Observation time - we talk about this every winter. Sun angle.
People have strong opinions on this. Here's mine...it really comes down to rates. If it's legit +SN and 33 degrees in early March, it WILL accumulate on ALL surfaces. It might struggle midday, but heavy snow (like verifiable 1/4 mile vis or less) will overcome sun angle and to a large degree...temps.
I cleared off my sidewalk at 11am. It is snowing "nicely" right now...verified steady light snow. It's currently 28 degrees and it's January 19th. All of my paved surfaces are 100% wet. Snow is melting on contact despite being several degrees below freezing and still in January.
It really is about rates.
Now, if it was December 22nd and 22 degrees...this same rate of snow would likely be sticking to all surfaces.