Thursday, October 7, 2010

December 2008 (Lots of snow discussions!)

December 30, 2008

This is a very difficult forecast to make. First of all, tonight and tomorrow, it will be rainy and windy. A winter storm warning is in effect for the mountains for 1-2 feet of snow. A typical winter storm... that's pretty much it.
The forecast for Thursday is SO complex and SO complicated. Usually, as time gets closer, models converge on a situation. Here, they have deverged. One model, the GFS, brought a 963 low into central Vancouver Island two days ago for Thursday. The NAM brought a weak 1000 mb low into SW Washington. That's a huge difference in strength, and a huge difference in track.
Now the models look like they have finally converged on a scenario, although they still are far from lining up. They take the low pretty much right over Seattle at 985 mb. The NAM is still weaker and the GFS is still stronger... but at least there is some agreement now.
All this confusion is because of different zones of low pressure forming around this swath of moisture. The GFS first brought one big low pressure center and the NAM brought three really close together. Now both of them bring two.
While this while relax the wind, it could make for some extremely heavy snow in the mountains. It could even make for some extremely heavy snow in the north interior. The NWS says NOTE THAT ON A
So if the low tracks further south, we could see some snow!
The whole thing is very confusing though, so stay tuned!

Deceber 25, 2008

I know its been a while since I have posted. I've been extremely busy with last minute shopping and Christmas stuff (not to mention tired out from all the previous weather). But I decided I better keep a regular schedule if I want people to keep reading my blog. Now that the snow for the lowlands is pretty much over, I'll resume to a more regular routine.
Its late and I'm wiped out, but the main story looks to be less snow down here, but a WHOLE lot of mountain snow. Friday/Saturday could have urban flooding as a lot of the snow melts and .5 inches of rain falls on top of it. The mountains meanwhile are going to get hammered. By Tuesday, it is possible that 5 FEET of snow will have fallen in some spots. Alpental opesn tomorrow, and I hope to be the first one on the slopes. Good night!

December 20, 2008
Actual: (too early again)
This is going to be crazy. This storm will be life-threatening.
As of 11:17 AM Saturday morning, the storm is moving faster than expected. New radar shows the leading edge of precipitation slowly making its way to the NW, with the leading edge near Olympia right now. This storm will dwarf the convergence zone we had on Thursday. Although snow totals here should be about the same, there will be NO question in your mind that this storm was clearly the greater of the two.
First, let’s get to some extremely low temperatures that occurred early this morning. This morning was EXTREMELY cold throughout Western Washington, due to the arctic air that was already in place and strong radiational cooling (cooling at night where heat radiates back into space). I never thought I would see this in my lifetime, but some places in Western Washington actually had lows below 0 degrees! Arlington had a reading of -3 this morning! Seattle had a low of 14. All this does for us is to up the chances that all precipitation will be snow. The cold temperatures alongside the faster-moving front confirm that we will see a mainly snow event without much sleet or freezing rain north of about the Tacoma area.
I’m typing this up on Microsoft Word to see if I can post pictures, which I haven’t been able to do on Facebook. Then I will copy this text and put it into the recent news section of my group on Facebook: we will see if the photos work! If they do, you probably will learn a lot more and get a greater in-depth look at what we are expecting as far as snow and wind.
This is a high-confidence scenario. Models have been remarkably consistent with the winds and precipitation, so there should be no questions about who will get the heaviest amounts of snow, how will get medium amounts, and who will get little or even none.
First, let’s break down the weather warnings in Western Washington.

Oops so that picture didn’t even work on Microsoft Word. What we are looking at is a BLIZZARD WARNING for the Olympics, Western Strait of Juan de Fuca, North Coast, West Slopes of the North Cascades and Passes, and West Slopes of the Central Cascades and Passes. This means that heavy snow with sustained winds over 35 mph is occurring or imminent. This is life threatening folks. Do NOT travel in this. You could die. Actually.
A lesser but still significant WINTER STORM WARNING is in place for all of Western Washington and Eastern Washington, apart from the Cascade foothills and Sequim where little or no snow is expected. Amounts here could range from 2 FEET by the Kitsap peninsula to 3 inches near Bellevue.
Why the huge range?
This storm is packing some potentially catastrophic easterly, downslope winds. Depending on where you live, these winds could either act to increase the amount of snow you will receive or decrease it. People living on the Kitsap peninsula will have these winds slam into the Olympics, creating an orographic (topographically induced) effect on snow totals, pushing them up. The foothills will have these same winds, but much stronger. However, they will be traveling DOWN mountains instead of traveling UP them, acting to decrease the snow totals here. Seattle will be between these two areas as far as snowfall is concerned, with anywhere from 3-8 inches likely. Sequim will be shadowed by the Olympics much like Seattle was on Wednesday, so they will see little, if any snow. I laugh at Sequim. :P
However, this storm is no laughing matter. This is SERIOUS. The media hyped up the storm earlier in the week about the same amount as this one. These storms are TOTALLY different. This storm is MUCH, MUCH stronger. Can’t stress that enough. Let’s see if I can post a UW model run of the amount of snow we are expecting.

As you can see, the highest amounts look to be in the mountains and on the Kitsap peninsula, with the lowest amounts by Sequim and the foothills, especially Enumclaw.
Alright, let’s get to wind.
As much as snow is a concern, my biggest concern is wind. Winds could reach HURRICANE force in places near the foothills. Here are some MM5-GFS model runs for the winds. Notice how they get stronger, peaking early Saturday night/early Sunday morning.

