Good evening from Southern Connecticut Weather.
Last night we talked about an exceptionally potent setup that would trigger a major storm, and now we have high enough confidence in a major hit to issue this first call. Longtime followers know that at SCW we tend to lean conservative--we do not believe in hype, and when we speak, we want to speak from a place of thoughtfulness and no-nonsense analysis.
So let's set the record straight in case there's any confusion: this will be a blockbuster storm, but we are not expecting a historical impact type of storm. This storm is unlikely to be a Mount Rushmore storm (I believe our top four storms in CT history are the Blizzard of 1888, Blizzard of 2013, Blizzard of 1978, and October 2011 Snowstorm). This is a high end storm, but not on that level.
However, between the snow and the Arctic cold that both precedes and lingers after this storm, we could very well be looking at the most impactful week of winter weather in decades.
That's a big statement, so allow us the time to back it up with the data. This forecast will look at both the storm itself and the cold, because they heavily impact one another.
Let's dive in.
Last night we talked about an exceptionally potent setup that would trigger a major storm, and now we have high enough confidence in a major hit to issue this first call. Longtime followers know that at SCW we tend to lean conservative--we do not believe in hype, and when we speak, we want to speak from a place of thoughtfulness and no-nonsense analysis.
So let's set the record straight in case there's any confusion: this will be a blockbuster storm, but we are not expecting a historical impact type of storm. This storm is unlikely to be a Mount Rushmore storm (I believe our top four storms in CT history are the Blizzard of 1888, Blizzard of 2013, Blizzard of 1978, and October 2011 Snowstorm). This is a high end storm, but not on that level.
However, between the snow and the Arctic cold that both precedes and lingers after this storm, we could very well be looking at the most impactful week of winter weather in decades.
That's a big statement, so allow us the time to back it up with the data. This forecast will look at both the storm itself and the cold, because they heavily impact one another.
Let's dive in.
Above: the first call snowfall map. It speaks for itself. This is a broad brush for now, and as we get closer and get a sense of whether there's a real chance of mixing, and where banding may set itself up, we will likely drill down some more. The "error tail" here would favor us taking the numbers up to an extent, rather than taking them down, but we'll see by the time we issue the final.
The last time we had a widespread 12" snowfall was 2021. The high end snow totals in the central CT event in 2024 was fairly localized. The last time BDL recorded 18" of snow in a 48 hour period was the Great Blizzard of 2013, where it recorded 22.3" of snow. The last time BDR recorded 18" was also the Great Blizzard of 2013, where it recorded its all time two day record of 30.0".
Overall Setup
The overall setup hasn't changed since last night, except with one crucial change that brings heightened potential...and uncertainty.
As we said last night, extreme temperature regimes can trigger extreme atmospheric responses. You can see that something extreme is on the way by looking at the national hazard map.
The last time we had a widespread 12" snowfall was 2021. The high end snow totals in the central CT event in 2024 was fairly localized. The last time BDL recorded 18" of snow in a 48 hour period was the Great Blizzard of 2013, where it recorded 22.3" of snow. The last time BDR recorded 18" was also the Great Blizzard of 2013, where it recorded its all time two day record of 30.0".
Overall Setup
The overall setup hasn't changed since last night, except with one crucial change that brings heightened potential...and uncertainty.
As we said last night, extreme temperature regimes can trigger extreme atmospheric responses. You can see that something extreme is on the way by looking at the national hazard map.
As you can see above, the extreme cold is definitely on the way. We see extreme cold warnings, which replace wind chill warnings, all across the upper Midwest and into New England. You also see cold weather advisories across the Midwest, our region, and all the way into the south.
This is a high end blast of cold in both geographic scope and intensity. It will be the key ingredient in triggering development of our storm as it creates an intense baroclinic zone, that is the boundary between the warmth from the Gulf and cold in the north. As the moisture rises over the cold dome, boom, blockbuster.
This is a high end blast of cold in both geographic scope and intensity. It will be the key ingredient in triggering development of our storm as it creates an intense baroclinic zone, that is the boundary between the warmth from the Gulf and cold in the north. As the moisture rises over the cold dome, boom, blockbuster.
