Saturday, December 5, 2009

Snowy Sequim and Port Angeles; Major Cold

Snowy Sequim: Picture courtesy of

You want to enjoy a bit of snow in western Washington...head to the typically driest place in the region... Sequim (or actually the foothills behind Sequim and Port Angeles). In eastern Washington? No problem. Head to the eastern slopes of the Cascades--Leavenworth would be a good base. If you want your cold-sensitive plants to survive...protect them today. And if you don't want to help support your local plumber, take precautions for cold. This is some of the coldest air we have seen in a while.

An interesting period of ahead, with some twists on the cold air invasions of the past. But first lets review what has happened.

Yesterday, cooler air moved in behind an upper level trough of low pressure. This trough forced a low level transition to northerly flow and enough upward motion to create a narrow band of precipitation that moved southward yesterday afternoon...with a few hundredths of an inch of rain (and even some very, very light snow in higher locations). The models underplayed this feature a bit, which is not uncommon. (this is an issue some of us are working on--there is a deficiency in the model precipitation physics that causes very light precip to evaporate too readily before it hits the ground).

With general clearing behind the band, temps fell last night, with temps dropping into the mid and even low 20s away from the water. (see graphic). And fog reformed in the south Sound. I should note that such fog is very dangerous..capable of icing roadways significantly. Remember--black ice on the roadway is the number one weather killer in our state!

Today will be cool (temps in the upper 30s to lower 40s) and there will be some sun after the fog burns off. But the big act is coming later today.

A second upper trough will through tonight (see graphic) and behind it REALLY cold air will move in and very strong winds will hit certain locations. Cold air will surge across the Cascades with a strong easterly and northeasterly component. As the air pushes up the eastern slopes of the Cascades there will be light snow (see graphic) and as the air pushes through the Fraser River Valley strong winds will hit NW Washington..passing through or just north of Bellingham, over the San Juans and Gulf Islands and then directly towards the NW Olympics (see graphic).

The air, which is really quite dry, will pick up a little moisture over the water (not that much) and will be forced upwards by the NE Olympics..the result will be snow--several inches easily. Now most of this will be in the foothills behind the Sequim to Port Angeles area--the question is how far to the water will it spread...certainly will decrease rapidly toward the water. But you can't feel sorry for these folks...they enjoy the best weather in the region and they need to share in the wet wealth once in a while. (My NW weather book has a lot of material on the Sequim snows and the Fraser gap flows if you want to learn more. )

Winds will increase down the Strait and will be quite strong at its eastern entrance near Tatoosh. We are talking about sustained 30-40 mph with gusts above 50 mph in the windy locations I just noted. The famous Tatoosh easterly gales. This area used to be called the "graveyard of the pacific" and for good reason.

Cold air--but not quite as cold as that coming through the Fraser--will push across the Cascades under strong easterly flow. And on Sunday western Washington will have a cold "moderated" arctic air mass over us. The strong easterly flow will make sure we will be clear.... lots of sun, with winds over the Sound from the northeast to east. Winds over the Cascade crest will be savage. I would not ski on Sunday..the conditions will be too severe. We are talking about wind chill temps WAY below zero.
Highs in the 30s over the lowlands.

Then comes plumber's paradise. With cold air in place and winds dying down, we will see very cold lows on Monday AM (see graphic). Teens will not be unusual in western WA. I am going to go out in an hour and bring in all my deck plants and mulch everything vulnerable. And disconnect all your hoses on the outside of your house or apartment. You know the drill.

Low Temps on Monday Morning

But the fun doesn't end. We will stay cold (moderating a bit) next week. No significant precipitation in sight and California is going to get hit hard by heavy rain and potential flooding (something that often happens during El Nino years). But that is another story.

Monday will be cold and sunny..and Monday night and Tuesday morning will be also very cold. Eastern Washington will be savage...with temps dropping into the single digits all over the place on Monday morning.


smokejumper said...

