I show this chart every time I visit a school:
It shows the past 14 winter’s worth of snow in Portland. Specifically at the NWS forecast office out in Parkrose. We all know it didn’t snow last winter (officially) of course. But often I’ll ask kids to point out anything interesting they see. Generally they point out two things.
1. Sometimes it snows a whole bunch in one winter here in Portland
2. There seems to be a pattern, with a heavy snowfall once every 5 years.
I think the first assumption is valid…every once in a while we get a “snowy” winter. Sometimes that’s just one storm or two. Other times it’s a collection of smaller snowfall events.
As for the 2nd? We’ve seen 4 winters with little/no snowfall here in Portland, is it time for THE BIG ONE? The short answer is that this is too small of a sample. Take a look at a chart going back another 14 years, that’s 28 winter’s worth of snowfall totals:
The “pattern” isn’t really a pattern is it? There is one error in the chart. 98-99 should read 2″, not zero. So we went 5 winters with little/no snowfall before the 2004 snowstorm (January). But then before that time it was a real mish-mash of snowfall. An occasional ZERO year followed by varying amounts. The last time we had 4 years with such a low total (little or nothing like the early 2000s) was from 73-77. During that 4 winter stretch only 1″ fell in Portland! That was the first time in Portland’s history.
So is it going to snow this winter? Statistically the odds would favor it, although if you add one more ZERO to the chart above for this coming winter, it would not be unprecedented. In fact if nothing fell for the next 3 winters, it would only match that spell in the 1970s. Let’s hope that’s not the case!
Chief Meteorologist Mark Nelsen