I know winter has just commenced, but after a brief bout of temperatures near seasonal a strong cool signal is anticipated to bring a renewed threat of snow to the South Coast of BC.
I'll break this down by the events:
1) Through Friday December 23rd
- A very robust upper level trough is snaking its way down the coast of BC. let's see where it is forecasted to be tomorrow morning using my favourite level of the atmosphere, the 500 mb level; consequently, you can see where each trough and ridge lies (see right).
- This is the most marginal snow event chance because it's still not quite cool enough for straight snow in most regions
- Light, wet flurries for parts of Vancouver overnight into Friday AM
- Things get more interesting for the LM tomorrow as the atmosphere cools and precipitation pivots into the forecast area
The common conundrum of the mild west coast will be present. As temperatures are beginning to cool enough for snow, the atmosphere will be in the process of drying, ultimately before outflow conditions take hold through Christmas. so, locally 5-cm of wet snow over higher terrain is possible through pre-dawn Saturday.
2) Boxing Day Impactful Snow?
Classic overrunning (Pacific moisture moves over cold air) snow event with a respectable low moving into Haida Gwaii on Boxing Day below 990 mb.
- Look for a classic 5-15 cm snow event for parts of Vancouver Island, less near sea level and southern sections, before ultimately changing to rain for most as the onshore flow becomes a little too strong with SE winds near the strait
- Snow will likely be delayed until later in the afternoon and into the early evening for Metro Van, but also watch for 5-15 cm range across lower mainland with less for SW regions through early on the 27th
- This has the potential to bring 20 cm to higher terrain including SFU and North Vancouver at this point...but preliminary numbers are a little dangerous to put out this far in advance
3) News Years Snow Threat?
Still too far out, but another cooling trend typical of the La Niña pattern looks to take hold during the New year which will bring more marginal snow treats and below seasonal temperatures to most of British Columbia
So there you have it. Lots of fun weather to track for the holiday season.