Good evening to you from Southern Connecticut Weather!
As Greg mentioned yesterday, we’re looking at a powerful coastal storm that will impact the region from Friday into Saturday. Over the past couple of model cycles, we’ve seen the storm trend a bit stronger and a bit colder, and as such, we’re watching it closely for a chance of wintry weather in the interior portions of the state. Some of the guidance brings a significant snowstorm to the interior elevated areas, while other guidance is further north and would result in a mainly rain event.
Generally, we’ll see the storm approach from the west Friday morning, with precipitation making it into the state by early Friday afternoon. As the storm hits high pressure to our north, it will redevelop into a coastal system, bringing the bulk of the precipitation to the state later Friday afternoon through Saturday morning. Precipitation should exit by Saturday afternoon. At first, temperatures will be below freezing through the column away from the shoreline, so any initial precipitation should fall as snow. However, warm air will quickly move in as the system continues to push north, and most areas should quickly flip to rain. It then remains to be seen if we will see a flip back to snow as the system deepens and colder air is drawn in.
The main variables that are influencing the eventual result of the system (i.e., if it is able to dynamically strengthen and produce snow across the state) are how far north the midlevels can get and how strong the storm ends up being. Further north midlevels introduce warmer air aloft, which cuts down on snow potential in favor of a messy sleet/freezing rain mix. A stronger storm with better inflow would generally promote a more well defined CCB (Cold Conveyor Belt, or wraparound band), which could lead to dynamic cooling and cause a borderline thermal profile to flash over to heavy wet snow if sufficient precipitation rates present themselves.
To show what these different solutions look like, here are soundings from the GFS and NAM valid for 8 PM Friday night at Bradley Airport, along with the surface reflections for the same time. Soundings are essentially snapshots of the column for a given location at a given point in time; it shows temperature, wetbub and dewpoint through the column from far aloft down to the surface, and also shows mixing and saturation of the airmass. For the purposes of this exercise, we’re focusing on the red temperature line.
As Greg mentioned yesterday, we’re looking at a powerful coastal storm that will impact the region from Friday into Saturday. Over the past couple of model cycles, we’ve seen the storm trend a bit stronger and a bit colder, and as such, we’re watching it closely for a chance of wintry weather in the interior portions of the state. Some of the guidance brings a significant snowstorm to the interior elevated areas, while other guidance is further north and would result in a mainly rain event.
Generally, we’ll see the storm approach from the west Friday morning, with precipitation making it into the state by early Friday afternoon. As the storm hits high pressure to our north, it will redevelop into a coastal system, bringing the bulk of the precipitation to the state later Friday afternoon through Saturday morning. Precipitation should exit by Saturday afternoon. At first, temperatures will be below freezing through the column away from the shoreline, so any initial precipitation should fall as snow. However, warm air will quickly move in as the system continues to push north, and most areas should quickly flip to rain. It then remains to be seen if we will see a flip back to snow as the system deepens and colder air is drawn in.
The main variables that are influencing the eventual result of the system (i.e., if it is able to dynamically strengthen and produce snow across the state) are how far north the midlevels can get and how strong the storm ends up being. Further north midlevels introduce warmer air aloft, which cuts down on snow potential in favor of a messy sleet/freezing rain mix. A stronger storm with better inflow would generally promote a more well defined CCB (Cold Conveyor Belt, or wraparound band), which could lead to dynamic cooling and cause a borderline thermal profile to flash over to heavy wet snow if sufficient precipitation rates present themselves.
To show what these different solutions look like, here are soundings from the GFS and NAM valid for 8 PM Friday night at Bradley Airport, along with the surface reflections for the same time. Soundings are essentially snapshots of the column for a given location at a given point in time; it shows temperature, wetbub and dewpoint through the column from far aloft down to the surface, and also shows mixing and saturation of the airmass. For the purposes of this exercise, we’re focusing on the red temperature line.
You can see that on the NAM, the system is further to the northeast compared to the GFS. This is allowing for more warm air to be drawn in, resulting in a much warmer profile. You can see that the temperature warms above freezing both in the midlevels and at the surface, so the result here would be a cold rain for the area. On the GFS, however, the midlevels come close to going above freezing, but never quite get there, and the column remains marginally cold enough all the way down to the surface. As such, this would likely be a heavy wet snow for the interior. Either way you slice it, the coastline is looking at mostly if not all rain.
Of course, the question you’re probably asking right now is which set of guidance do I believe and how much snow do I think we’re going to get? Well, at this point, it’s a bit too early to say. There is certainly the potential for a substantial snowfall in the interior elevated portions of the state, but I would say that right now, it’s a coin flip at that we’d see a plowable(3”+) snow somewhere in the state. Should the northern camp of solutions (NAM, GGEM, UKMET) be correct, we’ll just be getting a lot of cold rain, whereas if the southern solutions are correct, we could looking at close to warning level snows in those interior elevated areas. The usual rules for marginal situations apply here; the further north you are and the higher up you are, the more snow you are going to get. We also have to keep an eye out for sleet and freezing rain; with the warm midlevels but colder surface, it’s always a possibility.
Hopefully, we will begin to see a move one way or another on the guidance overnight, and will be either able to write off any significant winter threat or issue a snowmap tomorrow morning. Either way, we’ll have an update by mid-day tomorrow, so make sure to check back then. Thanks for reading SCW!
-SA
Of course, the question you’re probably asking right now is which set of guidance do I believe and how much snow do I think we’re going to get? Well, at this point, it’s a bit too early to say. There is certainly the potential for a substantial snowfall in the interior elevated portions of the state, but I would say that right now, it’s a coin flip at that we’d see a plowable(3”+) snow somewhere in the state. Should the northern camp of solutions (NAM, GGEM, UKMET) be correct, we’ll just be getting a lot of cold rain, whereas if the southern solutions are correct, we could looking at close to warning level snows in those interior elevated areas. The usual rules for marginal situations apply here; the further north you are and the higher up you are, the more snow you are going to get. We also have to keep an eye out for sleet and freezing rain; with the warm midlevels but colder surface, it’s always a possibility.
Hopefully, we will begin to see a move one way or another on the guidance overnight, and will be either able to write off any significant winter threat or issue a snowmap tomorrow morning. Either way, we’ll have an update by mid-day tomorrow, so make sure to check back then. Thanks for reading SCW!
-SA