As you can see, the winds intensify through the afternoon. This last frame, which shows the winds at 2200 hours local time (10 PM) shows sustained winds of over 50 knots near the foothills, especially those like North Bend and Enumclaw. The winds should remain this strong until about 1 AM, when they will start to die, although still INCREDIBLY strong. I’m going to make an attempt to convince my mom to drive me out there at night so that I can experience and get some video footage of this. My mom is probably going to say no, and for good reason. This is very dangerous. Still, if I do go, you can bet I will be out there reporting with 80 mph gusts behind me and windchills of -25.
Cliff Mass says that the models often overestimate the strength of these winds, and forecasts sustained winds of 34-45 with gusts to 60-70. I’m going a little higher, with sustained winds 40-50 with gusts 70-80, possibly as high as 100 in isolated spots.
These winds will knock out power and cause extreme damage to foothill locations, especially those of MAPLE VALLEY, NORTH BEND, and ENUMCLAW (Enumclaw is generally the windiest foothill).
With the arrival of high winds and cold temperatures comes two other concerns: Frostbite/hypothermia and Carbon Monoxide poisoning. Windchills will approach -25 degrees Fahrenheit and power could be out for weeks. DO NOT PUT A GENERATOR IN YOUR HOUSE TO MAKE HEAT. PUT IT OUTSIDE. Carbon Monoxide is a colorless, odorless gas produced by combustibles. Remember how many deaths occurred in December 2006 because of our windstorm? This event is less widespread and people living in the foothills are more accustomed to these events, but I hope that the message gets out that Carbon Monoxide can kill you and you should NEVER be in an unventilated area with a generator or other combustible appliance.
That’s pretty much all for now. The extended looks cool and we may see some more snow, but not an event as dangerous as this. Long range models even showed some more arctic air masses working their way down through here next week. Hang on to your hats…
On a lighter note, here were some of the temperatures recorded this morning.
Univ of Washington 19
Mountlake Terrace 13
Lake Forest Park 9
Woodinville 8
S Everett 8
S Whidbey Island 8
Marysville 3
Arlington AP -3

Looks like pics didn't show, oh well. Can't have everything in life.

December 19, 2008
Predicted: 27 18
Actual: 27 20

Snow totals from this event can be found here:!/topic.php?uid=33875355514&topic=5804

