A Day Of Sunshine In Northwest Washington After A Tiny Tornado In Snohomish County

Mar 31, 2017

A tiny twister appeared in the town of Monroe this week — nothing major, but enough to grab people’s attention. KNKX weather expert Cliff Mass says it’s not unheard of around here. Property damage to a few RVs was the extent of the unfortunate event.

“We do get tornadoes around here occasionally, but it’s pretty infrequent,” Mass said.

The National Weather Service confirmed the twister as an "EF0," the weakest type. It had a speed of about 75 mph. Meteorologists at the Seattle-Tacoma offices of the NWS measured its path and charted a damage zone of about 100 by 15 yards wide (1,500 square feet.) There was tree damage and objects dragged anywhere from 1 to 5 feet from their original locations.

"So, it wasn’t that strong. And it was associated with a convergence zone,” Mass said. “We sometimes see tornadoes with convergence zones in spring.”

Convergence zones are when air goes around the Olympics, generally from the west, and then comes together again over Puget Sound. That produces a band of clouds and precipitation.  Upward motion from those dynamics can produce some thunderstorms and convection, which in spring time leads to tornadoes.

 “So that’s why we sometimes get these very weak tornadoes with convergence zones,” Mass said of the typical Northwest weather pattern.

In 2013, a twister touched down in the town of Frederickson, near Tacoma.  That one was in the transition time to fall. 

Another Gray Forecast This Weekend – Except On Friday  

“Today is going to be perfect,” Mass said of Friday’s weather forecast.

There’s a little bit of rain to get through before a day of sunshine on Friday, with temps up around 56-57 in the lowlands of Puget Sound, and even warmer in the southwest part of the state. “So a very nice day – no rain.”

Then a weak front moves in on Saturday night – so it will cloud up and showers will start somewhere between 4 and 6 a.m. on Saturday morning.

“I expect some steady rain in the morning [on Saturday] as the front comes through,” says Mass. “The front will get through by maybe two o'clock.  So you’ll see it opening up – there could be a few residual showers over the lowlands and the showers will continue over the mountains.  But it will improve late in the day on Saturday." 

Mass says at that point, temperatures will drop down a bit to around 53 degrees.

"On Sunday, an upper-level trough [of low pressure] will come through.  It doesn’t have a lot of moisture to work with.  But I expect temperatures to get into the low 50s. It will be mostly cloudy with a few scattered showers on Sunday," said Mass.

Warming Up Next Week

Then the situation should get better, Mass says.

“A ridge of high pressure starts building in on Monday and Tuesday. And the temperatures on Tuesday and maybe Wednesday will stun you. We’re talking about the potential for temperatures in the 60s – the warmest we’ve seen for a long, long while. So that's something to look forward to,” said Mass. 

To hear the forecast along with Cliff’s discussion of why and how this winter has been a rotten one for Northwesterners, you can click on the “play” icon at the top of this post.

The weekly KNKX feature 'Weather with Cliff Mass’ airs every Friday at 9 a.m. immediately following ‘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.