It might be hard to believe, but after widespread lows from -5 to -15 across the state this morning, a storm is on the way, and for much of the state, the majority of precipitation from that storm will be in liquid form.
Tonight: High pressure in control. Low temperatures will be a bit tricky, because some clouds are expected to arrive later at night. Clouds should spread in from SW to NE after midnight. Tonight could be a night where Tolland and Windham Counties have the coldest low temperatures, since the clouds could very well take the longest to get there. Even having said that, the clouds will be of the high variety when they first get here, so even if there are some clouds, radiational cooling will still be possible, although it won't be as strong. Weighing all these options results in low temperatures ranging around zero degrees, with mid single digits above zero along the south coast to mid single digits below zero in Tolland and Windham Counties.
Tomorrow: Complicated forecast for a few reasons. First, timing the arrival of precipitation. Right now, a consensus timing would say that snow develops around mid afternoon in the southwest to around dinner time in the northeast. Next, high temperatures. Temperatures will be starting off very low, as mentioned in the "tonight" section and it will be generally cloudy tomorrow. However, we will have strong warm air advection. Also, precipitation with overrunning (warm air riding on top of cold air) tends to arrive faster than progged. However, the air mass is currently extremely dry (near record low dew points) and this could hurt that factor. Also, how heavy will the snow be when it first starts? Will it just be several hours of flurries or will it come in and snow like mad for a few hours? All of these factors may not be answered until the last minute with nowcasts, and there are factors on the "pro" and "con" sides to each one of these. For now, the best way to go is to call for high temperatures in the upper 20s to mid 30s with snow arriving in the timetable I outlined. Precipitation will start out as all snow everywhere.
Tomorrow Night (will be separating tomorrow night from Tuesday, as is against my convention, but for good reason this time): Another complicated forecast. Snow will change to a wintry mix and then rain from south to north through the night. Snowfall accumulations will be determined based on a few things... First, how hard does the snow come down when it first arrives (as outlined above)? Will the snow start a few hours earlier than progged? These two are important, because they could affect the amounts of snow, even if the changeover time (generally 3 to 6 hours after the start time) is hit perfectly. Another factor to consider (and this is more important for icing, rather than snow, since this affects the surface temperature more than anything else), is, if the air is still dry, could evaporational cooling cause a sudden drop in surface temperatures that models are not handling right now? At this time, I feel snowfall totals will range from a coating to two inches across most of the state(With some local jackpots of up to 3" possible), with two to four inches in the northwest portion of the state. In the coating to 2" zone, the 1" amounts will probably be more common right along the Long Island Sound, especially in southeast Connecticut, with 2" and even some 3" amounts more common in northern areas. In the northwest zone zone, the 2" amounts would be more common next to the 1-3" zone, and a few 5" totals may not be out of the question in the Litchfield Hills (they will have the advantage of being far enough west to get into the heavy precipitation earlier, but far enough north and higher elevation to keep the column cool enough longer).
Here's our forecast snowmap for this event.
Tonight: High pressure in control. Low temperatures will be a bit tricky, because some clouds are expected to arrive later at night. Clouds should spread in from SW to NE after midnight. Tonight could be a night where Tolland and Windham Counties have the coldest low temperatures, since the clouds could very well take the longest to get there. Even having said that, the clouds will be of the high variety when they first get here, so even if there are some clouds, radiational cooling will still be possible, although it won't be as strong. Weighing all these options results in low temperatures ranging around zero degrees, with mid single digits above zero along the south coast to mid single digits below zero in Tolland and Windham Counties.
Tomorrow: Complicated forecast for a few reasons. First, timing the arrival of precipitation. Right now, a consensus timing would say that snow develops around mid afternoon in the southwest to around dinner time in the northeast. Next, high temperatures. Temperatures will be starting off very low, as mentioned in the "tonight" section and it will be generally cloudy tomorrow. However, we will have strong warm air advection. Also, precipitation with overrunning (warm air riding on top of cold air) tends to arrive faster than progged. However, the air mass is currently extremely dry (near record low dew points) and this could hurt that factor. Also, how heavy will the snow be when it first starts? Will it just be several hours of flurries or will it come in and snow like mad for a few hours? All of these factors may not be answered until the last minute with nowcasts, and there are factors on the "pro" and "con" sides to each one of these. For now, the best way to go is to call for high temperatures in the upper 20s to mid 30s with snow arriving in the timetable I outlined. Precipitation will start out as all snow everywhere.
