The phrase "snowfall accumulation" refers to the amount of snow that has built up or collected on the ground over a certain period of time. Full definition
Let's start with the record five - plus feet of snowfall accumulation in Erie, Pennsylvania, in late December. (climaterealityproject.org)
Oswego County: a Winter Storm Warning which is in effect until Friday at 10:00 a.m. Total snowfall accumulations of 6 to 12 inches are forecast. (thebronxchronicle.com)
The latter is especially true for land ice (Antarctica and Greenland) because you have to wait for snowfall accumulation and conversion to ice. (ceassessment.org)