As mentioned before, a cursory analysis suggests that higher snow depth at the end of winter could explain the unexpected "resilience" of Fairbanks snow cover compared to earlier decades. And so we might hypothesize that snowfall has increased over time, but this is not borne out by the data; the chart below shows the March 15 snow depth (purple markers) and the accumulated snowfall (green markers) between the date of establishment of the winter snowpack and March 15. The long-term trend in snowfall is essentially zero, but there is a rising trend in snow depth (admittedly quite small - about 2.5" over the 90-year history).
What about liquid equivalent precipitation? If snow density has increased, then precipitation and snowpack water content may have increased despite no change in accumulated snowfall. Surprisingly, liquid equivalent precipitation also fails to show an increase over time, and in fact there is a slight decreasing trend, although that's mostly because of the incredibly wet winter of 1936-37.
So if precipitation and snowfall haven't increased, then is the snow depth trend just an artifact of changing measurement practices and/or location? Perhaps, but I'm inclined to believe that snow depth (and presumably snowpack water content) really have increased, because it helps explain the meltout dates.
If we take the ratio of the snow depth to total precipitation, we find a result that suggests there really has been a change in the characteristics of Fairbanks winter precipitation over time; recent decades have produced a notably higher end-of-winter snow depth per inch of precipitation in the previous winter.
Assuming that measurement practices are not to blame, there are only a couple of explanations I can think of here. One is that cloudiness may have increased, perhaps along with humidity, so that snow evaporation has declined and there is more snow left at the end of winter. There would be little actual melting of snow prior to March 15, but snowpack can be affected by sunshine, humidity, and wind. I wouldn't be surprised if cloudiness has increased, but rising temperatures typically dictate rising evaporation rates even if relative humidity increases a bit, so I am not sure how plausible this explanation is.
Another possibility is that Fairbanks used to see more of its winter precipitation as rain, not snow. Admittedly this seems like an absurd proposition, because freezing (or plain) rain has been a notable winter problem in recent years and seems unlikely to have occurred more often in the colder winters of the past. However, we do know that a few winters of long ago (e.g. 1936-37) produced some extreme rainfall events, so perhaps we shouldn't dismiss the idea out of hand. It may be conceivable that the recent climate has produced more of the winter's precipitation as snow, thereby contributing more to the snow pack - but more dense snow, so as not to increase the total snowfall (or else snow depth measuring practices have changed over time).
Can anyone suggest other aspects of the problem that I may have overlooked? It would be nice to be able to nail down a good explanation for why meltout dates have defied the long-term warming trend.