Good evening from Southern Connecticut Weather.
The active pattern is revving up as we have our next storm system coming into better focus. Although this is a storm of modest intensity overall, the timing and precipitation type will likely make this a high impact storm. Do not look at the snow map below and write this one off. Snow, ice, and rain are on the table.
The active pattern is revving up as we have our next storm system coming into better focus. Although this is a storm of modest intensity overall, the timing and precipitation type will likely make this a high impact storm. Do not look at the snow map below and write this one off. Snow, ice, and rain are on the table.
Above: the first call snow map for the coming storm. At this time, we expect a widespread 1-3" of snow and sleet, and although it is not pictured a glaze of freezing rain is also likely in interior CT. If the storm trends a bit colder, these numbers could go up in tomorrow's final call.
Overall Setup
Winter weather advisories are up for all of Connecticut with the exception of the immediate shoreline, as we track the next system poised to impact the region on Thursday. The first step actually happened today, with a push of cold that will get us well below freezing tonight and keep many below freezing tomorrow. This push of cold is well timed, because a system from the west will run into the cold on Thursday.
While the primary system travels well to our northwest, we likely see a weak low spawn to our south. The broader (warmer) system running into the cold creates an overrunning situation, that will lead to snow for all before a change to a mix/ice, and for far southern CT the possibility of a flip at the end to plain rain. These are tricky systems, with impacts highly dependent on how long low level cold can hold on.
Overall Setup
Winter weather advisories are up for all of Connecticut with the exception of the immediate shoreline, as we track the next system poised to impact the region on Thursday. The first step actually happened today, with a push of cold that will get us well below freezing tonight and keep many below freezing tomorrow. This push of cold is well timed, because a system from the west will run into the cold on Thursday.
While the primary system travels well to our northwest, we likely see a weak low spawn to our south. The broader (warmer) system running into the cold creates an overrunning situation, that will lead to snow for all before a change to a mix/ice, and for far southern CT the possibility of a flip at the end to plain rain. These are tricky systems, with impacts highly dependent on how long low level cold can hold on.
Above: an image explaining the process of overrunning. This can happen year round, so it's not unique, but we haven't had the cold the last several winter seasons to allow for overrunning in the region. In the winter, the dense cold at the surface allows for mixed bag situations. Image courtesy of Allister Aalders.
The thickness of the cold to precipitation type, and below shows how warm layers impact precipitation type.
The thickness of the cold to precipitation type, and below shows how warm layers impact precipitation type.
Above: GFS, which is on the colder side, showing a snow to mix to rain depiction. Truthfully, models often underestimate the low level cold, which means this is more likely a snow to mix event inland and snow to mix to rain event at the coast.
Timing
Timing for the system overall is fairly straightforward, but timing the precipitation changeovers is tricky. Broadly speaking, this is an all day Thursday event. However, looking deeper I'm expecting things to start as snow statewide between about 4-8am. That will have implications on schools for sure. At the coast, we probably start mixing by late morning, with the mix line moving through northern CT in the early afternoon hours. Everything should be winding down by late Thursday afternoon. This is another fast mover in a fast pattern.
Snow Accumulation
As mentioned earlier, that 1-3" of snow and sleet doesn't tell the whole story. With the initial burst of snow, it could be moderate at times and maybe heavier if we have the system amp up a bit as it approaches. There's not a lot of precipitation with this event, but it's the timing and type of precipitation that's the issue. Along the coast, I expect less snow, but the cold will be in place statewide, which means that there will be snow and some icing.
Inland it will take the longest for the snow to change over, but when it does sleet and freezing rain will be likely. Adding a glaze of ice on top of snow will make things a mess. Even at the coast, most of the day could very well be near to below freezing, so freezing rain may be an issue for a time there too.
Wind/Power Outages
Because this system isn't terribly powerful, I'm not expecting significant wind. In addition, the lack of additional precipitation also means that any icing that occurs will be impactful, but probably not enough for significant power issues. I think we see isolated to scattered outages at worst. I'm not expecting much more than a glaze to maybe a tenth of ice--enough to cause real problems on roads and sidewalks, but not enough to bring down trees and power lines.
Impact
For now, I think it's best to lean a bit conservative on overall snowfall and icing because the Euro still is a bit warmer than most guidance, and the NAM is still a bit weak with the amount of precipitation given how modest the storm intensity is as of now. That said, it's not that much difference between 1-3 and 2-4" of snow. The real story is the likelihood of sleet and especially freezing rain. Given the timing of the system, having snow to ice means widespread cancellations statewide, even if temperatures struggle above freezing Thursday afternoon.
As always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
Thank you for reading SCW.
-DB
Timing
Timing for the system overall is fairly straightforward, but timing the precipitation changeovers is tricky. Broadly speaking, this is an all day Thursday event. However, looking deeper I'm expecting things to start as snow statewide between about 4-8am. That will have implications on schools for sure. At the coast, we probably start mixing by late morning, with the mix line moving through northern CT in the early afternoon hours. Everything should be winding down by late Thursday afternoon. This is another fast mover in a fast pattern.
Snow Accumulation
As mentioned earlier, that 1-3" of snow and sleet doesn't tell the whole story. With the initial burst of snow, it could be moderate at times and maybe heavier if we have the system amp up a bit as it approaches. There's not a lot of precipitation with this event, but it's the timing and type of precipitation that's the issue. Along the coast, I expect less snow, but the cold will be in place statewide, which means that there will be snow and some icing.
Inland it will take the longest for the snow to change over, but when it does sleet and freezing rain will be likely. Adding a glaze of ice on top of snow will make things a mess. Even at the coast, most of the day could very well be near to below freezing, so freezing rain may be an issue for a time there too.
Wind/Power Outages
Because this system isn't terribly powerful, I'm not expecting significant wind. In addition, the lack of additional precipitation also means that any icing that occurs will be impactful, but probably not enough for significant power issues. I think we see isolated to scattered outages at worst. I'm not expecting much more than a glaze to maybe a tenth of ice--enough to cause real problems on roads and sidewalks, but not enough to bring down trees and power lines.
Impact
For now, I think it's best to lean a bit conservative on overall snowfall and icing because the Euro still is a bit warmer than most guidance, and the NAM is still a bit weak with the amount of precipitation given how modest the storm intensity is as of now. That said, it's not that much difference between 1-3 and 2-4" of snow. The real story is the likelihood of sleet and especially freezing rain. Given the timing of the system, having snow to ice means widespread cancellations statewide, even if temperatures struggle above freezing Thursday afternoon.
As always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
Thank you for reading SCW.
-DB
