Good afternoon from SCW!
It’s been quite a minute since I’ve written one of these…mostly because it’s been quite a minute since we’ve had a legitimate snow threat to talk about here in Connecticut. Let’s see if we still remember how to handle it 🙂.
As Don outlined yesterday, all eyes are on a coastal low that will track northward over the next couple of days, eventually reaching the state on Saturday evening and bringing heavy precipitation to the state. For inland areas, we’re confident that this precipitation will fall as snow, with warning level amounts likely. However, for the immediate coastline, it’ll be a battle between strong dynamics keeping temperatures cold and warmer Atlantic air being drawn in. Yesterday, the models were a bit more confident in the former scenario, today, we’re seeing some signs of the latter, but it’s really still too close to call. For those of you near the coast, this is a lower confidence forecast than inland - things can and likely will change. With all of that said, let’s dive into the models.
Model Review
Let’s start with what we have consensus on. All models agree that a coastal storm will track south of Connecticut Saturday night into Sunday, and all models agree that copious amounts of liquid equivalent will fall. Here’s a view of the whole system on the RGEM model - graphics courtesy of Tropical Tidbits.
It’s been quite a minute since I’ve written one of these…mostly because it’s been quite a minute since we’ve had a legitimate snow threat to talk about here in Connecticut. Let’s see if we still remember how to handle it 🙂.
As Don outlined yesterday, all eyes are on a coastal low that will track northward over the next couple of days, eventually reaching the state on Saturday evening and bringing heavy precipitation to the state. For inland areas, we’re confident that this precipitation will fall as snow, with warning level amounts likely. However, for the immediate coastline, it’ll be a battle between strong dynamics keeping temperatures cold and warmer Atlantic air being drawn in. Yesterday, the models were a bit more confident in the former scenario, today, we’re seeing some signs of the latter, but it’s really still too close to call. For those of you near the coast, this is a lower confidence forecast than inland - things can and likely will change. With all of that said, let’s dive into the models.
Model Review
Let’s start with what we have consensus on. All models agree that a coastal storm will track south of Connecticut Saturday night into Sunday, and all models agree that copious amounts of liquid equivalent will fall. Here’s a view of the whole system on the RGEM model - graphics courtesy of Tropical Tidbits.
Models are generally aligned with 1” or more of liquid equivalent across the state, with some of the stronger models (namely the GFS) showing over 2” in some spots. Using a standard 10:1 snow to liquid ratio, that’s a double digit snowfall verbatim.
Below is the total liquid equivalent through Sunday evening from four models - the GFS, Euro, NAM, and RGEM. The first two are lower resolution global models, while the second two are higher resolution regional models - sometimes the latter are more effective at identifying more localized variances in precipitation. Images courtesy of Pivotal Weather.
Below is the total liquid equivalent through Sunday evening from four models - the GFS, Euro, NAM, and RGEM. The first two are lower resolution global models, while the second two are higher resolution regional models - sometimes the latter are more effective at identifying more localized variances in precipitation. Images courtesy of Pivotal Weather.
All models are showing a healthy amount of precipitation, and there is a pretty good amount of wiggle room in any direction. I don’t expect this storm to suddenly dry up or shift away from us - at this range and with this much consensus, we can be pretty confident that a storm is coming and it is going to impact Connecticut.
That said, it’s worth calling out that the NAM and to a lesser extent the RGEM are showing an area of stronger precipitation through the middle of the state, with the SE and NW portions being to the edge of that max. This can sometimes suggest the development of a stronger band, with areas of subsidence on either side of it. If that band does set up and where it does will be critical in determining ultimate snowfall amounts, and until we get closer to go time, zooming in on that is almost fruitless. Just recognize that there’s some variance potential as is usually the case with banding.
What is a lot less clear though are temperatures. Yesterday, we had decent model consensus on a solution that was just cold enough to keep the entire state mostly or all snow. Today, we’ve seen a couple models tick ever so slightly warmer, which would be enough to introduce mixing and rain to the shoreline. This is far from a sure thing, though - we’re still about 60 hours out from the core of the storm, and a colder solution is well within the envelope of possibilities. For that matter, so is a warmer solution, where coastal areas would see mostly rain and even inland valleys could see some mixing. We don’t expect that right now, but we certainly aren’t safe from it occurring.
To illustrate the variance, let’s take a look at the NAM (warmest model) and GFS (coldest model). NAM is on the left, GFS on the right, images are 925mb temp (temp slightly above the surface), surface temp, and 3 hour precipitation - all of these are for 10 AM on Sunday.
