Good afternoon to you from Southern Connecticut Weather!
As we discussed last night, there are two more winter threats in the pipeline for the next couple of days as a very strong arctic airmass moves into the state this evening. This discussion will focus on the first of those two that will take place tomorrow morning, with a separate snowmap and discussion being issued for Monday’s event later this evening.
A strong shortwave is currently tracking across the upper Midwest, shown on radar below. This shortwave will continue to move almost due east throughout the day, and will pass over or just south of the state early tomorrow morning.
As we discussed last night, there are two more winter threats in the pipeline for the next couple of days as a very strong arctic airmass moves into the state this evening. This discussion will focus on the first of those two that will take place tomorrow morning, with a separate snowmap and discussion being issued for Monday’s event later this evening.
A strong shortwave is currently tracking across the upper Midwest, shown on radar below. This shortwave will continue to move almost due east throughout the day, and will pass over or just south of the state early tomorrow morning.
Over the past few model cycles, there has been a defined trend to strengthen the core of the system, with the most recent GFS and RGEM runs now bringing warning level snows to a small area. Connecticut continues to be right on the borderline, with shifts in track as small as a few miles making the difference as to how much (if any) of our state gets in on the significant band of snows. All model guidance is in good agreement on there being a very strong and dynamic band of precipitation just to the north of the low, and combined with the arctic air that will remain in place, that will be enough for a period of very heavy snow for a few hours tomorrow morning. Combine that with the high winds that are forecasted for New England tomorrow, and you have a miniature blizzard on your hands for a localized area. We could even see some thundersnow due to the convective nature of this storm!
While it’s clear that someone is going to see a substantial amount of snow out of this system, the question is who it is. Modeling, as it has strengthened the storm, has also shifted the path of the low slightly north, which would result in the heaviest snows being from the I90 corridor up into northern MA and southern NH/VT. Should that track verify, the low would essentially track right on top of us, and the boundary layer would warm just enough for the system to be mostly rain, ending as a bit of mix and snow, while most of MA and southern NH/VT would see close to 6” of snow. Here’s a look at the 12z RGEM, which shows this evolution well.
While it’s clear that someone is going to see a substantial amount of snow out of this system, the question is who it is. Modeling, as it has strengthened the storm, has also shifted the path of the low slightly north, which would result in the heaviest snows being from the I90 corridor up into northern MA and southern NH/VT. Should that track verify, the low would essentially track right on top of us, and the boundary layer would warm just enough for the system to be mostly rain, ending as a bit of mix and snow, while most of MA and southern NH/VT would see close to 6” of snow. Here’s a look at the 12z RGEM, which shows this evolution well.
As of now, that evolution is near the consensus outcome on the modeling, and as such I have decided not to call for substantial (>3”) snows just yet across the state.
However, there is a second, smaller cluster of guidance that tracks the low a bit further to the south, allowing northern areas of the state to remain in the cold sector of the storm. Here’s a look at the 12z NAM, which shows that idea well.
However, there is a second, smaller cluster of guidance that tracks the low a bit further to the south, allowing northern areas of the state to remain in the cold sector of the storm. Here’s a look at the 12z NAM, which shows that idea well.
The end result is a substantial snowfall across northern areas of the state, while southern areas would see rain to a mix, ending as some snow. While at this time I don’t think that this is the most likely solution, there is enough guidance showing it to make be not completely confident of mostly rain in the state. Furthermore, thinking back to past events, modeling is notoriously poor with boundary layer and surface temperatures, as it frequently fails to take into account the dynamic cooling that occurs when you have heavy precipitation and below freezing temperatures at all levels of the column except the surface. Essentially, what happens is that the below freezing precipitation cools the marginal air around it just enough to keep it from melting, and the end result is a heavy wet snow.
Below is our forecast snowmap for this event.
Below is our forecast snowmap for this event.
I’ve decided to highlight northern areas of the state for the potential of receiving up to 6” of snow. I don’t think that it is a likely outcome, but the possibility is enough that I’d rather mention it and bust high than ignore it and have a lot of surprised people Sunday morning. I’d probably put the odds of more than 3” in that zone at around one in four; low but not unreasonably so.
Elsewhere, I’m expecting precipitation to start as rain before changing over to snow early Sunday morning and tapering off by 8-10 AM. On the shoreline, I think precipitation will mainly be rain, with a coating to an inch of snow possible on the back end, however, further inland, I think that the changeover will take place in time for one to three inches to accumulate, with the higher amounts being found further north and at the higher elevations. Winter Weather Advisories are in effect for Hartford, Tolland and Windham counties from the NWS in Taunton, MA, and those could be expanded when we hear from the New York and Albany offices later this afternoon. UPDATE: Albany has issued a Winter Weather Advisory for Litchfield county.
Compounding the impacts of this system will be the very strong winds that are expected, with sustained winds of 20 to 30 miles per hour and gusts over 50 miles per hour likely. High Wind Warnings have been issued by the National Weather Service for the entire state. The combination of wind and heavy snow could produce some near-blizzard conditions for a short time, especially if the southern track verifies. Some isolated power outages are likely, and downed trees are possible as well. All in all, a wild couple of hours tomorrow morning are likely.
And remember, this is just the first of two systems in the pipeline! We’ll have another discussion coming in a few hours with a first call snowmap for Monday, which looks to bring more accumulating snow to portions of the state. Until then, please ask us any questions you may have, share this post with your friends and family, and enjoy the rest of your Saturday. We’ll see you soon!
-SA
Elsewhere, I’m expecting precipitation to start as rain before changing over to snow early Sunday morning and tapering off by 8-10 AM. On the shoreline, I think precipitation will mainly be rain, with a coating to an inch of snow possible on the back end, however, further inland, I think that the changeover will take place in time for one to three inches to accumulate, with the higher amounts being found further north and at the higher elevations. Winter Weather Advisories are in effect for Hartford, Tolland and Windham counties from the NWS in Taunton, MA, and those could be expanded when we hear from the New York and Albany offices later this afternoon. UPDATE: Albany has issued a Winter Weather Advisory for Litchfield county.
Compounding the impacts of this system will be the very strong winds that are expected, with sustained winds of 20 to 30 miles per hour and gusts over 50 miles per hour likely. High Wind Warnings have been issued by the National Weather Service for the entire state. The combination of wind and heavy snow could produce some near-blizzard conditions for a short time, especially if the southern track verifies. Some isolated power outages are likely, and downed trees are possible as well. All in all, a wild couple of hours tomorrow morning are likely.
And remember, this is just the first of two systems in the pipeline! We’ll have another discussion coming in a few hours with a first call snowmap for Monday, which looks to bring more accumulating snow to portions of the state. Until then, please ask us any questions you may have, share this post with your friends and family, and enjoy the rest of your Saturday. We’ll see you soon!
-SA
