For three consecutive runs in a row, the American GFS forecast model has suggested that it’ll be cold enough to produce a sizeable snowstorm in the eastern United States in time for Halloween. Has it happened before? Yes. Will it happen this year? It’s too early to tell.
The American GFS forecast model is one of many that meteorologists use to aid their forecasting work. Run several times each day, the deterministic model output runs through various scenarios of how the atmosphere will evolve over time, spelling out where highs and lows on a weather map will be featured. They also analyze the complicated physics and dynamics that occur well above the surface; they also incorporate data from the ground; lack of snow cover or the presence of snow cover could alter forecast output. On a short-term basis, models, including the GFS, can be especially accurate. But in the extended range, especially beyond five days, the accuracy begins to become unreliable. While the GFS and other global models like it can be right about conditions 10+ days in the future, it’s more likely than not that they’ll be off.
While snow in places like New Jersey is rare for Halloween, it isn’t completely unheard of. In 2011, up to 19″ of snow fell on parts of New Jersey, breaking records in the Garden State that went back to 1895. That October snowstorm arrived just months after Hurricane Irene had brought devastating floods to the region. Because many trees still had their leaves, heavy wet snow weighed them and their branches down, taking down tens of thousands of trees around the region. With massive power outages as a result, many communities postponed or cancelled Halloween activities that year. The October snowstorm was deadly too: 39 people died in the storm, including 8 in New Jersey, 10 in Connecticut, and 6 in Massachusetts.
In 2012, what was left of Hurricane Sandy became an inland blizzard. More than 2 feet of snow fell in portions of Maryland and West Virginia while parts of Tennessee had more than a foot of snow. And while people in New Jersey and New York were still recovering from the immediate aftermath of Sandy, a snowstorm impacted the area, bringing up to a foot of snow in the region.
October snow is more common in northern New England and the higher terrain of the Appalachian Mountains.
Because the current American GFS forecast model output for Halloween is too far out to put much weight in its outlook, people shouldn’t rush out to stock up snowstorm supplies anytime soon. But with days getting shorter and temperatures getting colder, snow is likely to fall sooner rather than later. Whether it arrives early in late October is anyone’s guess for now, but it does bear some watching in the days and weeks ahead.