Weather or Not: Todd Gross Responds

From time to time Todd Gross will be answering some questions here in a column called “Weather or Not.” Got a question, not necessarily weather related, you’d like to ask Todd? Well, ask him.

How is it that snow accumulation seems to differ inside and outside of Rt 128? or I-495? Are those roads on some type of natural divide of some kind? Or is it just the way weather reporters present the weather?

The rain-snow line coinciding with Rt. 128 has to do with the coincidental distance from the coastline, around ten miles back in from the coast. That is where, often, the dividing line is between an easterly wind and a northerly wind during a storm. This "coastal front" that forms, is very often, right on Rt. 128, cutting inside it a little bit around Lexington. This works for most of the SW, W, NW, and N side of Rt. 128, but not around Cape Ann or the south side of Boston.

Rt. 495 is another story. It corresponds more roughly to the weather, although the uplifted area just NW of Rt. 495 has a major impact on the rain vs. snow line - first the area of uplift around Harvard, Ma, then the larger uplift which really flanks Rt. 190.