The below forecast outlines expected snowfall accumulations and impacts through tomorrow evening. The post goes through accumulations, timing, and a couple model scenarios. To view our more detailed analysis, including travel impacts and forecasts for school closures, along with additional weather model analysis, be sure to try a Premium subscription here. All school closure forecast updates will be directly emailed to subscribers throughout the upcoming few days of storm threats. Otherwise, please enjoy the Free forecast below. An update will be posted this evening should conditions dictate:
PRECIPITATION TYPE/TIMING: One thing is for sure with this storm; it is all going to be snow. Every model shows temperatures falling as the precipitation begins into the mid/upper 20s across the region with colder temperatures aloft as well. This indicates snow could be relatively fluffy and we could see ratios in the 12:1 to even 15:1 ratio instead of the standard 10:1 ratio. As for timing, that is lower confidence. Most models show a chance of snow arriving by 6 or 7 AM. Some have it beginning in New Haven County, which is possible if the storm is further east as it takes time for light bands of snow tomorrow morning to rotate back west into the region. Other models show a slightly more direct hit with snow beginning as early as 3 or 4 AM across the region, but the general consensus is that snow does not really begin to fall at a rate to even coat the ground until 6 AM at the earliest. From there, steadiest snow can be expected between 8 AM and 2 PM, when steady light snow should continue to awhile. Then, the precipitation shield gradually breaks down through the afternoon, as we can expect scattered on and off snow showers to continue into Monday evening. A chance of light snow showers could even continue into overnight Monday night, but any briefly moderate snow showers should die down before that. Minor snowfall accumulations will be possible Monday night and again into Tuesday, however, with additional updates on that coming in the next day.
ACCUMULATIONS: Across the region anywhere from a dusting to 5 inches of snow remains possible. As was the case with the last storm, once again it looks like New Haven County will see the worst impacts and Westchester County should see the least impacts. This leads to a forecast where Westchester County sees 1-3 inches of snow through Monday evening, while New Haven County is instead expected to see 2-4 inches of snow through that timeframe. Fairfield County is the true battle zone, as northern portions of the County could see only an inch or so but southeastern portions could see up to 4 inches. For now, I continue to favor the solutions where total accumulations in Fairfield County stay broadly below 3 inches, so the forecast is still for 1-3 inches of snowfall in Fairfield County as well, but there is a chance that I may need to boost both the Fairfield and New Haven County forecasts by about an inch if there is even a slight jog west in model output (or a couple of the more amplified models verify). That has been a trend this winter, though a couple other pieces of model guidance that had been performing well indicate it is actually less likely that we see more than 2-3 inches widespread, so there’s definitely some confusion. Up to another inch or so of snow is possible Monday night from lingering snow showers, though that will be more of a focus later tonight into tomorrow once I figure out the exact track of this upcoming storm, as how the lingering energy interacts with the region will be impacted by how this first storm tracks.
BRIEF TRVEL NOTE: This all creates a very tricky impact analysis because it is a non-trivial amount of snow falling across the region, but at no point do snowfall rates look to exceed .5 inches per hour, and even then that is the maximum rate for an hour or two during the middle of the day. Overall, this storm looks relatively manageable. The less intense snowfall rates makes it seem like road crews should be able to keep up through the day, but surface temperatures in the mid to upper 20s means that snow should easily be able to stick to roads, even treated ones, and that they could accordingly be a little slick through the day. This makes for an increasingly hard judgement call as to exactly how bad conditions will get on roadways, so I do emphasize using as much caution as necessary if traveling tomorrow.
BRIEF MODEL NOTES: I want to dive into some of the model scenarios. To start, as I typically like to do, I want to show the latest SREF model probabilities for snowfall. Here we see the snowfall probabilities on them through 4 PM tomorrow. New Haven County sees about an 80% chance of an inch of snow, while Fairfield County sees about a 50% chance and Westchester County sees about a 35% chance. Note that this is based off a 10:1 ratio, and given the colder temperatures I expect ratios of closer to 12:1 or 15:1, so that should raise the probabilities slightly, though with so little snowfall it will not make that significant a difference. To the right of that we see only New Haven County is shown having any chance of reaching 4 inches of snow, and even there it is around a 10% chance. The SREFs have been performing relatively well this winter, and this output certainly seems to be downplaying the impact potential tomorrow across the SWCT/NY region.
Next we have the HD NAM, which is one of the more aggressive models. However, even the HD NAM only has very light snow showers struggling to overcome dry air at 7 AM tomorrow, as seen here. Finally by 10 AM we see relatively steady light to briefly moderate snow move in, as seen here. But that breaks down and moves out by 2 PM here as the precipitation shield falls apart. Through 4 PM the model shows 1-2 inches of snow in Westchester County, 2-3 inches of snow across Fairfield County, and 3-5 inches of snow across New Haven County, seen here.
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