Good evening from SCW,
We’ve got an impactful storm on the way, with heavy rain, noticeable winds, and high-elevation snow expected for the region starting late tomorrow evening and going into early Saturday. While everyone will see precipitation, we’re expecting accumulating snow to be confined to the interior, and any noticeable impacts from snow to be confined to the northwest hills, where a substantial amount of heavy, wet snow is likely.
Let’s take a look at the setup. Below is a loop of simulated radar from the GFS from Thursday morning through Saturday afternoon, courtesy tropical tidbits.
We’ve got an impactful storm on the way, with heavy rain, noticeable winds, and high-elevation snow expected for the region starting late tomorrow evening and going into early Saturday. While everyone will see precipitation, we’re expecting accumulating snow to be confined to the interior, and any noticeable impacts from snow to be confined to the northwest hills, where a substantial amount of heavy, wet snow is likely.
Let’s take a look at the setup. Below is a loop of simulated radar from the GFS from Thursday morning through Saturday afternoon, courtesy tropical tidbits.
This model run depicts a pretty classic coastal storm track for us, with low pressure coming up from our southwest before transferring to a coastal low south of our region. With a colder airmass in place or stronger blocking to our north, this would probably be a substantial snowstorm for the region. However, the system is moving into a marginal airmass, and that, combined with the relatively weak blocking, is allowing enough warm air to be sucked into the system such that the lower elevations are primarily cold rain. As the storm begins to push to the east, we’ll see temps drop enough for most areas to switch over to snow, but there probably won’t be enough moisture left for more than a light accumulation, if any at all.
The story is very different in the NW hills, however, where elevation will allow for colder air to be trapped for longer, which, combined with heavier precipitation rates, should create just enough dynamic cooling for the predominant precipitation type to be heavy wet snow. The range of model solutions ranges from keeping the hills all snow for the duration to mixing with and changing to rain during the peak of the storm when the warm nose is furthest north - we’ll look to hone in on the more exact timing tomorrow once we get some model consensus.
To show that, let’s take a look at soundings (essentially, profiles of the atmosphere) for 1 PM on Friday at ~1500 feet in the NW hills.
The story is very different in the NW hills, however, where elevation will allow for colder air to be trapped for longer, which, combined with heavier precipitation rates, should create just enough dynamic cooling for the predominant precipitation type to be heavy wet snow. The range of model solutions ranges from keeping the hills all snow for the duration to mixing with and changing to rain during the peak of the storm when the warm nose is furthest north - we’ll look to hone in on the more exact timing tomorrow once we get some model consensus.
To show that, let’s take a look at soundings (essentially, profiles of the atmosphere) for 1 PM on Friday at ~1500 feet in the NW hills.
On the GFS (left), colder air is still holding on in the column, with temps only warming right at the immediate surface. Verbatim, I’d still expect this to be a snow sounding in periods of heavier precipitation, as dynamic cooling would keep the column at 32f down to the surface. On the Euro (right), however, it’s a different story, as temps are at/above freezing all the way down from 850 mb (several thousand feet above the surface) and, outside of perhaps the heaviest precipitation, this would just be cold rain. Which temperature profile ends up being the most accurate will ultimately determine snow totals in the hills; as we see models come to a consensus tomorrow, we’ll likely have to adjust our snow forecast one way or another.
As far as total precipitation goes, all models are looking healthy with QPF, with a general 1-2” of liquid expected across the state. We’re certainly not worried about precipitation making it into our area with this storm; it’s the temps that are going to rule the day here for snow accumulations or the lack thereof.
Forecast
As far as total precipitation goes, all models are looking healthy with QPF, with a general 1-2” of liquid expected across the state. We’re certainly not worried about precipitation making it into our area with this storm; it’s the temps that are going to rule the day here for snow accumulations or the lack thereof.
Forecast
As we discussed above, we’re expecting substantial impacts from snow to be limited to the NW hills. That said, with an elevation based event like this one, it’s almost impossible to show all of the details on a map, so consider it as somewhat of a guide. Generally though, in the highest elevations (above ~1500”), we expect the event to be substantially if not all snow, with close to if not warning level totals likely. The next band down (~1000-1500’), is the toss-up zone, where the cooler model solutions would bring a substantial amount of snow to the area while warmer solutions would be a quick inch or two and then over to rain. We mostly blended the models for this zone and then hedged just a hair colder, but this is definitely the area that I’m less confident in, and I wouldn’t be surprised to see tweaks in either direction tomorrow here. Below ~1000’, we’re relying on back-end snow to bring any accumulations we see. If the cold air comes in faster than expected or heavier bands of precipitation linger as the storm moves away, we could see a couple of inches, but I expect most outside of the NW hills to be closer to a coating than anything more.
This map is essentially a blend of model solutions that slightly favors the colder solutions, mostly due to the heavy precipitation rates and models often underestimating the amount of cold air available to our north. I think it would take a fairly large shift in guidance to bring totals up substantially, but we’ve certainly seen those shifts before… so never say never. On the other hand, however, a slight shift warmer on models would lead to this primarily being a rain event for all outside of the highest hills in NW CT (2000’+), which, while I don’t think is likely, is still an outcome that’s within the range of plausibility. We’ll hopefully get some more confidence tomorrow and will keep you updated.
