What does it take to melt a foot of snow?

This is a very pertinent question, given the current status of the weather. First of all, we are dodging a bullet for now, given the snow to our southwest and the massive inversion which kept temperatures yesterday in the teens and might keep us well below freezing most of today, even as temperatures aloft are well over 50 degrees! The chart below shows this; blue diagonal lines are temperatures gradients (in C) and the thick red line is the temperature at different levels of the atmosphere. Notice how it starts well below 0 but climbs, quickly, to above 10 (50F). (click the image to enlarge)

If it were going to be 50 for the next two weeks, well, bye bye snow. But it's not. According to the latest model run, the warmest air is in place right now through this afternoon—it's close to 60 (yes, 60 above) higher in the atmosphere, and it's probably 50-50 that it gets to freezing here at the surface today (the sky is still cloudy at 11:00 here in Saint Paul). And while it will remain rather warm for the next few weeks, this is by far the warmest day above, and by not mixing down those warm temperatures, we are really escaping the worst of it.

What happens beyond is a crapshoot. More sun would definitely aid in the depletion of the snow, as would more moisture. However, the models are being rather finicky on how much moisture is going to ride up in to the warm air. Last night, they were showing more than three inches of mostly-melted precipitation in the next two weeks. Now they are showing considerably less. And the most recent runs are showing a split flow with rather consistent temperatures topping our in the 30s for several days, but not skying towards 50 at any point (today would have been the day, but the inversion is helping us). And the temperatures, at least in the short term, should follow a nice diurnal pattern, so that lows will be around 18 around dawn, peak around freezing in the afternoon, and then fall off quickly. This is not a recipe for snow depth disaster.

In any case, back in December I ran the data to look at snow depth during the past 100 years in the Twin Cities. With the current situation, I am going to delve back in to that data and look at what it takes to melt snow in January. I'll look back to find Januaries with snow depths of at least 8 inches, and see what the weather was following. In other words, I want to know what it would take, weather-wise, to melt our base.

(Why just January? In January the sun is within a few degrees of the solstice, i.e. not very high. Come February and especially March, as the sun gets higher in the atmosphere its effect on snow melt increases dramatically, even if it is not reflected in the temperatures. Day lengths matter as well. Do data from past Februaries and Marches, when you can melt a foot of snow with two sunny, 50 degree days, is not particularly pertinent.)

23 megabytes of data have to be good for something, right?