PORTLAND, Ore. (KOIN) – It’s the million dollar question. Will we see snow in Portland this winter?
The honest answer to that is it’s too hard to know that far in advance. Forecast models that can reliably predict snowfall amounts, months ahead of time, simply do not exist.
However, there are some methods that can be used to help provide a credible winter outlook, even if the snow is still a few months away. Long range forecasts are built using complex climate signals and weather trends over previous decades.
I spent the last few weeks diving into the trends to come up with my own winter outlook for the 2019-2020 winter season. Here are my thoughts:
El Niño Southern Oscillation (ENSO). What is it and why does it matter?
The first spot to look for winter weather cues is over the Pacific Ocean. Researchers have continued to track sea-surface temperatures along the tropical equator since the 1950s. The shifting body of warmer or colder than normal water is called the El Niño Southern Oscillation (ENSO). It can play a major role on influencing our winter weather in the Northern Hemisphere. For more details on ENSO, click here.
Current observations show we are in an ENSO-Neutral pattern that will likely continue through wintertime.
This is a bit unhelpful since neutral winters don’t provide much of a weather pattern to base a long range forecast on. El Niño winters tend to bring warmer and drier than normal conditions to the Pacific Northwest. As the counter part, La Niña winters tend to provide cooler and wetter weather to the Pacfic Northwest.
ENSO-Neutral winters can be bone dry or deliver the snowy goods to Portland. The only safe thing to say is that this winter will be a wild card.
Tracking Previous ENSO-Neutral Winters
To dive a little deeper, I looked at previous snowfall patterns for the past 20 ENSO-Neutral winters since the 1950s. Historically speaking, there have been several ENSO-Neutral winters providing 10+ inches of snow in Portland.
Note how many of the top snowy years at PDX include La Niña and ENSO-Neutral winters.
ENSO-Neutral winter odds also favor (at PDX):
- 30% chance for 10 inches or more
- 65% chance of at least 2 inches
- 25% chance of Trace amounts or 0 inches
And here’s a fun fact: Of our top 10 snowiest winters since 1980, 60% of them have come during an ENSO-Neutral winter. 20% during La Niña and 20% during El Niño.
I also took a closer look at five specific ENSO-Neutral winters following an El Niño winter. I called these my analog years, since they most closely resembled our current ENSO pattern.
On average, those winters provided an early start to the snow season with an active December and January.
Lowland Snow Outlook
So it’s a bit of a wild card here. Neutral winters have provided bone dry and snow free seasons, but also excessive snow at PDX. With that, I have hope for snow.
With the odds slightly more in favor of a couple big snow events in Portland, I think we will run the heavier side of snow this season. I’m betting we see one large snow event before the new year, and one or two after the new year.
Here is my official forecast — or let’s call this a “wishcast” — for snow in Portland (at PDX) this year.
What about ski season?
As for skiing this winter, ENSO-Neutral years have historically given near normal snowfall amounts throughout the winter season. The average opening date at Mt. Hood Meadows is around November 23. All ENSO-Neutral winters since 1980 have opened for business before Thanksgiving.
If you’re still on the fence about getting a season’s pass, I would say the odds are in favor of a fine snow season.
Lessons learned from last winter: Don’t buy into the hype
We all know what happened last winter in early February when a historic snowstorm with 14 inches was forecast in Portland a full week in advance. Word spread like wildfire. The city went nuts (for kale)!
The issue with sharing a snow total forecast too far in advance is that weather models are always refining their outputs with every model run. Model run updates come out about twice to four times per day (depending on the model) and tend to decrease their amounts each run.
So of course a weather graphic with 14 inches of snow over Portland went viral when one local news station decided to post an article on it. News of historic snow continued to spread to local newspapers, and then into our communities. People panicked, and soon enough, grocery stores had no kale left.
When the snow storm rolled through five days later, models had severely decreased forecast snow totals. A hefty 4.9 inches of snow did drop in the east Portland metro area, meanwhile the west side saw little to no snow at all.
It was a major forecast bust to everyone who still expected 14 inches of snow in Portland. Yet the burden was carried by every meteorologist regardless of whether they prematurely hyped up the excessive snow forecast or not. This is what all media meteorologists need to avoid doing this winter. It’s simply not okay.
So as we move into our snowier months, take any extended snow forecast with a grain of salt. We really don’t have much certainty on snow amounts more than 2 days out. #dontbuythehype