Timing & Impacts
If you are hoping for widespread school cancellations, this is not the storm for you. Expect precipitation to move in Thursday night for most of the state. Areas away from the coastline may see a short period of snow at the very beginning of the storm, but that will quickly transition to a wintry mix and then to rain as warmer air works in. Precipitation continues overnight Thursday into Friday morning; if the northwest hills do change over to rain, I’d expect it to happen after sunrise on Friday. Precipitation begins to move out and become more scattered late on Friday, but things likely won’t fully clear out until very early Saturday morning. As colder temps come in on Friday evening, any areas in the hills that turned to rain will turn back to snow, and we may see some brief snow across lower northern areas to wrap things up, though any accumulations will remain minimal. The morning commute is likely to be tricky regardless of whether you are seeing rain or snow, and while widespread cancellations are not expected in Connecticut, they are likely in the NW hill towns, possible in NE hill towns, and far less likely elsewhere. There may be more scattered to widespread delays depending on how quickly things change over to rain.
For most, the main impact will be a wet, windy, raw Friday; it will definitely not be a great day to be outside. In the NW hills, where heavy snow is expected, difficult driving conditions are likely, and the risk of power outages from heavy wet snow is elevated. I don’t think the wind alone will be strong enough to cause major issues, but the snow and wind combined can be a strong one-two punch that will (especially if the snowier side of the forecast verifies) cause power outages, downed trees, etc. Nothing out of the ordinary for this region during the winter, and definitely nothing we haven’t seen before, but taking the usual preparation and precautions (making sure you have some food and water, gas for your generator if you have one, warm clothes, fully charged phones, etc.) will always serve you well.
All in all, expect a cold and wet Friday for most of the state, with a tricky forecast for the NW hills leading to high uncertainty around the risk for heavy wet snow. Luckily, we clear out for the weekend, with mostly sunny skies (especially by Sunday) and crisp temps expected; perfect for holiday shopping, decorating, and, for those of you in the NW hills, shoveling!
We’ll be back tomorrow with a final call. Until then, ask any and all of your questions on our social media pages, share our discussion with your friends and family, and thank you for reading and trusting SCW.
-SA
This map is essentially a blend of model solutions that slightly favors the colder solutions, mostly due to the heavy precipitation rates and models often underestimating the amount of cold air available to our north. I think it would take a fairly large shift in guidance to bring totals up substantially, but we’ve certainly seen those shifts before… so never say never. On the other hand, however, a slight shift warmer on models would lead to this primarily being a rain event for all outside of the highest hills in NW CT (2000’+), which, while I don’t think is likely, is still an outcome that’s within the range of plausibility. We’ll hopefully get some more confidence tomorrow and will keep you updated.
Timing & Impacts
If you are hoping for widespread school cancellations, this is not the storm for you. Expect precipitation to move in Thursday night for most of the state. Areas away from the coastline may see a short period of snow at the very beginning of the storm, but that will quickly transition to a wintry mix and then to rain as warmer air works in. Precipitation continues overnight Thursday into Friday morning; if the northwest hills do change over to rain, I’d expect it to happen after sunrise on Friday. Precipitation begins to move out and become more scattered late on Friday, but things likely won’t fully clear out until very early Saturday morning. As colder temps come in on Friday evening, any areas in the hills that turned to rain will turn back to snow, and we may see some brief snow across lower northern areas to wrap things up, though any accumulations will remain minimal. The morning commute is likely to be tricky regardless of whether you are seeing rain or snow, and while widespread cancellations are not expected in Connecticut, they are likely in the NW hill towns, possible in NE hill towns, and far less likely elsewhere. There may be more scattered to widespread delays depending on how quickly things change over to rain.
For most, the main impact will be a wet, windy, raw Friday; it will definitely not be a great day to be outside. In the NW hills, where heavy snow is expected, difficult driving conditions are likely, and the risk of power outages from heavy wet snow is elevated. I don’t think the wind alone will be strong enough to cause major issues, but the snow and wind combined can be a strong one-two punch that will (especially if the snowier side of the forecast verifies) cause power outages, downed trees, etc. Nothing out of the ordinary for this region during the winter, and definitely nothing we haven’t seen before, but taking the usual preparation and precautions (making sure you have some food and water, gas for your generator if you have one, warm clothes, fully charged phones, etc.) will always serve you well.
All in all, expect a cold and wet Friday for most of the state, with a tricky forecast for the NW hills leading to high uncertainty around the risk for heavy wet snow. Luckily, we clear out for the weekend, with mostly sunny skies (especially by Sunday) and crisp temps expected; perfect for holiday shopping, decorating, and, for those of you in the NW hills, shoveling!
We’ll be back tomorrow with a final call. Until then, ask any and all of your questions on our social media pages, share our discussion with your friends and family, and thank you for reading and trusting SCW.
-SA
