Wednesday, February 7, 2018

Curious Comparisons with Previous Snow Drought Years

After several days of cloudy weather, the 6 or so inches of recently new snow combined with bluebird skies this morning will probably make for one of the nicer ski days in about a week and a half.  I wish I was skiing, but I'm not, so I thought I'd dig into the archives for some curious comparisons of this year with previous snow drought year.

I will focus on SNOTEL observations from Snowbird, because they are convenient, although they only go back to the 1990 water year (the water year begins on 1 October and is denoted by the calendar year in which it ends) and changes in the site characteristics, exposure to wind transport, and other factors means that this isn't a perfect comparison.  Nevertheless, we shall plow forward.

At this site, we currently have 12.1 inches of snowpack water equivalent.  There are actually three other water years at or below the unlucky 13-inch mark on this date: 1992 (12.4"), 1994 (12.0"), and 2007 (11.2"). 

Of those water years, 1992 (mustard colored line) took a dramatically different path to sub-13" infamy.  It featured significant storminess in late October and November, reaching 10.4" of water equivalent on 3 December, which represents a robust early season snowpack.  Then the spigot turned off.  December and January were also only 1.4ºF warmer than the 20th century average in the northern mountains, so unlike this year, snowpack losses at lower elevations and on southern aspects were probably more limited compared to this year (although this is admittedly speculative). 

The 2007 water year also featured more early season snow than this year and it tracked near or just below median through mid December, when the spigot turned off.  Temperatures in December and January were 0.3ºC cooler than the 20th century average, so despite this being a poor snow year to date, the healthier holiday snowpack and cooler temperatures would have yielded better skiing overall than this year. 

So, if you are looking for an analog since 1990, 1994 is it.  That season tracked very close to this one, and featured intermittent storms separated by dry periods (note the sawtooth like pattern for both season).  It also was 2.9ºF warmer than the 20th century average temperature in December and January.  The National Centers for Environmental Information hasn't published the temperature numbers for January yet (they usually come around the 10th of the month), but one difference is that this year is probably going to be quite a bit warmer than that. 

A curious thing about the 1994 water year is that on January 5–6, Alta set the state record for 24-hour snowfall with 55.5" of snow.  Although the graph above is for Snowbird, this event is clearly evident in the trace.  The water content of that snow, based on measurements at Alta, was 3.2", for a water content of 5.8%.  In addition, that year featured a major storm cycle from Feb 8-12 when the snowpack water equivalent increased from 12.5 to 19 inches.  Several day's later, an avalanche fatality occurred on Peak 10420 near Brighton, with the run now named Lane's Leap after the victim.  I mention this as a reminder that even if we do get a game-changing storm cycle in the next few weeks, we are still probably going to be dealing with persistent, tricky avalanche conditions in the backcountry. 

As we look forward to the future, the NAEFS forecast plume shows nothing significant happening through the weekend from a precip perspective.  Maybe a few snow showers.  After that, perhaps a trough will flirt with us, although spread right now ranges from practically nothing to about an inch of water. 

Really, only 5 runs produce more than 0.6" of water and a foot of snow.  Thus, such a dump might not be impossible, but it is a low probability outcome.  As I've said many times this season, keep expectations low and hope for the best.  


  1. The most disturbing part seems to be that in all of those snow year analog searches, all of those other years experienced a significant surge in SWE in February. We don't seem to have a chance on that, given by some of the long range models, and echoed by CPC's 8-14 day outlook, taking us into the last few days of February. If that holds true, there will be no analog to this water year.

    1. Indeed. This comparison is based on the past, not the future, which continues to be bleak. I have weathered the poor snow year reasonably well until this past weekend. Thinking a road trip might be needed soon.