Strait-effect Snow, Wind Chill, and Record-Breaking Cold


I'd like to start off this post by elaborating on a rare strait-effect snow event that happened during the early morning hours.

CYQQ (Comox Airport) observation:

METAR CYQQ 061400Z 30007KT 1/4SM +SN BKN005 OVC010 M04/M05 A3026 RMK SF5SF3 /S06/ SLP247

For those who speak 'METAR,' S06 denotes that a ferocious snow squall quickly moved over CYQQ during the early morning hours between 1300Z and 1400Z (5 and 6 am) and dumped 6 centimetres of snow in a single hour. +SN indeed! 

All schools in the Comox Valley were closed as a precaution, as the couple centimetres of snow compacted from the previous day, and froze with the arrival of a stronger arctic outflow event, and the quick, heavy snowfall on top of the ice made road conditions especially dangerous. I completely agree with the decision to postpone classes.

But what happened?

There's a very cold air mass of central BC right now. The pressure difference is higher than normal with the low pressure system passing to our south and that's helping draw the frigid air through a myriad of channels and mountain passes, including the largest, the Fraser River Gap.

This can create extremely localized snow squall events for Vancouver Island, similar to lake effect enhancement off the Great Lakes, creating the the early morning snowprize!

As the dense, frigid air meets the 'warm' waters of the Strait of Georgia, the stable air picks up some moisture, but it's still lacking that critical lifting mechanism to create clouds and subsequent precipitation. When air flowing out of Jervis Inlet slams even into a relatively small Texada Island, it can be enough to initiate the instability and convergence to initiate a narrow band of heavy snow. The mountains and rugged topography on Vancouver Island also cause orographic uplift, creating the necessary conditions for these severe squalls to linger. It's very hard to predict where these squalls will form, and they'll always be a challenge for forecasters.

I have to give credit to meteorologist Chris Doyle, as midway through this post, a tweet appeared in my twitter feed that is very pertinent to this post. Such perfect timing, and further emphasizes this dynamic event:

The Next 72 hours

  • FRIGID wind chills for Fraser Valley, up to -20 anticipated in the windiest of locations
  • Arctic outflow will slowly ease over the next 48 hours, lowering wind chill values
  • the omega blocking pattern we've been so accustomed to over the Pacific looks to fold like an aluminum can over the next few days (to the relief of every mountain resort in BC)
  • Potential next week for a significant winter storm to all coastal regions, but low confidence and high uncertainty at this time. No guarantees at this time
  • There's also uncertainty in how quickly we'll moderate and return to seasonal
    • models often overestimate how quickly we'll return to climate norms
    • I'll more inclined to go with a slow moderation and a return to above zero temperatures by next Wednesday or Thursday

Let's Talk Temperatures

Last time YVR had a temperature below -10C was in December 2008, and I believe there's a substantial chance for this low of a temperature the next couple of nights. If there was any snow cover whatsoever it would be easily within reach, but unfortunately the low pressure system yesterday was slightly too far west and the air was far too dry with the outflow winds.

So right now I'll peg it at a 50/50 probability at this time.

I expect temperature records to fall in Campbell River and Comox due to enhanced cooling with the snow cover, although those records the next several days are from a particular severe early season cold snap of 1972.

 925 mb temperatures approaching the mid negative teens along the coast for Saturday morning. Note how far south the zero degree isotherm extends into northern California

925 mb temperatures approaching the mid negative teens along the coast for Saturday morning. Note how far south the zero degree isotherm extends into northern California

But, I can tell you this. We're entering the longest SUB zero degree stretch for the South Coast since December 16th-22nd 2008. Exciting times!

Stay warm!

Next post I'll be discussing if there's a difference between a wet-cold and a dry-cold. One of the most common excuses I hear British Columbians use when discussing our cold snaps with the rest of Canada.

Or are we just wimps?

What do you think? Is there a noticeable difference? Have you traveled the country and experienced this wet-cold and dry cold difference? I'd like to hear about it.