That said, it’s worth calling out that the NAM and to a lesser extent the RGEM are showing an area of stronger precipitation through the middle of the state, with the SE and NW portions being to the edge of that max. This can sometimes suggest the development of a stronger band, with areas of subsidence on either side of it. If that band does set up and where it does will be critical in determining ultimate snowfall amounts, and until we get closer to go time, zooming in on that is almost fruitless. Just recognize that there’s some variance potential as is usually the case with banding.
What is a lot less clear though are temperatures. Yesterday, we had decent model consensus on a solution that was just cold enough to keep the entire state mostly or all snow. Today, we’ve seen a couple models tick ever so slightly warmer, which would be enough to introduce mixing and rain to the shoreline. This is far from a sure thing, though - we’re still about 60 hours out from the core of the storm, and a colder solution is well within the envelope of possibilities. For that matter, so is a warmer solution, where coastal areas would see mostly rain and even inland valleys could see some mixing. We don’t expect that right now, but we certainly aren’t safe from it occurring.
To illustrate the variance, let’s take a look at the NAM (warmest model) and GFS (coldest model). NAM is on the left, GFS on the right, images are 925mb temp (temp slightly above the surface), surface temp, and 3 hour precipitation - all of these are for 10 AM on Sunday.
Looking first at the precipitation maps, we see that the GFS is much more aggressive than the NAM, indicating a stronger system. This isn’t a surprise, given what we saw above, where the GFS was the wettest overall and the NAM the driest (and notice the banding on the GFS here as well).
Next, let’s look at 925mb temps just above the surface - the GFS is a bit colder overall than the NAM, but both are still below freezing.
Finally, looking at the surface temps, we see the GFS is just about at freezing across the state (temps 32-33 degrees aside from the hills which are colder) while the NAM is above freezing everywhere (temps 34-38 degrees).
The GFS solution would be snow, the NAM solution rain. Why? In marginal temperature profiles, heavier precipitation can cool the column to be “just cold enough” to support snow all the way to the surface. The increased cold from the heavier snow on the GFS cools the air around it juuuust enough for it to remain snow to the surface, while the NAM isn’t able to bring that colder air down and therefore we see rain. The other models are in the middle, but the NAM is definitely more of a warm outlier than the GFS is a cold outlier - notably, the most recent 12z Euro was a tick colder and closer to the GFS than previous runs were.
Ultimately, precipitation type is going to come down to three things.
Unfortunately, we don’t know the answers to these questions yet…so for the shore, where things are the most marginal, confidence is lowest. That said, it’s time to put a map out there, so let’s take stock of where we’re at and put some numbers on the board.
Forecast Snowmap
Here’s our forecast snowmap for the event. Across most of the state, we’re expecting six to twelve inches of snow, with lesser amounts on the immediate coastline, where mixing and rain may cut into totals.
Next, let’s look at 925mb temps just above the surface - the GFS is a bit colder overall than the NAM, but both are still below freezing.
Finally, looking at the surface temps, we see the GFS is just about at freezing across the state (temps 32-33 degrees aside from the hills which are colder) while the NAM is above freezing everywhere (temps 34-38 degrees).
The GFS solution would be snow, the NAM solution rain. Why? In marginal temperature profiles, heavier precipitation can cool the column to be “just cold enough” to support snow all the way to the surface. The increased cold from the heavier snow on the GFS cools the air around it juuuust enough for it to remain snow to the surface, while the NAM isn’t able to bring that colder air down and therefore we see rain. The other models are in the middle, but the NAM is definitely more of a warm outlier than the GFS is a cold outlier - notably, the most recent 12z Euro was a tick colder and closer to the GFS than previous runs were.
Ultimately, precipitation type is going to come down to three things.
- How strong is the eventual storm and how intense is the precipitation?
- How strong is the high pressure to the north of us?
- How cold is the antecedent airmass we’re working with? If it gets a hair colder or warmer tomorrow/Saturday than expected, that can influence things one way or the other.
Unfortunately, we don’t know the answers to these questions yet…so for the shore, where things are the most marginal, confidence is lowest. That said, it’s time to put a map out there, so let’s take stock of where we’re at and put some numbers on the board.
Forecast Snowmap
Here’s our forecast snowmap for the event. Across most of the state, we’re expecting six to twelve inches of snow, with lesser amounts on the immediate coastline, where mixing and rain may cut into totals.
