Good evening from Southern Connecticut Weather. 

Well, there's no time to take much of a breath after the blizzard that ended yesterday, as the fast flow pattern that has been a hallmark of our winter amps up once again. In the last week we've had three events, and three more possibilities are on the table in the coming seven days. This discussion will take a look at each, with most of the focus put on the event that's coming in less than 12 hours. It's pretty late for a discussion, but that's the product of the fast flow. Let's dive in. 

Above: the snow map for tomorrow's event. I'm going with a general 1-3" through the entire day. 

General Setup
This one is pretty easy in terms of identifying the setup. A clipper is coming! What had practically been on the endangered species list the last few winters has made quite a comeback. Simply put, tomorrow a clipper will quickly dive down from Canada and zip through the region. It'll be in and out in just a few hours. 

​The GFS below captures it nicely. If you blink you'll miss it. 

The Forecast
Timing
If you recall from a week or two ago, I mentioned how the Arctic presses that had been another core feature of the winter were effectively done, but that had the impact of making this period the most favorable yet for snow chances. This is because we will be right in the battleground between colder air to our north and warmer air to the south. This only gets enhanced as spring tries to overpower winter in late February/early March.

If this clipper was arriving even three hours later, I'm not writing about it here. However, it's coming in the morning as temperatures are just starting to rise out of their morning lows, which means snow is mostly on the table. 

Currently temperatures around the state are well below freezing, and as the clipper arrives in the morning we will see our temperatures shoot up. It'll be a race between the precipitation arriving and temperatures getting above freezing. 

Snow breaks out between 5-8am from west to east. The snow lasts until between 11am and noon. Because this is an early morning event for the most part, most of the state should remain snow, even as the temperature tries to beat the arrival of the precipitation. This gets tricky in SE CT, where some models actually enhance the snowfall a little while the system is racing through while others have the temperatures winning out and flipping the area to rain before that happens. I think the snow will win out. 

By the afternoon, most of us are above freezing and the snow is melting everywhere. That said, we will have a low but nonzero chance of snow squalls later in the day. That's something that will be a nowcast. 

Here is a side by side comparison on the high resolution NAM, showing the precipitation between approximately 4am and noon and temperatures during the same time period. 

Snowfall accumulation and overall impact
This would normally be a minor event at best, but the timing is the worst it could possibly be. Not only will we have black ice given the melting today and refreezing that is happening tonight, the snow is coming in right during the AM commute. As a result, we will likely see widespread delays and some cancellations tomorrow morning. Because the snow is likely to last into the late morning that may make it tough for some school districts to make a call on delay vs cancellation, though I am guessing that losing two days already will make folks want to get the school day in badly. 

​By the afternoon we're fine, but the timing is rough. Expect a limited but moderate impact on the roads tomorrow. 

As for the snowfall totals, again, we're expecting a general 1-3". Given the race between the precipitation and temperatures, I expect the most snow to fall in northern CT, especially the hill towns. In southern CT, lower amounts are expected, but watch out in SE CT where there could be a sneaky period of enhancement. 

Thursday-Friday Potential 
Ok, this is one that has trended all over the place. Just two days ago, this looked like a signifiant winter storm on the guidance. Since then the models have all but dropped it, that is until earlier today, when the GFS and the GFS AI at least for that run brought it back. Some. 

This is a trend gif showing what the GFS has predicted for the same Thursday evening for the last two days. 

As you can see, it went from pretty big storm to out to sea to maybe some light snow. Here's what the Euro has done. After also projecting a big storm the Euro and its AI version want nothing to do with it. 

What does this mean? It means there is some fairly high uncertainty on what will happen Thursday night into Friday. At this time, it looks like a miss overall, or glancing blow at worst. The model runs tonight and tomorrow should settle it. 

What's the deal with next week?
Earlier today I saw that the hype machine was already going somehow about next week. We always give the same caveat that a week away is an eternity, but what are we seeing?

At least right now, the models are signaling that a storm will develop in the Midwest and quickly get shunted east. With us being the battleground between warmth and cold that likely means that the storm will target our general area. Below is are the GFS and Euro ensembles. Note the shade near our region, which depicts lower pressures. This is a fairly strong signal for some type of storm.