I really needed a breather yesterday. That's why I didn't write a forecast. I love this group, but enough is enough (Emmett Akeley knows this for a fact). Of course, the forecast for the next few days is as challenging as the last, maybe even more. We will have a very warm Pacific system overrunning frigid air, and this could have a variety of effects for Seattle.
First, let me give my opinion on the weather events over the past couple of days, including what I did well and what I could have done better.
For Wednesday, the schools should have never canceled. The lack of snow was expected. We were supposed to see an inch at most, probably less. The problem is that the media ALWAYS overhypes snow events. When there is a CHANCE of snow, the media makes it seem like snow is CERTAIN. Of course, meteorologists have to do some things too. And I learned some lessons from that storm.
I should have emphasized the fact that we probably wouldn't see snow more. People were surpirsed that we didn't see snow but I wasn't. I thought I had made that clear. But looking back at my forecast, I realized that I really hadn't. So in the future, I will emphasize the FACTS about snow more, cause the media usually only acts to screw things up (cause that is how they make money, right? By having names like "Storm of the Century" and captivating the audience so they get more viewers). Next time, I will try to make this more clear.
Also, this storm reinforced my belief about convergence zones. You can often predict that they are going to happen, but it is hard to predict WHAT will happen. Wednesday night, while I was forecasting 1-5 inches of snow, Fox was forcasting 1/10. We were both wrong. Totals were more like 3-8 inches. The funny thing is my initial forecast was the most accurate... 3-6 inches. Funny how that works. People paint an intial forecast, then freak out as details change, but if they stayed with the initial forecast, they would have been more correct. I'm not saying that longer range forecasts are more accurate, in fact they never really are because model errors are magnified over the long run. Still, that's how it worked yesterday, even if it was by chance. That's called irony.
Remember how I was saying it wasn't really a convergence zone? That was exactly what happened. Instead of two winds colliding, the warmer southerly wind, since it was less dense than the colder northerly one, lifted over it. This lift created snow showers. This zone stayed over us for quite some time, dropping anywhere from 3-8 inches of snow over the Seattle area. I did a better job then most of forecasting this, but still, the NIGHT before, all models were saying we would get about 2 inches at the most. I got kinda lucky, and although there is definitely some skill, I just chose the right side. In reality, just cause I forecasted this event better than the NWS or tv stations doesn't mean I'm somehow more skilled than them. I most certainly am not. I'm a kid, and they are professionals. Except for Q13 Fox. They just suck in every regard. =D
Looking at the snow totals, it looks like the snow lottery winners in the Seattle area were Beacon Hill, with Amie Szeto from Beacon Hill reporting a little over 8 inches before it was all said and done. Of course, we had an accidental report of 4 feet from Sammy Lesnick, and Jamie Daudon posted a grand total of 60 feet from the Arctic circle, but these reports are questionable at best. Generally, the highes snow totals appeared to be right around Beacon Hill and Mt. Baker. Places further north, like Wallingford and Magnolia, only got 3-4 inches. Since the temperatures were below freezing all day, there wasn't that much of a variation in snow amounts with elevation (for once)
I was up all night of course waiting for snow... I woke up at 3 A.M., too excited to fall asleep again. I looked at the radar and saw a convergence zone (an actual one) forming right over my house. As it got stronger, it got wider, and the snow intensity increased. One common misconception that I have seen is that we received hail. We recieved something similar, but not the same. We received snow pellets, which are extremely common with convergence zones, actually more common than snow itself with narrow, intense ones.
At around 5 A.M., a HUGE lightning flash struck extremely close to my house... probably 40-100 yards away. There was no pause at all between the lightning and thunder, and the flash was nearly blinding. At first, I thought it was a huge power surge. It then began to snow very heavily. Shaken but not stirred, I continued checking the radar and chatting on facebook (which in retrospect was probably not smart at all). A minute later, another lightning flash struck very close to my house. This one was a little further away, but still extremely loud. At that point, I shut off my computer and all electronic appliences. I didn't want a power surge to ruin my computer, and I didn't want to get indirectly struck because I was holding an AC/DC appliance. I walked outside real quick (boy I am full of dumb ideas) to see if I could feel the charge in the air. I could, and my hair started to stand up. I actually think I explain somewhere in the discussion topics another experience with static electricity in which I almost get struck by lightning. It should be under "unusual weather experiences" or something. If it's not or you want to hear more, just write on the wall and I'll tell the story. :)
Alright... so let's get to the forecast... oh man... just remember that if I get this oen wrong, the fact that I got yesterday cancels out any egging opportunity. Sorry Max Elvis David and Christopher Swanson, but you may have to be eating omelets for the next 6 months.
So... the forecasting models show three possible major weather events here. First... a major windstorm could be on tap for the foothills of Western Washington. Models have slacked off a little on this one, but some are still adamant (the GFS) in bringing SUSTAINED winds of over 60 mph to some foothill locations (most notably, North Bend) with gusts approaching 100 mph. This would be an extraordinary wind event. Meanwhile, winds in Seattle would be much less, with gusts maybe over 45 mph. I'll talk about timing later, but the winds appear like they will be the worst late Saturday night and early Sunday morning, as the low pressure system approaches from the west and high pressure remains centered in Eastern Washington. This event has some serious potential, and you bet that I will be up in North Bend to capture some footage if we do indeed have the high winds that some models are forecasting.
Next... snow
We could see a much more widespread snow event. Seattle proper could see 1-6 inches of snow, and places like Hood Canal could see as much as 2 feet! Places like West Seattle will see much more snow than places like Bellevue. The further east you go, the lower the amounts will be.
Why, you may ask?
When air flows down, it warms and dries. It should still be very cold (since the air in Eastern Washington is so cold) but it should be VERY dry. This dry air will limit snowfall in those areas. Of course, Seattle is right between the areas where little snow is expected and where a ton is expected. So expect a steep gradient.
These overrunning events are extremely hard to forecast. Be on the lookout for meteorologists pushing back the start times for precipitation. This usually signals that the total snow accumulation will be rather limited. We really don't know how much snow we will get until the storm is actually on top of us and we can see how this storm interacts with the local terrain.
Third, we could see freezing rain...
And I just heard on the radio that Paris Hilton's house got broken and 2 million dollars worth of jewelery got stolen. Tell me why Paris Hilton has 2 million dollars worth of jewelery and people who actually do stuff, even if it's flipping burgers, live in poverty? Oh well...
Sorry. Back to the freezing rain, this will be a classic overrunning event, where warm Pacific air overruns cold, arctic air. What you can get is rain forming because the air aloft is warm, but then freezing as it hits the ground because the ground is still below freezing. Too early to go into depth about that... but it could happen.
These overrunning events are extremely difficult to forecast... but I have confidence that we will at least see some snow before it is all over. I may do an extended forecast later, but I've spent about 45 minutes writing this, and I'm ready for a break. The extended looks cool, but not cold, although we may see some colder air filling in after Sunday, which would again freeze snow to the roads, although not a hard freeze.
Jeez... this is a pretty good workout. I hope I don't throw up... jk
As of 12:34, pretty much all of Western Washington has a winter storm watch, and the eastern lowlands (mountain foothills) have high wind warnings.

December 17, 2008
Actual: (too early)

So... as soon as the new weather models came out last night, I really wanted to write a new forecast. I was really tired though, so I didn't. The new models showed two things: first, they showed an even stronger snow shadow over Seattle. A snow shadow is where air sinks and dries off of a mountain range (in this case the Olympics), leaving little moisture for areas downwind of them). Second, they showed warmer temperatures as the low pressure system moved further north than expected, bringing southerly winds with them. I had that "sinking feeling" that A.) There was going to be school tomorrow B.) I would end up with an egg on my face before the week was through and C.) I was going to have to suddenly do a lot of homework.
Luckily for me, the school districts don't know about the UW atmospheric sciences page! (I highly suggest you check it out, just google it and look at the forecasts)
Really though, I wasn't that off. Snow totals were an inch less than I expected, and I expected an inch.
I can't stress this enough though. DON'T GIVE UP HOPE!!! I EXPECT to see snow tonight, especially in north Seattle. A convergence-zone thing will occur, expect it's not really a classic convergence zone. It is more akin to a deformation band, which is diverging air aloft and converging air at the surface. Main point is... at around 7 P.M. tonight, temperatures will cool back below freezing and snow will begin. The band of snow will be centered in N. King/S. Snohomish counties, but it will slowly drift south.
Convergence zone snow amounts are extremely hard to predict. I actually believe that the worst case scenario would leave a foot in Seattle (best case for me). Anywhere from 1-5 inches looks more likely.
Alright I'm gonna go bench 5 Billion tons of weight right now, but I'll make another update when I'm done. Just wanted to explain what is going on, and that snow is still in the forecast.

