Good evening from SCW.
As expected, Winter Weather Advisories now cover the entire state, as our third winter storm of the last two and a half weeks approaches Connecticut. This is expected to be another moderate to high impact event, with high impacts for areas away from the immediate shoreline. In fact, some schools and school districts are beginning to close, and I expect widespread cancellations tomorrow across the state.
This is not a snow dominant event, but rather a mixed bag storm where we have an elevated risk for significant icing away from the shoreline.
As expected, Winter Weather Advisories now cover the entire state, as our third winter storm of the last two and a half weeks approaches Connecticut. This is expected to be another moderate to high impact event, with high impacts for areas away from the immediate shoreline. In fact, some schools and school districts are beginning to close, and I expect widespread cancellations tomorrow across the state.
This is not a snow dominant event, but rather a mixed bag storm where we have an elevated risk for significant icing away from the shoreline.
Above is our snowfall map.
The Setup
Overall, there is no change in the synoptic look of this event. High pressure has established itself over our region, which will lock in low level cold as a surface low develops and passes to our south. As the precipitation advances this evening, snow will begin overnight. This is a Cold Air Damming situation (CAD) where surface temperatures will be hard pressed to rise above freezing (especially in the valleys) even as the upper levels of the column warm above freezing.
Timing
For most, the snow will begin in earnest after midnight. The exception is SW CT where things may begin an hour or two before midnight. As warmer air filters into the column above the surface, we will see a gradual transition across the state from snow to sleet and then freezing rain. Along the shoreline, this transition will be relatively quick. Eventually, the immediate shoreline may change over to plain rain during the late morning hours. This is not a reason to let your guard down though, as just a degree to two will make the difference between a cold rain and additional freezing rain that could bring a little more than a glaze.
For inland areas, we are looking at the greatest impacts taking place during the morning hours, with moderate to briefly heavy snow early in the morning transitioning to sleet and then freezing rain. Inland areas are unlikely to go above freezing. How quickly the transition from sleet to freezing rain is critical, as icing becomes more significant with more prolonged freezing rain. Interior areas of southern Connecticut are at the greatest risk of prolonged freezing rain, while northern areas of CT are more likely to see more snow and sleet.
Mixed precipitation is likely to continue in Connecticut throughout the day, though there will be periods of lighter precipitation. This may actually work against interior CT, as freezing rain generally accumulates more efficiently on surfaces during lighter periods. This is why widespread cancellations, rather than delays, are now expected.
- The 1-3 and 2-5 inch ranges cover total snow and sleet accumulation.
- There is special text that shows our expectation of a glaze of ice along the shoreline and between .25-.50 inches of icing for interior Connecticut.
- Greater icing will be toward southern portions of the purple zone, while higher snowfall/sleet accumulations will lie toward the northern end of the purple zone.
The Setup
Overall, there is no change in the synoptic look of this event. High pressure has established itself over our region, which will lock in low level cold as a surface low develops and passes to our south. As the precipitation advances this evening, snow will begin overnight. This is a Cold Air Damming situation (CAD) where surface temperatures will be hard pressed to rise above freezing (especially in the valleys) even as the upper levels of the column warm above freezing.
Timing
For most, the snow will begin in earnest after midnight. The exception is SW CT where things may begin an hour or two before midnight. As warmer air filters into the column above the surface, we will see a gradual transition across the state from snow to sleet and then freezing rain. Along the shoreline, this transition will be relatively quick. Eventually, the immediate shoreline may change over to plain rain during the late morning hours. This is not a reason to let your guard down though, as just a degree to two will make the difference between a cold rain and additional freezing rain that could bring a little more than a glaze.
For inland areas, we are looking at the greatest impacts taking place during the morning hours, with moderate to briefly heavy snow early in the morning transitioning to sleet and then freezing rain. Inland areas are unlikely to go above freezing. How quickly the transition from sleet to freezing rain is critical, as icing becomes more significant with more prolonged freezing rain. Interior areas of southern Connecticut are at the greatest risk of prolonged freezing rain, while northern areas of CT are more likely to see more snow and sleet.