We shared it last night and we're sharing it again, above is what an overrunning setup looks like. The depth of the cold over us will in effect supercharge our storm, as it will help create an environment incredibly efficient at wringing out as much moisture as possible from the atmosphere.
Last night we mentioned that a more efficient phasing of the northern and souther lobes of energy would trigger a more potent coastal storm, and the trend today has been toward that. Critically, that would extend the duration of the storm, with moisture still getting thrown back into New England well into Monday.
The GFS, which has been the least bullish to an extent, shows this too today. Note the darker shades of blue on the surface depiction below. That means heavier precipitation. Note also how the snow lasts through most of Monday. If that were to be the case, it would increase the chances of more snowfall.
Last night we mentioned that a more efficient phasing of the northern and souther lobes of energy would trigger a more potent coastal storm, and the trend today has been toward that. Critically, that would extend the duration of the storm, with moisture still getting thrown back into New England well into Monday.
The GFS, which has been the least bullish to an extent, shows this too today. Note the darker shades of blue on the surface depiction below. That means heavier precipitation. Note also how the snow lasts through most of Monday. If that were to be the case, it would increase the chances of more snowfall.
Now, with a bigger push of warmth hitting the wall of cold, and the lows above the surface likely cutting to our west, it increases the chance of mixing in coastal areas--after the bulk of the snow has fallen. No one should be reading this and believing that all of a sudden it will be raining in Norwalk at any point during this storm. It will be a frigid storm, and much colder than normal when we're snowing. This is just highlighting that if we have dry slotting (which happens in high end storms) or things tick north it may lead to periods of sleet. That's something we'll be watching. In this instance, being close to the sleet line may mean some high end snowfall rates.
The Forecast
Ok, so what does this mean for your backyard?
Big snow.
Timing
It looks like we're getting into better agreement for timing for onset, but keep in mind that there's still uncertainty over the end time.
There is a chance the onset time slides a little later in the morning, but overall the expectation is that snow begins from SW to NE between 6-10am. It may take a little time for the atmosphere to saturate because temperatures will likely be near zero or in the single digits Sunday morning, but once things get going we will quickly go to moderate and heavy. It is strongly advised to be off the roads once this begins.
The Forecast
Ok, so what does this mean for your backyard?
Big snow.
Timing
It looks like we're getting into better agreement for timing for onset, but keep in mind that there's still uncertainty over the end time.
There is a chance the onset time slides a little later in the morning, but overall the expectation is that snow begins from SW to NE between 6-10am. It may take a little time for the atmosphere to saturate because temperatures will likely be near zero or in the single digits Sunday morning, but once things get going we will quickly go to moderate and heavy. It is strongly advised to be off the roads once this begins.
Above is the 12z Euro, which has led the way and been one of the most aggressive models. Snow begins Sunday morning and quickly goes moderate to heavy. The heaviest happens Sunday afternoon through the the evening. By early Monday morning we likely start seeing the precipitation intensity slacken, and this is one of the periods we think the sleet risk may be at its highest. Note how close the mix line is by about 1am Monday morning.
This the the higher confidence portion of the forecast, but this is where it gets tricky.
Do we get that coastal enhancement to extend snow?
This the the higher confidence portion of the forecast, but this is where it gets tricky.
Do we get that coastal enhancement to extend snow?
Here's what the Euro depicts, and right now the idea is gaining steam. If the cleaner phase were to happen, it would kind of prolong the coastal low from moving away so fast and enhance snow across much of the region. This is lower confidence, but if this feature were to happen it would enhance the chance of higher snow totals. It'd also mean that Tuesday would also be a day full of cancellations statewide as we clean up.
Snow Accumulation
This is a big dog. There will be big accumulations from Virginia all the way to Maine. There are a few reasons for this, and they have to do with the depth of our cold. To do this, we need to look at the vertical profile of the atmosphere, a sounding. Below are Hartford (top) and Bridgeport (bottom).
This is a big dog. There will be big accumulations from Virginia all the way to Maine. There are a few reasons for this, and they have to do with the depth of our cold. To do this, we need to look at the vertical profile of the atmosphere, a sounding. Below are Hartford (top) and Bridgeport (bottom).
