Good evening from SCW!
We’ve got a major winter storm on our hands for tomorrow evening into Thursday that will bring significant snow accumulations to the entire state. In this discussion, we’ll dive into our final snow map, look at what’s changed since yesterday, show the uncertainties that remain in the forecast, and discuss timing and impacts. We’re also going to be live on our Facebook page tonight from 7-8 PM to take questions on this upcoming system, so feel free to stop by and say hello! With that, let’s jump right in.
Forecast Snowmap
We’ve got a major winter storm on our hands for tomorrow evening into Thursday that will bring significant snow accumulations to the entire state. In this discussion, we’ll dive into our final snow map, look at what’s changed since yesterday, show the uncertainties that remain in the forecast, and discuss timing and impacts. We’re also going to be live on our Facebook page tonight from 7-8 PM to take questions on this upcoming system, so feel free to stop by and say hello! With that, let’s jump right in.
Forecast Snowmap
Our final call for the event is the same as our first call yesterday; 8-16 inches of snow statewide. We tried to tighten up the ranges this afternoon and introduce multiple zones to the forecast but decided as a team that there is too much uncertainty remaining in the models regarding where the best banding develops (more on that in a minute) to get more specific, and we’d rather have a large range and be right than try to get too fancy and end up missing the mark. Details are good, but only if they are accurate and reliable. That said, we will continue to watch the guidance, and should there be an opportunity to get more specific tomorrow, we will publish a revised map.
Models, Trends, and Changes
When Don wrote yesterday, he showed the Euro and Canadian models, which were big hits for the state, and also showed the GFS model, where totals were lower because banding stayed to the south of Connecticut. He suggested that the model was on an island and away from its own ensembles, and expected it to move north to match the consensus. By and large, that’s what happened, but we also saw a noticeable shift north in the consensus track as well through the midday runs, so much so that we were starting to get concerned about potential mixing in southern areas and the heaviest banding confined to the NW hills.
However, on the most recent 18z runs, we’ve seen a shift back south on the models, suggesting that we may have reached the extent of the north trend. The current position of the system is ideal for strong banding to develop over Connecticut, resulting in big snow totals for those lucky (or unlucky depending on your point of view) to end up under it.
Here’s a look at the five most recent runs of the NAM from 18z yesterday to 18z today. Notice how the heaviest banding (darker blues) shifted from central CT on yesterdays run up into MA and southern NH before coming back down into CT on the most recent run, and notice that along the shoreline, warmer air and lower precip rates are enough to turn things over to mixed precipitation for a time.
Models, Trends, and Changes
When Don wrote yesterday, he showed the Euro and Canadian models, which were big hits for the state, and also showed the GFS model, where totals were lower because banding stayed to the south of Connecticut. He suggested that the model was on an island and away from its own ensembles, and expected it to move north to match the consensus. By and large, that’s what happened, but we also saw a noticeable shift north in the consensus track as well through the midday runs, so much so that we were starting to get concerned about potential mixing in southern areas and the heaviest banding confined to the NW hills.
However, on the most recent 18z runs, we’ve seen a shift back south on the models, suggesting that we may have reached the extent of the north trend. The current position of the system is ideal for strong banding to develop over Connecticut, resulting in big snow totals for those lucky (or unlucky depending on your point of view) to end up under it.
Here’s a look at the five most recent runs of the NAM from 18z yesterday to 18z today. Notice how the heaviest banding (darker blues) shifted from central CT on yesterdays run up into MA and southern NH before coming back down into CT on the most recent run, and notice that along the shoreline, warmer air and lower precip rates are enough to turn things over to mixed precipitation for a time.
Overall, the trend has clearly been towards enhancing the banding aspect of the system – this snapshot from the RGEM shows it sell, with a heavier band of snow into southern VT/NH, a dryslot in northern CT/MA, and then another band in southern and eastern CT. Note that this is one of the more northern solutions; plenty of other models pull that larger band down into northern CT, but I like this view to show the structure of the system as the two bands are clearly outlined.
