A Little Bit Of Light Snow This Morning, Then Changing To Rain

Thursday, November 25, 2010
8:59 A.M.

Hey ya'll, so we are seeing a little bit of light snow this morning. It's not that big of a deal because it is going to change to rain later in the afternoon and it will melt. I suspect some roads will still be slushy (especially sidestreets) but as time goes on we will warm up enough that that slush won't last too long either. I've gotten less than an inch so far at my house, and most other places will receive the same amount of snow before it changes to rain, save the hills and up north in Bellingham where you could see up to 2 and 3 inches respectively. A WINTER WEATHER ADVISORY is in place for all of Western Washington except the Cascades, where a WINTER STORM WARNING is in place for a foot of snow.

Other than that, there isn't too much to talk about. The DOT handled the roads nicely with salt, which of course, I didn't really like, but it was ok because I got school off anyways. Salt kills engines and the environment, but it works. Still, I like seeing the arterials white with snow. I went skiing down some back in 2008. THAT was fun.

We will be gradually warming up to "balmy" temperatures in the mid 40s with showers most of the time, except some drying during the weekend. No big storms look to be headed our way.

However, there could be another arctic outbreak on the horizon. It looks very unlikely at this point, but some models have been showing some arctic air spilling down. Right now, it is much too far to our east. We will see if we get some more Fraser River outflow. This would be in approximately one week. I'll keep you posted. LAWES level 1.

But it heads off much further east later. Still, an impressive arctic high!

Of course, the mountains are looking good for snow. Here's the Alpental base...

And here's Snoqualmie Pass...

So the lowlands are done with snow for a while, but the mountains will get some, and there is a possibility, albeit slim, that we could return to colder weather next week. Have a great day and give thanks for the snow we did have. :)

0:26 minutes

Visibility

Ok, visibility kinda sucks, at least right now. It may change. I'm not sure why. Maybe because the snow is giving off some moisture, maybe because there is more particulate matter. But it will get better throughout the day today. I might talk with Scott Sistek more about this. For those of you who don't know Scott, he's the man. Find him on "Scott Sistek Weather" on facebook. In addition to his insights, me and a bunch of weather nerds always post stuff on his wall. It's a really cool community, and those who are excited about weather should check it out.

Midnight Update

Monday, November 22, 2010
11:50 P.M.

So the snow has now largely come to an end. Don't be surprised if you see a flurry, but I doubt you will see any additional accumulation.

Generally, I've been hearing of about 5 inches of snow in the Seattle area. I have 5 inches at least. Very, VERY cool stuff. I'm pretty darn happy right now. And the mountains are getting tons too.

This has been pretty crazy. This much snow this early. Let's hope that it is a precursor of things to come. I think I already said this too, but Barrow, Alaska was warmer than Seattle today.

The big stories now are going to be cold and wind. First, let's look at some temperatures. This model below shows the 7:00 A.M. (generally coldest part of morning this time of year) temperatures for Tuesday morning. Seattle will likely get down to 20 degrees or so. Even areas near the water will still be below freezing.

By the way, tomorrow will feature SPECTACULAR visibility. The atmosphere is very dry, there is little air pollution, and it will be completely sunny. There will be a marked difference. When you don't have humidity or particulate matter clogging up the atmosphere, you can see a lot further. That is why deserts (except when they have dust storms) are often very good for viewing stars - very low humidities.

The day after tomorrow (haha) will be even colder. Here is the same chart 21 hours later (the morning low will occur earlier because the sun will be out).

Even colder for Seattle! You can already see warming off the coast - that is part of the high pressure that gave Barrow a high of 34 today coming in. Yeah, it's that big of a high pressure ridge. But in Seattle, lows will get into the mid teens. Outlying locations could get to 0 degrees.

This graphic shows how dry the air mass is by measuring the RELATIVE HUMIDITY of the atmosphere. It is for mid-morning tomorrow. See that orange around us? It means we have a relative humidity of 25 %. That is extraordinarily dry. And colder air masses hold less moisture (90 degrees 100% relative humidity is much more humid than 50 degrees 100% rh) so a subfreezing air mass with a relative humidity of 25 % is extremely dry.

Haven't shown the relative humidity graphic before. It's a cool one. :)

Now - winds! The saga never ends. The winds are blowing like crazy up north right now, as this graphic shows. This shows what was forecasted for 10 P.M., so it is actually an old graphic, but that is when the winds peaked and this is how fast they were. Note - these are SUSTAINED winds. Multiply by 1.5 to get gusts (approximation).

You can see a very localized, but intense, area of winds up north.

These winds will weaken, but winds will spread throughout Puget Sound Tuesday as this graphic indicates.

