Weather Blog

Day 3 Of Arctic Blast Watch

Day 3 Of Arctic Blast Watch
(This story has now been updated as a new entry in the blog. Read the new story here)

It's Day 3 of Arctic Blast Watch, and so far, we're still on track.

In fact, I'm actually quite amazed at the consistency of the forecasting models. They've been hinting at a change to cold weather for over a week now for this upcoming period, and the Friday through Sunday forecast has been remarkably consistent.

The biggest changes so far to the forecast are perhaps some strong wind now into the equation Friday, and some better hints at a little snow sometime next week. More on that below. (And there might be a little Christmas present from Mother Nature as well :) )

And how strong is this winter event, potentially? They're even freaking out about it in Los Angeles with one meteorologist there predicting this will be an arctic event not seen there since before 1950. (What does that exactly mean for Los Angeles? A high of only 59? :) )  That's a result of the arctic air dropping all the way down the West Coast.

As always, you the reader can put in your own forecasting notes and questions using the commenting features below. You can also e-mail me directly anytime at scotts@komonews.com and I can post the Q and A in the commenting field.

Anyway, the set up so far is still about the same as yesterday.  A big ridge of high pressure out in the Pacific Ocean is expected to drift to the west. That will push the jet stream way up north into Alaska, then down the backside of the ridge along the B.C. coast and into the Pacific Northwest. (Normally, that ridge is farther east, which shoves the arctic air farther east into the Rockies and Midwest)

That shift will allow a storm system to drop out of Alaska and the Yukon and move south along the B.C. coast and into Washington.

Here is the time-line, updated and tweaked Wednesday evening at 5 p.m. Friday Morning through Afternoon (Updated Wednesday evening)

With all the focus on snow and cold, I suppose we should start raising a bigger warning flag on the potential for wind on Friday, which is looking a bit more ominous than it has over the past few days.

Forecasting modes are showing the storm strengthen as it drops in from the northwest and turns inland somewhere between the central Washington Coast and southern Vancouver Island. (Not surprising it would be strengthening since it's got a lot of mild air in front of it and cold air behind it).

The preferred forecast solution right now is based on a track in the middle -- coming in over Forks and rolling right down the Strait of Juan de Fuca and into about Everett.  That's the scenario the following watches are based off of from the National Weather Service, but would need to be tweaked if the storm track drifts farther north or south:

A HIGH WIND WATCH is now in effect for the coast, Strait of Juan de Fuca, San Juan County and Western Whatcom County from Friday morning through early Saturday morning.  The coast could see northwest winds of 35-45 mph, gusting to 60 mph starting as early as 10 a.m.. These winds will last into the evening before tapering late Friday night.

For the Strait of Juan de Fuca areas (Joyce, Port Angeles, Sequim, Port Townsend), strong west winds may develop around noon of 25-35 mph, gusting to 50 mph, then perhaps increasing to gusts of 60 mph Friday evening before tapering off toward midnight.

For Whatcom/San Juan Counties, northwest wind will develop Friday afternoon and be 25-35 mph gusting as high as 50-60 mph.   These winds could be potentially more damaging than usual due to their northwest orientation along the coast and northern areas, instead of the typical south to southeast wind we associated with typical windstorms and the way the trees and natural landscape are braced to usually weather.

For the rest of the area, including Puget Sound and Southwestern Washington, wind speeds are expected to be out of the south and gust as high as 45-55 mph, likely in a 4-7 p.m. time frame for peak gusts, then slowly tapering toward midnight. A Wind Advisory may well be posted there as we get closer to the event.

Now, let's talk alternatives. One model last night had the low coming in around Hoquiam and cutting across Seattle. This would leave the coast in a weird situation where you'd have strong northwest winds along the north coast, and strong south winds along the south coast, and fairly calm in the middle. Same goes for I-5 corridor -- strong north winds north of the low, strong south winds south of the low, freakishly calm near the storm center.

Another model this afternoon had the low tracking across Vancouver Island and then into Vancouver, B.C.  This would throw the northwest winds out the window and give everyone the typical south to southwest wind, and be more widespread. In this case, all areas could see gusts to 50-55 mph, with the north coast perhaps hitting a few 60s.  But this model seems to have the low coming at us more due west than the northwest that most of the other forecasts had been pretty consistent in, so I think at this point, this is the less likely scenario.

Wait, There's More:

Aside from the wind, it will feature heavy mountain snow. A WINTER STORM WATCH has now been issued from Friday morning through Saturday morning for as much as 1-2 feet of snow, combined with strong wind and blowing snow. Snow levels will be way under pass level, so all passes will be affected.

With strong winds possible in the passes, this could make near whiteout conditions and pass travel very dangerous. I know it's a weekend, but if there's any way to get over the pass Thursday or very early Friday, by all means, go then.

Friday Night

As the storm passes, the wind will quickly slow down and shift to a more northerly direction and the cold Yukon air will rush in behind. This will still be close as to whether enough cold air gets here to make it snow in the lowlands while there is still some residual moisture left from the storm. I'd say at this point, snow levels will probably only make it down to about 500-700 feet. However, there are a few events in play that could make for snow down to the surface in a few spots.
 
