Some notable shifts in the forecast models this morning has increased my confidence that we will see some decent snowfall totals in Western Washington. Portland friends – you’ll probably be seeing a variety of precipitation types throughout the week.

There was a pretty large difference in the storm tracks between the European (Euro) and the American (GFS) forecast models yesterday. The GFS was sending those storm systems well to our south, which would have kept us very cold but mainly dry. Meanwhile the Euro’s storm track was further north, which kept us a bit warmer but brought plentiful precipitation.

Today’s GFS runs have caved towards the Euro solution…in a rather bullish way with high snow totals, meaning the GFS has shifted the storm track further north which then brings more precipitation into Western Washington. We’ll see if the GFS sticks with this solution or flip flops again to something completely different than the Euro, but this morning’s trend was encouraging.

I’ll be breaking down what the models are currently showing for each chance of snow, but note that there is still plenty of time for totals to change, especially for systems at the end of the week.

System #1: Wednesday PM

An arctic front will drop southward into Western WA Wednesday afternoon, depending on how much convergence we get along that front, we could pick up some light snowfall accumulations. Right now, the Euro and the GFS aren’t sold on Seattle getting any accumulation with this. Some of our higher resolution models were showing hit or miss totals on the magnitude of 1-4” last night but have since backed off with totals between 0-1”. Arctic fronts are hit or miss in terms of precipitation, so we may end up with no snow at all, flakes in the air, or some accumulation. I’m leaning towards a drier solution with this one, but can’t rule out a dusting of snow with the best chance around Port Angeles Sequim where orographic lifting will aid in precipitation.

Regardless, this arctic front will open the door for that really cold air to start filtering into the Puget Sound region. High’s on Thursday will only make it into the mid 30s as our next storm system approaches

System #2: Thursday-Friday

A low pressure system approaches the Oregon coast during the day on Thursday bringing the moisture we want into the PNW. Snow will increase from the south during the morning reaching Seattle right around the middle of the day. Most of that snow will stay south of Seattle, with the bullseye between Seattle to Portland. There is still time for totals to change, but 1-4” of snow is a safe bet around Seattle, with 4-7” possible towards Olympia through Friday morning.

Portland folks, 1-4” of snow also seems reasonable with this storm system. However, that will be dependent on how much cold air gets pulled in from the gorge. PDX will probably start off with a rain or a mix of rain and snow, transitioning into some sleet and freezing rain, before then changing to snow. When that transition happens will then determine which end of totals you fall on.

Another caveat of this storm system is that it will create a strong cross cascade pressure gradient, which is great for bringing cold continental air into the western valleys, but also does a great job of drying the atmosphere out. This drying out of the atmosphere near the foothills will eat away at snow totals a bit with this weaker storm system. So for all of you on the eastside, you will probably see the lower end of snowfall totals with this one. This drying is noticeable in the 4km resolution UW WRF-GFS model, which shows those lower totals in green for the eastside.

Those Cascadia winds will be ripping again through the gaps in the terrain, so be prepared for gusty winds and bitter wind chills around North Bend, Snoqualmie, and Monroe. Fraser outflow will also crank up so those wind chills will be brutal up in Bellingham and the San Juan’s.

System #3: Friday PM – Saturday

Light snow Friday morning should taper off briefly before the “big” storm system approaches the coast Friday evening. This low pressure approaches further north towards the Washington coast before dropping further south, which will put Seattle in a better position for heavier snowfall. Right now models are showing snow starting in Seattle during the early morning hours on Saturday with steady snow falling for most of Saturday. Down in Portland it looks to be another mixed bag of precipitation with periods of snow, sleet, and freezing rain…downright messy!

With this storm being further out, we’re less confident on snowfall totals, but another 2-6” of snow in Seattle seems like a fairly safe/encompassing range to throw out right now. It is important to note that again, we will be battling that offshore flow eating away at snow totals in parts of the central sound, so some of those typical sweet spots for snow may end up on the lower end with these two storms. Below are the 24 hour snowfall totals ending at 10pm Saturday:

Looking at the ensemble’s, a notable chunk of members are throwing out some pretty big totals, so the possibility is there that this will be a major storm. That being said, this storm makes landfall further north than system #2 which means that there is a smaller margin of error. A few ensemble members do show that low going north towards BC which would bring warm southerly flow into the lowlands.

Like I said earlier, the 12z GFS went nuts, so some of the totals shown in the GEFS members (bottom chart) are extreme to say the least. The European EPS members (top chart) are more believable, but still have plenty of members with large totals.

System #4???

Some of the models, including today’s wild 12z GFS, want to keep the Puget Sound region cold enough for more snow Sunday afternoon into Monday before finally moderating to warmer temperature. Only time will tell for that one, and we’ve already got our hands full with the first few systems

Wrapping all of this up:

We are very confident that it is going to snow, and we are pretty confident that we’ll see accumulating snow of at least a few inches. We have a ton of cold air to work with to our north and east along with precipitation nearby. After a lackluster winter in the snow department, this is a pretty great setup to see. The chance that we see some major snowfall with this setup is there. While I would like to see a few more model runs showing better consistency, I think it is worth it to be ready for the chance of significant accumulations. It is going to be a fun and very wild week of PNW forecasting!