In both images, a lot stands out. First, there is plenty of cold throughout the column. Even though there's a risk of mixing along the coast, the surface is plenty cold as it stands.
Second, look to the left. There is excellent lift throughout the column. In this case, the dendritic growth zone is right where we want it, and the lift takes advantage of it for hours. That means we likely get consistent moderate to heavy snow with excellent snow growth.
Second, look to the left. There is excellent lift throughout the column. In this case, the dendritic growth zone is right where we want it, and the lift takes advantage of it for hours. That means we likely get consistent moderate to heavy snow with excellent snow growth.
Then we have the coastal low. This is where the cold aloft is major. As easterly-ENE flow pulls moisture from the ocean over the region, that moisture just piles up and gets wrung out over the region. We're looking at a high precipitation event, and that, combined with the prospect of high ratios means that we are likely to get big totals.
If we can get more moisture with the coastal low on Monday to flow over the Arctic air...it just ups the ante. We won't really know if that's probable until Saturday.
These are ensemble totals for total precipitation for the storm. This combined with higher than 10:1 ratios overall strongly suggest totals in excess of 12". The National Blend of Models (NBM) shows consensus on an inch of liquid at least.
If we can get more moisture with the coastal low on Monday to flow over the Arctic air...it just ups the ante. We won't really know if that's probable until Saturday.
These are ensemble totals for total precipitation for the storm. This combined with higher than 10:1 ratios overall strongly suggest totals in excess of 12". The National Blend of Models (NBM) shows consensus on an inch of liquid at least.
As a result, we currently have a broad brush of 12-20", with a chance that these numbers are refined some as we get closer and understand where banding (which will promote higher ratios) will land.
Now, 12-20" is a big zone. That's how it goes in big dog events. Not everybody is going to go that high, but there is enough risk that for now we have that as the ceiling. Hill towns, I'm looking at you.
Wind & Power Outages
Fortunately, at this time we do not expect significant wind. In fact, that probably helps keep the ratios higher for snowfall, which also meets a fluffy snow. As a result, we think the power outages are minimal.
Overall Impact
This is likely to be a high end event. There will be heavy snow, high end accumulation, and cold temperatures throughout the storm, especially if the mix line remains well to the south. Road conditions will be severely impacted from Sunday possibly through Monday, with residual impacts possible into Tuesday. Everything is likely to be closed on Monday, with a chance of delays and cancellations on Tuesday.
We'll get through this, but take it seriously.
And now, the cold...
High End Arctic Blast
Now, 12-20" is a big zone. That's how it goes in big dog events. Not everybody is going to go that high, but there is enough risk that for now we have that as the ceiling. Hill towns, I'm looking at you.
Wind & Power Outages
Fortunately, at this time we do not expect significant wind. In fact, that probably helps keep the ratios higher for snowfall, which also meets a fluffy snow. As a result, we think the power outages are minimal.
Overall Impact
This is likely to be a high end event. There will be heavy snow, high end accumulation, and cold temperatures throughout the storm, especially if the mix line remains well to the south. Road conditions will be severely impacted from Sunday possibly through Monday, with residual impacts possible into Tuesday. Everything is likely to be closed on Monday, with a chance of delays and cancellations on Tuesday.
We'll get through this, but take it seriously.
And now, the cold...
High End Arctic Blast
Above: the European model projection for wind chills at approximately 7am on Saturday. A cold weather advisory (replacing the old wind chill advisory) is up for the entire state during this period.
We have been talking a lot about the winter storm, but we've also been talking about the big Arctic blast. As you know by now, it is responsible for the storm and is coming straight from the Arctic in unusually unmoderated form.
The big low temperatures that were once projected for the weekend have become more uncertain, as they've moderated some as we pump the heights in front of our Sunday storm. The cold is still legitimate however, and we need to take heed that we're entering what may be a historic stretch of cold weather. We may have gotten a warning shot across the bow earlier this week, when parts of the state went well below zero.
To be sure, it gets cold in Connecticut. We've had much lower lows and much lower high temperatures than what we're likely to see, but in CT we don't get too hot or too cold, and too hot or too cold for too long because of the moderating influence of the Atlantic. This means that while we may get extreme blasts of warmth and cold, they don't last long.
That may be different here.
