February 26, 2024

The Snow has Arrived and Much More is on the Way

This afternoon I biked home in light snow and it was magical.   And the Northwest will enjoy a lot of snowflake magic during the next week.

Tonight (Monday) it is cold enough to snow with any significant precipitation intensity.

The latest radar shows two precipitation snowbands from two convergence zones:  one downstream of the Olympics and the other downwind of the mountains of Vancouver Island (see below).  Snow is being observed in both.


The latest NOAA HRRR model forecast predicts more snow in these two bands (see the one-hour snowfall ending at midnight below).  Perhaps an inch in favored areas.   But nothing that will really cause much of a  problem in the western lowlands.

But the big action is still ahead...not for the lowlands, but for the mountains.  Very heavy snowfalls.   And then another chance for lowland snow on Sunday.

Tomorrow afternoon a vigorous Pacific warm front will move across our coast, bringing strong, moist southwesterly winds that will push up local terrain.  The map at around 5000 ft (850 hPa pressure) on Wednesday morning at 4 AM illustrates the situation.  Very strong winds from the southwest at that level.  This is a very wet pattern


No more snow at low elevations, but feet of snow will fall in the mountains.  The accumulated snow total through 1 AM Thursday is shown below.  3 feet in some places



Later this week, a supercold upper-level trough will settle over our offshore waters, leaving western Washington and Oregon quite cold, with rain and snow showers even near sea level.  Northern California gets hit hard with rain and snow.

All and all, very good news for West Coast water supplies and regional skiing.






February 24, 2024

Heavy Snow in the Mountains and Snowflakes over the Western Lowlands are Now a Certainty

We are now close enough in time to predict a snowy future:   many feet in the mountains and a good dusting in several western Washington locations near sea level.

Some dramatic changes in our weather are ahead starting tomorrow (Sunday) afternoon.

During the afternoon, a very strong cold front will move through western Washington, bringing powerful winds and rapidly declining temperatures. 

To illustrate, below is the predicted surface weather map for 1 PM Sunday, with pressure (isobars, solid lines),  surface winds, and near-surface (800 meters) temperatures (shading) shown.

I have indicated the frontal location on the map (red line), with cold air (blue color) behind it.  


Do you see the large change in pressure over western Washington (lots of lines)?   That will cause strong southerly winds, with gusts to 30-45 mph over the lowlands. 

After the front moves through, it will be game-on for regional snow.

Snowfall accumulations from 4 PM Saturday through 1 PM Sunday, right before the cold front moves into western Washington, is moderate, with perhaps a half-foot over the northern Cascades.


One day later, as cool, moist Pacific air from behind the cold front has pushed through, and the mountain snowfall is getting impressive, with higher elevations getting 2 feet or more.  Look carefully and you will see some snow reaching sea level, particularly north of Everett.

 

More snow will fall on Monday night and Tuesday morning, bringing mountain snowfall totals of 1-2 yards by Tuesday Afternoon.

The European Center model forecast is similar, and if anything more generous with the snowy bounty, with the totals through 4 PM 3 March pretty impressive.  much of the Cascades receiving more than 45 inches.


The NOAA Climate Prediction Center is going with the chilly, snow-laden message with its prediction for search March being much colder and wetter than normal in the West (see below).




And did I mention that El Nino is starting to collapse?

A lot of reasons to expect our water situation and snowpack may not be too bad starting summer.

The Snow has Arrived and Much More is on the Way

This afternoon I biked home in light snow and it was magical.   And the Northwest will enjoy a lot of snowflake magic during the next week. ...