Alright, it's 6:04, and I'm back. First, before I talk about the weather, I want to share a very funny story about my weightlifting. I had not had anything to eat this morning, so my blood sugar level was very low. I also had a VERY intense workout. So intense that I threw up. Once I started feeling nausea, I headed to the elevator to get on a floor with a restroom. I started feeling REALLY bad in the elevator. I hopped out on the 8th floor, looking for a restroom, and not having the sense to just look for a trash can (my mind was racing at that point). Suddenly, right in the middle of the sports bar, I threw up. I covered my mouth with my hand, still not thinking about the obvious; a trash can. A lady behind me saw me, had a startled look, and walked away. Suddenly, more volumes of gastric fluid lurched up my esophagus. I couldn't hold it no more. A plethora of (well, I don't want to gross you out... it wasn't too bad). Then, a little asian lady working at the counter got mad at me. She was like, "You throw up? Dummy!" I felt kinda bad and offered to help her, but I think she was worried I would throw up on her and make matters worse. I felt extremely sweaty, not only because I had just thrown up but because everybody was looking at me. At one point, a college kid with a hoodie walked out of the elevator and gave me the most despicable, contemptuous look. It was bad...
But hilarious in retrospect.
What does this have to do with weather, you might ask?
I wouldn't have been at the WAC weight room, and wouldn't of had this great story to tell, if the forecast wasn't so hard!
So what happened?
The problem in Seattle is that even when there is a slight chance of snow, the media hypes it up SO much. If there is a 50 percent chance of snow, they will say it is certain. And when that 50 percent doesn't come, the only ones not surprised are the meteorologists. I'm frankly not surprised at all that we didn't see any snow today. The Olympic snow shadow was in full effect today, blocking out ALL moisture headed towards our area. I thought it would block out most. I was only a little off, but since we are talking about snow, that effect gets magnified. It was also warmer than expected due to the low pressure system tracking more to our north, which brought a warmer southerly wind as opposed to a colder northerly one.
Tonight though, I am much more confident that we will get snow. And here's why...
Now, the Olympics will not act to limit our snowfall. They will help create it! But how, you might ask?
This nightmare for forecasters but hero for kids forms when a NW wind hits the Olympics and splits. One part goes into the Strait on Juan de Fuca, and another part goes through the Chehalis Gap. They meet in Western Washington, and when they meet, there is often precipitation (and often snow). The most often place for the PSCZ to meet is right on the Snohomish/King county line. Take a look at the radar right now. You will see a stationary band of snow from about Lake Forest Park north. This is the convergence zone. Over the course of this night, the convergence zone will shift down south, dropping anywhere from 1-5 inches of snow with it. This is a pretty wide range, and it is really hard to predict where the convergence zone will go. We could even get over 5 inches. And, of course, there is always that possibility that we could get none. But all in all, I am MUCH more confident that we will get snow tonight with this convergence zone. The only things that could really mess us up are if the convergence zone stays north and the air mass doesn't cool off as much. All models are in agreement that those things will not happen though.
Here's my time frame:
7-11 P.M. The convergence zone will be in full force, especially over northern king and southern Snohomish counties. Some places to the south will see light snow or mixed snow and rain showers, but these will increase in intensity and snow percentage due to the convergence zone sliding south and temperatures cooling.
11 PM-4 AM: The zone will shift south and stall over the Seattle area, bringing some snow with it.
4 AM-7 AM The zone may shift even further south, towards Sea-Tac or so, before finally fizzing out.
I hope I am right. If I'm not, I am going to be SCREWED tomorrow.
Do a snow dance... for me =)
No extended forecast tonight... do you really care what the weather is going to be like in a couple days? I'll continually update this page as new information comes in.

So the new weather models came in. And they brought some news with them. Drumroll…
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The snow still looks on track! A few details have changed though. The snow looks like it will arrive much later in the evening (well technically tomorrow morning). One model, the GFS, says the snow will arrive in Seattle at 3-4 AM and last for a couple hours, dropping approximately 1-2 inches of snow here. Another model, the NAM, says that the snow will arrive in Seattle at 6 AM and last a little longer with some higher snow totals… anywhere from 1-4 inches. I can’t stress this enough. Don’t freak out that it isn’t snowing now.
In the event that there is school tomorrow, bring eggs. Throw them at me. Or bring something to make fun of me. It would be hilarious. Especially people in band class. That would be AWESOME!!!
However, if I’m right, ya’ll gonna respect my authority. And I still think I’m we are gonna get snow tomorrow.
As for which model to go with, I am going with the NAM. This could complicate matters again because of timing… so again I don’t know what the school district is going to do. In any event… snow will stick to the roads.
Charlie Phillips thinks there will be snow, and Charlie Phillips thinks that there will be a complex decision to make by the school district. If all goes well though, there should be no school on Thursday.
Thank you God.

