If you live in Connecticut or nearby areas, you might notice some light snow showers late tonight into tomorrow morning. Closer to New York City, there’s even a chance of freezing drizzle. But what’s causing this? The answer lies in something called an inverted trough—a term that sounds complicated but is actually pretty interesting.
A trough in weather terms is an elongated area of low pressure. Normally, these troughs extend from north to south. An inverted trough is the opposite—it stretches from east to west, usually north of a low-pressure system. Think of it like a tail sticking out from a storm system, but pointing in a different direction than usual. These inverted troughs can pull moisture into colder areas, creating tricky winter weather setups. They’re often weak, but they can still produce light precipitation—sometimes snow, sometimes freezing drizzle—depending on the temperature.
Tonight’s situation is a good example of why forecasting can be challenging. A low-pressure system is passing well to our south, and a very weak inverted trough extends north from that system into our region. At the surface, temperatures are cold—mostly in the 20s in Connecticut and lower 30s near NYC and Long Island. But aloft, temperatures near freezing are not enough to usually support snowfall. This combination means precipitation type, or “p-type,” is uncertain. Inland Connecticut will likely see light snow where the atmosphere is slightly colder, while areas near the coast could see freezing drizzle if temperatures stay below freezing. If temps rise just a bit, it could be plain rain instead, especially as we head through the day Saturday.
7AM Saturday Morning – European Model
The good news is that amounts will be very light. Snow will likely only amount to a dusting at best, and freezing drizzle would produce just a thin glaze of ice where it occurs. Rain near the coast will also be minimal. Still, even a light glaze of ice can make roads slippery, so the NWS has stated to watch out for a Winter Weather Advisory if confidence increases.