This type of structure is not uncommon in large storms, but it means that there are areas of high totals right next to areas of much lower totals, as the banding tends to create subsidence on either side of it and hence a dry slot with lower precipitation rates or even none at all. What’s less clear is where the banding ends up. If we see the storm stay in the same position that it’s in now, we’ll likely see a heavier band along the shoreline and then another one in the NW hills, with the center of the state in a relative minimum (but still a significant snowfall). However, any small shift north or south will cause a shift in that distribution, hence why we kept a broader range across the state. I’m hoping that we can zoom into two zones (likely 8-12” and 10-16”) tomorrow as we get more clarity on the final track and hence band placement, but we’ll see if we can get any better consensus.
To sum it up – we’re still on track for a large system, but the trend is towards a more banded precipitation shield, meaning that there will be high amounts of variance in totals across relatively small distances and it’s difficult to know where the relative mins and maxes will be.
Remaining Uncertainty
We covered a lot of this in the above section, but let’s briefly sum up what we know and don’t know.
What we know:
What we don’t know:
Timing and Impacts
Timing
Here’s a loop of the entire system (1 PM Wednesday to 1 PM Thursday) from the RGEM. Take this as a general idea of how the timing progresses and not as an indicator of where the heaviest snow will fall, as there’s still quite a bit of uncertainty with the banding.
This type of structure is not uncommon in large storms, but it means that there are areas of high totals right next to areas of much lower totals, as the banding tends to create subsidence on either side of it and hence a dry slot with lower precipitation rates or even none at all. What’s less clear is where the banding ends up. If we see the storm stay in the same position that it’s in now, we’ll likely see a heavier band along the shoreline and then another one in the NW hills, with the center of the state in a relative minimum (but still a significant snowfall). However, any small shift north or south will cause a shift in that distribution, hence why we kept a broader range across the state. I’m hoping that we can zoom into two zones (likely 8-12” and 10-16”) tomorrow as we get more clarity on the final track and hence band placement, but we’ll see if we can get any better consensus.
To sum it up – we’re still on track for a large system, but the trend is towards a more banded precipitation shield, meaning that there will be high amounts of variance in totals across relatively small distances and it’s difficult to know where the relative mins and maxes will be.
Remaining Uncertainty
We covered a lot of this in the above section, but let’s briefly sum up what we know and don’t know.
What we know:
- A large snowstorm is coming to Connecticut from tomorrow evening into Thursday morning.
- Significant snow accumulations are expected across the entire state, with double digit totals likely in many areas.
- Model consensus is strong on the general track of the system.
- There will be several bands of very heavy snow and the areas that spend the most time under them will report the highest totals, accumulations of over a foot are expected there.
- All snow is expected for most, with a small chance of mixing in SE areas.
- Strong winds are expected for a period of time along the shoreline, lighter gusts inland.
- The Wednesday evening commute could be impacted, especially in southern and western areas, and the Thursday morning commute will be heavily impacted.
- Snow will exit the state by Thursday afternoon.
What we don’t know:
- How will the models trend in the final 24 hours with the eventual track?
- Where will the heavy snow bands develop and where will they remain?
- Will we see mix/rain for a brief period on the south coast?
- How heavy/light will the snow be?
- Will there be potential power outages?
Timing and Impacts
Timing
Here’s a loop of the entire system (1 PM Wednesday to 1 PM Thursday) from the RGEM. Take this as a general idea of how the timing progresses and not as an indicator of where the heaviest snow will fall, as there’s still quite a bit of uncertainty with the banding.
Generally, we’ll see snow break out during the late afternoon into early evening in southern and western areas, and by 8-9 PM we should be snowing across the entire state. Interestingly, there is a fair amount of spread in the models with regards to timing; the RGEM has snow across the entire state by rush hour tomorrow, while the hi-res NAM and GFS hold any snow off until after 6-7 PM and don’t get the entire state going until late into the evening. I’m hedging a bit towards the faster models as storms generally both come in and leave a little earlier than modeled, but we’ll clarify tomorrow in our updates.
