This presentation explains the basics of daytime snowpack warming over terrain and introduces SWarm.
SWarm is a free spreadsheet that uses the maximum solar radiation to estimate daytime warming 10 cm below the surface over idealized terrain. You can select the date, latitude, expected cloud cover, and days since snowfall to see how these factors can influence the daytime snowpack warming down 10 cm.
For more on SWarm, see Laura Bakermans' paper at the 2008 ISSW in Whistler, BC.
Bruce Jamieson and Laura Bakermans, 2011, CC BY-ND.