January 28, 2017

Winter classified as extreme

From the National Weather Service, 

Winter So Far Classified as Extreme

   Probably no surprise, but the Accumulated Winter Season Severity Index has been classified as Extreme for Walla Walla and Yakima Washington and Pendleton and Redmond Oregon. 

   The index, developed by Dr. Barbara Mayes-Boustead with the National Weather Service in Omaha and Steve Hilberg with Midwestern Regional Climate Center, tracks the persistence and intensity of cold, snowfall, and snow depth and compares each winter going back to 1950-51. For a winter to be classified as "extreme", it must rank above the 95 percentile in severity.

   This winter starting December 1st has scored very high in the combination of intense cold and large snowfall. This, in turn, has kept snow on the ground for an unusually long period time.

   The index scores for Pendleton and Walla Walla were sitting around 375 early this week. Most years, it’s less than 150 at this time. Yakima’s index scored 425, well above the usual amount around 250. Redmond’s index scored 452, not too far off the record of 556 for this time of year.

   Just looking at the persistent cold, Pendleton normally has only 12 days where the temperature fails to reach 32 degrees during the daytime from December 1 to January 22. This winter there have been 24 days, just short of the record of 28 days set in 1985-86.

   For the same period, there have been 38 days with snow on the ground in Pendleton. Normally there are only 15 days of snow cover. The record is 52 days again set in 1985-86.

   Comparing to last winter, Yakima had a severe winter, while Redmond, Pendleton and Walla were classified with a mild or moderate winter season. More information is available by clicking the Resources tab at http://mrcc.isws.illinois.edu/

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