Winter is Coming! Long Range Forecast by Matt Zaffino

Early season snow has begun to fall from Mt. Hood to Mt. Bachelor getting winter enthusiasts around the state (and country!) a buzz for another year of winter fun. Matt Zaffino, KGW Chief Meteorologist provided Ski Oregon and partners a long range winter forecast of what to expect in the coming months.

First off, yes, there is a strong El Nino brewing, in fact, it’s very strong. It may develop into the strongest on record. And yes there’s “The Blob”: a batch of warm water in the North Pacific (three actually) for a couple of years now. Here’s the latest:

El Nino is strengthening. The Blob appears to be weakening. This bodes well for El Nino to be a bigger influencer than The Blob for this winter. The Blob was likely a response to high pressure parked off the West Coast the last two winters, so it was an oceanic response to the atmosphere. Those are easier and more quickly restored to normal than an atmospheric response to oceanic conditions, which is what El Nino is.

So I favor the influence of El Nino over the influence of the Blob. This is good news for Oregon snowpack and rainfall this winter, I believe.

A little more background: the sample size for strong El Nino’s is.. wait for it… two. Yep, that’s it. Not exactly a statistically robust number. But it’s still interesting to see how Oregon did in those El Nino years. Looking at Mt Bachelor, it had way above average snowfall for the 1982-83 season, with 534” or 136% of average. For the 1997-98 the season snowfall totaled 333”, or 85% of average. Farther north and about 2,000 feet lower at Government Camp on Mt Hood, snowfall for the 1982-83 season was 74% of average, for 1997-98 it was 71% of average. Interestingly, just up the road but more importantly, back up in elevation to about 6,000 feet, Mt Hood Meadows did much better than Government Camp in both the 1982-83 and 1997-98 seasons:

1982-83 dumped 623 inches of snow at Meadows, a whopping 145% of the 429 inch average snowfall. 1997-98 brought a respectable 385 inches, or 90% of average.

This highlights two points: each El Nino is different from the next, but both of these strong El Nino’s favored higher elevation snowfall more than lower elevation snowfall.

The long range forecasts I’ve seen for the Northwest range from warm and dry (classic El Nino) to cold, wet and snowy by The Old Farmer’s Almanac. I’d be willing to bet against that one.

I think it’ll be a better year than last year for most of Oregon, but with some fairly dramatic differences across the state. As with most El Nino’s southern Oregon is likely to fare better than northern Oregon. But the strength of this El Nino and a few other factors make me optimistic for the entire state. I don’t think it’ll be an exceptionally cold year… too much west to southwesterly flow aloft. So, lower elevation ski areas are likely to suffer from that. I see the snow level consistently in the 4,000 – 5,000 foot range, not so much in the 1,000-2,000 foot range. From Mt Bachelor south I expect average to above average snowfall, from Mt Bachelor north, average to slightly below average. Northeast Oregon probably around average or slightly below.

If we get hammered early, say frequent storms and heavy snow in November to early December, don’t be surprised if it shuts off after that. I’ve often seen split flow develop after an early start like that, and then it remains pretty dry. This could be ok if we pile up a good base and then get good weather. At least the roads and access will be good. Message here is if we get the goods early, take advantage.

Unlike La Nina, El Nino is an amplification of the climatologically favored positions of the ridges and troughs we see in the atmosphere. So once a certain pattern develops, it can persist for weeks. That could be great news if it’s a massive west coast El Nino fire hose. But if the storm zone is focused more on say California, that may mean a long dry spell in Oregon.

• Better than last year for all of Oregon.
• Not a particularly cold winter.
• More snow from Mt Bachelor south. Should bode well for Mt Ashland.
• If there’s an early start, don’t take it for granted, take advantage.
• Best odds for low elevation (1,000-2,000 ft) snow may be in March, as El Nino should be weakening then.

Matt Zaffino

Chief Meteorologist