Updated at 10:17 P.M. Wednesday
I forgot to mention that even if we don't see a convergence zone, we could see a few pop-up showers that could drop some zone. In fact, the radar shows some headed towards us right now, but they also look to be fizzling out.
Talk about high stakes.
Hope to not see most of you tomorrow...

December 16, 2008
Predicted: 31 19
Actual: 31 20 (So close...)

Get ready...
Its been cold, but its been dry as well. There were probably fewer clouds in the sky than fingers on my hand the last two days. But here comes the moisture.
Here's a horrible joke that doesn't make sense at all.
Q: What do you get when you mix moisture and cold temperatures?
A: Snow!
That may be the worst joke I've ever told, and believe me, I've told some pretty bad ones. That wasn't even even a joke actually. That was just a statement of blatant obviousness determined to be a joke by yours truly. Maybe because it just fit into that form so perfectly, or maybe because I just love telling horrible jokes that only make sense literally.
Alright enough with the trigonometry... let's get off these tangents.
Tonight, clouds will be on the increase as a low pressure system drops down from Canada. This is the southern fringe of the system that will give us snow tomorrow.
Alright... enough of this cloud gibberish... let's get down to what matters.
Snow should first start in the northern zones at around 1 A.M., save perhaps a few isolated flurries before that. The snow should work its way into the Puget Sound area by 6 A.M. However, the snow in Seattle should be rather limited at first because of a snow shadowing effect off of the Olympics. So Seattle may get an inch from this storm, maybe more, maybe less. However, later in the day, a convergence-like zone will form north of Seattle, which could bring some snow there, and it will later drift down south through Seattle. As I believe I said yesterday, this could act to balance snow totals out. All in all, the Seattle area will probably see anywhere from 1.5-5.5 inches of snow. However, these amounts could be significantly higher if that convergence zone stalls over Seattle and is stronger than currently expected. Any snow that falls will stick to the roads. The roads are frigid and the temperatures will be at freezing or below. This could complicate the morning commutes for the rest of this week, especially Thursday and Friday.
All you students are probably wondering about school. Frankly, for Wednesday, I have no idea what the district will do. There should be some light snow in Seattle by 6-7 A.M., but not enough for it to really a problem on the roads. And the districts usually make their decisions at 4 in the morning or so, so there wouldn't be any snow on the ground then.
It all comes down to if the district decides to play it safe and foresee the snow situation, or if they take a risk. For that, I can only provide the forecast. The district, as you all know, has a mind of its own.
Thursday will almost certainly be a snow day. Friday should be one too, as the temperatures on Thursday will not climb above freezing. In fact, they will stay in the mid 20s. Even if Thursday is not a snow day, there is a small chance of a snow day Friday as one model showed a weak arctic front dropping down from the north, which would drop a quick inch of snow or so, and then freeze it solid to the roads. Only one model (NAM) showed this though, so the probability of this happening isn't terribly high.
Sunday, the models bring some more snow into the area. It doesn't look like quite as much as before, but it is really to early to pin down any amounts. I will have to wait a day or maybe two before I can begin to make any reasonable estimates.
Also, the extended now looks cool, and not cold. If the models are correct, we should be under the influence of a maritime polar airmass, not a continental one, as the trough in the jet stream that is giving us all this cold weather shifts over to the east. This would be a great pattern for snow to the mountains, with snow levels around 1,000 feet. That's about 1,000 higher than it is right now though.
Stay warm and do some snow dances!

Wednesday: 34 28 snow
Thursday: 31 27 snow showers
Friday: 27 18 mostly sunny
Saturday: 25 17 high clouds
Sunday: 32 25 snow

December 15, 2008
Predicted: 29 20
Actual: 30 20 (what now Jeff Renner)

