A well advertised snow event is on our doorstep for Vancouver Island and the Lower Mainland, but I can't quite tell you how much snow will fall. I'll show you why:
We look to three main computer models to look for clues on certainty and confidence when it comes to a specific forecast.
Snow forecasts are tricky in general. On the South Coast, the moist Pacific jet stream always wins out, but it's been suppressed and our flow is offshore. Look:
Model confidence is low on timing & track and temperature of the air aloft the Lower Mainland and Vancouver Island
- Puts a single 990 mb low west of Tofino late Thursday. By Friday night it's located close to Tofino before filling (weakening) near the NW tip of Washington State
- Keeps a dry outflow (keeping the atmosphere dry with winds blowing from the Interior) limiting the heaviest precipitation for parts of the LM. Also, warms the temperatures aloft the most so r/s mix and plain rain near the coastal sections for Friday with snow inland. This would still be a nasty snow event for parts of Vancouver Island
- Timing late Thursday, but the concern with this model remains the amount of warm air advection (WAA) from the southerly flow brought in by this system
- Much stronger low pressure system, but also eventually weakens (fills) near Forks, Washington
- Faster timing. By Thursday evening snow could begin for the Lower mainland, but this model is colder and continues snow through Friday and Saturday. Regions near the water could still mix with rain though. This is a true snow lovers solution for the LM and Vancouver Island. Potential for up to 30 cm for some in an solution like this
- Notice the three separate regions of circulations; much different than the other two models
- Therefore it creates the weakest low, but not the least amount of snow. We really don't want a strong low, snow lovers. This signature shows the system is not phasing the energy properly and takes on a double barrel (two center of lows)...
- Latest call time for snow (snow would start early Friday) with straight snow throughout the day. IN particular, this low and solution shows very heavy snow for the Victoria BC region that needs to be watched closely. I won't post those snowfall maps yet..
In closing, the GFS is too dry and warm at this moment and remains what is called an outlier. I favour the cooler and snowier models at this point. 5-15 cm feels good for the LM at this point through Saturday, but we can't rule out a little less or a little more at this point. Southern Vancouver Island is looking intriguing at this point. Confidence is still low-to-medium for specific snow amounts.
For those that asked: