The Upcoming Northwest Heatwave and Snowmelt

 It is now certain that our region (and the entire western U.S.) will experience a welcome spring "heatwave", with substantial snowmelt causing a surge in river levels.

The origin of the big change is the development of a major upper-level ridge along the West Coast later this week.  To illustrate, here are the forecast 500-hPa heights (think of it as pressure around 18,000 ft) for 5 AM Friday.  The red colors indicated heights/pressures well above normal).   This major ridge is associated with warmer-than-normal air that will rapidly sink, warming by compression.

The latest National Weather Service predictions for Seattle indicate temperatures reaching the mid-70s on Friday and Saturday.  Add another ten degrees for the Columbia Basin.

The recent UW WRF model forecast suggests that some places in the west will get into the 80s in western Washington, with Portland rising into the mid-80s.

Folks are going to go wild after one of the coolest springs in Northwest history.

And then there are the rivers.....

Our snowpack is now above normal and this warmth will cause substantial melting of snow, particularly over the eastern slopes of the Cascades.   Currently, the snowpack is above normal over most of Washington State.    Way above normal in Oregon.

The surge in temperatures will result in substantial snowmelt, with some rivers rising rapidly.   Consider the situation on the Yakima River at Umtahum (see below).  The river will rise to near-record levels for the date by next weekend.  Snowmelt inspired spring flooding was a tradition in the Northwest before the dams went in.

Folks forget that the dams save many lives and much property by storing the water from springtime snowmelt, something the anti-dam crowd should learn more about.




Comments

Post a Comment

Popular posts from this blog

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

A Much Colder Than Normal April: But How Unusual?

Image
  April was a chilly month over the Northwest, but how chilly?     It turns out the answer depends on where you are located. The difference between this April's temperatures from normal across Washington State (below) shows that the entire state was well below normal.  The eastern side of the state was particularly frigid:  some areas were more than 6 degrees below normal.   Considering the west side of the state, the April mean temperatures at SeaTac Airport are plotted below.   This April was the coolest since 2011. April 2020 was in 15th place for the coolest April since the mid-1940s and was a bit more than 4F below normal.  So if you felt that you were cheated out of normal spring warmth...you are right. But if you really wanted to experience extraordinary April cold you had to be east of the Cascade crest. Consider Yakima.  Wow.  It had the third coldest April temperature since the mid-1940s.   And the all-time record in 1955 was only slightly colder. If you want a longer-te
Read more