Snowpack Update: Slightly Low Today But More Snow is Expected

It is just past the new year and folks are wondering about our snowpack.  What is the current status?  Will La Nina give us abundant snow in the future?    This blog will take these questions on.

First, the current status.  Here is the percentage of normal of snowpack (from the wonderful SNOTEL web site).  Snow water equivalent (SWE) is shown, the amount of liquid water that would result from melting the snow/ice.   

Low values (less than 50% of normal) in Oregon, California, and Nevada.   But much better over WA state, at 75% to 100% of normal.  Low, but not significantly down.
A better view is found in an expanded image over WA State.  The Olympics and north Cascades are in good shape, but the central and southern Cascades are closer to 75% of normal.  Enough to open our ski areas and not to worry about water next summer.

The snow levels (elevation of hitting snow) on the western side of the Cascades are certainly higher than during  the past few years. 

I can demonstrate this with the NOAA snow analyses for the region for this and the past two years (below), showing you the snow depths on January 6 for 2016, 2017, and 2018. 

Much less this year. Less snow over the high plateau of eastern Oregon, and MUCH less over the middle to lower slopes of the Olympics and Cascades.

 Interestingly, the average conditions (temperature and precipitation) over the past 90 days have not been that unusual over WA state (see below), with temperature being near normal and precipitation above normal.  But averages can be deceiving, we just haven't gotten the right weather set-ups for snow:  much of the time we had high pressure (cold and dry), with occasional warm/wet periods.  Neither are great for snow accumulation in the mountains.

But there is great reason for hope.

This is a La Nina winter, and the effects of La Nina (more snow in our mountains) usually don't snap in until after the New Year.  The latest sea surface temperature anomalies (difference from normal) over the central tropical Pacific show we are firmly in a La Nina, with colder than normal ocean temperatures (see below).  La Nina's tend to produce cool/wet conditions over the Northwest: which means SNOW.

To put it another way, the atmospheric dice are weighted for Northwest snow!  What about the new model forecasts from the UW WRF forecast system?  (see below).  Encouraging.

For the next 72 hr, substantial snow (.5 to 3 feet) in the north Cascades and southern BC.

And even more for the next 3-day period (ending 4 AM Friday).

So if you enjoy skiing and winter sports, I would be optimistic.  Things are ok now, but may get very good during the next month.  But no guarantees.

Nighttime views of lake effect snow bands over Lake Superior

Suomi NPP VIIRS Day/Night Band (0.7 µm) images, with morning minimum temperatures at Embarrass, Minnesota [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) images, with morning minimum temperatures at Embarrass, Minnesota [click to enlarge]

Shown above are detailed nighttime views of multiple lake effect snow (LES) bands over Lake Superior, provided by Suomi NPP VIIRS Day/Night Band (0.7 µm) images on 04 January, 05 January and 06 January 2018. These “visible images at night” were possible due to ample illumination by the Moon, which was in the Waning Gibbous phase (at 92% of Full on 04 January, 84% of Full on 05 January and 75% of Full on 06 January). The continued flow of arctic air across the still-unfrozen waters of Lake Superior (and the other unfrozen Great Lakes) was responsible for the formation of these and a variety of other LES bands.

For perspective, the daily morning minimum temperatures at Embarrass, Minnesota are also plotted on the images — on these 3 days Embarrass was the coldest official site in the US (including Alaska).

The VIIRS images were captured by the Space Science and Engineering Center direct broadcast ground station.