Tomorrow Night (will be separating tomorrow night from Tuesday, as is against my convention, but for good reason this time): Another complicated forecast. Snow will change to a wintry mix and then rain from south to north through the night. Snowfall accumulations will be determined based on a few things... First, how hard does the snow come down when it first arrives (as outlined above)? Will the snow start a few hours earlier than progged? These two are important, because they could affect the amounts of snow, even if the changeover time (generally 3 to 6 hours after the start time) is hit perfectly. Another factor to consider (and this is more important for icing, rather than snow, since this affects the surface temperature more than anything else), is, if the air is still dry, could evaporational cooling cause a sudden drop in surface temperatures that models are not handling right now? At this time, I feel snowfall totals will range from a coating to two inches across most of the state(With some local jackpots of up to 3" possible), with two to four inches in the northwest portion of the state. In the coating to 2" zone, the 1" amounts will probably be more common right along the Long Island Sound, especially in southeast Connecticut, with 2" and even some 3" amounts more common in northern areas. In the northwest zone zone, the 2" amounts would be more common next to the 1-3" zone, and a few 5" totals may not be out of the question in the Litchfield Hills (they will have the advantage of being far enough west to get into the heavy precipitation earlier, but far enough north and higher elevation to keep the column cool enough longer).
Here's our forecast snowmap for this event.
The next question will be icing. Models generally have a bias of getting the cold air out faster than reality, especially in sheltered valleys away from the coast. We may have to wait for the super short range models, like the HRRR and RAP to really have a good handle on this. There really isn't much of a mechanism to hold the cold air in, since there really isn't a damming high to the north. On the other hand, as I mentioned previously, any lingering dry air can help create this problem, by cooling the surface evaporatively as precipitation breaks out. A faster onset of heavier precipitation would help this to occur. For now, thinking most icing near the coast is minimal (but keep in mind, it doesn't take much ice to create problems). West is best if you want icing, and the highest probability of seeing several hours of icing would be in sheltered valleys in the Northwestern part of the state, given the storm tracking well to the west of the area. Yet another idea to ponder is that the recent Arctic outbreak has left the ground frozen solid. It isn't inconceivable that rain could still freeze on contact when the surface is 33 or 34 degrees.
Another concern will be flooding. The aforementioned frozen ground is conducive to flooding, because water does not run off a frozen ground. We'll have fresh melting snow in all of the state and some existing snowpack in some areas to exacerbate the problem, as well. With total precipitation amounts of 1-2" expected, this could produce a flood problem, and is also something that will need to be monitored.
As we head into Tuesday morning, the entire state will be raining by then and melting off whatever snow or ice has fallen. There could even be a line of thunderstorms Tuesday morning! This storm will already produce wind gusts in the 40 MPH range from the pressure gradient alone. Aloft are very strong winds, in the 60-70 MPH range and higher! If we get any thunderstorms, some (not all) of those winds could mix down and some brief strong to severe thunderstorms are possible, especially along the south coast! This is the first time I ever remember going from well below zero temperatures to possible strong thunderstorms in 48 hours, but that is why I love meteorology: It changes constantly and you never know what you are going to get! Rain pulls out by around rush hour on Tuesday evening. Temperatures may show a wide range. Most predominant temperatures will be in the 50-55 degree range, but some sheltered valleys in the Northwest could be stuck in the low 40s all day, and the SE coast may make a run for 60!
The longer term is largely quiet. Not much energy was given to this section due to the fact that we have a storm in the day 1-2 time frame and the fact that it will be largely a quiet period.
In the long term, temperatures should be at or below normal for Wednesday and Thursday. A warm frontal system moves through Thursday night into early Friday morning, and sparks a round of light precipitation. This could produce minor snow and sleet accumulations, especially away from the coast.
After that, the coming weekend should become increasing warm, with some normally warmer locations, i.e. southern locales away from the coast and interior valleys making a run for 60 degrees on Sunday!
However, briefly looking into the long range, it does look like winter makes a return, perhaps in a big way, with more cold and snow threats, beginning around February 22-24 and perhaps lasting well into March- stay tuned!
Now, here are some maps, regarding the upcoming storm.
This map is the GFS model's total precipitation for the upcoming storm- rain, snow, and ice combined. You can see most of the state is 1-2" of precipitation, with the extreme Southwest possibly in excess of 2".
This map shows the winds a few thousand feet above the surface. You can see that if any stronger thunderstorms did occur along the south coast, there is the potential for locally strong wind gusts! Spencer will be adding a snowmap to this, as well!
-GP!
-GP!
