Cool....Cold....Coldest....Then Warmup?

Well, it's finally here. The cold snap I've been talking about since the end of November has arrived in a modest fashion, with YVR recording temperatures in the low single digits today (or upper 30's for my American readers). 

I have to give my accolades to the forecasting technologies available in 2013, that can effectively predict the future through state-of-the-art ensemble forecasting. Folks, this wasn't possible in the 1980's.

Look at the NAEFS ensembles from November 24th, already locking into the cold pattern we would start to experience an incredible 11 days later, with even some control members picking it up a little bit earlier. We've reached a point where picking up on these long term, large synoptic scale features is becoming the norm up to two weeks in advance!


How's our old friend the omega block (discussed earlier here), developing way out in the Pacific Ocean between 140-145W?

Remember, look for the Ω shape.


That's one healthy looking ridge (for now...), but in the next 72 hours, the right side of the omega block will bring significant troughing pattern to our region,  and with it bring some cold air advection into the Pacific Northwest. The amount of energy this system can bring down from the arctic into lower latitudes is monstrous, and it's the prime set-up to bring very low temperatures to the region from BC to California and beyond.

There's been a lot of hype around snow already, and I'd like to set the record straight.

Do I believe YVR will see snow from this cold event?


When? NO idea right now, still too early. I have my ideas with time frames, but I'm not confident we'll see a significant accumulation until after this weekend.

But, I'll give you a little tip, and if you don't mind pass it along to a few other people.

For example, last night a photo was widely circulated on social media showing a ginormous amount of forecasted snowfall for Seattle metro area last night, using the WRF-GFS forecast model:


If we were to derive a forecast of this one model, these are the ludicrous snowfall amounts:

Port Alberni, BC: ~ 32 inches

Vancouver, BC: 12-16 inches

Seattle Metro, Washington State: 16+ inches

I know it's sometimes fun to look at super long range forecasts and fantasize and hype what the weather could be, but one rule of thumb to go by for snowfall forecasts:

Ignore them if they're further than 72 hours out.


Don't pay attention to them. Seriously. The one above in particular is a whopping 180 hours into the future, where we can barely grasp where the cold and warm air will be.

To prove my point, here is the following run of the WRF-GFS. Little different, eh?


Take home message: Don't trust snowfall projections. Especially more than 72 hours out.

But how are the next 72 hours looking?

With model support, it's going to get a lot colder, but just how cold remains a little hard to nail down. One thing is clear, we have one healthy omega block; in fact, one of the most beautiful I've ever seen in my time tracking weather systems and storms:

Healthy Omega.png

The image above shows a lot of energy coming down from the Yukon and the Northwest Territories, and it's been ever so slightly shifting further west and digging a bit more, at least with the NAM runs.

This upper level trough is due in our region on Thursday, and flurries are expected along the coast. I'm expecting little to no accumulation, but there could be a few surprise locations picking up a few cm, but it will be very scattered and spotty. Stay updated on the short range forecasts. They will change.

Expected Temperatures


Temperatures Friday morning will be downright chilly away from the water. Temps at the 925 mb (700-800m ASL), are projected to be around -15C just east of YVR, with a lot of ensemble forecast agreement here.

This cold air is going to be entrenched in our area for some time, and will take a significant pattern change to scour out the cool, dense air. Even if the omega block moves eastward, cold air will remain in place below the planetary boundary layer (below 1.5km).

I still think when this is all said and done, will be a significant arctic outbreak for BC and the west coast, not only because it's relatively early, but also the length and projected cold temperatures.

There's also the possibility our beloved omega block gets 'pinched off,' which would throw yet another forecasting wrench into the long range forecasters. Most forecasters are being cautious and conservative and going with a gradual warm up, beginning early next week. Meteorologists in the public eye can't have the luxury to take as many forecasting risks, because they would quickly lose public support and trust.

 Latest NAM 00Z, shows the omega block being undercut by a trough at Saturday 12Z. Latest GFS, not so much.

Latest NAM 00Z, shows the omega block being undercut by a trough at Saturday 12Z. Latest GFS, not so much.

Let the fun begin. Stay warm, readers.

Fast facts:

  • 686 days since YVR has recorded a sub zero high (January 19th 2012)
  • Coldest temperature at YVR past 10 years
    • -15.2C December 2008
  • Coldest all time temperature at YVR
    • -17.8c in January 1950 and December 1968
  • Coldest recorded temperature since records have been kept
    • January 17th, 18th 1875: -20.5C (New Westminster Station)