Good evening to you from Southern Connecticut Weather!
Well, after taking an extended break for most of February and March, Mother Nature has decided to bring back winter with a final storm chance for the region before warmer air looks to arrive next week. However, as the theme for this winter has been, she didn’t choose to make it easy, and instead threw us several curveballs that have become synonymous with the theme of the winter in the minds of forecasters all across New England. Yesterday, this system was modeled as a deep, mature coastal storm that had a classic look to it for a region wide heavy snow event. On the overnight guidance though, a leading shortwave appeared over western PA and Ohio that mucked up the flow for the approaching coastal, limiting phasing opportunities and resulting in deamplification of the followup threat, the same theme we’ve seen all winter. Our attention now turns to a more strung out system, where we will rely on midlevel forcing to produce heavier snow instead of regionwide dynamics.
The Models
While the models agree that the blockbuster storm is off the table, there are still questions remaining as to what the end result will be for us. The modeling is split down the middle into two fairly distinct camps; those models that bring the system over the 40/70 benchmark, and those that bring it well southeast. Those on the benchmark are also stronger and more consolidated. This is because the antecedent setup, with a stronger/better placed western ridge, less interference, and more phasing, allows for the storm to strengthen, and as a result, track closer to the coastline.
The first camp is represented by the NECP guidance (NAM and GFS), as well as the Canadian RGEM. These models bring the system well to the southeast of the 40/70 benchmark, and are poorly formed, with a deamplified, strung out progressive mess of a system. As a result, no well-defined precipitation shield makes it into our area, and we are left with a ragtag collection of snow showers, light snow, and the occasional moderate band or two. This is shown well on the simulated radar from the hi-res version of the NAM, where verbatim the model is depicting just some light rain showers(In actuality, it would likely be snow showers as the algorithms assume temps >32 automatically equal rain, but that is not the case).
Well, after taking an extended break for most of February and March, Mother Nature has decided to bring back winter with a final storm chance for the region before warmer air looks to arrive next week. However, as the theme for this winter has been, she didn’t choose to make it easy, and instead threw us several curveballs that have become synonymous with the theme of the winter in the minds of forecasters all across New England. Yesterday, this system was modeled as a deep, mature coastal storm that had a classic look to it for a region wide heavy snow event. On the overnight guidance though, a leading shortwave appeared over western PA and Ohio that mucked up the flow for the approaching coastal, limiting phasing opportunities and resulting in deamplification of the followup threat, the same theme we’ve seen all winter. Our attention now turns to a more strung out system, where we will rely on midlevel forcing to produce heavier snow instead of regionwide dynamics.
The Models
While the models agree that the blockbuster storm is off the table, there are still questions remaining as to what the end result will be for us. The modeling is split down the middle into two fairly distinct camps; those models that bring the system over the 40/70 benchmark, and those that bring it well southeast. Those on the benchmark are also stronger and more consolidated. This is because the antecedent setup, with a stronger/better placed western ridge, less interference, and more phasing, allows for the storm to strengthen, and as a result, track closer to the coastline.
The first camp is represented by the NECP guidance (NAM and GFS), as well as the Canadian RGEM. These models bring the system well to the southeast of the 40/70 benchmark, and are poorly formed, with a deamplified, strung out progressive mess of a system. As a result, no well-defined precipitation shield makes it into our area, and we are left with a ragtag collection of snow showers, light snow, and the occasional moderate band or two. This is shown well on the simulated radar from the hi-res version of the NAM, where verbatim the model is depicting just some light rain showers(In actuality, it would likely be snow showers as the algorithms assume temps >32 automatically equal rain, but that is not the case).
The GFS is slightly more bullish, which would bring an couple inches of snow to southern and eastern areas and perhaps a coating to an inch for western and northern areas, but the general idea is the same; no big deal.
Here’s a look at the total precipitation on the 18z GFS and 18z NAM.
Remember, 10mm = .4” of liquid = ~4” of snow.
Here’s a look at the total precipitation on the 18z GFS and 18z NAM.
Remember, 10mm = .4” of liquid = ~4” of snow.
The second, more exciting camp, contains just about all of the foreign guidance (Euro, GGEM, UKMET, ICON, JMA). This group, while still having trended east over the past 24 hours, has maintained enough separation between the waves to provide some room for our main shortwave to interact with the upper ridge and phase, and the result is a more consolidated system that is closer to the coastline. These models bring in the initial snow Sunday afternoon from some initial overrunning, and then bring the precipitation shield from the coastal storm into the state Sunday evening and overnight. As has been the case with pretty much every system we have seen this year, those in the southern and eastern portions of the state are closer to the low, and as a result, see more of the heavier precipitation than those in the northern and western portions of the state. In this scenario, we’d see light snow breaking out late Sunday afternoon across the state, with moderate to occasionally heavier snow continuing throughout Sunday night before tapering to light snow and then snow showers Monday morning. While this cluster of models differs in how far back the heavier snow makes it into the state, the general consensus is pretty well defined for a low end warning event(6”+) in eastern portions of the state and an advisory level(3”+) event in western portions of the state.
The UKMET and ICON models are outliers among the guidance in that they bring the heavier snow much further west, and would bring warning level totals to pretty much the entire state. To me, this is a bit of a warning flag, since both models have had a very good handle on the regime that we’ve been in over the past several months and have performed admirably in the systems we had this year where we saw consistent NW ticks leading up to game time. As such, while I hesitate to believe their outlying solutions at this point, I do think that they lend more support towards this second camp of guidance rather than the complete miss.
