Monday, March 2, 2020

Quiet Work Week Ahead

Forecasts point to a fairly quiet work week with the storm-track to our north and high pressure in control. 

The NAEFS ensemble shows flat-line conditions (i.e., no precipitation) through the work week and then a lot of uncertainty about what will happen as the next trough moves into the western U.S. for the weekend. 

Temperatures look to be on the rise each day and will be quite mild near the end of the week.  Below is the NWS forecast for Salt Lake City.

Mountain Dell Nordic skiers should get out this week as I suspect it will be difficult to keep things going there after this coming weekend. 

The dry week also means losing additional ground relative to climatology in the upper-elevation snowpack race.  I've mentioned previously that things are not a lock for an above average spring runoff statewide and a look at the latest SNOTEL observations shows a somewhat mixed bag.  The central Wasatch and Oquirrhs have most sites at or above 90-100% of average for early March, but elsewhere, there are quite a few stations running below 90%. 

Thus, what happens from here depends strongly on the weather over the next 4-8 weeks.

Consider for example Parley's Summit.  That SNOTEL is actually just above peak median, which usually comes around April 1st.  Ideally, what happens from here is that it continues to accumulate snow and then the melt occurs quickly, maximizing runoff and reservoir recharge.  This is what happened last year (green line). 

On the opposite extreme, the spigot turns off and we warm up.  The melt occurs more slowly and the runoff is less efficient.  More snow is lost to sublimation. 

Even upper elevations remain vulnerable.  Snowbird at present sits at 37.1 inches of water equivalent.  This is well above median for the day (27.7 inches) and just a shade behind last year (37.3 inches). 

However, Snowbird is still behind peak median, which is 43.1 inches on May 1st.  Ideally the snowpack peaks then and we have an efficient spring runoff.  However, if the spigot shuts off early, we don't reach the median peak and the runoff is less efficient. 

The next few weeks it will be interesting to watch how things evolve.  Is this week a harbinger of things to come or a temporary week of spring fever?  Time will tell. 

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