The Great Portland/SW Washington Snowstorm of April 11, 2022

 Portland residents will be telling their grandchildren about this one.

The great Portland April snowstorm.

The latest NOAA/HRRR forecast shows bountiful snowfall over the lowlands of SW Washington and NW Oregon for the 24 h ending 5 PM Monday, with several inches around Portland.    A drive down I-5 tomorrow morning may be exciting.  A drive through the Gorge could be dangerous.  And the southern Cascades will be hit hard.


The even higher resolution UW forecast model has a similar solution (see below)


This snow is very welcome, considering that the Oregon snowpack is currently below normal.  A late-season snow blast has a major impact on fire season.

Why this extraordinarily late cold/snow event?

We start with a very deep upper-level trough (see the forecast for 5 AM Monday below for 500 hPa...about 18,000 ft).  Very impressive.


And this trough induces a deep low center (see the surface forecast for the same time), which draws in cold air from the north.  In addition, heavy precipitation from this system will cause the atmosphere to cool by evaporation and through melting of snow falling in from above.


Anyway, a bit of  Northwest weather history will be made tomorrow.

Want to learn more about northwest weather? Sign up on Patreon to join my monthly weather discussions. Click the button below to get started. 

Comments

Post a Comment

Popular posts from this blog

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

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

Strong Atmosphere River Heads into British Columbia and Southeast Alaska

Image
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska.   And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor.  You can see the current of moisture extending from near Hawaii into central BC.  This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California.   A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
Read more