I wanted to publish a brief update on some of the most recent trends this morning to keep you ahead of what I am seeing. As I said yesterday overrunning precipitation often moves faster than any weather modeling can pick up on, and thus flurries are already breaking out in Greenwich, Stamford, and Norwalk. They will stick on contact and will keep moving to the east over the next hour or so, though more steady snow that will cause even more problems is still a few hours out. That heavy snow will hit the region by 4 PM, though, and with it will come very serious travel trouble. The steadier associated with the main low pressure center could move in as soon as 2 PM, which is why I am advising everyone to stay off the roads after that point.
Early dismissals were rightly called in every district in the county and I am glad that I continued to raise percentages last night to signify that this would be the case. Attention now turns to Wednesday. My first percentage chance for delays/snow days on Wednesday will be released between 12 PM and 1 PM today when the steadier snow is being tracked on radar. One of the biggest model trends is towards that NAM/RGEM duo I mentioned last night that shows most snow ending by 1 or 2 AM across the entire region. The latest NAM has the steadiest snow out of here by 11 PM and keeps lingering snow showers only until 3 or 4 AM at the latest. What this means for schools is that the falling snow will not be an issue as the snow should be done by 4 AM or so. Instead, it is accumulations and Departments of Public Works, like I have been saying all along, that will determine whether schools will close. By this evening I should have a very good idea of whether it is more likely that schools just delay or whether they close altogether, but I will have a first attempt at this in the very early afternoon so make sure to check back for the latest then.
In terms of accumulations, overnight guidance actually came together well into a better consensus. My 11 PM analysis predicted well what weather guidance was going to do, as there was a slight trend towards the NAM/RGEM scenario of around half an inch of liquid at the coast, a little less inland and most of the storm ending by 1 AM. This means that I remain very confident with my snowfall amounts of 5-10 inches at the coast and 4-8 inches inland. It seems I am slightly on the lower side of some of the forecasts that I am seeing, but gusty winds will likely keep ratios from hitting or approaching 20:1, especially at the coast, and that is why I remain so confident with the ranges I have put out. What the biggest surprise with the overnight guidance likely is is that now the heaviest snow looks to fall between 4 and 8 PM, with snow slowly tapering off from there. It is an initial burst of mesoscale banding in that 4-hour range where we could see 4 inches of snow in 4 hours in some areas, which is why all travel would be extremely treacherous in that time frame. Moderate snow will continue for about 4 hours after, and then light snow for another couple of hours before it will all wind down. So no major changes in accumulations, but again the timing has been bumped up as this is a quick-moving storm that will be out of the area by morning. The RAP short range model shows this as well and it has been quite accurate with the storm, adding confidence to this slight change in timing while also adding confidence to accumulation numbers that it currently supports.
To recap, still 5-10 inches total at coast, 4-8 inches inland, with snow starting now and getting steadier over the next few hours. By 2 PM please avoid all travel, though if possible avoiding it after 12 PM would be best, and roads will likely be better late Wednesday morning or early Wednesday afternoon. Heaviest snow between 3-7 PM now with moderate snow until 1o PM and lights snow until around 1-2 AM ending from west to east with a few snow showers possibly continuing until as late as 3 or 4 AM. Confidence is quite high with all these details, and a school impact forecast will be released later today so make sure to check back in for that and additional updates on this storm.