Good evening from Southern Connecticut Weather!
It has been a very cold start to December. One of the coldest in decades! The abundance of cold however has not come with an abundance of snow. In December, our snowfall climatology becomes more favorable as we move through the month, making it easier for storms to bring snow to the state, though it doesn't always work out that way. We have been tracking the potential for a system to bring snow to CT on Sunday, and now there is enough confidence to start talking about it in detail.
It has been a very cold start to December. One of the coldest in decades! The abundance of cold however has not come with an abundance of snow. In December, our snowfall climatology becomes more favorable as we move through the month, making it easier for storms to bring snow to the state, though it doesn't always work out that way. We have been tracking the potential for a system to bring snow to CT on Sunday, and now there is enough confidence to start talking about it in detail.
Above: The SCW First Call snow map for Sunday. We are expecting a general 1-3" of snow across the state, with the highest totals south and east of I-84. It's possible some areas could see more, but we're not confident enough to introduce a 2-4" zone at this time.
Overall Setup
Although the forecast is fairly straightforward now, the road to get to this point was not. A weak shortwave riding along a trough that will bring us a reinforcing shot of cold early next week is expected to develop well offshore on Sunday. How much that system amplifies and how closely it tracks to the coast will make the difference in how much snowfall we get from the developing precipitation shield.
For days, the guidance was either split on the impact here, or outright putting any chances of snow on life support. I quietly believed this was a contender to bring snowfall given the pattern, and in the last few days we've indeed seen a trend toward an amplified enough and north enough system to bring snow into the state on Sunday. This is a fast moving and weak system, hence the relatively minor snowfall totals.
One of the last holdouts was the GFS, which had barely forecast any snowfall into the state with the system being weak and well out to sea. It has gradually changed its tune.
At 500mb, where so much of the "action" actually happens, you can see how we end up with a weak and well south system: the trough while relatively strong is positively tilted, rather than negatively, which means that the storm cannot amplify much. There's no blocking to slow it down, and the shortwave can't get much further north.
Overall Setup
Although the forecast is fairly straightforward now, the road to get to this point was not. A weak shortwave riding along a trough that will bring us a reinforcing shot of cold early next week is expected to develop well offshore on Sunday. How much that system amplifies and how closely it tracks to the coast will make the difference in how much snowfall we get from the developing precipitation shield.
For days, the guidance was either split on the impact here, or outright putting any chances of snow on life support. I quietly believed this was a contender to bring snowfall given the pattern, and in the last few days we've indeed seen a trend toward an amplified enough and north enough system to bring snow into the state on Sunday. This is a fast moving and weak system, hence the relatively minor snowfall totals.
One of the last holdouts was the GFS, which had barely forecast any snowfall into the state with the system being weak and well out to sea. It has gradually changed its tune.
At 500mb, where so much of the "action" actually happens, you can see how we end up with a weak and well south system: the trough while relatively strong is positively tilted, rather than negatively, which means that the storm cannot amplify much. There's no blocking to slow it down, and the shortwave can't get much further north.
This is the surface result on the GFS.
The Euro on the other hand has been a bit more organized at 500mb, and the result is a more definitive period of light snow on Sunday.
Here's the result at the surface. Note the more northwest precipitation shield.
At this point, we're just looking at model noise, so let's get to the forecast.
Timing
One of the key characteristics about this system is that it's a quick mover. Right now, it looks like snow will break out in the state right around midnight Sunday, with the bulk of the snow happening on Sunday morning. Snow should be out of the state by noon.
Snow & Ice Accumulation
Again, the forecast here is pretty straightforward. If we see a more amplified and/or north system, we will see more snow. If this trends southeast, most will end up on the lower end of our snowfall range. It was a close call to put much of southern CT and SE CT in a 2-4" zone, but there's not enough confidence in that.
Although this is not likely to bring a lot of moisture to our area, the snowfall ratios may be higher than the standard 10:1, meaning expect a light, fluffy snowfall. On the other side however, it looks as if drier air will try to erode the precipitation shield, which would counteract more precipitation being wrung out from the atmosphere. Although there's the chance it starts out as light rain in southern CT with temperatures near freezing early Sunday, unlike our last winter storm, cold air will be advecting into the state rather than being pushed out because of the storm track. We expect a virtually all snow event statewide as a result.
The best chance of a plowable snowfall is south and east of I-84. In NW CT and maybe into the CT River Valley in northern CT you may be one of the lower snowfall accumulation spots unless the banding signal ticks northwest.
Wind & Power Outages
We don't have a significant pressure gradient with this system, and the system is weak and well offshore. We are not expecting meaningful wind or power outages.
Overall Impact
The timing of the system for Sunday morning, the relatively low snowfall totals, and speed of the system all point to this being a minor impact event. There will be slick roads Sunday morning so do watch out for that. The main thing we're refining now in the forecast in how amplified the system is, and how closely it tracks to the state. There is still time for some changes either way, but overall the main story is that this looks like our first statewide accumulating snow event, with more bitterly cold conditions to follow before a potential thaw later next week.
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
One of the key characteristics about this system is that it's a quick mover. Right now, it looks like snow will break out in the state right around midnight Sunday, with the bulk of the snow happening on Sunday morning. Snow should be out of the state by noon.
Snow & Ice Accumulation
Again, the forecast here is pretty straightforward. If we see a more amplified and/or north system, we will see more snow. If this trends southeast, most will end up on the lower end of our snowfall range. It was a close call to put much of southern CT and SE CT in a 2-4" zone, but there's not enough confidence in that.
Although this is not likely to bring a lot of moisture to our area, the snowfall ratios may be higher than the standard 10:1, meaning expect a light, fluffy snowfall. On the other side however, it looks as if drier air will try to erode the precipitation shield, which would counteract more precipitation being wrung out from the atmosphere. Although there's the chance it starts out as light rain in southern CT with temperatures near freezing early Sunday, unlike our last winter storm, cold air will be advecting into the state rather than being pushed out because of the storm track. We expect a virtually all snow event statewide as a result.
The best chance of a plowable snowfall is south and east of I-84. In NW CT and maybe into the CT River Valley in northern CT you may be one of the lower snowfall accumulation spots unless the banding signal ticks northwest.
Wind & Power Outages
We don't have a significant pressure gradient with this system, and the system is weak and well offshore. We are not expecting meaningful wind or power outages.
Overall Impact
The timing of the system for Sunday morning, the relatively low snowfall totals, and speed of the system all point to this being a minor impact event. There will be slick roads Sunday morning so do watch out for that. The main thing we're refining now in the forecast in how amplified the system is, and how closely it tracks to the state. There is still time for some changes either way, but overall the main story is that this looks like our first statewide accumulating snow event, with more bitterly cold conditions to follow before a potential thaw later next week.
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