​The EPS is on top and the GEFS is on the bottom. 

All we know at this point is that a storm is possible, but anything putting out snowfall projections or even model maps like the one below. It's hype...for now...

Good evening from Southern Connecticut Weather! 

We're still digging out after yesterday's blizzard, but with an active pattern it's more important than ever to get this grade out while things are still fresh. 

For new followers, we grade our major forecasts. We do this for a few reasons. First, it's tradition. You don't see a lot of places grade their forecasts, and we're proud of doing something that while painful at times, sets us apart.

Second, it provides accountability. Longtime followers know that core to what we do is avoiding hype. We always aim to provide calm, fact-based, well-reasoned analysis to give you the information you need without having you feel impending doom every time you want to know how bad a storm might be.

Of course, we want to do this by maintaining a certain standard of accuracy. As a reminder, I'm not a meteorologist by training. While we have one "on staff" the majority of the team has no formal training. By publicly releasing grades of our forecasts, you get to see just how accurate our big forecasts are, and learn what went right and what went wrong. While we don't follow what others do, we know that online especially a lot of weather accounts are only good for yapping and engagement farming.

​We aim to be helpful. 

Third and perhaps most important, it makes us better. No forecast is perfect. It doesn't matter who you are. The key to getting better at anything is to learn from your mistakes. To provide the highest level of service to you, we need to know where our biases are so we can limit them when writing a forecast. A review also helps us track over time which models are best for certain situations. 

Ok, with that out of the way, how did we do with the biggest storm of the season?

​It's grading time. Let's dive in. 

Above: the verification map for our blizzard. Figuring out which reports to use was tough because there is substantial variation (as we thought) in snow totals. To make it as objective as possible we used 1) follower reports that followed our measuring/reporting instructions; 2) National Weather Service public reports--but only after noon on February 23. Earlier reports, which would likely have under count snow totals as snow really ended around 5pm on the 23rd, were not counted here. I also used a handful of reports from folks I know around the state that can be trusted to measure accurately. 

Forecast Grades
Timing
This did end up feeling like the toughest part of the forecast, and as I was watching the storm roll in that feeling didn't change. 

What made this most difficult was the pre-storm snow that was and wasn't related to the storm. We were inundated with questions about whether Sunday morning and afternoon activities would be fine, and so we needed to accurately predict when things would get bad more so than when things would start--since light snow was around the state even in the morning. 

We were right that the light snow in the morning would not impact morning activities. Good. 

We were right with the general timing of the storm. It did truly arrive between about 4-8pm. Excellent. 

We were only partially right in how the snow advanced in the state. We said it would arrive from west to east, and while it did start out that way in SW CT, the storm really arrived from south to north. That may seem small, but it rendered our bullet points that broke down when western/central/eastern CT would see snow irrelevant. That's worth a deduction. Fortunately, we had a bit of a backdoor cover with the general timing being clearly stated and accurate.  

From there, the timing forecast was excellent on balance. We were right that conditions would quickly deteriorate. Station reports generally had locations go from high visibility light snow to much lower visibility light to moderate snow within an hour of onset. We said that would be the time to get off the roads and that was critically on point. 

We said that the worst of the storm would be 8pm Sunday to 8am on Monday. That was mostly right but slightly off. On Monday the worst of the conditions really started winding down between 10am and noon. The forecast for the worst wind, which was from midnight to noon Monday was spot on. The coastal flood forecast was also accurate. 
 
The only other thing that was off was the timing of the end. The lighter snow came in earlier than 4pm, and the storm was effectively done hours before 10pm. 

While not perfect, the timing forecast was still pretty solid, especially where it mattered. Deductions on missing the direction of approach and those few hours at the end of the storm. 

Grade: B+

Snowfall Accumulation

Above: a repost of the verification map. 

We weigh snow accumulation double because that's what people care about. As you see above, our forecast was for a general 16-24" of snow across the state. As we said in the forecast, this was heavily dependent on how close the storm tracked to us, which would determine how much moisture got pushed into the state.

At the end of the day, the storm ticked just southeast of where the models were at the time if the final forecast. That's not a surprise, as that happens often with coastal storms. We accounted for that. 

