Let the fun begin. First snow is now being reported in Greenwich, and this snow will very slowly overspread SW CT from west to east over the next few hours. Once it begins, it won’t take long to stick as surface temperatures are generally at or just below freezing, though it is light enough to start that it will take a decent amount of time for that first inch to fall. Still, that snow is beginning now and will be covering the entire region within the next few hours. It will start as all snow down to the coast, and will remain that way through around 11 PM tonight. Between 11 PM and 1 AM tonight we see a warm nose between 775mb and 825mb begin to work in aloft, and even though temperatures around 900mb will be very cold, snow will be melting further up in the atmosphere. It will then refreeze, producing sleet in that time frame, so even though frozen precipitation down to the coast is possible even through 1 AM, most accumulations will end by around 11 PM when the sleet really mixes in. Then, between 1 AM and 3 AM there could be a period where surface temperatures in coastal areas (but away from the IMMEDIATE coast) are below freezing, and that is where up to a tenth of an inch of ice accretion is possible, but likely in pockets, and I don’t expect much more than a coating of ice or so along the coast. It could briefly cause problems, but as temperatures rise above freezing that ice should melt and by 3 AM I can guarantee that the coast will be plain rain. This is why the delay percentage chance at the coast is so low, as there will only be residual cleanup from the snow/ice overnight that will be left by morning, and assuming that goes well there will not be more dangerous conditions coming for the coast during the day tomorrow. There really is not much new to cover with that forecast.
Further inland it begins to get a little bit more complex. They will remain generally snow as well through 11 PM, and I expect most inland areas to have seen around 3 inches through 11 PM. Sleet may begin to mix in, but it will take slightly longer, with most areas being sleet by around 1 AM. By that point snow accumulations will cease, and the region will peak with a general 4 or 5 inches of snow. Then, freezing rain will dominate, possibly mixed with sleet, through 3 AM, similar to the coast. It is after that where things get interesting. Winds will generally be ENE, helping warm things up slightly just south of I-84, but not by much. Through 6 or 7 AM the region will generally be between 32-34 degrees, and it is that small range that is ever so hard to forecast. This means that icy patches could last into the morning rush inland, and that worries me regarding schools. The current forecast for inland SW CT is that there is a 45% of some impact to schools tomorrow, 40% being a delay and only a 5% chance of snow days south of I-84 because precipitation is guaranteed to go over to all rain at some point between 5 and 7 AM if it does not earlier. Patches could remain icy, and whenever dealing with an extended period (more than an hour or two) of freezing rain, it is often better to play it safe rather than sorry. Freezing rain is the most dangerous form of precipitation because it creates black ice almost instantly on roads, which is difficult to see. It will likely come down to a town-by-town and valley-by-valley basis which districts end up delaying tomorrow further inland, as that one to two degrees in the morning will be the difference between wet roads and very slipper and dangerous roads. By 8 or 9 AM conditions across all of SW CT should be much safer for travel.
That’s really all I have for right now, but I do plan on releasing another update around 8 PM tonight, and of course more will follow that as well. Make sure to keep it here for the latest.