At first, I expect heavy snow across the entire state through the evening hours. By around midnight, we should see the storm start to form distinct snowbands, and areas under the band will continue to see very heavy rates while areas between bands will likely slow down a bit. We’ll see bands continue to move across the state through the overnight, and then most models show a final push of heavier snow across the entire state as the backside of the storm swings through and it exits to the east. That push of heavier snow will likely fall during the morning commute on Thursday, so if you are traveling to work, leave plenty of extra time and take it easy out there!
Wind
The highest gusts will be along the shoreline, where wind gusts could approach 40-45 mph for a time overnight during the height of the storm. We could verify a blizzard at some stations, but I don’t think we’ll meet the criteria (heavy snow and 35mph+ gusts for 3+ hours) at most (if any) stations away from the shoreline. Some models do suggest a brief period of stronger winds inland Thursday morning as the low moves to the north, but I don’t think it will be long enough to verify a blizzard anywhere but the shoreline (and the snow rates will likely have slowed down a bit by then). Still, wind gusts of 25-35 MPH are likely inland, enough to cause noticeable blowing snow and limited visibility.
Here's a look at the peak winds on the GFS - notice the area of stronger gusts expands inwards on this panel. For the rest of the system, they are confined to the shoreline, so I don't expect blizzard conditions to be met anywhere but the shore.
Power Outages
Whenever heavy snow is involved, power outages are a possibility. Don wrote yesterday that we expect the snow to be lighter; while that could still be true, if we see a more northerly solution, that suggests a heavier, denser snow in our southern zones. I think the shoreline is most likely to see outages due to the winds and potential for lower snow ratios, but I don’t think they will be widespread. That said, if you frequently lose power in your neighborhood, I’d be ready.
Closings and Delays
Most schools are currently virtual, however, for those with in-person operations, I would expect most if not all to close their buildings on Thursday. By the afternoon, conditions will improve significantly, so some businesses may opt for a half-day schedule, but I don’t think it will clear up in time for schools to sneak by with a delayed opening.
Overall Impact
While the timing is ideal for travelers and the lack of high wind will keep us from a major power outage scenario, we still think that this is a high-impact event. Widespread double digit snow totals have been rare in Connecticut in recent years, and when we see them, they tend to leave a mark. Expect difficult and hazardous travel Wednesday night into Thursday morning and an enhanced risk of power and wind issues along the shoreline and in traditionally favored areas.
If possible, we’ll have a revised map out tomorrow morning, and regardless will be providing you with frequent updates throughout the day and into the night. As always, we look forward to your questions, comments, and interactions here and on our social media platforms – use the buttons below to follow us and don’t hesitate to send us your questions on Facebook and Twitter. Plus, don’t forget our live discussion and Q&A from 7-8 PM on Facebook Live!
Hope to see you all soon, and as always, thank you for trusting SCW.
-SA
Whenever heavy snow is involved, power outages are a possibility. Don wrote yesterday that we expect the snow to be lighter; while that could still be true, if we see a more northerly solution, that suggests a heavier, denser snow in our southern zones. I think the shoreline is most likely to see outages due to the winds and potential for lower snow ratios, but I don’t think they will be widespread. That said, if you frequently lose power in your neighborhood, I’d be ready.
Closings and Delays
Most schools are currently virtual, however, for those with in-person operations, I would expect most if not all to close their buildings on Thursday. By the afternoon, conditions will improve significantly, so some businesses may opt for a half-day schedule, but I don’t think it will clear up in time for schools to sneak by with a delayed opening.
Overall Impact
While the timing is ideal for travelers and the lack of high wind will keep us from a major power outage scenario, we still think that this is a high-impact event. Widespread double digit snow totals have been rare in Connecticut in recent years, and when we see them, they tend to leave a mark. Expect difficult and hazardous travel Wednesday night into Thursday morning and an enhanced risk of power and wind issues along the shoreline and in traditionally favored areas.
If possible, we’ll have a revised map out tomorrow morning, and regardless will be providing you with frequent updates throughout the day and into the night. As always, we look forward to your questions, comments, and interactions here and on our social media platforms – use the buttons below to follow us and don’t hesitate to send us your questions on Facebook and Twitter. Plus, don’t forget our live discussion and Q&A from 7-8 PM on Facebook Live!
Hope to see you all soon, and as always, thank you for trusting SCW.
-SA