Today was pretty cold. The coldest we've been in two years (we had a couple of days in 2006 that were about this temperature). It was cold, but it was sunny. There was hardly a cloud in the sky. That's usually the way it works in western washington. When we are cool, we are usually under the influence of a polar maritime airmass (storms coming from the Gulf of Alaska). But for us to get cold, we have to be under the influence of a polar continental airmass. And these airmasses are brought to us by domes of high pressure, because that is what arctic air is. The colder the air, the denser it is, and the denser the air, the higher pressure it is. Arctic highs have the highest high pressure of any high pressure systems. That was pretty bad wording, but basically it means that arctic high pressure systems are stronger than temperate or tropical ones, because the air involved with them is colder, and therefore denser. The higher the pressure, the harder it is for lift to occur, and lift is what creates condensation, and condensation creates clouds and precipitation. There were hardly any clouds in the sky today. This is another reason why it is hard to get snow here... when you finally do get cold temperatures, there's no moisture to be found.
But have no fear... clouds will soon reappear.
A low pressure system of moderate strength will drop down from Canada of Wednesday morning. All precipitation will be snow. Earlier we were thinking of more widespread 3-6 inch amounts, but new model guidance suggests a rain shadow over the Seattle area, which would give us amounts of 1-2 inches, while other places could get as much as 6-7 inches. However, a convergence zone may develop in the wake of this low pressure system, which could bring more snow to Seattle. So all in all, it MIGHT balance out. Convergence zones are very tricky to forecast though, so no guarentees. One thing for sure is that the Seattle metropolitan area will be shadowed from snow by the Olympics. Sorry people. We will still get snow though, and 1-2 inches of snow sticking on the roads is MORE than enough to close the schools.
About school closures... this system is coming in Wednesday morning at right about the time of the morning commute. This will make it tough to forecast if schools will close. Whether or not the close Wednesday, I think they will be closed Thursday and Friday. Even though we don't have a lot of snow, the road temperatures are very cold, and any snow that falls will stick to them.
Thursday=residual showers, much like Sunday.
Friday=REALLY cold... highs will struggle to get into the mid 20s as an even stronger arctic high dives down from Canada.
Saturday and Sunday: this is where things get really interesting. Models are all over the place on this one. The GFS model (American) shows a strong low pressure system coming to our north, which would give an initial period of heavy snow and then possibly change it over to rain. The ECMWF (European) shows a weaker low pressure system coming into our south, so we would have less precipitation, but more of it. Giving forecasts for snow would be like finding the needle in the haystack at this point, but the models suggest a snow event perhaps heavier than the one we will have on Wednesday. Heck, if you took an average of the two models, we could see some REALLY heavy snow.
After that, ANOTHER arctic air mass comes through. And snow falls on Christmas! Then another comes through. And another. The models have only been semi-consistent with this pattern, but still, we could be in the cold for a long time. Ice skating on that pond? How bout ice skating on Greenlake? (well probably not that cold)
Stay warm!

Tuesday: 31 19
Wednesday: 31 22
Thursday: 28 26
Friday: 26 18
Saturday: 31 21

Also, just to clear things up, the low temperatures are for the morning of the day. That means there is the morning low, and then the high. For example, the low on Tuesday would be Tuesday morning, not Wednesday morning. Not sure if you knew that, but this is just to clear up all confusion.

December 14, 2008
Predicted: 31 23
Actual: 30 26

The real cold has begun! Friday was cool, Saturday was cold, but today was really cold. And this week is gonna be RAW. This will be the longest, coldest stretch of weaher since 1990. For many of us, that means this will be the coldest Seattle weather we have faced in our life. People are all worried about whether it will snow or not, and I am too, but I'm excited about it being cold too. There is a little pond near my house that frequently freezes. I remember when we had an extended period of cold in 2004 and I could walk on it. I was in 7th heaven then. There's nothing like walking on something you see liquid all the time. I'm expecting to be able to walk on it again this year, and maybe even go ice skating. It's really shallow, so if I fall in, I will be EXTREMELY cold (and actually at a risk for hypothermia since the water will freeze to me after I get out) but I won't drown.
Monday and Tuesday will be frigid but dry and sunny. Nuff said.
Wednesday is where it gets interesting. A low pressure system drops down from the north, and with the cold temperatures in place, all precipitation will fall as snow, except maybe a mix over the coast. We can expect 3-6 inches of sticking snow with this system. It will stick to the roads as well since they are very cold. This storm could close the schools for sure, and Wednesday could very possibly be your last day of school for 2008 if winter break starts next week for you. Not guarenteeing anything of course, and you know how hard snow is to forecast, but at least we won't have to worry about temperatures being on the fringe.
Thursday will be a day of residual snow showers, much like today. Friday will be dry and probably even more cold than tomorrow or Tuesday. Another arctic air mass will dive southward, and this mass will be larger and colder than the one we are into right now. Expect temperatures in the mid to low 20s. Brr!
The weekend, and Sunday in particular, is where things get really interesting. A large Pacific storm will drop from the NW and come in just south of Seattle. This is nearly a perfect track for heavy snow in Seattle. Although the air mass will be warmer and snow isn't as sure of a bet as Wednesday, the snow will be a lot greater in quantity because this Pacific storm will have a lot more moisture than the one expected on Wednesday. Also, since it is coming just south of Seattle, winds here should be from the north, which would keep temperatures from warming too much and in fact just draw down more cold air. I am not saying this forecast is definite at this point, and models have been flip flopping around with it a lot. If the event happened as computer models show it today though, the Seattle area would see heavy snow with totals anywhere from 6-12 inches down to sea level. Cross your fingers, do some snow dances, but don't jinx it. The trick is balance. Appease the Snow God, but don't annoy him.

Monday: 29 20 partly sunny
Tuesday: 29 19 mostly sunny
Wednesday: 30 25 light snow
Thursday: 31 26 snow showers
Friday: 25 16 bitterly cold and sunny

December 13, 2008
Predicted: 36 22
Actual: Too early yet...

