Wednesday, November 4, 2015

Snow Arriving Right On Time For Snoqualmie Pass

Wednesday, November 4, 2015
6:02 pm

A view of foggy Snoqualmie Pass from Chair 2, Alpental. Credit: ME!

When I talk about snow in the Cascades, I often tend to focus on Snoqualmie Pass. This is probably because this is where I have skied most of my life (particularly Alpental), but Snoqualmie Pass is also the largest pass through the Cascades, with the exception of the Columbia River Gorge separating Oregon and Washington. Snoqualmie Pass is also the pass that will be most affected by global warming due to its low elevation. Snoqualmie Pass will never have another ski season after 2100; take it to the bank! They may get decent (by 22nd century standards) snowfall amounts on a particular year, but running a ski season will no longer be profitable. Temperatures will be too high.

However, we've still got 85 years to go until then, and we should get a few solid decades from Snoqualmie Pass before they demolish the chairlifts and relocate to Camp Muir. I'm no economist, but I know that our snowpack won't truly bite the dust until we get to the latter half of the century.

Credit: Cliff Mass

However, I do have good news for Snoqualmie Pass. I expect them to be open by Thanksgiving. Not only do the models agree with me... climatology agrees with me as well.

Credit: Western Regional Climate Center

The above graph shows the amount of snow on the ground at Snoqualmie Pass throughout the year. I know it isn't the most current graph; but it gets the point across. Around November 1, Snoqualmie Pass starts to build a snowpack, with the snowpack reaching a peak in mid-March and gradually melting away, finally doing so by June in all but the most extreme snow years.

The below graph shows the average snowfall per day. Again, snow generally starts accumulating in November, reaching a peak in January, and decreasing slightly until the beginning of April, at which point it begins to drop off more rapidly, essentially ending by mid-May (though as the blue line shows, there are exceptions!). 

Credit: Western Regional Climate Center

Here is another version that is less precise but is easier to read. It shows the average snowfall at Snoqualmie Pass by month from 1949-2009.

Average snowfall at Snoqualmie Pass per month (1949-2009). Credit: nwBroweather

Finally, here are some satellite pictures of snow depth from NOAA showing how much snow has fallen over the Cascades since our atmospheric river event on Halloween. Credit: National Operational Hydrologic Remote Sensing Center.

Even though a large portion of the Olympics and Cascades have gotten substantial snow, including Alpental and even the top of Summit Central, Snoqualmie Pass itself has yet to see snow. This will change early next week, when an upper-level low will slide into our area and give showers and cool temperatures to the region. Snow levels will fall around 3,000 feet, right where Snoqualmie Pass lies.

Valid 04:00 pm PST, Wed 11 Nov 2015 - 180hr Fcst. Credit: UW WRF-GFS

Additionally, as we continue to get cooler and darker, Eastern Washington will become significantly colder than western Washington, meaning that Snoqualmie Pass will become insulated from warmer Pacific systems sweeping the region when it has an easterly wind, keeping snow levels locally at pass level (or causing sleet/freezing rain). If Snoqualmie Pass did not have this effect, they would get much less snow. Areas near 3,000 feet on the Olympics are generally snow-free for much of the winter, and Snoqualmie Pass is actually colder during the winter than Paradise Ranger Station on Mt. Rainier at 5,400 feet (thank you Mattias Keese for the information). For example, Mt. Hebo in the Oregon Coast Range at 3,154 feet typically only has a couple feet of snow on it at various points throughout the winter, while Snoqualmie Pass averages eight feet by March.

The latest GFS model paints a pretty rainy picture for us through mid-late November, with a large atmospheric river near around Friday the 13th. While models are not good at predicting synoptic weather events more than a week in advance, they can predict trends, and they have been consistent with giving us some pretty wet weather at the end of next week. This precipitation would fall as rain at Snoqualmie Pass, but with a steady parade of storms off the Pacific and temperatures cooling quickly in the higher latitudes, I think that Summit West will be open to burn off some post-turkey calories.

Total accumulated rainfall from 00 UTC 11/5/2015 to 00 UTC 11/21/15. Credit: NCEP

Speaking of snow, the annual Northwest Snow and Avalanche Workshop is occurring this Sunday at the University of Washington. I've actually never gone, but I'm planning on going this year. Hopefully I will see some of you down there!


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