Portland, Oregon, May Be America's Most Winter-Fatigued City in 2016-17

Jon Erdman
Published: January 17,2017

About halfway through meteorological winter, Portland, Oregon, might be the U.S. city most tired of winter this season.
"Isn't it much colder in parts of Alaska and North Dakota?" you might be asking. "Hasn't there been feet of snow in California's Sierra or Michigan's Upper Peninsula? Isn't Portland near the Pacific Ocean?"
Yes, that's all true, but compared to an average winter, Portland might be the most miserable location so far.
Hear me out on this.

Five Storms in Over Five Weeks

During some winters, certain areas become punching bags as stubborn patterns lock in for weeks, if not months. Probably the best recent example was New England's record-smashing snowy season of 2014-15, that included Boston.
Over the past five-plus weeks, four separate winter storms have plagued Oregon's largest city.

Named Winter Storms to Affect Portland, Oregon, December 2016 - Jan. 16, 2017

Caly (Dec. 8, 2016)	1 inch snow, 0.75 inch ice
Decima (Dec. 14, 2016)	2.3 inches snow (also, major Eugene, Oregon, ice storm)
Iras (Jan. 7-8, 2017)	0.4 inches snow; 0.5 inch ice
Jupiter (Jan. 10-11, 2017)	Up to 15.5 inches in metro

Winter Storm Helena just missed Portland, but dumped 20 inches of snow near Bend, Oregon, and led to some relatively rare snow along the southern Oregon coast.
Winter Storm Jupiter was an unexpectedly crippling snowstorm. The city's heaviest snowstorm since February 1995, Jupiter led to abandoned vehicles on snow-choked roads.
(MORE: Why Atmospheric Rivers Are Both Hazardous and Essential)

Tree branches, broken from the weight of heavy snow, are scattered on the ground of the park blocks across from the Portland Art Museum in Portland, Ore., Wednesday, Jan. 11, 2017.
(AP Photo/Don Ryan)

On Tuesday, Portland was under an ice storm warning from Winter Storm Kori, which would be the fifth winter storm in less than six weeks.
On average, Portland sees measurable snow four days a year. Through Monday, it has already had five such days this winter.
Following 8 inches of snow from Winter Storm Jupiter at the National Weather Service in Portland, at least 1 inch of snow remained on the ground through Monday, a streak of 7 straight days.
(MORE: 5 Things You Should Know About Ice Storms)
While you wouldn't bat an eye about this streak in, say, Minneapolis or Caribou, Maine, NOAA's ACIS database said there were only eight longer streaks on record at Portland International Airport or the NWS office, where official data is now taken, dating to 1940.

1. 29 days (Jan. 13 - Feb. 10, 1950)
2. 20 days (Jan. 20 - Feb. 8, 1949)
3. 13 days (Jan. 20 - Feb. 1, 1943)
4. 12 days (Jan. 27 - Feb. 7, 1956)
5. 10 days (Dec. 29, 1968 - Jan. 7, 1969)
6. 9 days (Dec. 19-27, 2008)
7. 8 days (Jan. 6-13, 2004 and Jan. 26 - Feb. 2, 1969)

Portland averages just two days each winter with at least 1 inch of snow.

Cold Streak

Given the number of winter storms, it's no surprise the winter has been much colder than usual for this somewhat maritime climate.
Through Monday, there hadn't been a single day warmer than average so far in 2017. That streak began on Dec. 28, a streak of 20 straight days colder than average.

Snow and ice cling to tree limbs as downtown Portland, Ore., is reflected in the Willamette River under blue skies, Thursday, Jan. 12, 2017.
(AP Photo/Don Ryan)

Going back further, 41 of the past 44 days from Dec. 4 through Monday were colder than average.
As of Tuesday morning, the city hadn't risen above freezing since the previous Thursday. The last time an entire calendar day stayed above freezing was Dec. 29, according to NWS-Portland.
Looking at the month of January so far, only 1979 had a colder January through the first 16 days of the month, according to the Southeast Regional Climate Center (SERCC).
If the month ended now, it would rank as the third-coldest month on record at Portland International Airport or the NWS office site, behind only January 1950 (27.0 degrees mean temperature) and January 1949 (27.7 degrees).
Finally, for "meteorological winter" (December through February), 2016-17 is second coldest through Monday, warmer than only 1978-79, according to SERCC.
Using a combination of snowfall, snow depth, and days with highs that fail to rise above freezing, the Midwest Regional Climate Center has computed the Accumulated Winter Season Severity Index (AWSSI), a winter misery index for several cities in the U.S. so far this winter.
While there is no data available for Portland, the MRCC has calculated an "extreme winter-to-date" in several Northwest cities, including Redmond, Oregon, Yakima, Washington, and Boise, Idaho.
(MORE: Where the Snow Season Has Already Topped 200 Inches)

Plot of the Accumulated Winter Season Severity Index (AWSSI) for the winter season-to-date through January 16, 2017, for Redmond, Oregon, indicated by the black line. The purple-shaded area of the graph indicates what AWSSI values are considered "extreme" for the season-to-date. The yellow-shaded area would be considered average.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 Why So Harsh a Winter?

Just 60 miles east of the Pacific Coast, it's usually no problem for milder, Pacific air to surge into the Portland metro area ahead of Pacific storms, shoving any cold air out of the way. This is why Portland averages only 4 inches of snow a year.

How cold air occasionally gets drawn into Oregon's Willamette Valley, including the city of Portland.

Occasionally, Arctic high pressure plunging south out of western Canada is so strong and deep that it doesn't simply bank against the eastern slopes of the Cascades, but squeezes through the Columbia River Gorge, which forms much of the border of Oregon and Washington.
In these cases, the cold air surges on strong easterly winds into the city of Portland, plunging southward into the rest of the Willamette Valley as far south as Eugene, or can even surge westward to the coast over the coastal ranges.
As discussed, this has been happening a lot this winter.
When this happens, cold air can get stuck in the valley for an extended time. Some Pacific frontal systems aren't strong enough to dislodge the cold Willamette Valley air.
Sometimes, these weaker systems simply reinforce the cold air supply from the Columbia Gorge. As a result, moisture overrides that cold air to wring out snow, sleet or freezing rain.
(MORE: Where Freezing Rain is Most Common in the U.S.)
Combine this persistent, pervasive cold air with an active western storm track, in contrast to recent past years dominated by a jet-stream blocking dome of high pressure, and you have a rough winter for the Northwest.
Recently, there's been a bit of a feedback loop in that the heavy snowpack, by local standards, from Winter Storm Jupiter hasn't allowed temperatures to warm up much. This raises the concern for ice from Winter Storm Kori.
With apologies to places also hard hit so far, such as Bismarck, North Dakota, Oregon's largest city has earned the "worst winter" title so far.

Jonathan Erdman is a senior meteorologist at weather.com and has been an incurable weather geek since a tornado narrowly missed his childhood home in Wisconsin at age 7.