Maybe we should just dub it the forecast wrecker?
The Olympic rain shadow turned predictions for a deluge of rain upside down this week, ensnaring the Seattle metro in a web of dryness the majority of the time. Instead of 2 inches of rain in 72 hours, we collected just 0.22—an amount barely worthy of an umbrella.
The dismal totals—no doubt appreciated by most—were the result of strong winds blowing from the west above the surface. As these upper-level winds crossed the coastline into our state, they slammed into the Olympic Mountains, wringing out most of their moisture along the western edge. Places like Forks took the brunt of this, with the city measuring a whopping 5.47 inches on Tuesday and another 2.02 yesterday.
The joking ends Tuesday.
Over the past 10 days, we’ve been teased with spits and spats of rain—a burst of precipitation here, a passing shower there—but nothing substantial and widespread has affected the region. That all changes in the next 48 hours, with the arrival of a powerful storm system bent on delivering some serious rainfall—to the tune of an inch or more.
Two out of three ain’t bad, right?
Light rain has interrupted the dry weather that began in the metro area yesterday—the first rain-free day of the month in Seattle—but it’ll be gone by the time Monday rolls around, giving us our second dry day of the past three.
Going back even further, it’s been relatively dry around here since last Wednesday, with no more than .06 inches of rain falling on any day between now and then. The calmer, quieter weather stands in stark contrast to the driving rains that pummeled the Sound early last week, dropping 2 inches of rainfall on Seattle in the first four days of the month. Even now, despite almost a week of tranquil conditions, December’s rainfall tally remains solidly above average, with 2.18 inches in the gauge at Sea-Tac since the month began.
Forget the umbrella. The Olympic rain shadow has us covered.
Upper-level winds over Western Washington are blowing straight from the west today, placing the Olympic Mountains directly in the path of rainfall intended for the Seattle-to-Everett corridor. When that happens, precipitation that would otherwise reach the metro area is wrung out along the western slopes of the Olympics—effectively blocking a large swath of King and Snohomish counties from receiving much, if any, rainfall. (During the fall and winter, the upper-level winds are usually from the southwest, ensuring Seattle stays wet.)
Sure, it rained yesterday, and sure, it rained pretty hard in some spots. Boeing Field, after all, saw .18 inches from a midday thunderstorm, and heavy showers pounded areas north of Everett as a strong line of storms—including a waterspout by Whidbey Island—moved through.
Compared to what fell from the sky nine years earlier, however, yesterday’s downpours were mere sprinkles.
Torrential rains swept through Seattle on Oct. 20, 2003, making for the wettest day in the city’s history. 5.02 inches of rain was measured in the gauge at Sea-Tac Airport, shattering the previous daily rainfall record of 3.41 inches from Nov. 20, 1959. The mark for the most rainfall in a 24-hour period was also easily broken, with the 3.74 inches that fell from Oct. 5-6, 1981 well over an inch shy of the October ‘03 deluge.
Last year, we kicked off October with 11 straight days of rain.
This year, things couldn’t have begun on a more different note.
With no rain expected until Friday, the first 11 days of the month will go down as completely dry—Seattle’s driest start to October since 1991, when rain held off until the 16th of the month. In addition, the lack of any moisture today means that at day’s end, we’ll have only seen .03 inches of precipitation since July 23—making for the driest 80 days on record.
Soak it up now, because by this weekend, we’ll be drenched.
After a dry day on Sunday—rumor has it the sun even managed to peek through the overcast skies yesterday afternoon—the rain has returned for today.
Currently, light-to-moderate rain is falling across Puget Sound. As we work our way into the evening hours, that rain will continue to increase, becoming heavy after midnight. Then, just as tomorrow morning’s commute gets underway, a seemingly magical act will take place. The winds up high will shift to the west—and the rain will shut off completely.
All hail the Olympic rain shadow.