Where Winter Weather Has Already Been Extreme This Season
Published: November 14, 2017
Winter hasn't technically arrived yet, but parts of the United States have already dealt with extreme winter weather conditions this fall.
According to the Accumulated Winter Season Severity Index (AWSSI), more than a dozen cities from Minnesota to the Pacific Northwest have seen an extreme season of cold and snow through early November.
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This index takes into account the "intensity and persistence of cold weather, the frequency and amount of snow and the amount and persistence of snow on the ground," the Midwest Regional Climate Center said. Wind and mixed precipitation, such as freezing rain, are not a part of the index.
For any given location, the start date of the winter season is defined as when the first measurable snowfall (at least 0.1 inches) occurs or when the first high temperature of 32 degrees or lower is recorded. The start date is Dec. 1 for any location that does not see either of those happen before that date.
The index uses five categories – mild, moderate, average, severe and extreme – to rate the severity of winter weather at any given point in the season.
AWSSI national index values as of Nov. 13, 2017. City locations are color-coded based on the severity of the season so far, as shown by the legend at the top.(Dr. Barbara Mayes Boustead and Steven Hilberg, Midwest Regional Climate Center)
"The categories are site-specific ... because what constitutes a severe winter, say, in Washington D.C. or Atlanta would be considered mild in Chicago or Minneapolis," said Dr. Barbara Mayes Boustead, a co-creator of the AWSSI and a forecaster at the National Weather Service in Omaha, Nebraska.
Across the northern tier of the Lower 48, 13 cities have had "extreme" winter weather conditions as of Nov. 13, according to the index, but several more have had "severe" winter conditions across the northern Great Basin, Plains and Great Lakes states.
Four cities have had a "mild" winter so far. Note that mild doesn't just refer to temperatures, but winter weather conditions have been mild compared to average, based on the index's factors mentioned above.
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Let's take a look at some individual cities and see just how harsh or mild their winter has been through this point in time.
The Harshest So Far: Upper Mississippi Valley, Northern Rockies, Northwest
Well-above-average snowfall played a role in the extreme winter misery that cities from the upper Mississippi Valley to the Pacific Northwest have seen so far. Temperatures have mainly been below average since late October, as well.
- Duluth, Minnesota: Duluth averages 86.1 inches of snow throughout the entire winter, according to 30-year average data (1981-2010) from the National Weather Service. Through Nov. 13, the city had already measured 20.5 inches, nearly one-quarter of its average seasonal snowfall – and it's not even Thanksgiving yet. Additionally, November's mean temperature was over 10 degrees below average through Nov. 13, featuring colder-than-average temperatures every day.
- Havre, Montana: Havre had picked up 17.5 inches of snow as of Nov. 13. The northern Montana city receives 39 inches of snow in an average winter, so it has already seen almost half of that in October and (not even half of) November alone. Temperatures were also running 17.6 degrees below average for November as of Nov. 13.
- Seattle: Seattle saw its third-earliest measurable snowfall in more than 120 years of records on Nov. 5 when 0.4 inches accumulated at Seattle-Tacoma International Airport. Snow is not typically seen in the Seattle area in early November. In addition, temperatures are generally running just over 2 degrees below average for the month of November through Nov. 13.
The black line shows the quick rise into the "extreme" category in Duluth, Minnesota, on the AWSSI due to the cold and snowy conditions so far this season.(Midwest Regional Climate Center)
Average, Moderate or Mild: Much of the Midwest and East
A lack of persistent cold and snow has played a role in the average, moderate or mild winter conditions that many other midwestern and eastern cities have seen to this point.
- Caribou, Maine: The northern Maine city is one of only two Lower 48 cities currently in the "mild" category of the AWSSI (the other is Alamosa, Colorado). Caribou has not yet picked up any measurable snowfall this season, with only a trace of snow recorded on both Nov. 7 and Nov. 10. That was nearly a month later than the average date of the first trace of snow, Oct. 12, and just shy of the record-latest date of Nov. 13, 1977. Also, October finished 8.1 degrees above average and was the warmest such month on record, according to the Southeast Regional Climate Center. The warmth continued into early November with a high of 62 degrees Nov. 3 and 61 degrees Nov. 6; average highs in early November are in the low to mid-40s.
- Elkins, West Virginia: Elkins is classified in the "moderate" category of the AWSSI as of Nov. 13. This city has also not seen measurable snow, though it picked up a trace of snowfall on Oct. 29 and Nov. 10. Additionally, above-average temperatures were generally in place for much of October and into the first week of November.
- Fairbanks, Alaska: One of two Alaska cities in the "mild" category of the AWSSI (the other is Utqiagvik, formerly Barrow), Fairbanks is not exactly lacking in snow, but November has been almost a top-10 warmest-to-date through Nov. 12, according to the Southeast Regional Climate Center. It has also been the fourth-warmest fall-to-date through Nov. 12, topped only by 1938, 1979 and 2002.
The black line shows that Caribou, Maine, is holding in the "mild" category on the AWSSI due to the lack of persistent cold and snowy conditions so far this season.(Midwest Regional Climate Center)
Brian Donegan is a digital meteorologist at weather.com. Follow him on Facebook, Twitter and Instagram.
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