Hey Cliff,

I live on the east slopes. I think models are over estimating the amount of moisture to work with. I let you know how it turns out.

JewelyaZ said...

Why is Probcast so out of whack? Last night, they called for 16, range 11-21. The actual low at our house was 28.4 and the low at the King 5 School Net station 0.8 miles away (Phantom Lake) was 29. Eight degrees from the highest Probcast called from seems like a BIG variance.

They are calling for the high today to be 39, range 36-41. It's already 39 so I'm having a hard time believing that too.

It seems like Probcast is awesome in warm weather and pretty good when we're in the 50s and 60s. But when it goes below freezing with weather conditions like these, it's often quite wrong. What a bummer... because it's a brilliant tool... and I hate to see it SO wrong that it's hard to believe its forecasts in general.

Any insight you have would be welcome.

Michael Dempster said...

I love this blog, Cliff. Bought your book when you spoke in Oly, love it, too. Thanks for the good work. Hope you never tire of the blog!!! I have one suggestion each for these wonderful works:
The book: In a subsequent edition, significantly enlarge the index. E.g., could not find "trough." Have been similarly stumped on other occasions.
The blog: I love the graphics. Take the pretty red and blue one in today's (Dec 5) blog: Often the lay weather enthusiast, such as I, can't find a)comprehensible names for what the graph represents ("absolute vorticity?" Couldn't find vorticity in your book's index, either) and b)comprehensible units represented by the pretty colors. On the graphic in question, all I see explaining the units is "10 to the minus 5 and g to the minus 1." I know the maps are prepared for meterological professionals, and your book for the lay person, and maybe the blog for those of us inbetween (I'm an elementary school science specialist). What would you suggest, short of meteorology courses at a local college, to better comprehend your graphics?
Thanks, Cliff, as I said, love your stuff!
Michael Dempster

Josh said...

El Nino I thought doesn't hit till January on. It least that is what we were saying when we were having all those rains. Is it convenient now to say it?

RubySaysMontana said...

I am in Cle Elum tonight and it started snowing about 1/2 hour ago! Welcome to the white stuff!

Cliff Mass Weather Blog said...

I think I can explain this. Probcast is only as good as the models that drive it (probcast statistically postprocesses the numerical weather forecasts). It can fix things to some degree...but only if the problem is persistent and there is data. The models forcing probcast were all too cold. The most difficult situation for the models are cold, stable boundary layers like we get in winter. In contrast, heat waves where the atmosphere is well mixed are much easier. Probcast can not be beat by anything for max temps during warm periods...but cold periods are its achilles heal. Anyway, probcast is not perfect and it is useful to know when it does best. Still need people to watch these automated systems. Hope that helps....cliff

DeAnne said...

It's 32F, clear and calm at the Washington coast. nice for the clam dig at Mocrocks tonigh.

theartist said...

It's snowing in Mukilteo! Hello first white stuff of the year. :)

~curious george said...

I caught your act at Elliott Bay Books. Major fun, thank you. I already owned my own copy of your book, but had you autograph a new copy for my brother- we use your forecasts for hiking in the North Cascades.

Here's my question: the cover of your new book: the words "Cliff Mass" are positioned perfectly on a cliff mass... that seems so much like your sense of humor... please confirm...

Kadri said...

Snowed some last night in Maple Valley right around 6:30pm. Occasionally more than flurries here as I type this on Sunday morning. The streets look white and quite slippery. Looking forward to that sun later on so I can go and rescue the last remaining dahlias before they suffer too much from the cold. Love your blog!

Temira said...

Hi Cliff,
Thanks for the great blog. Down here in the Gorge yesterday, we had 35+ mph east winds with a .06-.09 gradient from PDX the DLS and not much more east or west of that. I've never seen such strong winds through the central Gorge with so little gradient. (And let's just not talk about the 35-65mph we had on the mountain) Any chance you could talk a little about what drove yesterday's east winds? And please come down and give a talk sometime! Thank you!