In what will be shocking to zero people in Washington state, a gigantic plume of water vapor stretches from nearly southern Japan all the way to Seattle. It’s just the most recent wet slap in the face the Pacific Northwest has received in its record-wet winter and spring.
Many places in the state have gone more than 25 days without sunshine in the past month. One area around Gifford Pinchot National Forest southeast of Seattle has gone all 30 days with nothing but clouds and rain
Seattle itself has accumulated nearly four feet of rain since Oct. 1, making this the wettest such period on record.
On Tuesday, the moisture plume stretched across over 6,000 miles of the Pacific Ocean. On his blog, atmospheric science professor Cliff Mass at the University of Washington points out that this “mega moisture plume” is rare for the time of year:
The model precipitation forecasts for the next few days is extraordinarily unusual for late April, with some aspects unique for any time of the year.
We are talking about an amazingly long and wide precipitation/moisture band coming from the west that will bring record amounts to some locations from Northern California to Southern Washington.
The depressing fact: Here in the Pacific Northwest we are living through a record-breaking wet winter and spring, and the action is not over yet. The good news: We should transition to an El Niño next winter, which should be associated with a different, and drier, atmospheric circulation.
Seattle is now at 44.67 in. of rain since Oct 1st – wettest Oct-Apr on record. Quillayute is approaching 10 FEET of rain since Oct 1. #wawx
— NWS Seattle (@NWSSeattle) April 24, 2017
Because of the terrain, the Pacific Northwest is particularly susceptible to these atmospheric rivers, or moisture plumes. As warm, moist air rides up over mountains, the moisture wrings out in the form of rain.
“For example, the total precipitation ending at 5 PM Wednesday, brings 2-5 inches over the Oregon Cascades and the coastal mountains,” Mass wrote Sunday. “Importantly, northern CA gets heavy precipitation, which is quite rare in late April.”
Looking forward, there’s enough confident high pressure and warmer weather in the forecast for the National Weather Service to get a little cheeky in its morning weather briefing.
“Model solutions fall back into alignment Saturday with ridging overhead and dry conditions with … wait for it … afternoon highs in the lower 60s,” forecasters wrote. “Cautiously optimistic for that.”