It will be cold and windy, especially in the sound. This graphic doesn't show Seattle getting real strong winds, but all you need to do is shift the gradient a little, so I would still be on the lookout for some gusts tomorrow. Places over water, however, will take the main beating. These winds, however, will be nowhere near as strong as the ones being witnessed right now over the San Juans. A high wind warning is in effect for those areas right now. Winds over most of the sound look to be below advisory level for most of the day (except in that dark band of blue and green).

One last graphic - the 1000-500mb level thickness model is regarded as "the" model to determine the true strength of an arctic outbreak. Simply put, it measures the temperature of the lower atmosphere. More complexly put, it measures the distance in decameters from the 1000mb air pressure level to the 500mb air pressure level in the atmosphere and calculates how cold it is based on the distance, with a lower distance being colder (cold air is denser, takes up less space) and a higher distance being higher. Heat waves generally have a value of above 580 decameters in Washington. You have to start thinking about snow when it gets to 522 dam (dam=decameters). Right now, it is like 507 dam. That is extremely low.

This is for tonight at 1 P.M. As I write this now it is 12:51 A.M. Yeah this has so far taken me one hour, but I enjoy doing it. I was watching the Bourne Trilogy but decided I'd rather write an update.
You can see that there is clearly a lot of arctic air in Western Washington. If this was in December or January, I would seriously be concerned about highs getting out of the teens. No joke. They might reach twenty. But we are gonna get an arctic blast that has not been diluted too much.

Wow! The models actually showed this 16 days ago. Not this exact scenario, but this idea. Pretty crazy. Then they shifted to highs in the 40s, believe it or not. There is not a lot of data over the arctic, so models commonly have problems with these situations. Given that it is a La Nina year, I expect that we will see more arctic outbreaks. This is definitely a good way to start. :).

To wrap it up - cold tomorrow and FRIGID Wednesday morning, before moderating while remaining mostly dry through Wednesday. A more active, typical storm track will return after a system affects us on Friday.

1 hour, 12 minutes (now I'm going to post how long I've worked on these. Hopefully someday I can count them all up. :)
Charlie

Yes, I failed!!!

Monday, November 22, 2010
6:22 P.M.

WOOHOO!!! I can't believe this is happening. Winter storm warning and 2 inches of snow and counting! The models predicted zip. Cliff Mass predicted zip. Scott Sistek predicted pretty much nil. I gave you a 5% chance of snow. The National Weather Service was just ignoring the models and going on their own judgment, which I thought was silly because one of the models was very very consistent (the GFS) in showing no precipitation whatsoever for us. Well, they were definitely wrong. And we have gotten very cold. I just got a report from Nicholas Efthimiadis of an air temperature of 23 degrees with three inches of snow. The extremely cold weather and extreme warm weather in Alaska due to a huge ridge over the central Pacific that is making all this possible in the first place has given us something I thought I would never see in my lifetime. Barrow, Alaska, the northernmost point in the U.S. and well within the arctic circle (they are seeing no daylight right now) is warmer than us. That is truly phenomenal. They are 25 right now. We had a high of 32, they had a high of 34. I don't know what else to say but that I'm completely blown away. I can't ever recall a time of that happening.

So what is happening tonight?
Right now we have periods of light snow that I expect will intensify in the next hour or so. Now, most weather guys would tell you that and just end it there. But I'm not content. This blog is about explaining WHY some things happen, so that you can leave each read with a better understanding of Pacific Northwest weather and have an appreciation for it.

 As you can see, there are some snow showers around the area. There is not much upper-level motion in the atmosphere right now - that is: the precipitation isn't really moving - but as you can see, there is a fairly wide swath of snow to our north, with some embedded heavier rates (like the yellows you see). Now, this isn't moving much, but it is moving to the south very very slowly. Snow has already increased around my area, however. There is a good chance that this feature could give us quite a bit of snow, especially it stalls over us and intensifies. By quite a bit of snow, I mean above 4 inches. That is a possibility, particularly if this feature has a convective element to it. A convective element is pretty much instability in the atmosphere.

Alright, so we got that out of the way. What will happen tonight?
The models have been pretty consistent with wind. I haven't seen the new GFS come out, so this is the model from this morning, but I suspect that the forecast will now be for even higher winds because the low that did come in was MUCH stronger than forecast. I'm sure you were able to figure that one out. this will create tighter pressure gradients. I would not, under any circumstances, be surprised to see a 80 mph gust up by Bellingham. Even Seattlites will encounter brisk windchills in the teens with gusts up to 40 miles per hour, or perhaps even 50 miles per hour in spots. I will look again at the new models when they come out tonight and update this forecast. But anyways, here's a graphic for 10 P.M. tonight, showing some rather high wind gusts from the northeast, especially by Bellingham. Windchills there will be below 0 in most spots. Cold temperatures combined with losing power present a danger, so if you know people who lose power or do lose power, do things to keep warm. Start a fire. Get a blanket. Use a generator if you have one, but do NOT under any circumstances put the generator in your house. This causes asphyxiation and you will die.

