Weather Blog

Only 1 more shopping day until Frigidness

Only 1 more shopping day until Frigidness
UPDATE: Several new watches and warnings have just been issued, including a Winter Storm Watch for several lowland areas for snow potentially as early as Friday afternoon or evening. I'm typing it up now, expect an update soon..

Boy, you look out the window today, and it hardly seems possible we're a mere 24 hours or so away from our first winter-like storm of the season. But I'm sure power crews are getting their people on standby, the sanding trucks are getting full of sand, and our TV reporters are making sure our blue KOMO all-weather jackets are clean and ready to report for duty.

But it's something snow and cold weather fans have been waiting for all winter. And they've got a legitimate gripe.  I mean, if it can already snow in Houston this December, and also in New Orleans, where 70 degrees in winter is fairly common, you have to figure us northerners should be allowed a little taste ourselves.

The forecasts Thursday morning are getting tweaked once again, as the forecasting models continue to play 3-card Monte with where this first storm will make landfall Friday. I had just written this nice, long forecast based on the where the forecast models last night had the storm going, because they were all consistent. And then the Thursday morning models came in and....

... now think the low will go in much farther south.  This potentially monkey-wrenches the wind forecast but possibly helps the snow forecast. (This is like spending two hours on the New York Times crossword puzzle, only to find you bonked a word toward the end and it affects 15 other words you put in and have to nearly start over :)

In the grand scheme of things, the forecast still remains set up for potential strong winds in places on Friday, potential snow showers in places Friday night through Sunday, and then everyone goes into the deep freeze Sunday through Wednesday at least.  In all, wind and cold will likely be this series of events' calling card, with snow probably just a bit player, although some are for sure hoping I've just jinxed it and we'll have 14" in spots.

Here is the (new) rundown, updated Thursday morning: Friday Morning through Afternoon

Wind and mountain snow are still the big story for Friday. The mountain snow is easy to predict -- there will be a lot. The wind is still proving to be a challenge.

Forecasting models late Wednesday night had everyone on the same page and it was the scenario we had been trumpeting as most likely anyway, so the forecast looked good.  But then two of the UW models Thursday morning now bring the low in much farther south. 

The storm is still expected to strengthen as it drops in from the west/northwest, reaching a center strength of about 980-985 millibars as it comes inland. That's a pretty good strength for a wind event around here, although not historical. (The big-big wind events of the past 50 years have had storm strengths in the 960-975 range). Still, this storm will be somewhat unique in that it's not taking a typical windstorm track,  in where the storm comes from the southwest and crosses east/northeast across Northwestern Washington and southern BC, giving everyone some form of a south wind.

In this case, the storm is expected to make landfall somewhere along the Washington coast -- originally between Forks and Hoquiam, but now this morning trending toward between Long Beach and Hoquiam. The low center will then track due east across the I-5 corridor, crossing the freeway somewhere between Tacoma and Longview.

This sets up a very weird situation where wind direction could vary as much as 180 degrees and speed could vary as much as 40-50 mph over a relatively short distance. That's because places near the center of the low might not have much wind at all, while places south of the low will have the strong south wind, and places north of the low could have a very strong north/northwest wind.  (As I mentioned, we usually don't have areas in our region on the north side of an intense, developing low. And in the past, when strong lows have gone in to the south, its track usually means a weaker north/northwest wind on its north side. The topography alignment of the Straits of Juan de Fuca and Georgia could also come into play in this exact scenario for strong winds up north.)

So that's the set up, here's the specifics:

A HIGH WIND WATCH remains 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., although latest forecasting models seem to delay the entire shebang about three hours from earlier forecasts, so perhaps Noon or so is a better start time here. These winds will last into the evening before tapering late Friday night.

Again, this will greatly depend on the track of the low.  The north and possibly central coast could end up getting a double whammy of gusty south/southeast winds in the midday hours then quickly turn to the north/northwest as the low passes by to your south.

For the Strait of Juan de Fuca areas (Joyce, Port Angeles, Sequim, Port Townsend), strong west winds may develop around 3-5 p.m. of 25-35 mph, gusting to 40-45 mph, then perhaps increasing to gusts of 50-55 (60?) mph late Friday evening before tapering off toward midnight. This is still based on a more northerly track of the low and it would not appear to be this bad if the low comes in where the models think Thursday morning. But still, it's best to prepare for the possibility.

For Whatcom/San Juan Counties, northwest wind will develop Friday evening. This still looks pretty good. How fast will be the question. The High Wind Watch is for 25-35 mph gusting as high as 50 mph, but if the low comes in down around Long Beach, the wind speeds would likely be less up here.

If strong winds do develop here, 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.

Southwestern Washington could end up being the wind winner here. With a Long Beach landfall it's Southwestern Washington and northern Oregon that would end up getting the brunt of the wind, with south winds perhaps gusting as high as 50-55 mph.

For the Puget Sound area, find your favorite dart board and let the dart fly.  With the low at this point expected to cross somewhere south of here, winds would likely be north and not as strong -- maybe 20-30 mph gusts. It could even end up calmer if the low comes up north right over the Seattle-Tacoma-Everett metro area, although I expect there to be some brief burst of gusty winds chasing after low once it passes into the Cascades.  We'll also have to watch for localized wind events with this low interacting with the varied terrain, but it's possible most of the Seattle area misses out on most of the wind party.

Now, let's talk alternatives.  Let's say the models change their mind and bring the low back north into the Hoquiam to Forks landfall. That would set up the original forecast of stronger winds up north and through the Strait.  So everyone be prepared for wind, but just know it's highly uncertain just exactly how this will shake out.

Wait, There's More:

Aside from the wind, it will feature heavy mountain snow. A WINTER STORM WATCH has remains in effect 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 all areas 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, but a more southerly track of the storm will help get the cooler air in here quicker, perhaps getting some rain/snow mix showers in Western Washington even during the very late evening and perhaps some straight snow near the Canadian border. I'd say at this point, snow levels will probably only make it down to about 500 feet in the Puget Sound area. 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 is still in the potential playbook and 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 or mix or a non-sticking snow 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.  I do suppose a heavier shower could knock down the snow levels briefly to the surface, but that would start to melt once the shower stopped and the snow level recovered back up a few hundred feet. 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, but again, a heavier shower or lingering convergence zone could trigger some snow in lower elevations.

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 -- Snow Showers Possible

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.  It also appears that we will still have some hit-and-miss showers running around, which would be all snow. 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

(Not much change here or beyond Thursday, but most of the focus has been on Friday's forecast so far. I'll take another peek at this later this morning.) 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 -- Find That Blanket

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 -- Maybe a little midweek snow?

Monday, and Tuesday 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.

Long range forecast models now show perhaps another weak system dropping out of the north on late Wednesday into Thursday. This would bring light snow showers to the region if it verifies. It'll bear watching.

Beyond that, the trend now is to gradually pull out of this arctic pattern by the following weekend, and as of now, the forecast models have backed off a White Christmas (boo!) although still rainy with mountain snow.  We'll keep watching that.   If nothing else, it'd be nice to at least ski by Christmas :)