The initial storm has passed. Here are some of the peak gust from this storm as of 4 P.M. yesterday. The winds were definitely not over by this point, but this is the only data I could find.
Destruction Island: 95 mph
Forks: 69 mph
Hoquiam: 58 mph
Alki Beach: 52 mph
520 Bridge (Seattle): 51 mph
Oak Harbor: 49 mph
Seattle (Magnolia): 49 mph
Friday Harbor: 47 mph
Shelton: 46 mph
Seattle (Sand Point): 46 mph
Tacoma/McChord AFB: 46 mph
Bremerton: 45 mph
Tacoma/Gig Harbor (Narrows): 45 mph
Seattle (Sea-Tac): 45 mph
Everett: 43 mph

Winds were generally what I expected, except at Destruction Island. Destruction Island is a coastal headland that commonly gets some of the strongest winds in Washington. Almost hitting the triple digits though... that really demonstrates the power of this storm. As I think I said before, the upper level orientation of this storm wasn't favorable for extreme winds in the Puget Sound area, it was much more favorable for the coast and Strait of Juan de Fuca. When a storm is coming in from the SW (like most of our windstorms) a very strong gradient develops on the southern side, and the upper level movement of the storm helps to enhance the winds since the surface and upper-level winds are working with each other. With this storm, the gradient was there, but the upper-level winds were actually coming from the NW. Because of this, the strongest winds in many places occured after the low had passed, something pretty unusual, although not that unheard of, especially for the Strait of Juan de Fuca, which commonly receives strong surges of NW winds after the passage of a low pressure system. Still, it a sub 980 low were to come where it did but come out of the SW, winds in the I-5 corridor would have been MUCH stronger, with gusts as high as 80 mph. Still, the winds here were very impressive, and Lake Washington was quite a sight!
I don't mean to be cocky or anything, but I forecasted this storm better than EVERYBODY else, even the NWS and Cliff Mass. However, there are two things that are different with my situation. First of all, I got lucky. I simply chose to follow the right forecast model. Part of this was from thourough analyzation of satellite pictures, models, and historical situations, but still, I got lucky. Second, places like the NWS HAVE to issue winter storm warnings when there is a remote possibility of significant snow. If the low pressure system tracked further south, places in Western Washington could have seen up to 10 inches of snow. If this occured, I would probably get some eggs thrown at me on school on Monday. Imagine what would happen to the National Weather Service or TV stations.
But the bottom line is, I was right and they were wrong. :)

Now... the cold.
You probably haven't thought of 37 degrees as warm. That was the temperature at Sea-Tac this morning. However, that is probably the warmest it is going to get all week. We have a VERY cold week ahead of us.
Today, we do have a fair shot at getting some snow. An arctic boundry will drop south from Canada, and this could bring trace-3 inch amounts in the Puget Sound area. Forecast models this morning are weaker with this feature than before, but I still think that it will manage to drop some precipitation (probably graupel or snow) before it is all said and done. After this front passes, it will get really cold. Whatever snow there is on the roadways will freeze. Great news for students not wanting to go to school on Monday, and bad news for those trying to get to work.
Sunday, it will be a lot colder and a little drier. There will be some snow showers as a low pressure system to our south destabilizes the atmosphere, allowing for some pop up showers. While these showers will be few and far between, one thing will be certain: they will be in the form of snow. Let's hope a huge one hits the superintendent's house!
Monday-Wednesday next week is the real cold. Highs will be in the 20s, and lows will be in the teens. One feature that the models have been consistent with is a low pressure system dropping down from Canada. If this occurs, precipitation WILL be in the form of snow. For once, it is an easy forecast! We will still have to see if it happens, but if there is moisture then, it WILL fall in the form on snow. No questions asked.
After that low pressure system, another very cold arctic air mass will slide into Western Washington on top of the one we already have.
Long range forecasts suggest that we will be cold for a long time. Some long range models have hinted at HUGE snowfalls in Seattle on the weekend before Christmas. However, if we can't predict snow 6-12 hours in advance, what makes us think a week is like shooting apples in a barrel? Still, it's exciting. Bring on the snow!

Sunday: 31 23 few snow showers
Monday: 27 18 mostly sunny
Tuesday: 24 19 partly sunny
Wednesday: 30 26 snow
Thursday: 29 20 snow showers

December 11, 2008
Predicted: 47 39
Actual: 45 41

Wow! This is probably the most difficult forecast I have ever done. A TON has changed since I wrote last night. Right after I wrote about high winds for the Seattle area, new forecasting models came in and showed a whole new solution... the low coming into the SOUTH of our area. This would just bring us a lightish northerly wind... and increase our chances for snow. A winter storm watch was issued for Western Washington, and a wind advisory was not issued. However, the new model runs of the 00 NAM-MM5 model at the UW show an entirely different scenario: the low coming back up to the north again, and deeper. One way to tell how strong the winds will be is to look at the pressure gradient. A great measure of approximate wind speed is to look at the gradient between Portland. The NAM model shows a pressure gradient of 20 mb! That is huge... the biggest since the December 2006 Hanukah Eve storm. On the other hand, the new GFS model keeps the old scenario, with the low coming in near Hoquiam and weaker. This would give us weaker winds, and a better chance of snow. Personally, I would like higher winds over a increased snow chance, because I don't think that we would get snow in either scenario. The NAM model though... if that were to follow through there would be some very strong winds. One thing of note though... the movement of the storm is not conductive to a strong southerly wind. The storm is dropping in from the northwest, and this means that the upper level orientation of the storm will not match the surface level, and the winds will likely not be as strong. Still... 20 mb is an absolutely ludicrious pressure gradient. A lot will change between now and then, but this new solution just indicates how unique and complex this setup is. The models should be locking on something less than 24 hours out, but they haven't. Whether all hell breaks loose or nothing happens, there will be surprises that weren't forecast. That I can guarentee.
The high winds for the coast and strait are still looking on track. Waves on the coast will approach 30 feet!
Now to the snow... after the front passes, a convergence zone will likely develop in the wake of the low. With the cool and unstable air behind the front, expect snow levels to be dropped to the surface... or lower.
Just kidding... but seriously... this zone could spread heavy snow in a narrow band between Seattle and Everett. The placement of convergence zones is extremely hard to forecast... so the whole central/northern sound area should keep an eye out for snow.
After Friday night, the airmass will turn significantly cooler. Not yet super cold though. Showers will still be around, and these could be in the form of snow or a rain/snow mix. Saturday night, colder air will filter down from the north. Sunday, an arctic front may drop a quick inch of snow or two around the puget sound area. After the front, it could freeze solid. Next week will be extremely cold, with highs as low as the low to mid 20s and lows into the teens. More on all this later. The windstorm is the main focus for me right now, and I have a lot of homework to do as well. Stay tuned. :)

