by David Murphy
The ocean saves the shore!
During the winter, the temperature of the ocean water is milder than the temperature of the land. This is because water, with its molecules in constant motion, has an enormous ability to store and transfer heat. Consequently, water is far less able to react to temperature change than solid land. As a result, the ocean doesn't experience temperature extremes. In the summer, it's cooler than the land. In the winter, it's warmer. And this means the air above it is also milder. A portion of this milder air often drifts or blows in from the ocean over coastal communities, making them warmer, too.
It's now easier to understand why a winter storm that produces lots of snow inland has a hard time producing anything more than rain and maybe some sleet closer to the coast. As the storm approaches, it encounters that warmer air flowing in off the ocean and its snow melts and turns to rain. You often see this on Storm Tracker 6 Live HD during winter storms. The radar will show snow near Philadelphia (gray or white), but a change to an icy mix closer to the shore (blue) and finally all rain near the coast (green). Depending on the strength and direction of the wind, this rain-to-snow line can sometimes shift miles inland, occasionally changing the precipitation in Philadelphia to rain, too!
Each storm is different, though. It's always a challenge trying to calculate how that rain-to-snow line will behave during a storm and how much or little snow different areas will receive. But the bottom line here is that it's the mild ocean that leads to less snow at the Shore.