Digging into the data and comparing it to the ensembles, what I found is that we could be entering a period of consistent cold that we don't see often. Historic doesn't mean coldest ever, but if these numbers get close to verifying we may be in one of our coldest periods in at least the last 25 years if not longer.
Let's start with the expected cold.
We have been talking a lot about the winter storm, but we've also been talking about the big Arctic blast. As you know by now, it is responsible for the storm and is coming straight from the Arctic in unusually unmoderated form.
The big low temperatures that were once projected for the weekend have become more uncertain, as they've moderated some as we pump the heights in front of our Sunday storm. The cold is still legitimate however, and we need to take heed that we're entering what may be a historic stretch of cold weather. We may have gotten a warning shot across the bow earlier this week, when parts of the state went well below zero.
To be sure, it gets cold in Connecticut. We've had much lower lows and much lower high temperatures than what we're likely to see, but in CT we don't get too hot or too cold, and too hot or too cold for too long because of the moderating influence of the Atlantic. This means that while we may get extreme blasts of warmth and cold, they don't last long.
That may be different here.
Digging into the data and comparing it to the ensembles, what I found is that we could be entering a period of consistent cold that we don't see often. Historic doesn't mean coldest ever, but if these numbers get close to verifying we may be in one of our coldest periods in at least the last 25 years if not longer.
Let's start with the expected cold.
Above: the 12z EPS depicting deep and persistent Arctic cold over the eastern U.S. all the way from tomorrow into February. While we may have a "warm" day scattered in there, if not, we may threaten some records for length of cold.
We can already discern multiple cold blasts. The first happens in advance of our Sunday storm. Saturday and Sunday look frigid. Then we can expect a reinforcing shot of cold as the storm departs Tuesday. From there, we'll see how frequent this overall hemispheric pattern pushes cold into the region.
Here are predicted numbers by the Euro and GFS ensembles for Hartford and Bridgeport for the foreseeable future. These will change, but I want you to see the trend.
EPS on the top.
We can already discern multiple cold blasts. The first happens in advance of our Sunday storm. Saturday and Sunday look frigid. Then we can expect a reinforcing shot of cold as the storm departs Tuesday. From there, we'll see how frequent this overall hemispheric pattern pushes cold into the region.
Here are predicted numbers by the Euro and GFS ensembles for Hartford and Bridgeport for the foreseeable future. These will change, but I want you to see the trend.
EPS on the top.
Now for the GFS Ensembles.
You can take your pick with them, but the length of the cold is extraordinarily impressive. Verbatim, this kind of persistent cold starting Friday would put us in rare territory in terms of length and possible intensity of the cold.
It was 2018 that we last had a historic long duration outbreak of cold, but once you get past that you need to go to 2015 or 2005, and depending on how cold we get, even further back.
It was 2018 that we last had a historic long duration outbreak of cold, but once you get past that you need to go to 2015 or 2005, and depending on how cold we get, even further back.
Days below freezing is easiest to track. The GEFS has 15 days at or below 32 at BDL as a model mean, while the EPS has 14. That would be the longest streak in 21 years, and tied for 4th longest on record.
Let's get colder.
Let's get colder.
If the ensembles were to verify--keep in mind these are not just operational models we're pulling here, it could mean the longest streak since 2018, and if another day could be tacked on, perhaps the most consistent cold going back much further.
Let's get even colder.
Let's get even colder.
This is the coldest, but by far most impressive. Here the Euro and GFS ensembles diverge. If the EPS were right, however, BDL would have a shot at its coldest period using this metric since 2018, or if Monday trends colder--1979.
For Bridgeport, if that cold snap in the wake of the storm happens, it'd be the coldest stretch using this metric, which is not a cherry picked stat, since 1982. Each blast would possibly come with extreme wind chills as well.
So while we of course track the storms, we need to be mindful of the cold. What's coming isn't something we see often, and it could be historic.
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
For Bridgeport, if that cold snap in the wake of the storm happens, it'd be the coldest stretch using this metric, which is not a cherry picked stat, since 1982. Each blast would possibly come with extreme wind chills as well.
So while we of course track the storms, we need to be mindful of the cold. What's coming isn't something we see often, and it could be historic.
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
