After 15 days without any measurable precipitation at YVR, the streak is highly in jeopardy come tomorrow.
You know what this means?
Ding Dong, the ridge is dead.
What We Know...
Our current ridge:
Back on January 21st, I wrote about the initial signs of a pattern change. Now it appears a frontal system will finally penetrate the ridiculous resilient upper ridge that is currently in the process of weakening.
The frontal system will also produce snow for Whistler mountain and lower freezing levels by Tuesday afternoon. I'm also confident Mount Washington will also see some snow (in the order of 10-15 cm), as it's desperately needed to cover the eroded base held together by the incessant work of the groomers. At the very least, ski hill operators will be thankful mountain temperatures will finally fall below 0C, and stay there for a prolonged amount of time.
We also know February is going to be significantly cooler than the weather that was experienced in Junuary, and depending on where the offshore ridge set's up, could deliver several NW tracking low pressure systems to the coast, coating our mountains (and lowlands for that matter) with much needed champagne powder.
Ensemble Vs. Deterministic Issues
I've also noticed a trend that must be addressed with regards to medium range weather forecasting (10-14 days) using strictly deterministic forecasts. Ensemble forecasting must be a part of a weather forecaster's tool box for attempting to predict weather outside the 7 day window. Posting a day-10 deterministic snowfall amount gives very little insight into what the weather will actually be like.
Especially in winter-like patterns, the deterministic computer models tend to have very little skill beyond 7 days. In summer, they've been getting better (ECMWF predicted Hurricane Sandy 10 days before landfall).
The deterministic forecasts (GFS,ECMWF,GEM, UKMET) run at a much higher resolution than the current ensemble prediction systems. This is great and all, but deterministic forecasts do not account for uncertainty. Model output is extremely sensitive to initial conditions. The small initial errors in observations paired with errors in several other parameters grow to become very large by about day 7 or 8;ultimately, this creates a very poor forecast if taken at face value.
I should also note, ensembles tend to underplay extreme weather events and smooth out extremes, so a very significant modified arctic outbreak may still be in the cards.
We still don't know, but the trend is there.
Current Ensemble Consensus
Current models suggest a significant cooling event during the first couple days of February and possible outflow conditions developing as well. It seems this winter is lacking such a typical jet stream position that delivers snow to our peaks. Either a ridge plops itself over our neck of the woods, or blocking pattern forms between 140-160W, but this pattern may allow low pressure systems to slide down the coast, depending on where the offshore block may eventually ends up.
In closing, February is looking much more dynamic and exciting for at least the first couple weeks -- a welcome change from our tranquil January. Stay tuned.