First and foremost is a potential Convergence Zone late Friday evening and through the night. This could be enough of a trigger to bring snow to the ground in the North Seattle to Everett corridor and points east (especially since a good chunk of that area is 300-500 feet). Other places that could see some sea level-ish snow would be the Hood Canal area where you get upslope snow off the Olympics in a northeast wind scenario, or the Olympic Peninsula south of Highway 101, where you get some upsloping off the Olympics in a due north wind scenario. This will all depend on the wind pattern in the wake of the storm and the storm's track -- whether we'll get a northwest, north, or northeast wind. So this is a heads up.

Again, I think the main Seattle area would still be rain at this point as general snow levels will be over 500 feet without other help to make it lower, but we'll have to watch any Convergence Zones. Lows will be generally in the mid 30s, with a few spots near low 30s.

Saturday

Cooler air keeps pushing into the region, likely now dropping the snow levels near sea level by the afternoon. I'd expect a few showers around Saturday morning and midday, and they could be snow or a mix, with snow a better chance with a bit of elevation. It doesn't look like we'll be quite cold enough for sea level snow until the afternoon.

One wild card in this scenario is a secondary trough of low pressure dropping by. Right now, forecast models are still deciding whether it'll be close enough or have enough strength to bring any more moisture our way. The Tuesday evening models seemed to back off on this scenario, but the models Wednesday were trying to put it back on the table

If that trough ends up coming through closer, it could bring a greater chance of snow showers, or in addition, could help make the air unstable and we could get some "pop-up" snow showers, akin to those pop-up rain showers we get in the spring. High temperatures are only expected in the mid-upper 30s and breezy north winds will make it feel colder.

Saturday Night -- Clearing Out, Gettin' Cold

As Saturday night approaches, and cold air keeps pouring in, lows will drop well below freezing -- with mid 20s in the Seattle area and teens expected in the outlying areas. Depending on that trough, there could be a few snow showers still roaming around in the evening and early night hours.  Some recent models now hint this may be the case. Also in the realm -- We'll have to watch in case an arctic front drops out from the north as the next shot of cold air arrives. Sometimes that can put down a quick inch or two across the region. Anyway, whatever showers fall Saturday night would be snow down to the water, and it could freeze solid during the night.
 
Sunday -- Here Comes The Really Cold

Forecasts continue to trend with a increasing risk of snow showers here too, down to sea level, as that moisture still lingers around.  In the meantime, what we call an "arctic high" will have dropped down out of the Yukon and continue settling into British Columbia. This will bring a re-enforcing shot of cold air to the region, courtesy of the Fraser River Valley.

The Canadian Cascades will block most of the arctic air from just spilling into Western Washington, but there is a hole in the dam -- the Fraser River Valley, which extends from central B.C. into Whatcom County. This "leak" will allow that arctic air to flow into Western Washington. Those that live at the mouth of the valley -- Bellingham, Lynden, Ferndale, Sumas -- know this ritual well. It's like standing at the end of an icy blow drier.

So for Sunday, expect very cold weather. For most of Western Washington, highs will only be in the low 30s with a stiff north breeze of 15-30 mph (especially in the Puget Sound area) making wind chills even lower. But up in Whatcom County, I expect winds to be stronger -- not sure how strong yet, but probably 30 mph or so as that arctic air races out of the Fraser. Highs there will likely stay in the 20s, and wind chills will be much lower.

Sunday Night -- Cue Jack Frost

By now, we're dry,  but with the cold air in place and mostly clear skies, this could be the coldest night we've had in a while -- I haven't looked but I'll bet it might be colder than anything we saw last year. Lows in Seattle will likely drop to the low 20s, with teens widespread outside the city and perhaps even low-mid teens in the really cold spots like Olympia and in Bellingham.

Next Week -- Start Dreaming?

Monday, Tuesday and Wednesday all stay dry and cold with highs and lows similar to Sunday -- perhaps a little colder overnight Tuesday -- lows could get into the teens even in Seattle.

Beyond that, forecasting models are still not all on the same page, but there is increasing evidence that this cold pattern will last all through next week and possibly into the week beyond, leaving at least the door open for lowland snow, if only some moisture would pay us a visit.

Overall, it looks generally dry, but there is also some evidence that we could have some sort of lowland snow event sometime around the end of the week. Again, not too much consistency for details yet -- in fact, one Wednesday model backed off of it again, leaving us dry.  As you can see, I'm really sticking my neck out there to begin with trying to forecast snow around here more 7 days out there :)

(Other forecasters are probably reading this going: "He typed what?!?!?")  But as I've found, inquiring minds want to know. (And if the forecasts bust, I'll just distract you with some more cool Mt. Rainier photos and time lapses here in the blog.)

While my neck is stuck way out there, the very long range forecast, at least as of Tuesday night keeps us cold all the way through Christmas, and if you want to put stock in what a model shows 16 days out (not the smartest investment, but then again, look at your stock portfolio -- you could do worse) it actually shows a White Christmas.  Granted, forecasting snow 16 days out is akin to picking stocks via a dart board (see earlier parenthetical comment) but this is the first time in several years that I can remember a forecasting model even hinting at it, and it's been 18 years since our last White Christmas (1990, officially. 1996 was the day after. The fringe snow around the Sound last year doesn't count since it didn't hit Sea-Tac) so we're due!

On the other hand, Wednesday morning's version backs of the Christmas snow, instead perhaps a warming snow on the 22nd, but I'm sure it'll change 10 times between now and then. But at least it was on one forecast model run, so the computers thought it might be possible in some mathematical formula :)