Friday, January 2, 2009

Sun and Showers

Last night's system is through now and cold, relatively dry air has spread over the region. Some of you got some very light snow last night as the last precipitation bands came through and the temps had fallen sufficiently so snow could reach the surface. But the roads are generally fine.

Right now there are some instability showers (produced by cold air over warm water) and they should move into the region...mainly south of Tacoma (see satellite image). The mountains should have a breather after the snow pounding they have "enjoyed." Both the passes have about 70 inches of snow and the snowpack in the central Cascades is getting close to normal and being way below normal for much of the fall.

So a pretty benign day.

Tonight a weak system from off the Pacific will invigorate the snow showers...but they should be light--not more than an inch or so at most. Many of you will get nothing. Below the salt criterion.

Sunday morning will be dry and cold...but a much stronger Pacific frontal system will approach later in the day. For some locations, especially above 500 ft and SE of the Olympics (e.g., Kitsap) may see several inches of snow before warming aloft turns the lowland precipitation to rain all rain. Warmer, low-level locations near the water may turn very quickly and see no accumulations.

The biggest threat next week will be heavy precipitation in the mountains and the potential for river flooding. The NWS is already talking about it. My take is that this does not look like a major pineapple express event and that rainshadowing will spare the urban areas. We should watch the flood-prone rivers though.

15 comments:

Julia said...

Notable from that satellite photo is what I found when I went out to take a picture of The Mountain: clear skies everywhere except some very black storm clouds close in on Rainier.

SWSDuvall said...

Hello all,

This is my first post on this wonderful site - keep up the great work Cliff! Yeah! U of W as an alumu in Civil Engr and a weather spotter in Duvall (36" 12 day snow storm total), I can't leave the salt issue alone - sorry :(

The engr in me MUST do some math.

All this talk about the salt "ruining" Puget Sound had me doing some math. Puget sound's est. volume of water is: 211.9 Trillion cubit feet. Seawater contains on avg 2.2 lbs of salt/cu ft. So, the sound has ~422 TRILLION lbs of salt. If Seattle puts down 200 tons of salt (using Crawford County, PA as an ratio comparison), it would increase the sounds salt content by: 0.000,000,000,009,478%

Significant? I'll let you be the judge :)

Weatherfreak said...

Nice surprise this morning with solid 2.5" of snow here SE of Auburn. Went to bed to a soupy 37 deg. rain and fog and figured it was to warm to turn to snow. It was a nice treat considering the roads were not to bad. Melting fast now with some rare Jan. sun!

Enjoy!

Cliff Mass Weather Blog said...

All,
What I think is missing is a hard-nosed, careful analysis of the economic implications of the snow-ice close down of the city and region. I suspect we are talking about tens if not hundreds of millions of dollars in economic loss. And what about the serious risks for life and limb? And I haven't seen one piece of solid information that salting the roads one very year or two would bring any real environmental damage or impacts on our cars. With all our rain the salt would be washed off the cars quickly in any case. Lots of opinions thrown around...we should be able to get solid answers.
The city needs to do this in a responsible way...cliff

c said...

Clear blue skies and 36 in Olympia at 12:10 pm. Still 3-4 inches of snow on my lawn, but the driveway and roads are clear. I saw a fresh sprinkling of snow on the tops of the Black Hills early this morning, but it has melted now.

Mantini said...

With regards to salt, the fact is that we weather the snow most years just fine - other smaller storms in the 10 years since the no-salt policy have not caused anywhere near the widespread disruption that this one did. The mayor's "salt threshold" is just acknowledging the fact that every so often we do get major storms, and we need more than just our usual response to handle them. They have thrown together fairly arbitrary amounts that really just represent "a major storm" or "a 10-year storm" or whatever you want to call it. It's not as if they are going to refuse to use salt if it only snows 3.9 inches, so mocking their new policy is not helpful to anyone.

They bombed their response to this storm, and have amended their policies to deal with it in the future. Done, and done.

JewelyaZ said...

Let's learn about using salt and sand on roadway surfaces to keep them clear in winter weather from experts... these are people who love clearing roadways like Cliff loves looking at the weather models... Wisconsin Department of Transportation! These folks deal with LOTS of horrible winter weather, admittedly mostly on the flat, but you'd still expect them to know about the science of clearing roads. And they do. Here's some of their wisdom.
US Roads - Roads Management Journal

The studies I dug into on environmental damage had to do with groundwater contamination (Toronto), plant damage (upstate New York), and grass killing (Ohio), all places that apply salt many, many times a winter. A single application will have very minimal effects, judging by the TONS of salt per mile applied to roads in these places studied.

I know nobody wants to lose a single fuschia or hydrangea or other beloved plant to road salt, but I'd sign up to replace a few of my perennials after a storm like this last one if it meant our roads would be cleared and passable, personally.

We're lucky in Seattle and environs... none of our drinking water comes from anywhere downwater of where we're talking about applying salt, either. Of course I understand that drinking water comes from a closed system and that it WILL make a tiny difference somewhere... but I don't think it's a big enough difference to decide not to make our roads safer.

And it's SUNNY out!! Weird.

Joseph Ratliff said...

It's good to finally have a week where BIG windstorms aren't the front and center piece WITH the snow...or without etc...etc...

Although I feel for those who are living next to flood prone areas in the next week...looks like we are doing some SERIOUS warming up for the beginning of January. That plus lots of rain (Pineapple Express or not) ... well...

LJansen said...

Hi, Cliff. I have an outdoor event downtown tomorrow.

So you're basically saying probably no snow or at least very minimal on Saturday?

(You jumped right to Sunday in the forecast pretty much.)

Thanks for any info.

JewelyaZ said...

East Bellevue is having sunshine and super-heavy garbanzo-bean-sized hail right now, and for the last ten minutes. It's actually accumulating on the ground too. It sounds like the house is being beaten to death, especially the skylights. Cool stuff, this weird weather, even though it doesn't last long. Oh, and it's 39F outside... no way is the hail going to stay with us for more than half an hour.

MarkM said...

A general question Cliff: why do we refer to the Puget Sound Convergence zone rather than the Puget Sound Rainshadow which is what it seems like to me?

Anonymous said...

Thought I would mention I have a weather migraine, but only minimal joint achiness.

Something is coming, may not be a super severe event though.

I thought I'd mention this, since Cliff blogged about the Monday event that the weather forecasters missed, but my migraine-head and my joints definitely did not. I had said at the time, that I would mention my next weather migraine. Use the info as you wish. (Maybe 50% of we migraine suffers can predict weather)

Dude Diligence said...

To SWSDuvall: In classic and typical engineer fashion, you've done a remarkable and straightforward calculation. However, you've neglected to factor in the mixing that occurs with the Pacific Ocean through Admiralty Inlet and the Straits. The Sound's salinity is already a tad less than that of the oceans because of the influx of freshwater from rivers and streams. The concern about road salt having an adverse affect on the salinity of the Sound never was a concern.

I think some of the concerns may be the temporary increase in the salinity of freshwater streams affecting salmon and other critters, groundwater impact, and maybe moreso the corrosion of highway infrastructure (e.g. bridges) and our cars. The two local cities that I can think of that rely partly on groundwater supplies from shallow aquifers are Redmond and Renton. Seattle obtains its water supply solely from surface water from it's two watershed resources in the Cascades.

Anonymous said...

Snow on the car this morning - 7:45 AM. Not enough to scrape off, it was wet and appeared to already be melting. No snow on the ground. The car is parkled outside in the open (no carport or roof) on on the border of SeaTac/Kent. (Kent West Hill)

Anonymous said...

Sammamish uses salt -- and steel snowshovel blades -- so salt will run off into Lake Sammamish, and therefore will find its way into Redmond.