Arctic air clash could trigger a major snowstorm for New England. Here's the latest from Dave Epstein.

"Over the next several days, we're going to see a renewed mass of cold Arctic air descend into the United States, sending temperatures below their 30-year averages from Texas to Northern Florida and north to our area. This bitter cold, heavy air and the boundary between the warmer air to the south is going to act as a catalyst for a swath of snow and rain that will ride from the Mississippi Valley to the Ohio Valley and then off the Mid-Atlantic coast."

"The southern and northern extent of the snow shield is still in question, and this plays into our forecast for the upcoming weekend. There's no doubt that there's going to be a significant amount of snow for parts of the eastern U.S. that have not seen much snow, not only this winter but over the past several years."

"Once the storm exits somewhere along the Mid-Atlantic coastline, it will have to fight the cold, dense Arctic air that will overtake New England starting Friday night. I've seen situations where enough of the cold air relaxes to pull in the precipitation and that's where we get those storms with very light fluffy snow."

Cold Arctic air will descend across the United States, driving temperatures well below 30-year averages from Texas to Northern Florida and northward. The denser cold air forces warmer air to lift, producing condensation, clouds, and precipitation. That interaction will generate a swath of snow and rain moving from the Mississippi Valley through the Ohio Valley and off the Mid-Atlantic coast. Uncertainty remains about the southern and northern extent of the snow shield over New England and whether precipitation will be elongated east-west or concentrated within a stronger low. Cold, dense air overtaking New England starting Friday night could favor very light, fluffy snow, and it is unlikely that the precipitation will be anything but snow.

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