Dry weekend set to cap a likely record for March, but rain returns next week | KNKX

Dry weekend set to cap a likely record for March, but rain returns next week

Mar 29, 2019

Another warm, dry weekend is in the forecast for western Washington, adding to what has been an unusually parched month of March. KNKX weather expert Cliff Mass says he expects this to become the second-driest March ever recorded at Sea-Tac Airport, going all the way back to 1948.

He said Friday will be pretty dry except in the mountains, where a few showers and maybe even a thunderstorm are possible near the crest of the Cascades and the Olympics.

“But here in the lowlands, dry and temperatures getting up into the lower 60s, maybe mid 60s some places,” he said of Friday’s weather.

He predicts that weather will continue all weekend long, with temperatures inching up into the mid-60s, more dry skies in the lowlands and just a few showers in the mountains.   

CHERRY BLOSSOMS PEAK SUNDAY AT UW

Mass said it should be a lovely weekend for getting outdoors. He had a special plug for the big blooming event on the quad at the University of Washington in Seattle, where he is a professor of atmospheric sciences.

“Get out there for the cherry blossoms on the UW campus. They should be peak on Sunday, so that’s a prediction you can bet on,” Mass said.

Mass said the dry spell will continue through Monday, but a shift is expected Tuesday.

“Another weather system comes in,” he says, “so we’re going to go into a wetter pattern Tuesday and Wednesday, as some light to moderate showers come from a frontal system that moves through.

After that, Mass expects a return to rain and the proverbial "April showers."

“So, dry for the next few days, but then the spigot turns on again,” he says.

DRY HERE, WET IN CALIFORNIA

Mass notes the dry March weather in Seattle and western Washington is a stark contrast to what’s been happening in California this month.

“We’re about two inches below normal,” Mass said of the measured precipitation at Sea-Tac. But San Francisco has seen about three times as much rain as we have.

“We’ve had about 1.73 inches and they’ve had about 4.4 inches at the airport in San Francisco,” Mass says

Even Los Angeles has had more rain than the Puget Sound region, he said, with 2.1 inches measured at the airport there. 

WHY SO DRY?

Mass says the pattern driving the region's dry weather has occurred before in El Nino years.

“And that is a low pressure area developing off the California coast,” Mass said.

“What that does, is that low pressure center tends to bring storms into California,” he said. “The jet stream is south of the low. Moisture and fronts come right into California and then some of it swings up into us, but it’s very attenuated by the time we see it.”

That means we get clouds and maybe light sprinkles, while the heavy precipitation all goes into the Golden State.

POLLEN EXPLOSIONS AND WILDFIRES

This pattern also produces very dry wind in Washington because there is an associated high pressure system north of us. The pressure differential causes air to flow toward the lower pressure, which results in easterly winds, or winds from the east, toward the coast.

“Last week it was extraordinary. Remember that day when we had pollen problems and the strong winds coming from the Cascades? That’s because of this pattern,” Mass says.

“The easterly winds come down the Cascades, and as they do so, they sink, they get compressed and they warm. And when that happens, not only do the winds tend to speed up, but the air gets very, very dry.”

Mass says grass dries out very quickly and can catch fire immediately in these conditions. There were 49 fires reported last week on the west side of the mountains in Washington.

“All you need is an ignition source, and you get fires,” Mass says.

He doesn’t expect those fires to continue with wetter conditions returning next week. Mass also says the dry weather should not cause worries about the water supply because March is not normally a critical month for building snowpack or filling reservoirs.

“We’ve had a pretty normal winter,” Mass said “And looking forward into the next week or two, it appears that rain is coming back into the forecast.”

To hear the full conversation, you can click on the "play" icon at the top of this post.

Weather with Cliff Mass airs at 9:02 a.m. Friday, right after BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KNKX environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington professor of atmospheric sciences, a renowned Seattle weather prognosticator, and a popular weather blogger. You can also subscribe to podcasts of Weather with Cliff Mass shows, via iTunes or Google Play.