Before I get into the juicy details of potential lowland snow this week (scroll down if you're impatient), I want to illustrate the stark contrast and extreme variability between two winter seasons at Mt. Washington on Vancouver Island.
The picture below taken in December 2012 shows nearly 4 metres of snow for a mid-mountain base. Absolutely incredible conditions last year that mountain staff and local skiiers and snowboarders are desperate to see return to their beloved mountain.
Normally, Mt. Washington competes for some of the deepest powder in North America (and sometimes the world), but this year, like most winter resorts in the Pacific Northwest they're struggling.
Current Snow Base: 25 cm
Hang in there.
Changes will come and it's extremely unlikely this atypical blocking pattern will continue for much longer. A return to more zonal flow is inevitable, and with it our normal Pacific Storms will dump their renowed champagne powder on our noble peaks.
As a kid during a possible snowfall event, I would stare outside at the brightest street lamp on the block, hoping to catch a glipse of the big wet flakes falling to the frozen pavement below illuminated with the light above. As you can tell, from a young age I was obsessed with weather.
First, we'll look at a model or two for some guidence to try and figure out the most likely outcome for lowland snow potential this Thursday and Friday.
Now we're within 72 hours of the snow event, we can begin to start taking these mesoscale deterministic snowfall maps a bit more seriously.
Let's check our lowland snow checklist:
1) Modified arctic air (yes, it's coming)
2) Impending warm front moving in from the N/NW
- Typical overrunning snowfall event is in the cards
The WRF-GFS is going for a widespread swath of 5-10 cm of accumulation, with closer to 15 cm around Campbell River and the Lower Mainland with a changeover to rain close to the strait Friday morning. Places inland such as Abbotsford and the inland sections of Vancouver Island can expect a transition to rain early in the afternoon on Friday.
I still prefer the short range ensemble and probabilistic forecasting techniques for this event to gauge how likely it will be that the deterministic model will verify. Ensemble forecasting is not a panacea, but rather just another useful guidence tool for the meteorologist to use.
The map below created by the Weather Prediction Center Probabilistic Winter Precipitation Guidence (Say that 5 times!), showing the likelyhood that more than 5 cm of snow will accumulate during the next 72 hours. Right now the Vancouver region is showing between 70-80% probability, and Abbotsford and Campbell River with greater than an 80% likelihood.
Still a fair amount uncertainy with this event, and some mixing of rain will be expected along the immediate coast which will diminish accumulation.
Also, this is the first heads up for a potentially very messy morning commute for Friday AM. School delays will be inevitable if the forecast models hold their ground with expected snowfall amounts.
As the event draws nearly, I'm also going to be relying on some high resolution Canadian models to get a better idea on precipitation type and intensity and when the expected transition to rain will occur.
But what do the SREF's say? There's still a fairly large spread (to be expected), ranging from 2-15 cm. One of these solutions is most likely correct, but which one it is remains to be seen.
We'll have to wait and see...
Another update will follow tomorrow night.
One thing is certain, I'll be checking that street light Thursday night for any signs of falling flakes.