Blackcap Blog

Published at 19:38 on 19 February 2021

That is both my forecast and the official forecast. On the subject of the official forecasts, they are usually pretty good, and usually the same forecast I would give, were I a professional weather forecaster. The times I make a big stink are the times the official forecasts don’t make much sense to me.

Anyhow, if you’re planning outdoor activities, Saturday definitely sounds like the better day. The source of the moisture that will make Sunday (and the beginning of the work week) so wet is coming out of the tropical Pacific, so it will drag some relatively warmer air up our way with it. Expect some high temperatures in the fifties, maybe well into the fifties (Bellingham is often one of the warmest spots in Western Washington when a strong south wind is blowing, more on why that is the case sometime later).

That means snow levels will be rising, though at this time it seems likely they will stay (just) below the elevation of the Heather Meadows area. Still, if I were skiing, I would opt for Saturday. Some light snow which is drier because temperatures are still reliably below freezing sounds a lot nicer than copious amounts of heavy, wet “Cascade concrete” snow.

This will likely prove to be just a temporary mild interlude to a generally cool pattern that we are for the next several weeks. The long-range models have all been consistent with things staying on the cool side at least through the first half or March.

This also means that we’re not out of the woods quite yet when it comes to lowland snow; yes we can get lowland snow in March, sometimes significant amounts of it. I must emphasize, however, that at this time there is no specific indication of any such thing. The dice are merely loaded so that outcome has a higher chance than normal, that is all.

Published at 19:23 on 19 February 2021

A bit of introduction for the unaware is in order here: one of my many interests in the sciences is meteorology. As such, I follow a number of weather forums. Those with more money to their name than I subscribe to professional services that give access to raw forecasting model data.

Maps and other graphics were getting reposted to the forums from those professional services which showed something interesting was probably going to happen, curiously enough, right on the first day of winter: a powerful cold front would suddenly cause the snow level to drop to sea level. Since precipitation rates were forecast to be quite intense at the time, a few inches of wet snow were likely to accumulate.

More interesting is that both of the two historically most accurate forecasting models, the ECMWF and the GFS, converged on that scenario a few days out, and then kept on saying the same thing. It has long been my experience that when this happens, the forecast event almost always verifies. Yet the official forecasts, be they from the National Weather Service or Weather.com, had no mention of lowland snow that day.

That made no sense at all to me. Again, when both those models consistently agree on something, it really tends to happen. So I made a post about the likelihood of a snowfall to the /r/Bellingham Reddit forum. Skepticism ensued, followed quickly enough by flabbergasted amazement as “this guy on Reddit” forecast a snowfall that was not mentioned in any official forecasts.

Last weekend it happened again. The model guidance had converged quite nicely on a significant lowland snow event, with the vast majority of runs clustered right around the 6 to 8 inch range. The official forecasters only reluctantly started forecasting snow, and then only a few inches of it. This time the skepticism was tempered, because I had been right before.

I knew going into last weekend that if I was right a second time with a radically different forecast, a lot of people would have difficulty seeing me as something other than possessing supernatural powers, even though my logic for my forecasts was rather simple.

Eight to ten inches fell. My forecast was off, but only by a bit (10 inches of snow is not significantly more disruptive than 8). It is, however, way more disruptive than 3 inches, which was the high end of the range the official forecast was going for. So my status was assured. For now, at least.

Given that the community is now funding my access to the official forecast models, I owe them some at least semi-regular weather analyses, which I plan to post here.