Thursday, December 3, 2009

Cold and Dry and Maybe a Snow Flurry

The forecasts are stable and the models are in agreement--cold and dry with strong winds downstream of mountain gaps.
Today we started with a large pressure difference across the Cascades (see temperature and wind forecast for 10 AM above). Cold temperatures and associated high pressure west of the Cascades. There was very strong wind acceleration in the only sea level gap across the Cascades...the Columbia Gorge...with winds at locations such as Troutdale reaching 30-40 mph.

The next act is beginning...the first in a series of upper level troughs is moving through and behind it there will be an influx of colder, continental air (see plot). Not the primo stuff...but cooler than we have had during the past several days. I have included a surface chart for later tomorrow...with cooler air and northerly flow moving south--there is a large pressure change at the forward edge of the cold air. There could be a few snow showers tomorrow morning with this...particularly over the western Cascade foothills...but nothing of any note.

A second upper disturbance moves through Sunday and an even stronger pulse of cold air, with strong easterly and northeasterly flow follows (see figure). Will be an interesting day. A huge gradient will be established over the Fraser River Valley and strong winds will push into Bellingham, with further acceleration down the western Strait of Juan de Fuca. You will see the famous Tatoosh easterly gales! At one time this area was known as the "graveyard of the north Pacific" due to these winds and the rocks. You have delicate plants...protect them. When the winds die down on Monday morning the temperatures could plummet on the western side into the teens in some locations. Maybe even colder Tuesday am. Good weather for plumbers--could have some frozen and bursting pipes.

And watch the action offshore! As the cold air moves over the relatively warm water there will developing cumulus activity...including showers. There will be lines of convection...should be impressive.

Monday and Tuesday will be cold and sunny. That's far enough to forecast...but remember...sometimes the most interesting weather happens when a cold spell ends. I won't even mention that unspeakable four letter word: S**W. Don't even think about it.

23 comments:

RobbyRob said...

Cliff,

Thank you for the update, CTRL+F5 has been getting a workout lately on your site and when the gfs models are coming out. It will be very interesting to watch the models as we move toward the middle of next week.

Must read blogs said...

cliff i have a question: how is it that houston and parts of the southwest can have snow?

thaikarl said...

don't need no s**w. i'm wondering where the coldest/warmest spots in seattle are? is there a map somewhere that shows where the temperature varies + or - from the stated (seatac????) temperature in seattle area? is it going to be colder near the lake, warmer on capitol hill or queen anne? or the other way around?

smokejumper said...

Yeah, I'm glad you didn't mention the S word. Would have been a little premature, unless you were looking for higher ratings.

I remember the few years i lived on campus where it was so tough for it to snow. Seemed like it always had to be a quick hit, and tonights extnded GFS really backed off on any breakdown of the ridge. So if it is a slow transition, and you live in Seattle and love snow, good luck. El Nino is sadly upon us :(

JewelyaZ said...

I'm not thinking about the four-letter S word but I appreciate the warning for the plants. Time to bank the mulch up around the onions and carrots still in the ground!

athos said...

If it's going to be this cold, I'd rather it snow. It's this time of the year that I typically start to get frustrated with the oddities of the Puget Sound weather. Having lived back east where things make about 10x more sense, I find I miss the snow days, and watching the flakes fall. sigh

RobbyRob said...

It is warmer the closer you are to a body of water. I can watch the temperature rise from my car thermometer the closer I get to Lake Sammamish on west lake sammamish parkway. There is usually a 2-3 degree rise in temperature from I90 in issaquah to the lake. I believe the water holds its heat much better than the land, and that is why the pacific ocean moderates our temperatures and makes it so hard to receive snow here.

Tom said...

After last year I hate snow more than you can possibly imagine!

Craig said...

