Saturday, September 12, 2015

Early Wet Snow

Snow mixed with rain was reported at Fairbanks airport today for a period of slightly less than one hour.  This is the earliest snowfall reported in the hourly (or sub-hourly) observations since 1992, the year of the great September snowfall and cold snap (when the permanent winter snowpack was established on the 13th, and 10" was on the ground by the 15th).

I should mention, though, that the official climate history contains a trace of snow on earlier dates on a number of occasions in more recent years, presumably due to a passing flurry or a few stray flakes in a rain shower.  We also have the 0.1" of snow that was reported on August 25, 1995, although the daily minimum temperature was 44°F - I'm not sure what happened there.

Accumulating snow was observed today at the higher elevations near Fairbanks, such as on Ester Dome (2400') and Cleary Summit on the Steese Highway (2233') - thanks to Brian for pointing out the latter.  Here are some webcam shots.

Ester Dome:

Cleary Summit:

The chilly conditions are a change from what has been a relatively mild month so far (after the cold spell of late August).  Soon, of course, the term "relatively mild" will take on a different meaning, as the peak rate of seasonal cooling is only a month away.

Update 10am Sep 13: There's a report of 3" of new snow this morning on Keystone Ridge by 8:45am, with heavy snow continuing.  Here's a photo, courtesy of Heather Hrawiec:


  1. Once again as discussed over the last 2 years, will early snow lead to a warm Nov-Dec? I'm skeptical of today's reported mixed rain and snow as the temperature was 37 but the dewpoint was 34, which is a real snow killer. The shower that brought the precip must have been intense and lapse rates must be high. The university webcam was reporting 37.1F at that time too and it's 300 feet above the airport...
    Also what are the odds of seeing 65 degrees again before real winter sets in? What about 60?

  2. In my experience, steady precip often turns to mixed snow+rain at 37F and all snow at about 35, assuming there is not a warm layer aloft. Heavy showers can of course bring brief snow at much higher temperatures, especially when it's dry as you note.

    If the snow doesn't accumulate at the airport, then it doesn't quite "count" for the previously discussed analog. But a warm Nov-Dec is certainly more likely than not, based on the warm Pacific patterns.

    I'll look up the 60/65F probabilities as soon as I have a chance.

    Mike - you've contributed to the discussion a few times over the years - just want to make sure you're aware of the invitation to get together next weekend (or thereabouts), when I'll be in Fairbanks. Let me know if you have interest.

    1. Richard I'd love to but I'm out of town for work until the 22nd.
      It snowed for sure today, dew points were lower and temps were just a few degrees cooler. (That was until warm air advection took over and ended the snow)

    2. Richard,
      If you are still around after the weekend that's a different story.

    3. Mike,

      My last full day will either be the 21st or 22nd, depending on the weather. So the 22nd may be a possibility. Email me if you want me to let you know.

      According to the 1930-2014 history, there is a 38% chance of reaching 65F again this year, and a 71% chance of reaching 60F again (Sep 15 onwards). However, with a cold forecast, the chances are much lower than that. Assuming neither will happen in the next 10 days, the chances are reduced to 6% and 32%.

    4. Thanks Richard! Like you said the cool down in the next few weeks is very rapid.

  3. There's a report of 3" of new snow this morning on Keystone Ridge by 8:45am, with heavy snow continuing.