Mixed precipitation is likely to continue in Connecticut throughout the day, though there will be periods of lighter precipitation. This may actually work against interior CT, as freezing rain generally accumulates more efficiently on surfaces during lighter periods. This is why widespread cancellations, rather than delays, are now expected.
Above is the latest high resolution NAM depiction of precipitation from approximately 1am to 7pm Tuesday. Note how the state starts off as moderate to heavy snow, followed by a period of mixed precipitation. The rain is confined to the shoreline, and it will likely be the case that just a few miles inland we see icing. The afternoon brings lighter precipitation, but impacts are still likely.
Impacts
Let's break down the impacts in more detail.
Snowfall Accumulation--Moderate
If you could have a scale within a scale, this would be on the lower end of moderate. With an upper end of 5" expected and the vast majority of the state below that number, snow is not the story. Sure, some isolated locations may produce a 6 spot, but my belief is that the transition happens quickly enough where we don't get too far over 5 inch maximums in the state.
Snowfall Rate--High
Although snowfall accumulations will be relatively low, I do expect a period of moderate to heavy snow, with a period of moderate to heavy sleet. That will make road conditions, especially in the morning, an issue statewide.
Icing--Moderate
There is an elevated risk of a significant icing event, especially when it comes to freezing rain. We really see major issues when there is more than .50 inches of freezing rain accretion, but that is the higher end of our forecast. Issues are expected well below that threshold. Some guidance has shown much more freezing rain, but due to questions over how efficiently ice builds in this case in a few hours, we are not projecting over .50 inches of icing. This is something to watch closely.
Wind--Low
I do not expect much wind with this storm.
Power Outages--Low
I am tempted to go moderate here, but I think any power outages are more isolated to scattered rather than widespread. If there were more wind, I would be more concerned. In fact, there may be issues after the Arctic front if the ice hangs on through late Wednesday.
Timing--High
The timing is terrible. The heaviest is likely to fall during the AM commute, and mixed precipitation is likely to continue for most through the day, even as it becomes more spotty/lighter.
Road Conditions--High
The combination of moderate to heavy snow to start and then prolonged temperatures below freezing as mixed precipitation continues through the day has me inclined to call this high impact, though with so many cancellations expected I think road conditions may be better than if so many were out and about. It's certainly a bad day to be on the roads.
Overall, this is another moderate to high impact event, this time due to timing and the potential for icing. We will be providing updates throughout the storm.
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
Let's break down the impacts in more detail.
Snowfall Accumulation--Moderate
If you could have a scale within a scale, this would be on the lower end of moderate. With an upper end of 5" expected and the vast majority of the state below that number, snow is not the story. Sure, some isolated locations may produce a 6 spot, but my belief is that the transition happens quickly enough where we don't get too far over 5 inch maximums in the state.
Snowfall Rate--High
Although snowfall accumulations will be relatively low, I do expect a period of moderate to heavy snow, with a period of moderate to heavy sleet. That will make road conditions, especially in the morning, an issue statewide.
Icing--Moderate
There is an elevated risk of a significant icing event, especially when it comes to freezing rain. We really see major issues when there is more than .50 inches of freezing rain accretion, but that is the higher end of our forecast. Issues are expected well below that threshold. Some guidance has shown much more freezing rain, but due to questions over how efficiently ice builds in this case in a few hours, we are not projecting over .50 inches of icing. This is something to watch closely.
Wind--Low
I do not expect much wind with this storm.
Power Outages--Low
I am tempted to go moderate here, but I think any power outages are more isolated to scattered rather than widespread. If there were more wind, I would be more concerned. In fact, there may be issues after the Arctic front if the ice hangs on through late Wednesday.
Timing--High
The timing is terrible. The heaviest is likely to fall during the AM commute, and mixed precipitation is likely to continue for most through the day, even as it becomes more spotty/lighter.
Road Conditions--High
The combination of moderate to heavy snow to start and then prolonged temperatures below freezing as mixed precipitation continues through the day has me inclined to call this high impact, though with so many cancellations expected I think road conditions may be better than if so many were out and about. It's certainly a bad day to be on the roads.
Overall, this is another moderate to high impact event, this time due to timing and the potential for icing. We will be providing updates throughout the storm.
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
