Today is a typical post-frontal day, with unstable air producing showers and good orographic precipitation in the mountains. There is also a Puget Sound convergence zone enhancing precipitation north of Seattle and rain shadowing immediately east of the Olympics (see radar to see the precip and the surface chart to see the winds wrapping around the...
Windstorm Doesn't Look Likely
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I just took a look at the latest model runs...and I am not expecting a major windstorm anymore. As noted earlier, there has been a lot of disagreements between models, even today when we are within 48hr of the event. Something is making it difficult for the solution to gel...and I think I can tell you what it is.Take a look at the upper level forecast...
Quiet Day
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Well, another forecast problem. The NWS was going for rain today...and I can't figure out why. Anyway, they just shifted the forecast today to a dry one for most of region. The late Thursday/Friday storm is still uncertain. The best model...the National Weather Service GFS (Global Forecast System) model still has it in the latest runs...but weaker. The NWS NAM model (less skillful in general) doesn't have it at all. Comparing the forecasts of major international modeling systems...there is a lot of variability...but most are going for a weaker event. In contrast, in December 2006 the various modeling systems...
A Poorly Predicted Wind Event
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My profession did not do an adequate job today, when we had a significant, and poorly forecast, wind event. Both on the coast and here in the lowlands, wind gusts reached 50-60 mph near water and exposed locations, with the remainder of the area experiencing 30-40 mph gusts. The Evergreen Bridge had 40 mph sustained winds for two hours around noon....
Today's Rain and the Upcoming Potential Storm
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Well it is back to normal around here. A modest Pacific disturbance is moving through this morning with moderate rain in the lowlands (see high resolution visible satellite image). There is a low center right off the coast...see the notch in the clouds off of Forks...that is where it is. If you ran an animation of the cloud images you would see...
The Human Element: Part I
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The urban and local flooding prediction was dropped and for good reason. Other than some stopped-up drains there was little threat in the central Puget Sound lowlands since the temperatures were only warming up slowly and heavy rain was not forecast to occur.This is a good example of over-warning...something that does happen occasionally. Why does...
Perhaps I should not mention this..
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I try not to hype the weather...and one can't be sure about forecast model output more than 4 days out...but....the predictions of some the computer models for the end of the coming weak are extraordinary and possibly severe.We start with possibly a minor windstorm on Wednesday and perhaps a little snow. The a very powerful windstorm strikes the area on Friday..as strong as the Chanukah Eve event. And then back to snow.There is, of course, a lot of uncertainty that far out and perhaps I shouldn't have mentioned it...but now two modeling cycles have shown it. Anyway, we need to watch this carefully...if these storms...
Transition Day
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The temperatures in nearly all of western Washington are now in the 40s and warmer southwesterly flow has removed the persistent cold air. Take a look at the Seattle profiler winds and temperatures for the last day. 24h ago there was weak SE low-level winds and temps around 0C (32F) in the lower atmosphere...now there is fairly strong SW flow and...
Evening Update
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Temperatures have only slowly warmed, but now most locations have temperatures in the mid to upper 30s and have switched to rain (see map for current temps..the top left number at each of the weather stations). You will also see the strong southeasterlies over NW Washington and the central WA coast....interestingly enough these winds are forced by...
Plant Damage, Snow, Rain, Melt Out, and Avalanche Danger
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Walking to the bus stop this morning I saw increasing evidence of damage to plants and trees. Large branches broken off by the weight of snow, bushes bent over to the ground or broken. At the UW, the main road was blocked because of heavily leaning fir tree...snow loading had done the trick. Anyway, I suspect many of you will find quite a bit of...
More snow tomorrow?
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This event just doesn't end. Tonight temperatures will drop enough that wet roads...and particularly where the water is not deep..can freeze. I just walked home over some previously wet roadway..which is now frozen. Another issue today was flooding of some streets where slush and snow have clogged the drains. I dug out mine and released a huge amount of water that had pooled up. In 1996 my house almost flooded from such a stopped street drain. So if all of us tended to nearby street drains, a potential source of flooding could be avoided. There are some snow showers in the south Sound now...but nothing serious....
10 AM Update
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It is snowing fair hard in Puget Sound...and it appears that the snow is being focused by a weak Puget Sound convergence zone (check radar). The computer models have this feature (see graphic) and predict it will hold in through roughly 1 PM. So it ain't over yet. You can find sun today (see satellite image)...sun is shining on the coast and some...
Snowing Again
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I sit here, watching large snowflakes fall in the darkness outside my window. This is the last snow day in the lowlands for a while I suspect.The radar shows the story (see image): moderate to heavy precipitation north of Seattle that is bringing wet snow, with some rain in warm locations near water. Outside my house it is collecting in a slushy...
Christmas Eve Update
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I think we will see some more snow tonight...particularly at higher elevations. Temperatures warmed a great deal during the day, and lower elevations (less than 500 ft) generally switched to rain. Some of you at higher elevations did have snow most of the day...although it was generally the wet, sloppy variety. Anyway, the freezing level is starting...
