When one of the more infamous winter storms strike, there are a few ways to figure out if you'll get just rain or heavy snow.
Several factors determine precipitation type from nor’easters, including strength and cold air. But one of the most important components is exactly where the coastal low tracks in relation to the East Coast.
A nor'easter is a strong low-pressure system that affects the Mid-Atlantic, Northeast, and New England. Well-developed nor'easters are notorious for producing heavy snow, rain, wind, coastal flooding, and very rough surf.
The name comes from the continuously strong northeasterly winds that precede the nor'easter.
Here are the three main scenarios for nor'easters when they impact the East Coast.
When the center of low-pressure tracks just inland, the storm draws milder air from the Atlantic Ocean inland as well. This scenario usually will produce mainly rain near the coast, with snow farther inland only if there is enough cold air in place.
Near the coast, there will be rain, wind, coastal flooding, and some often travel delays.
This just-offshore track brings monster, full-blown nor'easters, especially when enough cold air is involved and deep strengthening occurs. Snow can be measured in feet, especially along the Interstate 95 corridor if the atmosphere is cold enough.
If temperatures are warmer, you'll often hear about a rain-snow line, and snow changing to rain, then back to snow sometimes.
Just a few miles east or west can mean the difference between 2 feet of snow, or a few inches and mostly rain.
Prolonged northeasterly winds also bring a significant coastal flooding threat and beach erosion.
When the coastal low forms off the Mid-Atlantic or Carolinas, then tracks out to sea instead of hugging the coast, impacts for the Mid-Atlantic and especially the Northeast tend to be limited to rough seas and wind.
Often the northwesterly winds across the Great Lakes in the wake of the storm will persist and cause snow downwind of the Lakes.