For most of the state, we don’t think precipitation type will be a major issue. Without the influence of warmer marine air, the high pressure to the north plus the just cold enough antecedent airmass plus the strong precipitation rates should be just enough to keep things all snow. With that in mind, the model average of ~1” of liquid would scale up to about 10” of snow, so 6-12” seems like a fair starting point. This far out, I want to stay a bit conservative as things could easily speed up or weaken a bit, though there is certainly possibility for higher totals as well - we’d need a cold, consolidated storm like the GFS, with some strong banding, to see that. We’ll see if we see that trend continue when we get to the final numbers tomorrow. It’s worth calling out that the NAM solution would bring substantially lower snowfall totals, with areas outside of the hills struggling to hit the 6-8” range. That’s an outlier solution right now, but certainly still within the envelope of possibilities - I’d say there’s a 10-15% chance we fail to reach 6” outside of the hills.
On the coastline however, the story is much murkier. A colder solution, like what’s shown on the GFS, would bring the 6-12” zone all the way to the coastline. A warmer solution, like the NAM, would bring mostly cold rain, with a couple sloppy inches on the front and back end. The middle ground keeps things mostly snow from the sky, but accumulations may be a struggle except times of heavier precipitation, and a changeover to rain during the middle of the storm may be possible. This far out, it’s impossible to know where we’ll land. I would probably lean ever so slightly towards the colder solution, given the influence of the colder high to the north and the fact that coastal storms often have a slight southeast trend (keeping us away from the warmer sector) in the final hours, but honestly at this point it’s only a bit better hunch than a coinflip.
So, for now, we’ll split the difference and go with four to eight inches for the immediate coastline, with some mixing with rain during times of lighter precipitation. This is the zone we’ll be watching most closely in the model runs to come, and we’ll hopefully have a bit more confidence in which way it’ll go tomorrow. The last thing I'll say for the shoreline is that there is the potential for a significant gradient across the first few miles inland. I could easily see a situation where the Cove in Stamford gets a couple wet inches, my old house in Hubbard Heights gets 6", and North Stamford gets a foot. When you have a marine influence on a marginal airmass, sometimes that extra mile or two makes all the difference. We'll see, but definitely something we're keeping an eye on.
Forecast confidence is moderate to high for the interior - the precipitation will definitely be there and absent a NAM like solution, the temperatures will be too. It’ll likely come down to the exact track and the banding for who gets the most snow, but ultimately those are things that we’ll just have to see play out - after all, that’s why we get to have a range when forecasting! The biggest bust potential is probably warmer temperatures, and the biggest boom potential would be the system strengthening beyond what’s currently shown on guidance. If a GFS like scenario were to verify, we’d expect widespread totals over a foot (and conversely, a NAM scenario is probably only a few inches with a lot of rain), though the odds of either aren’t something I’d bet on right now.
Forecast confidence for the coast is low. We know we’ll get a lot of precipitation, but we really don’t know how warm or cold it will be, and small shifts one way or the other are going to have a big impact. We’re hedging a little bit less snowy than the model consensus right now, so I’d probably lean a bit more towards these numbers going up vs. down, but when you look at the big picture, the magnitude of changes aloft is going to be relatively small/hard to model compared to the magnitude of changes in surface impact.
So, unfortunately, as hard as it is to say, we’re going to have to wait and see for the coast. We’ll be watching every model run as it comes in and will have the updates all the way up to go time, including an updated forecast map tomorrow evening. Give us a like on Facebook or a follow on Twitter/X to get the most up to date information.
Timing and Impacts
Saturday should be mostly dry, with precipitation moving in during the evening hours. Travel, flights, etc. should all be good to go until the very late hours of Saturday evening.
Overnight Saturday into Sunday, the storm strengthens, precipitation intensity increases, and warmer air tries to move in, potentially changing coastal areas to a mix or rain. Precipitation should remain consistent through Sunday morning before starting to taper from west to east Sunday afternoon, mostly clearing the state by sunset on Sunday. As a cold front comes in behind the storm, any remaining precipitation will shift back over to snow on Sunday afternoon.
Road conditions will likely be challenging from Saturday evening through Sunday, especially on secondary and tertiary roads away from the coastline. Things may clear up later Sunday afternoon, especially in southern and western areas, but avoiding travel on Sunday is probably a good idea if you can. I’d expect things to be good to go for the Monday AM commute - sorry, kids and teachers, but snow day potential appears unlikely.
Power outages are possible from wet heavy snow, though luckily winds appear to be on the milder side for this storm, so I don’t expect them to be widespread.
Snow consistency should be moderate to wet - perfect for snowballs and igloos. Send us your best snowplay photos - we love to see them!
The Bottom Line
For the first time in almost two years, significant snow is coming to Connecticut. While we don’t know quite how much for some areas yet, this will almost definitely be the largest storm since 2022 for every corner of the state. Plan ahead, prepare, and enjoy!
