October 17, 2016
As I write this, there are 9 inches of new snow at Timberline Lodge and the snow is still flying. We’re coming off two big windstorms and several days of stormy weather, including an EF-2 tornado on the Oregon coast at Manzanita.
I’m not predicting more tornadoes, but consider the last week a microcosm of the upcoming winter, and that bodes very well for Oregon snowpack and Oregon skiers.
Interestingly enough, after a summer of forecasts for La Nina this fall and winter, the La Nina watch was cancelled in September. But now, it’s back! Since we tend to do very well with Cascade snowpack in La Nina years, that’s one reason I’m forecasting an above average snowpack state-wide.
La Nina years, and importantly, years that are neither La Nina or El Nino years (we call these neutral years) tend to bring stormy winters to the Northwest. They tend to bring a lot of variability as well, meaning we can go from wet and cool to wet and warm to dry, with a few windstorms thrown in as well. Sounds like our weather form the last week, doesn’t it?
Below are a example of snowpack at Crater Lake in the southern Oregon Cascades (elevation 6500 feet) and Government Camp (elevation 4000 feet) on Mt Hood. I use these stations because there’s good data for these locations, they span the Oregon Cascades and give us a lower elevation (Government Camp) mountain site and a higher one.
First, let’s look at the last year, 2008-2009, that was a neutral, but La Nina leaning year. Meaning the metrics we use to define a La Nina were not met, but it was close.
Both sites started slow but really saw snowfall ramp up in December. You might recall this was the year of “Arctic Blast”, when deep snow also covered the Willamette Valley. Snowfall slowed down in January but ramped back up in February and March in northern Oregon. Government Camp picked up over 100” in March alone. So basically there was great snowpack all season long, but the freshies were found early and later in the season with a bit of a lull in January.
Remember, La Nina is an abnormal pattern of sea surface temperatures in the tropical Pacific Ocean that changes the heat and moisture distribution of the atmosphere, and therefore changes the position of the jet stream. There tends to be A LOT of variability in the Polar and Pacific jet stream positions in La Nina years, but also, a lot of storms that make landfall in the Northwest:
Next, let’s look at Cascade snowfall during the last La Nina year, 2010-2011:
Again, above average snowfall at both sites, with a bit of a flat line through January into mid-February. There’s that La Nina variability.
It’s highly likely we’re either headed into a weak to moderate La Nina, or a neutral (No Nino) year. Either way, both bode well for Oregon snowpack! I don’t have data for eastern Oregon, but we tend to get cold storms that move through the entire state in La Nina patterns and snowpack statewide usually benefits.
Considering the weather of the last week and what looks like an early start to our snowpack, I think there’s a better than average chance we’ll be skiing before Thanksgiving.
I think we’ll have well above average snowpack statewide, and solid low elevation snowpack too. I won’t be surprised to see another mid-winter lull, that seems to be a trend in recent winters regardless of El Nino, La Nina or No Nino.
Keep in mind, the absence or presence of a La Nina is not the only driver of our winter weather patterns. It’s just the one we most readily can recognize and quantify. There are other factors too. The “Blob” of warm water off the Oregon coast may be one factor, but the recent spate of storms is helping to mix the ocean and eliminate the blob, so I don’t think this will be a major player in our winter weather, especially at ski area elevations.
Bottom line: This should a great year to get a lot of use out of a season’s pass at your favorite ski area. As always, ski early and ski often. See ya on the slopes.
Matt Zaffino
Chief Meteorologist
KGW /KGW.com
[email protected]