As such, this forecast package is a two to one blend of the second and first camps, which comes out to a moderate event for eastern portions of the state and a lighter event for the NW corner. Should this second camp prove to be completely correct or even too far east, we would have to increase totals on the final call, and conversely, should the first camp be correct, we would have to sharply decrease totals. We are hedging our bets on the probability of a consensus emerging that is somewhere in the middle, as frequently happens in the world of meteorological modeling.
Here’s a look at the total precipitation amounts on the 12z GGEM and UKMET. Remember, 10mm = .4” of liquid = ~4” of snow.
The UKMET and ICON models are outliers among the guidance in that they bring the heavier snow much further west, and would bring warning level totals to pretty much the entire state. To me, this is a bit of a warning flag, since both models have had a very good handle on the regime that we’ve been in over the past several months and have performed admirably in the systems we had this year where we saw consistent NW ticks leading up to game time. As such, while I hesitate to believe their outlying solutions at this point, I do think that they lend more support towards this second camp of guidance rather than the complete miss.
As such, this forecast package is a two to one blend of the second and first camps, which comes out to a moderate event for eastern portions of the state and a lighter event for the NW corner. Should this second camp prove to be completely correct or even too far east, we would have to increase totals on the final call, and conversely, should the first camp be correct, we would have to sharply decrease totals. We are hedging our bets on the probability of a consensus emerging that is somewhere in the middle, as frequently happens in the world of meteorological modeling.
Here’s a look at the total precipitation amounts on the 12z GGEM and UKMET. Remember, 10mm = .4” of liquid = ~4” of snow.
The Forecast
Here’s our forecast snowmap for this event.
Here’s our forecast snowmap for this event.
In the eastern portion of the state, we’re expecting three to six inches of snow, in the central portion of the state along with SWCT, we’re expecting two to four inches of snow, and in the northwest corner of the state, one to three inches of snow. I wouldn’t be surprised to see some amounts that are above the higher end of those ranges considering that we will likely see some small bands of heavier snow form, but where they set up is anyone’s guess. Therefore, I included mentions of totals up to 6” in the 2-4” zone and 8” in the 3-6” zone as I do think we will see some totals around there, however, confidence in widespread >4” and/or >6” amounts depending on the zone is not high enough for me to increase totals there.
As far as timing goes, I expect snow to move into the state from south to north starting around mid-afternoon on Sunday. Snow will start showery and will likely be non-accumulating in coastal areas and in the lower elevations, but as the sun starts to set and the heavier rates start to arrive, I don’t see any issues with snow accumulating right down to the shoreline. Moderate snow, with some heavier bands isolated in there, will continue throughout the evening hours and into the overnight, before the system starts to pull away from west to east after midnight or so in the western portions of the state and by sunrise in the eastern portions of the state. There could be some residual snow showers through the morning rush on Monday, but I don’t expect widespread coverage to last that long. There will likely be some residual impact to the morning commute, but I don’t expect significant travel issues on Monday morning. Schools will depend on how fast everyone can get plowed out and not so much on road conditions, so it will probably be a district by district call whether to delay, cancel or proceed as normal as opposed to the essentially blanket closings that we often see during major events.
Impacts
Confidence/Alternative Scenarios
We’ll be back tomorrow evening with a final call snowmap and discussion, and will be providing rapid-fire updates throughout the afternoon and evening on Sunday as needed. Please consider sharing this discussion with your friends and family and on your social media platforms to spread awareness about this upcoming system(and to combat some of the insane hype and forecasts that I’m seeing), and thank you for reading Southern Connecticut Weather!
-SA
As far as timing goes, I expect snow to move into the state from south to north starting around mid-afternoon on Sunday. Snow will start showery and will likely be non-accumulating in coastal areas and in the lower elevations, but as the sun starts to set and the heavier rates start to arrive, I don’t see any issues with snow accumulating right down to the shoreline. Moderate snow, with some heavier bands isolated in there, will continue throughout the evening hours and into the overnight, before the system starts to pull away from west to east after midnight or so in the western portions of the state and by sunrise in the eastern portions of the state. There could be some residual snow showers through the morning rush on Monday, but I don’t expect widespread coverage to last that long. There will likely be some residual impact to the morning commute, but I don’t expect significant travel issues on Monday morning. Schools will depend on how fast everyone can get plowed out and not so much on road conditions, so it will probably be a district by district call whether to delay, cancel or proceed as normal as opposed to the essentially blanket closings that we often see during major events.
Impacts
- A moderate snowfall for most of the state, with plowable amounts likely in all but the far northwest corner of the state.
- Difficult travel late Sunday afternoon and evening, with some residual impacts to the Monday morning commute likely.
- Some flight delays Sunday evening are possible from Hartford and New Haven, as well as NYC airports and Boston.
- School closings and delays on Monday are possible, but far from certain.
Confidence/Alternative Scenarios
- The system verifies similarly to our current forecast, where most of the state sees a moderate snowfall with lighter amounts further north and west. Chance of verification: 45%
- The system verifies further to the west and stronger, resulting in a moderate snowfall for western areas and warning level snowfall in the eastern portion of the state. Chance of verification: 25%
- The system verifies like the NAM or GFS and is further east, resulting in little to no impact to the state. Chance of verification: 25%
- The models are temporarily confused, and the big bomb from yesterday comes back resulting in a significant(>10”) snowstorm for the entire state. Chance of verification: 5%
We’ll be back tomorrow evening with a final call snowmap and discussion, and will be providing rapid-fire updates throughout the afternoon and evening on Sunday as needed. Please consider sharing this discussion with your friends and family and on your social media platforms to spread awareness about this upcoming system(and to combat some of the insane hype and forecasts that I’m seeing), and thank you for reading Southern Connecticut Weather!
-SA
