Good evening from Southern Connecticut Weather.
Here we go. While we have seen some relatively large snowfalls in parts of Connecticut the last few years, it has been hard to get a major winter storm statewide. We've been tracking the upper level pattern for a few weeks now, and we have been tracking this discrete threat for approximately a week. Winter Storm Watches have been issued for all of Connecticut, and confidence is increasing that an area of low pressure will bring a high impact statewide event.
For those that follow weather closely, this has the potential to be the first megalopolis (DC to Boston) KU event since March 2018. This forecast will look at the overall progression of the storm and the five elements we will be graded on after our final forecast: snowfall accumulation, timing, wind, power outages, and overall impact.
Let's dive in.
Here we go. While we have seen some relatively large snowfalls in parts of Connecticut the last few years, it has been hard to get a major winter storm statewide. We've been tracking the upper level pattern for a few weeks now, and we have been tracking this discrete threat for approximately a week. Winter Storm Watches have been issued for all of Connecticut, and confidence is increasing that an area of low pressure will bring a high impact statewide event.
For those that follow weather closely, this has the potential to be the first megalopolis (DC to Boston) KU event since March 2018. This forecast will look at the overall progression of the storm and the five elements we will be graded on after our final forecast: snowfall accumulation, timing, wind, power outages, and overall impact.
Let's dive in.
Here's our first call map. I already know what some of you are saying: "All this hype for an 8" snowstorm? X model says we're getting this much!"
We believe it is prudent to blend guidance rather than latch onto one model. We look at the whole field, and here we are blending the European (and ensembles) along with the GFS (and ensembles), with the other global and some select high resolution models to a much lesser degree.
We weigh the bullish European model more in this instance. As you will see, that model has had CT locked in its sights for days now. As a result, our first call has a reasonable upper end of 16".
The GFS on the other hand, has been further south and weaker with the storm. We think it's off, but not necessarily to the extent where we don't even factor it into the forecast. Most important, it has a sharp cutoff to the north along the northern border of CT that would easily cause higher forecasts to bust if it were right. We think 8" is a reasonable floor for CT, which is a major snowfall in itself. But we know that snowfall accumulation isn't the only thing that makes a winter storm high impact.
We believe it is prudent to blend guidance rather than latch onto one model. We look at the whole field, and here we are blending the European (and ensembles) along with the GFS (and ensembles), with the other global and some select high resolution models to a much lesser degree.
We weigh the bullish European model more in this instance. As you will see, that model has had CT locked in its sights for days now. As a result, our first call has a reasonable upper end of 16".
The GFS on the other hand, has been further south and weaker with the storm. We think it's off, but not necessarily to the extent where we don't even factor it into the forecast. Most important, it has a sharp cutoff to the north along the northern border of CT that would easily cause higher forecasts to bust if it were right. We think 8" is a reasonable floor for CT, which is a major snowfall in itself. But we know that snowfall accumulation isn't the only thing that makes a winter storm high impact.
Overall Progression
Winter Storm Watches are up from Virginia to Massachusetts at this hour. That doesn't happen without a favorable upper level pattern. As I discussed earlier in the week, we have high latitude blocking in the form of a -NAO that is in place. Recall that those are usually a prerequisite for a major winter storm in Southern New England. In addition, our now departed Wave 1 is forecast to become a powerful low pressure and fill the 50/50 region, providing additional support for the coming low. Although this isn't quite a textbook setup, look at blocking as a traffic jam. When blocking is in place, traffic backs up. That allows for storms to develop in the right location and slowly move through the region rather than zip through.
This isn't the longest duration snowstorm, or the strongest, but it is likely to develop at the right time that allows for a dynamic situation to unfold.
Winter Storm Watches are up from Virginia to Massachusetts at this hour. That doesn't happen without a favorable upper level pattern. As I discussed earlier in the week, we have high latitude blocking in the form of a -NAO that is in place. Recall that those are usually a prerequisite for a major winter storm in Southern New England. In addition, our now departed Wave 1 is forecast to become a powerful low pressure and fill the 50/50 region, providing additional support for the coming low. Although this isn't quite a textbook setup, look at blocking as a traffic jam. When blocking is in place, traffic backs up. That allows for storms to develop in the right location and slowly move through the region rather than zip through.
This isn't the longest duration snowstorm, or the strongest, but it is likely to develop at the right time that allows for a dynamic situation to unfold.
Above: European model depiction of the 500mb progression from Wave 1 to Wave 2.
So what's the result? Let's talk snow.
So what's the result? Let's talk snow.
Snowfall Accumulation
We anticipate a major snowfall of at least 8-16" across Connecticut. Aside from what I mentioned earlier, there are a couple of things that make this storm different from some of our other recent events.
First, we expect this to be all snow, even at the coast. Today's minor event, in addition to slowing down traffic in the high latitudes, is also going to bring in a fresh shot of cold air tomorrow that will be reinforced by an Arctic high pressure as the storm begins late Wednesday. That means even down to the coast, we should see snow.
Second, the snow looks to be at the general or slightly higher ratio standard. That could enhance snowfall and ensure that we all see a warning level (6"+) event.
Third, the banding with the system looks robust across guidance. Even the GFS, which has kept the banding south, shows a very prominent band setting up in association with the storm. Most guidance (minus GFS) has that banding signature right over Connecticut. This is a compelling signal for at least 8" and likely much more across most of the state. The biggest risk for folks seeing the "floor" of 8" is far northern CT. Banding always creates a boom or bust scenario for us, so beware.
Although we're not weighing it as much as the Euro, the Canadian model below has a good illustration of how we think the storm will progress. If this holds true we're looking at widespread double digit snowfall across the state.
We anticipate a major snowfall of at least 8-16" across Connecticut. Aside from what I mentioned earlier, there are a couple of things that make this storm different from some of our other recent events.
