With the main story focusing on the forecast, I'll use the blog to highlight some cool stuff going on amidst the madness, most recent post at the top.

Sunday 10:35 p.m.:
I guess our weather could be worse :) Look at what happened in Tulsa, Oklahoma Sunday as that arctic front went through there. How exactly should you dress?
 
At 2:53pm: 75 degrees
3:07pm: 63 degrees
3:24pm: 55 degrees
3:53pm: 50 degrees
4:53 pm: 38 degrees
5:53 pm: 30 degrees
6:53 pm: 27 degrees
8:27 pm: 25 degrees, freezing rain.
 
They actually set their record high that day. 5 hours later -- freezing rain :)

Sunday 10:35 a.m.:
You might have heard us in weeks' past highlight a volunteer weather spotter network called "CoCoRaHs" (Short of Community Collaborative Rain, Hail & Snow Network) where people can join and report daily rain, snow and hail, and then the data is all combined into one database, available to the public.

It works for snow too -- you can see what people in the network have been reporting at this link (defaults to King County) then just adjust the map to change it to snow and for whatever county you live in or are interested in.  By the way, they are still looking for volunteers! If you'd like to join, information is available on their site.

Saturday 12:35 p.m.:
So, just how cold was it in 1990?  You've probably heard the references that this will be the worst arctic outbreak since then.

On Dec. 18, arctic air moved into B.C., much like now.  A Convergence Zone formed right over Seattle dumped as much as 12-18" right over the city, with areas just to the north and south getting hardly any .

Arctic air then moved in via blasting winds through the Fraser River Valley, reaching as high as 60-70 mph in gusts. This left the Seattle area in the grips of a frigid air mass for six days.

Here is how those days played out:
Dec. 18: High of 41, low of 21, heavy snow
Dec. 19: High: 24; Low: 17
Dec. 20: High: 21, Low: 14
Dec. 21: High: 20, Low: 12
Dec. 22: High: 26, Low 15
Dec. 23: High 30, Low 18
Dec. 24: High 31, Low 24
Dec. 25: High 36, Low 29, light snow (official last "White Christmas" at Sea-Tac)

It was actually close to normal on the 26th and 27th, and then another shot of arctic air arrived:

Dec. 28: High 33, Low 12
Dec. 29: High 22, Low 12
Dec. 30: High 39, Low 20

They warmed back to normal on New Years' Eve and that was the end -- they actually warmed into the 50s by Jan. 11.

Here's the same stats for Bellingham: (Thanks to Alan for e-mailng this to me)

18th: High 41, Low 16; flurries
19th: High 16, Low 12
20th: High 17, Low 11
21st: High 21, Low 8
22nd: High 24, Low 12; light snow
23rd: High 30, Low 8
24th: High 30, Low 23; light snow
25th: High 32, Low 25; light snow

28th: High 21, Low 9
29th: High 22, Low 6; light snow
30th: High 38, Low 16; heavy snow

Saturday 12:15 p.m.
You've been hearing it bandied about this weekend: "Snow above 500 feet" or something similar.  Wondering what elevation your city is? Take a peek at this list I've compiled of area elevations.

I compiled this using Google Earth, so you can do this yourself if you've downloaded that program.

Saturday: 11:50 a.m.
Just how cold this arctic air mass? Here is a map of current temperatures. Note that Canada is the second largest nation in the world -- and the entire country save for a few cities on the fringes is below freezing! This map will update every hour at about 15 minutes past.

Saturday 8:40 a.m.:
If you look down the page here, there's an entry on where to find current conditions, which is also a great way to follow the arctic air. But here are some links to specific cities along the Fraser Valley to watch the arctic air drop down and temperatures plunge :)

First, orient yourself with a map of British Columbia:
http://www.canada-maps.org/british-columbia-map.htm

And here are the current conditions for a few cities along the valley:
Williams Lake
Lytton
Bellingham

Also, for weather geeks, watch the pressure gradients -- i.e., the difference in pressure in milibars between Bellingham (BLI) and Williams Lake (YWL) -- it's the table on the upper right and most recent is on top.  Anytime that gets into the -15 to -20 range, that means there's a very strong difference in pressure between those two cities, with the pressure some 15 to 20 milibars higher in Williams Lake than Bellingham, and a strong northeast wind follows.  That's generated because cold air is very dense and thus is associated with very high atmospheric pressure.

Friday 6:35 p.m:
How did today's weather look in real time? Here's Friday's time lapse from Dr. Dale Ireland in Silverdale. Note Ichiro over there in the corner. He'll stand guard through the weekend as a impromptu snow measuring stick, Dale says :)

Friday 6:20 p.m.
OK, so it didn't snow much down here, but it snowed plenty up in the mountains. Crystal Mountain says they will open Saturday for limited operations after getting 6" Friday. Meanwhile,  Mt. Baker will open on Sunday after receiving 12" with this storm and more expected overnight.

Here's a photo from Crystal Mountain:


Friday 3:10 p.m.
A beer tornado? Take a gander at what KOMO photographer Doug Pigsley captured on video in Downtown Seattle Friday afternoon in the gusty winds:

Friday 2:30 p.m.:
Here are some good places to find current wind reports:
* 520 Bridge
* Washington State Ferries

And this site from the UW is the holy grail. There's a link at the top of the page that gives what the station codes represent. Column "SP" is sustained speed, "GS" is gust. But on some, if you look over to the right in the comments field, there's a "PK WND" designation, which is the highest gust reported in the hour.

It's given as a few numbers, like: "PK WND 13041/2103".  The 130 is the wind direction on the compass (so, a southeast wind), the 41 is the speed in knots, and 2103 is the time recorded in UTC, which is 8 hours ahead of PST.  So in this case, which is Friday Harbor in their 2 p.m. observation, they had a peak hourly gust of 41 knots from 130 degrees at 1:03 p.m.  To convert knots to mph, multiply knots by 1.15. (so, 47 mph.) Finally, if you look in the URL, there's a "what=0" at the end. You can change that '0' to a number to get past hours -- i.e., if you change the 0 to a 1, you'll get the observations from one hour back. '2' is two hours, etc.

Friday 2:10 p.m.:
* Wow, talk about a wind shift. The storm just passed Forks just before 2 p.m. and the wind went from 20 mph to a gust of 69 mph! The temperature also dropped from 46 to 39 degrees in 23 minutes!  Destruction Island Lighthouse, out in the ocean off the north-central coast -- has been reporting gusts of 75-85 mph for several hours today.

Friday 1:15 p.m.:
* There was a classic rain shadow today as the storm's front pushed inland and we got a strong, southwest flow. Here is a visible satellite: 

That was caused by strong southwest flow that squeezes out its moisture when it goes up the southwesern side of the Olympic Mountains. The air then dries out when it sinks down the northeastern side of the Olympics. And note who is in the middle of that clearing hole? Sequim, as usual. There's a reason they only get 18" of rain a year :)

* Pressure was falling quite rapidly as this storm energized offshore. This photo is from my father's weather station in Port Angeles:

Note the pressure going straight down. Port Angeles' pressure dropped 37 millibars -- from 30.17 to 29.12 on the inches of mercury scale -- between midnight and 1pm. Amazing!

Friday: 10:00 a.m.:
* So we've been tossing a bunch of weather watches, warnings and advisories. But what to they all mean? Here is a link from the National Weather Service that will explain the definitions of the warnings being issued today. (Note, this link is from the Baltimore Nat'l Weather Service office, but the information applies nationwide, so this info is valid for Seattle.)

I'll keep adding tidbits here through Friday and the weekend.