Friday: 42 33 stormy
Saturday: 36 22 snow showers
Sunday: 29 17 few snow showers
Monday: 25 18 sunny
Tuesday: 26 19 sunny

December 10, 2008
Predicted: N/A
Actual: 48 44

Wow! It has been a long time since I have posted. The weather has been SO boring that I have nearly forgotten about this group. But we have a LOT to talk about and a lot of action to occur over the next couple days. First, let's talk about Friday. As of now, there is a developing low pressure in the Gulf of Alaska that is going to drop to the southeast, pretty much right over western washington. There are three things this storm will do... it will bring 1-2 FEET of snow in the mountains above 1-2000 feet, it will bring a lot of wind, and it will usher in a maritime cool airmass, which in turn will usher in an arctic continental airmass.
First, let's talk about wind. I've been watching this system for some time and have been really intruiged by it. Models are switching rapidly but they've been remarkably consistent in general handling this storm. This storm will be driven by a strong jet stream and will represent the boundary between two strongly contrasting air masses. All these things support the cyclogenesis, or "bombing" of this low pressure system. Basically, this means that the low pressure system will intensify rapidly before it makes landfall. On wind, models are saying perhaps 70 knots sustained in isolated spots over the ocean. That's hurricane force. Let me repeat. That is hurricane force. The pressure of this storm, although not that deep (980-985 mb) is very compact. This means that the pressure changes are more pronounced, and there is a tighter gradient. The tighter the gradient, the stronger the winds.
The coast has a high wind watch for sustained winds of 30-50 mph with gusts to 65. There is also a high wind watch for the northern interior, with winds strong but a little lesser, maybe gusts from 50-60.
Nothing has been posted for Puget Sound so far, but there has been talk about maybe posting an advisory. People are forecasting winds of 25-35 mph with gusts to 45. I am going to go ahead and forecast higher winds though, winds 25-40 with gusts up to 55 and perhaps 60. I'm going to do this for three reasons: 1.) the low pressure system is moving very fast, which tends to speed up wind speeds. 2.) the low pressure is coming in very close proximity to Seattle, just a little north, which would put Seattle on the stronger southerly side of the storm. 3.) The flow may produce a mesolow on the lee side of the Olympics, which would speed up winds in Puget Sound and Hood Canal.
A lot can change between now and then, but for Puget Sound, the highest winds are forecast between 4-7 P.M. on Friday. Following the passage of the low pressure, storm force winds are possible over the Straight of Juan de Fuca and northern Puget Sound. These winds will be very strong (50-60 mph gusts) and WILL cause damage. Whether or not Seattle gets winds as strong as I am forecasting, high winds in the Strait are CERTAIN.
Snow: This system is going to bring gobs of snow to the mountains, which is great new, but snow levels will likely be too high for snow in the lowlands. Some snow may mix in, but it will not stick. If it were to snow anywhere, the higher elevation by Hood Canal would be a good bet.
Cold: Cold air will filter in behind the front on Saturday. Saturday will be cool, but not frigid. Highs will struggle to make it into the upper 30s, and with a few random showers about, most would be snow, especially at higher elevation. Saturday night and Sunday, a reinforcing shot of cold air may come in. An arctic front may bring some snow to sea level. Arctic fronts are weak and do not hold much moisture, but they can drop a quick inch of snow, and then freeze it solid in the storm's wake. Remember the Monday Night Football game in 2006? Seahawks vs. Green Bay? That snow fell to an arctic front, and once it passed, the arctic air froze everything solid in the storm's wake. We could see something similar to that, but it's not a sure bet. It's a long ways out. Forecasting models have been trending towards it, though. We will see what happens.
What happens after this?
We get VERY cold and dry. Highs next week will struggle to reach freezing, with lows into the upper teens and low 20s. If you have sensitive plants, protect them. Watch out for your pets too. Interestingly, models keep us cold and dry for a while. It is WAY to early to tell, but some more widespread lowland snow may occur at the end of next week.
Stay tuned...

Golly Gee! I almost forgot!
The convergence zone!
The convergence zone could bring SNOW Friday night/Saturday morning in the usual N. King S. Snohomish county areas. The snow could be fairly decent if the zone lasts for a while. Isn't weather so exciting?

Thursday: partly cloudy 47 39
Friday: stormy, mountain snow 41 35
Saturday: cool, rain/snow showers 37 27
Sunday: cold, few snow showers 33 23
Monday: REALLY cold and sunny 30 19

Scott Sistek's and Cliff Mass's weather blogs. They are chalk full of information. Google them. They are a GREAT resource.

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