Post Valentines Day Winter Update

February 14th is now behind us, leaving only 2 week to go in meteorological winter (consisting of December, January, and February) and also until the end of inversion season.  Although inversions can linger into early March, they are typically not the monsters that can exist through February.  

My impression is that this winter has been a little cold, but that's not supported by the observations from the Salt Lake City International Airport.  The mean temperature at the airport from December 1 to February 14 was 32.9˚F, which is comparable to the last two winters and the 39th warmest out of 149 winters since 1876, putting it ahead of 73% of the previous winters.  

Source: https://xmacis.rcc-acis.org/

The National Weather Service Salt Lake City Forecast Office has a nice graph that summarizes meteorological conditions at the airport for the water year, which begins on 1 October.  As shown below, the period from late December through mid January was generally warmer than average.  We've had a couple of excursions of cold, but nothing extreme (nor have we had extreme warmth).  

Source: https://www.weather.gov/slc/CliPlot

Basically, in terms of temperature at the airport, there isn't anything all that exceptional about this winter.  

What about the mountains?  Observations are not as complete at mountain sites, so I'll use the National Centers for Environmental Information divisional time series for the northern Mountains, which considers all available observations.  This covers December and January.  For those two months, the average temperature was 21.4˚F, just a shade above the 20th century mean of 20.9˚F (plotted) and a bit below the 1991-2020 average of 22.5˚F (not shown).  So, pretty close to average.  

Source: NCEI

Perhaps my impressions are also affected by snowfall.  Curiously at the airport, snowfall for the water year is currently almost right at average, with 38.7" so far.  I suspect that average is for 1991-2020, so perhaps we are actually a little below the 20th century average (I should calculate this, but I'm feeling lazy).  This despite precipitation being above average, so at least at the airport, the fraction of precipitation that has fallen as rain and/or the density of snow have been running higher than average.  

However, it has been a very good year at upper elevations, as everyone knows.  Basin-wide snowpacks are above median for February 14 statewide and in many cases well above median.  

That gives us a decent lead heading into the 4th quarter, but Mother Nature still has time to snatch defeat from the jaws of victory if she decides to give us a dry, warm March.  If you are rooting for the Great Salt Lake, you might notice that it is the Bear and Weber basins that have the smallest buffer relative to median, and they represent a majority of the Great Salt Lake inflow.  A look at how individual SNOTEL stations rate relative to the median water year peak shows many sites in the upper and lower Bear drainage ate still at 70-89% of peak.  

Thus, the natural snowpack "reservoir" is still not full at some sites.  Mother Nature still has time to snatch defeat from the jaws of victory if she shuts down the storm track and gives us a mild March and April.  For a big runoff, we really want the active pattern to continue until at least early April.  Let's hope that happens.  Good for skiing.  Good for runoff.  Good for the Great Salt Lake (assuming that water gets to the lake).