle has ever seen.

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And let’s be clear: What’s headed our way isn’t a gentle shower to rinse the stale air, lower fire danger and perk up our lawns. The forecast calls for rain, then heavy rain, and then more rain, well into next week.

“We really don’t want this much all at one time,” said Jeff Michalski, Weather Service meteorologist.

After 13 weeks with less than an inch of rain, the change could seem abrupt.

Michalski said the heaviest rain — up to eight inches in the Olympic Mountains, five inches in the Cascades and two inches in the Seattle area — could hit in a 48-hour period beginning Saturday evening, and be accompanied by blustery winds.

River levels around the region have been so low that even a serious soaking may not bring them up to flood stage, Michalski said.

But the Skokomish River in Mason County, one of the state’s most flood-prone streams, fills rapidly when the Olympics get a deluge.

And in some areas, it’s feared that dry, dusty earth may slip away more easily in rain-triggered mudslides.

The high-pressure system off the coast that has protected Western Washington from Pacific storms for weeks is breaking down, forecasters say.

The first rains could hit the coast about 5 a.m. Friday, and spread through the Seattle area within hours.

If that happens, Washington State Patrol Trooper Julie Judson will be bracing for a busy day.

“We always get a lot of fender-benders in the first rain,” she said, “people losing control of their cars.”

Judson says a couple of factors are at work.

One is that oil and grime built up on the highways over the dry season becomes slick in the first rain, before it can rinse off the roadway.

In addition, people have been using “summer-driving habits” in which they follow the car in front more closely, confident they’d be able to brake.

“We need to use our winter-weather driving skills,” she said. “Right behind rain comes ice and snow, and we have to be ready for it.”

Despite the dry conditions that started in July, this year has still had more than a normal amount of rainfall, due to an especially wet spring.

As of Tuesday, Seattle-Tacoma International Airport’s rainfall total for the year so far was 26.42 inches, compared to a normal total for the period of 22.79 inches.

But all is not gray and gloom on the horizon.

Although the near-term stretch is likely to be rainy, the longer-term vision is just the opposite.

Ed. O’Lenic of NOAA’s Climate Prediction Center in the Washington, D.C., area, said the Puget Sound area is expected to have less precipitation than normal over the next three months.

That outlook is based on ocean temperatures and other climate indicators.

O’Lenic said the readings make no guarantee about the weather, but are useful indicators for government agencies, utilities, water-resource managers, even investors weighing whether a power company is likely to make a profit.

“There will be times when the weather proves us wrong,” he said. “We’re just playing the odds to the best of our ability.”

Jack Broom:


or jbroom@seattletimes.com

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