I am in agreement that if it is going to be cold let there be snow. I know the planets need to align to get snow around here so it does look like a slim margin but can always dream. I am hoping there is a little front that forms on the leading edge of the arctic boundary and slides through puget sound. I know this does happen from time to time. Does not give a dumping but gives something. I live in Bonney Lake so it does not always make it down this far when that happens but I can always hope.

Touray said...

Thaikarl in answer to your question how can Hoston have snow?

Seattle is roughly the same lattitude as places in Eastern Canada.

Think of it this way. The Casacdes/CoastRange/Rockies basically act as a huge barrier against any cold air coming into our region.

The middle of the country is basically flat, and cold air can drop out of the North unhindered.

Plus you forget our weather comes right off the pacific ocean which is mild year around.

P.S. Cliff may have some other thoughts, but I'm sure he is busy right now.

RobbyRob said...

Seems like with each run of the GFS our colder weather lasts further into the week.

Kristina said...

S**W. Hmmm - slow? show? spew? skew? slaw? slew? What could it be???

Oh the weather outside is frightful, but the fire is so delightful, but since we've no place to go, let it s**w, let it s**w, let it s**w!

JewelyaZ said...

Cliff,
I am looking at the Bellevue (98008) Probcast and I have some questions... I know it's not "yours" per se but maybe you'll know.

First, they are calling for lows 10 degrees lower than everyone else -- 17 tonight and 21 tomorrow night. KUOW this morning said 30 tonight. That's a BIG difference! How come? Given that we got to 30 at my house last night, I'm calling b.s. on Probcast... I don't even think the top of their range at 21 for tonight will be right unless things change dramatically this afternoon.

Sunday, they are calling for 98008's high to be 31 (after that low of 21, potentially believable). The range for Sunday's high is 35-28. It may be a dumb question, but why doesn't that temp trigger a Chance freeze percentage entry? There's one on all the nights... seems if the DAYtime temp also has a chance of being below freezing that that chance would be useful.

I find Probcast very useful and enjoy the refinements that have been introduced lately, especially the precipitation range percentages. They help me plan my life, especially my outdoor and gardening activities.

The one big thing that remains missing is wind speed range predictions. THAT would be super-helpful... though I imagine that it is a non-trivial addition.

Thanks for all you do. Your work does Sagan proud. :-)

Michael said...

Cold and dry? Its raining outside right now in Bryant

Cliff Mass Weather Blog said...

Yes Michael,
Its raining! A narrow band of rain is moving south down the sound at the leading edge of the cooler northerly flow. About .06 of an inch here at the UW. The models from yesterday underplayed this feature...but it will be very short-lived...roughly an hour at any location...and then it WILL dry out for the next day...guaranteed!..cliff

SolvayGirl1972 said...

Thanks for the update Cliff (it's raining here near Seward Park right now). I was getting worried about my teenager coming home on the ski bus from Snoqualmie tonight (and picking her up in the Central District at 11:30PM).

Chris Christensen said...

Forecast now is for the cold to stay all next week and even beyond, but no moisture in sight...

Smiling, Beguiling said...

Rained in West Seattle. Hope the roads don't get too icy this evening as a result.

Meanwhile, I'm still hoping for sn*w. I actually LIKE the stuff. ;-)

SDintact said...

Wow. Very nice post. Well done to you....keep up the good job.

Must read blogs said...

i think its interesting that we are whining about this cold weather. When at WSU-Pullman in the mid 1990's it got to be 25 BELOW! This cold is nothing compared to that. At least cars start in this weather.

NCAA Football Contest said...

I hate to say I told you so, but read my comment from November 27 on Cliff's posting "Sun, Fog, and Rain Takes a Holiday." The cooler air is arriving!

Patrick said...

Yes, the shower Friday afternoon followed by colder temperatures was just enough to leave about 1/8" of ice covering my car.

The warmest place in Seattle is probably the Puget Sound shoreline, with all that nice moderating salt water. And along the shoreline, probably in downtown Seattle, where there's the most heat from buildings, cars, etc., leaking out.

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