Ground temp won't matter much with rates...and not uber heavy stuff either. The melting will help cool it to near 32. Now obviously a cold late season storm will help keep ground temps cooler.
I'm not. I am pointing out that snow can easily stick when it's moderate to heavy even if it was mild the day before. If you had those rates the other day, there is no question Methuen would have done just fine.
On 3/30/97 it was 70. On 3/31 at 3P it was heavy wet snow with 4" tire ruts on rt 24 south of Boston. If it's moderate to heavy, it will stick at 32F or lower.