Tuesday, September 30, 2014

Elevation-Dependent Snow

Fairbanks airport reported light snow for more than 12 hours this morning, but with temperatures no lower than 34 °F there was little or no accumulation on the valley bottom.  However, on UAF West Ridge, at over 600 feet elevation, the temperature was close to 32 °F and there was accumulation for a while before diurnal warming led to melting.  Up on Keystone Ridge (1600'), the accumulation was 3.5" by mid-afternoon.  See below for photos: the first courtesy of the Alaska Climate Research Center webcam this morning, and the second from Keystone Ridge at about noon AKDT.



In the 18-year history of observations on Keystone Ridge, measurable snow has been on the ground on September 30 on 9 occasions; and this snow remained throughout the winter in 6 of 9 cases.  So we might estimate approximately a two-thirds chance that today's snowfall represents the establishment of the permanent winter snowpack in the hills around Fairbanks; although with a healthy 3.5 inches reported, and below-normal temperatures expected by Friday, it seems the odds may be higher than that.

1 comment:

  1. This snow was interesting as it varied markedly by elevation as noted. While out driving the dog to a walk I saw cars covered with the stuff...likely residents from higher elevations than the valley floor.

    Looking up to the hills a few hundred feet above snow covered roofs were visibly common. None remains at in-town elevations as of 7 pm.

    I wonder how much of that retention difference depends on prevailing ground temperatures versus air temps? In other words, is the ground, structures, and vegetation currently warmer on the valley floor?

    Gary

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