We’ll be back tomorrow evening with an updated discussion and a final snowmap, hopefully with some more clarity in the coastal areas. In the meantime, join us on our social platforms for microupdates, Q&A, and more.
As always, thank you for trusting SCW. It’s a pleasure to serve you.
-SA
On the coastline however, the story is much murkier. A colder solution, like what’s shown on the GFS, would bring the 6-12” zone all the way to the coastline. A warmer solution, like the NAM, would bring mostly cold rain, with a couple sloppy inches on the front and back end. The middle ground keeps things mostly snow from the sky, but accumulations may be a struggle except times of heavier precipitation, and a changeover to rain during the middle of the storm may be possible. This far out, it’s impossible to know where we’ll land. I would probably lean ever so slightly towards the colder solution, given the influence of the colder high to the north and the fact that coastal storms often have a slight southeast trend (keeping us away from the warmer sector) in the final hours, but honestly at this point it’s only a bit better hunch than a coinflip.
So, for now, we’ll split the difference and go with four to eight inches for the immediate coastline, with some mixing with rain during times of lighter precipitation. This is the zone we’ll be watching most closely in the model runs to come, and we’ll hopefully have a bit more confidence in which way it’ll go tomorrow. The last thing I'll say for the shoreline is that there is the potential for a significant gradient across the first few miles inland. I could easily see a situation where the Cove in Stamford gets a couple wet inches, my old house in Hubbard Heights gets 6", and North Stamford gets a foot. When you have a marine influence on a marginal airmass, sometimes that extra mile or two makes all the difference. We'll see, but definitely something we're keeping an eye on.
Forecast confidence is moderate to high for the interior - the precipitation will definitely be there and absent a NAM like solution, the temperatures will be too. It’ll likely come down to the exact track and the banding for who gets the most snow, but ultimately those are things that we’ll just have to see play out - after all, that’s why we get to have a range when forecasting! The biggest bust potential is probably warmer temperatures, and the biggest boom potential would be the system strengthening beyond what’s currently shown on guidance. If a GFS like scenario were to verify, we’d expect widespread totals over a foot (and conversely, a NAM scenario is probably only a few inches with a lot of rain), though the odds of either aren’t something I’d bet on right now.
Forecast confidence for the coast is low. We know we’ll get a lot of precipitation, but we really don’t know how warm or cold it will be, and small shifts one way or the other are going to have a big impact. We’re hedging a little bit less snowy than the model consensus right now, so I’d probably lean a bit more towards these numbers going up vs. down, but when you look at the big picture, the magnitude of changes aloft is going to be relatively small/hard to model compared to the magnitude of changes in surface impact.
So, unfortunately, as hard as it is to say, we’re going to have to wait and see for the coast. We’ll be watching every model run as it comes in and will have the updates all the way up to go time, including an updated forecast map tomorrow evening. Give us a like on Facebook or a follow on Twitter/X to get the most up to date information.
Timing and Impacts
Saturday should be mostly dry, with precipitation moving in during the evening hours. Travel, flights, etc. should all be good to go until the very late hours of Saturday evening.
Overnight Saturday into Sunday, the storm strengthens, precipitation intensity increases, and warmer air tries to move in, potentially changing coastal areas to a mix or rain. Precipitation should remain consistent through Sunday morning before starting to taper from west to east Sunday afternoon, mostly clearing the state by sunset on Sunday. As a cold front comes in behind the storm, any remaining precipitation will shift back over to snow on Sunday afternoon.
Road conditions will likely be challenging from Saturday evening through Sunday, especially on secondary and tertiary roads away from the coastline. Things may clear up later Sunday afternoon, especially in southern and western areas, but avoiding travel on Sunday is probably a good idea if you can. I’d expect things to be good to go for the Monday AM commute - sorry, kids and teachers, but snow day potential appears unlikely.
Power outages are possible from wet heavy snow, though luckily winds appear to be on the milder side for this storm, so I don’t expect them to be widespread.
Snow consistency should be moderate to wet - perfect for snowballs and igloos. Send us your best snowplay photos - we love to see them!
The Bottom Line
For the first time in almost two years, significant snow is coming to Connecticut. While we don’t know quite how much for some areas yet, this will almost definitely be the largest storm since 2022 for every corner of the state. Plan ahead, prepare, and enjoy!
We’ll be back tomorrow evening with an updated discussion and a final snowmap, hopefully with some more clarity in the coastal areas. In the meantime, join us on our social platforms for microupdates, Q&A, and more.
As always, thank you for trusting SCW. It’s a pleasure to serve you.
-SA
