THE VALLEY
The winter of 2018-19 will likely see less than average snowfall in the Willamette Valley — but there’s a chance for at least one snow event in the valley before the end of 2018.
After the first of the year, the odds for warmer and drier weather increase, with a big ridge of high pressure possible.
There’s a potential for a lot of fog in the valley — caused by inversions — in January and February. There may even be offshore ridging if El Niño really takes hold.
The Willamette Valley will likely end up warmer than average when all the data between November and February is compiled. Or El Niño might not fully develop or we’ll end up in an ENSO neutral phase. If that happens, anything is possible.
When you consider we had a weak El Nino during 2014/15, it was certainly an active year for wind damage. According to the National Weather Service Portland, a windstorm on Oct. 25, 2014 delivered gusts up to 49 mph at PDX and caused power outages for about 140,000 customers in the metro area. On Dec. 14 a storm with 67 mph gusts measured at PDX knocked out power to about 85,000 customers. And a March 15, 2015 storm, again knocked out power with 58 mph gusts, leaving about 150,000 to 160,000 customers in the dark.
THE CASCADES
In an El Niño winter, snow pack in the Cascades tends to be below average. In fact, every El Niño since the 1970’s has produced below normal winter snowfall. Taking a look at the past six previous El Niño events, we can see this trend. There is one exception listed and that is the El Niño winter of ’06-’07. Many variables attribute to healthy snow pack and a good ski season in the Cascades. Skiers tend to like “powder days,” where light and fluffy snow drops from cold storms. With warmer temperatures predicted this winter, we may see fewer powder days and a snow pack that favors wet snow with a higher water content. This is great for our water supply and can also provide a safer and more stable snow profile in the back country.
THE COAST
Windstorms at the coast can happen during any ENSO phase. According to Washington State Climatologist, Nick Bond, a “strong EL Nino tends to get more wind storms. Weak to Moderate EL Nino phases are a real mixed bag. Tend to get fewer storms out of the NW/Gulf of Alaska, less shortwaves in general”.
What happens to local fisheries when the sea surface temperature is 1 – 2 degrees warmer than normal?
Bond says, “Right now our water temp is near normal but on the warmer side. Water temperatures are forecast to be warmer by Jan 1st. This is bad news for the marine ecosystem. Favored prey for salmon can’t thrive since salmon will migrate more slowly. Sea birds & mammals in general thrive more in cold weather waters”.
El Nino winters of 1982/83 and 1997/98 were so devastating to the Pacific Northwest because of the warming ocean. According to Bond, “a higher sea level at the equator moved along the coast which influenced the storm track”.
Could coastal populations be displaced by beach erosion this winter?
According to Bond, the “City of Astoria, Clatsop County are prone to coastal flooding. Winds ramp up, ocean temperatures are a little warmer, sea level is a little higher than normal. Flooding tends to be more common in El Nino winters. Strong ENSO can cause sea levels to rise 8-10” higher. Weak El Nino about 1-3″. Beach erosion has to do with the number of storms we see. Whether we’ll see more storms during El Nino is always hard to say. However, storms tend to point to California in El Nino”.
COLUMBIA RIVER GORGE
East winds and icing potential is the meteorologist’s cross to bear – always a tricky part of winter forecasting in Oregon and Washington. Cold wind paired with incoming moisture is a recipe for a snow or icing event for the metro.
The Gorge, some would say, is one of the most gorgeous passageways in the Pacific Northwest, as its mighty terrain features separate Oregon and Washington with the Columbia River. Travel 40 miles from west or east and you will find two completely different climates. This sliver of the PNW can turn paradise into a nightmare for travelers along I-84 in the winter.
The following information is a collection of 10 weak El Nino winter events, as determined by the Oceanic Nino Index standard. The information is a collection of weather variables (precipitation, snow, temperature) from two locations in the Columbia River Gorge during those 10 weak El Nino winter events.
Weak El Nino Years:
1952-1953
1953-1954
1958-1959
1969-1970
1976-1977
1977-1978
1979-1980
2004-2005
2006-2007
2014-2015
We examined historical data as far back as 1952 from two sides at opposite ends of the gorge. Bonneville Dam (Latitude = 45.6454 Longitude = -121.9523, elevation 62 feet, Multnomah County), and The Dalles (Latitude = 45.6069, Longitude = -121.2047, 150 feet, Wasco County).
Weak El Nino Results Location 1:
The Bonneville Dam on average will see around 33.68” of total precipitation. With a maximum of 56.52” in the 1952-1953 event, and a minimum of 12.30” recorded in the 1976-1977 event.
On average, around 16.38” of total snowfall. With an astonishing maximum of 67.3” from 1979-1980 and a minimum of 0.0” in 2006-2007.
The mean high temperature is 45.53 degrees, with a mean minimum temperature of 35.52 degrees.
One extra note, the 1979-1980 event was the coldest mean high temperature of 42.4 degrees and average minimum temperature of 33.5 degrees. As a result, this happened to be the same year that the massive snowfall total occurred.
Weak El Nino Results Location 2:
The Dalles mean total precipitation during the 10 events came out to 6.91”. With a maximum of 11.06” in 1977-1978 and a minimum of 1.51” in 1976-1977 event. With a mean total snowfall of 8.76”. With a maximum of 45.9” in the event of 1953-1954 and a minimum of 1.5” in 2006-2007. A mean maximum temperature of 46.1 degrees and a mean minimum of 31.9 degrees.
Conclusion:
Bonneville Dam vs The Dalles
Average Total Precipitation – 33.68” 6.91”
Average Snowfall – 16.38” 8.76”
Average High – 42.4 46.1
Average Minimum – 33.5 31.9
As expected, it is on average, more wet for those on the western edge of the Gorge than compared to those on the eastern side. With nearly double the amount of snow. High temperatures are slightly cooler, with a slightly warmer minimum temperature.
Additional Notes:
The last three weak El Nino events (2004-2005 / 2006-2007 / 2014-2015) brought lackluster snowfall totals to Bonneville Dam. With 2.3”, 0.0”, and 1.0” in respect to the year order above. Although it appears the pattern is trending that direction, there have been seven other weak El Nino years that produced over 5″ inches of snow with the outlier of 67.3” in 1979-1980. That being said, both 2006-2007 and 2014-2015 collected over 30” of total precipitation, leading to a mainly rainy winter event for the Gorge. February of 2014-2015 also brought an ice storm to the Western Gorge.