One to six inches of snow is/are expected.
Eight to twelve inches of snow has/have fallen.
'Inches' is plural, but we can also be referring to a lump sum which could necessitate a singular verb for each example above.
Singular or plural verb for each?
When you refer to a quantity as a mass, you usually use the singular.
Three miles isn't too far to walk.
Twenty dollars is too much to pay for one cake.
Six inches of snow is enough to shovel. One to six inches of snow is expected.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
A distance of three miles isn't too far to walk.
The amount (twenty dollars) is too much to pay for one cake.
A snowfall of six inches is enough to shovel. A snowfall of one to six inches is expected.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.