The San Juans in particular will get pounded. There may be some freezing spray, so it is a very bad idea to be out there. Storm force winds and frigid temperatures. Don't be out there tonight.

Photo disclaimer - I LOVE Andy Wappler. This is just a photo one of my friends made satirizing all weathermen who claim there will be snow, then students don't do their hw, and then they get bad grades. I do NOT think any weatherman is a douchebag. But if I had a final and I was lazy and the snow forecast didn't consolidate, I'd be kinda tempted to call the weatherman a douchebag. If I mess up and your grades are affected, there is an official 24 hour window from the beginning of the school day to the next where you may call me a "Douchebag."

Of course, the issue of people hating weathermen is going to come up, although I think it applies more for when snow IS forecasted and doesn't come true. It's easy to say "why didn't we think this" in retrospect, but the fact is, weather is a prediction. You never for sure know what is going to happen until it already is happening. So the best we can do from events like this is learn from them, and if we see a similar situation evolving in the models, take it with a grain of salt, because our models are not perfect. There lies the main difference in forecasting between the two powerhouses of Pacific Northwest weather prediction, the National Weather Service's chief forecaster Brad Coleman and UW's atmospheric sciences professor extraordinaire Cliff Mass. Cliff goes with the models more, while Brad has more human input. I'm generally with Cliff, although I do definitely take historical context, satellite, radar, and other stuff into context. He does too. Two years ago, the models were forecasting snow, but it was a really chancy situation and nobody believed it would happen. NWS said slushy accumulation of an inch possible. I said we could have 4 inches. We got 6. It's hard though, so cut us some slack.

The snow is increasing and will continue to increase. Tomorrow will be VERY cold. I need to eat dinner with my family, but I will look to make another update later tonight. Recap - up to 4 more inches of snow is expected tonight as this feature moves down from the north, keep an eye out for convection, and wear a coat. And PHOTOGRAPHERS!!! Take some shots tomorrow, it will likely be the clearest day of the entire year. Extremely low humidities, and the mountains will have snow. Parents are getting anxious. Ciao. :)
Your local weatherman,
Charlie Phillips

FOR THOSE INTERESTED IN POSTING SNOW TOTALS - Post them as a comment. Hardly anybody comments on my blog. I'd like to change that!!!

Snow chances today and tomorrow

Sunday, November 21, 2010
12:28 P.M.

Hey guys. Some of you saw some snow flurries this morning. Some of you did not. It depends on where you live and your elevation. I say some flurries but no accumulation. It was pretty though.

Let's discuss snow probabilities. I read Cliff Mass' blog the other night and he said "forget about snow in Seattle, it's going to Oregon." He's probably right. The models which are usually more accurate (the Euro and GFS) have been showing this scenario, and they have been showing it consistently. The Canadian model has also been showing it as well. The latest 12z run of the UW 4 km GFS, our region's best model, shows absolutely no accumulating snow for Seattle (except traces).

Notice how there is a good amount of snow south of Olympia. But we don't get any.
However, the NAM model does paint a better picture for snow enthusiasts and school procrastinators around the region. It shows a bit of snow later today, maybe accumulating to an inch in spots, although most places will see no accumulation. The bigger story is the Puget Sound Convergence Zone that it is forecasting for Monday. The timing would be weird - it is forecast to occur during the morning of the school day. But it might deliver a few solid inches of snow to the area if it does verify. However, the NAM has not been consistent, and the GFS is the preferred model here. Sorry guys.

However, as you can see, through 4 P.M. Monday, it shows 1-3 inches of snow over Seattle. Your biggest tool here will be the radar. Keep your eyes peeled to the radar because we may not know what is actually going to happen until it actually is.

I need to do more hw, but I'll update this more if needed. However, that's most of it right there. Perhaps some snow, but not likely. Any snow we do have is likely to be focused on South Seattle with points north and south getting some as well.

However, the models aren't accounting for the large wave of hope providing HOPE on some of the clouds here as well as a possible arctic front of BELIEVE sweeping down from the north. Thanks will. :)

Have a nice day,
Charlie

UPDATE - 1:09 P.M. The National Weather Service now has a WINTER WEATHER ADVISORY for all of Western Washington. 1-3 inches expected Monday, according to them, and up to two inches in isolated spots tonight. I'm not sure if I believe it yet though...