10 AM Update
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Wet snow is still hanging on in central Puget Sound...but precip has switched to rain in parts of NW Washington (e.g., north Whidbey, Bellingham) and in the south sound near Tacoma. The profiler at Seattle Sand Point shows temps near 32F in the lower atmosphere...classic melting pattern (see figure, height is in meters, temp in C--really something...
On the edge
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It is snowing now in much of the western interior, except for light rain around Tacoma, with rain on the coast. The temperatures aloft are right on the edge. Over Seattle, the temperature is 32 F for the first few thousand feet above the surface. In the business we call such a situation "isothermal" and that temperature is being dictated by the...
Snow versus Rain
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Tomorrow represents a classic problem for local meteorologists in winter...snow versus rain. Many winter events are on the margin around here because warm air from off the ocean is always close. Later tonight and tomorrow AM we will initially see snow.. in fact, take a look at the latest satellite and radar imagery....a disturbance is making landfall...
Stunning Pic and Snow
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Last night didn't get quite as cold as expected because of the development of low clouds during the evening...but still cold enough to turn everything to ice and keep it that way. There is a stunning picture this morning, which I have attached. This is a high-resolution visible image from the NWS geostationary weather satellite at 35,000 km above...
Update II
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The more I look at the forecast models, the more snow I see. Well, at least those who like a white holiday won't be disappointed.As I mentioned earlier, tomorrow morning will be icy...but no new accumulations. It was bad enough when I took the bus home from the UW---buses sprawled on roads, abandoned on the sides. One almost hit a pole while I watched....
Evening Update
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I will be talking about Wednesday's potential storm later, but one thing is certain...there will be serious icing conditions in a few hours. Today temperatures got above freezing in most of the region and there was considerable sun. The unplowed roads became wet and slush and tonight many will freeze. We have clear skies that will promote good radiational cooling to space. Temperatures will drop into the lower 20s for most and into the teens in the normally cooler spots (away from water, in valleys or low areas). Snow really promotes nighttime cooling since snow is an excellent radiator in the infrared (that...
Noon Update and Editorial
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Well...it looks like more snow is on the way. I just got a look at the most high resolution forecasts available in our region (the 4-km WRF-GFS if you like to impress your friends!) and a collection of other forecast models used to give some idea of forecast uncertainty. As this point they are suggesting that another batch of snow will began in the early morning hours Wednesday, snow through 9-10 AM, turn to rain, and then turn back to snow later in the afternoon. This would be a slushy mess. Right now, temperatures are getting above freezing...making things nice and slippery. Did you know that the colder ice...
The Break
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Yesterday was a significant snow event for the region with the lowlands receiving 3-8 inches in general, on top of the considerable snows of the past week. The last week or so has turned into the most snowy, cold period since the great event of the last week of December 1996. Take a look at the temps at Sea-Tac compared to normal (graph). Our HIGH...
5 and 9 PM Update
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There has been 1-3 inches of additional snow this afternoon, with many large flakes. The origin of this afternoon's snow is a band rotating around an offshore low (see sat pic--you can see the clouds swirling around the low). As clear from the radar..this band is associated with light to moderate precipitation. The band is over western Washington...
More Precipitation Today
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Lets examine what happened yesterday and then move to today's situation. Although the forecasts were not perfect, they did get a great deal correct. Looking at a range of reports (and I very much thank those of you who provided snowfall amounts), there was roughly 3.5 to 8 inches for the communities adjacent to central Puget Sound, while 6-15 inches...
8:30 PM Update
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There has been some "hot" comments about meteorologists hyping the weather....please be patient...it is too soon to throw in the towel on this event...although there are clearly deficiencies in the model's solutions. The winds have not accelerated as much as forecast...yet the pressure different across the mountains is extraordinary...nearly as high...
5 PM Update
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It is clear that the snow moved in in a few hours early...not an unusual timing error. A larger error is the easterly winds--which are substantially weaker than forecast by the high resolution models. They have picked up and will pick up further...but if they are weaker than expected that will increase the snow east of the Sound (since there will be less downsloping)...6 PM...winds started to really increase aloft....and gusts increasing at surface sites...cl...
A little early
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Very light snow has made it into SW Washington already....the models often start the light snow 2-3h late..and this an example of it. So light snow is now falling from Shelton to the SW and should get to PS by 2-3 PM.....the easterly flow will slow it up a bit...also as of 3 PM the easterly flow really hasn't revved up yet...slower than the model's suggested....but the pressure difference across the mountains has increased substantial...
The Storm tonight and Sunday
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This is going to be a complex event and I am going to take some time to describe it...and Sunday may end up different than some of the media is describing. I think we can have substantial confidence what will happen through 4 AM tomorrow...after that there is more uncertainty.Before first, I wanted to comment on the remarkable temperatures we are...