Mini-Cold Snap with a Chance of Sky Dandruff

Latest WRF-GFS run shows plunging 925 mb temps. Anything after about 10 or 11 pm that falls will be in the form of wet snow. Problem? Right now, the GFS is bone-dry for Friday.

Latest WRF-GFS run shows plunging 925 mb temps. Anything after about 10 or 11 pm that falls will be in the form of wet snow. Problem? Right now, the GFS is bone-dry for Friday.

Okay, so as promised our Arctic cold front is right on schedule, and set to arrive to the South Coast late Friday night -- You'll probably sleep right through it when a piece of the polar vortex (a lobe I suppose?), breaks off and migrates over Western Canada. 

But, if you came to this blog for magical answers on if/when it's going to snow, you're out of luck and might as well stop reading...

It's only Wednesday, after all.

Some models show moisture Friday night, others don't, so it's just too early to make a call, especially for later on the weekend.

First Guess #YVR Temperature forecasts for this weekend

Friday: 9C

Saturday: 3C

Sunday: 4C

Monday: 4C

Nothing absurd, and definitely not what the GFS model was suggesting last night, so that's a relief...

The best chance for a classic overrunning snow event is Sunday into Monday, but a lot of uncertainty remains as of now.

But now, as I write this the WRF-GFS is trying to develop a weak low of northern Vancouver Island during the day on Saturday, so this also a possibility as the cold outflow air can be a catalyst for cyclogenesis off the coast. That cold outflow is also a bit of a double-edged sward. Although it cools the atmosphere and can fuel cyclogenesis, it also creates a very dry atmosphere that requires more moisture to reach saturation, especially over the Fraser Valley.  

There's no point doubling up an already excellent diagram, so I'll use Chris Doyle's annotated NAEFS drawing highlighting a period of concern for a potential high impact event, but details are fuzzy:

#50ShadesofVan