First, we expect this to be all snow, even at the coast. Today's minor event, in addition to slowing down traffic in the high latitudes, is also going to bring in a fresh shot of cold air tomorrow that will be reinforced by an Arctic high pressure as the storm begins late Wednesday. That means even down to the coast, we should see snow.
Second, the snow looks to be at the general or slightly higher ratio standard. That could enhance snowfall and ensure that we all see a warning level (6"+) event.
Third, the banding with the system looks robust across guidance. Even the GFS, which has kept the banding south, shows a very prominent band setting up in association with the storm. Most guidance (minus GFS) has that banding signature right over Connecticut. This is a compelling signal for at least 8" and likely much more across most of the state. The biggest risk for folks seeing the "floor" of 8" is far northern CT. Banding always creates a boom or bust scenario for us, so beware.
Although we're not weighing it as much as the Euro, the Canadian model below has a good illustration of how we think the storm will progress. If this holds true we're looking at widespread double digit snowfall across the state.
Below, a look at the 700mb relative vorticity of the storm (left) and result (right) on the European model courtesy of Pivotalweather.com. You see where the best forcing is taking place on the left, and the result is heavy snow just along and north of that area on the right. That's a big signal for big snow. The European model and its ensembles has held this signal for days.
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To provide a complete view, however, we must look at the GFS. Now, it is out on an island, and its most recent ensemble trended northward in a meaningful way, but this operational look shows how just a shift south or less dynamic system could move much of Connecticut closer to the floor. Note how the banding is just south of CT. We think this has a low risk of happening, but because it's on the table, our floor is lower.
Timing
Timing the storm seems fairly steady forecast wise here. The first flakes should begin flying late Wednesday afternoon and evening from SW to NE. The heaviest of the snow happens during the overnight hours and Thursday morning, before winding down from west to east late morning into the afternoon. As it stands, the Wednesday evening commute could be impacted but looks ok right now, while the Thursday morning commute looks very messy and potentially hazardous given high snowfall rates. This timing can shift and needs to be honed in a bit more, so stay tuned.
Wind
This has blizzard potential at the shoreline. Remember that blizzards are defined as having 1/4 mile or less visibility and frequent gusts of at least 35mph for three consecutive hours. Because the shoreline is the best wind spot usually, that's the place that has the highest likelihood of verifying blizzard conditions. Inland is tougher, and although there is a fairly strong gradient that will produce windy conditions, it is unclear whether the low will be strong enough or close enough to bring that kind of wind. Highest gusts along the shoreline should be between 40-50 mph with less wind inland. This isn't a high end wind producing winter storm.
Power Outages
With wind and heavy snowfall likely, there will be power outages. However, we are expecting a more fluffy snow, which has a lesser impact on the electrical grid, and do not expect high end wind that could cause widespread damage. We think that the potential is there for isolated to scattered power outages statewide, with the highest risk near the shoreline. As usual, those that lose power in any wind event should be prepared in this instance as well.
Overall Impact
We think this is a high impact event statewide. While we are not expecting widespread power outages and a good portion of the snow is expected to fall overnight Wednesday, we think it will be a high snowfall with high snowfall rates possible Thursday morning with blowing and drifting snow even if there isn't blizzard criteria met. Should we see banding produce over CT it could be one of our higher end widespread snowfalls, relative to the last few years.
Although it seems like we've been tracking this for a long time and the storm is almost here, we're still about 48 hours from onset. There's a lot that can happen between now and then with banding signals and the intensity of the low that could change this first call forecast in one direction or another.
As it stands, we're forecasting a major statewide snowstorm, and we are forecasting this with higher than normal confidence.
Stay tuned.
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.
-DB
Timing the storm seems fairly steady forecast wise here. The first flakes should begin flying late Wednesday afternoon and evening from SW to NE. The heaviest of the snow happens during the overnight hours and Thursday morning, before winding down from west to east late morning into the afternoon. As it stands, the Wednesday evening commute could be impacted but looks ok right now, while the Thursday morning commute looks very messy and potentially hazardous given high snowfall rates. This timing can shift and needs to be honed in a bit more, so stay tuned.
Wind
This has blizzard potential at the shoreline. Remember that blizzards are defined as having 1/4 mile or less visibility and frequent gusts of at least 35mph for three consecutive hours. Because the shoreline is the best wind spot usually, that's the place that has the highest likelihood of verifying blizzard conditions. Inland is tougher, and although there is a fairly strong gradient that will produce windy conditions, it is unclear whether the low will be strong enough or close enough to bring that kind of wind. Highest gusts along the shoreline should be between 40-50 mph with less wind inland. This isn't a high end wind producing winter storm.
Power Outages
With wind and heavy snowfall likely, there will be power outages. However, we are expecting a more fluffy snow, which has a lesser impact on the electrical grid, and do not expect high end wind that could cause widespread damage. We think that the potential is there for isolated to scattered power outages statewide, with the highest risk near the shoreline. As usual, those that lose power in any wind event should be prepared in this instance as well.
Overall Impact
We think this is a high impact event statewide. While we are not expecting widespread power outages and a good portion of the snow is expected to fall overnight Wednesday, we think it will be a high snowfall with high snowfall rates possible Thursday morning with blowing and drifting snow even if there isn't blizzard criteria met. Should we see banding produce over CT it could be one of our higher end widespread snowfalls, relative to the last few years.
Although it seems like we've been tracking this for a long time and the storm is almost here, we're still about 48 hours from onset. There's a lot that can happen between now and then with banding signals and the intensity of the low that could change this first call forecast in one direction or another.
As it stands, we're forecasting a major statewide snowstorm, and we are forecasting this with higher than normal confidence.
Stay tuned.
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.
-DB