We don't get points for this, but we accurately highlighted the risk of a bust (in this case, snow totals below 12") in the CT River Valley. From our final call forecast:

You will note though that there is this shadowing effect in the CT River Valley. This happens when you have massive easterly flow downsloping into the valley, limiting the amount of moisture wrung out. All this could be overcome with banding over the area, but watch out in places like Hartford and Windsor Locks. The risk is higher for a "bust" here. 

Sure enough, a narrow corridor between Enfield to South Windsor ended up in the "sucker zone" and busted low. There are other parts of the state that saw general totals below our 16" floor, but if you note, even in the pockets of lower snow you saw some reports that were on par with the forecast in northern CT. Part of that for sure is lower snow. Another part of that may be measuring difficulty given the wind. 

Southern CT has had one heck of a winter. They cashed in once again with widespread 18+ totals. For southeast CT, this winter has been a dream for snow lovers. We had several reports above 24" and 30" totals in far SE CT. Amazing. 

Before the grade this leads me to the big takeaway. Some people whine about having large snowfall ranges but that's literally how these storms often work. I'm intentional with "whine" because I'm angry at myself for letting it get to me haha. Here's what we said in the final call forecast: 

Elsewhere, there's always the risk of subsidence (read: dry slotting) when you have extreme banding. Anything lower than 12" would be a bust in my book, and while the forecast is for 16-24" statewide, someone could very well end up with a lollipop of 30" if they get under extreme banding for longer than anticipated. Most probably end up in the 16-22" range, but we have ranges for a reason here. The bigger the storm, the bigger the range due to the unpredictable nature of banding. 

Exactly! 

In Greenwich alone we had credible 18" and 13" reports. In New Milford, we had credible reports that ranged from 14" to 19". In the Vernon area we had a measurement of 16" that was done meticulously, and the next town over had 11". By far the greatest example came in far SE CT, where we had one credible report of 20.5" right next to the predicted "lollipop" of 30" and 30.8"!

A 12-24" snowfall forecast would not have been perfect because of what happened in the northern CT River Valley corridor, but it would have been better than trying to do a more narrow range. So the next time we have a blizzard and you see a wider range than normal (if the data calls for it of course, we don't want to game the system), if you complain I am sending this discussion! 

Ok, now to the grade. Yes, a 12-24" map would have been better, as uncomfortable as it would be for some followers and yours truly, but forecasting 16-24" wasn't bad. Southern CT did a lot of heavy lifting for us as northwest and north central CT fell short of expectations. A narrow stripe of northern CT was an outright bust with 5 towns in bust territory. 

On the Good, Better, Best scale, this one fell right in the middle. Annoying, but that's just us grading hard.  

Grade: B+

Wind & Power Outages
This may not have felt as difficult a forecast as the timing forecast, or as weighty as the snow accumulation forecast, but this was easily the highest stakes part of the whole forecast. This storm definitely wasn't like anything we've seen recently. 

Before the National Weather Service had enough confidence to issue the warnings statewide, we were calling this a blizzard. That designation was officially achieved in coastal locations, and while it looks like it fell just short of the three consecutive hour criteria in interior CT, there's no doubt that we saw blizzard like conditions even if not officially a blizzard. 

We were right about the snowfall consistency and ratios oscillating with the banding, and it seems that while the snow had weight to it, it wasn't pure past or pure fluff, meaning we landed in the middle as forecast. 

In northern CT, our forecast was for maximum wind gusts of 40-50mph. Impressively, Hartford (city) gusted to 51, while BDL gusted to 54. Willimantic gusted to 49mph. That's within the range of acceptability so we're very happy with that. 

In southern CT, especially coastal sections, our forecast was for maximum wind gusts of 50-65mph. The highest gust came out of Groton, with a 68mph report. Bridgeport, Fairfield, Middletown, Meriden, New Haven all gusted over 50. Meriden put up an impressive 56mph report. Again, well within the range of acceptability.  

Scattered to locally widespread power outages were anticipated and that's what happened. Here's what we wrote: 

Locally widespread means that some towns may have significant parts without power, while another town does not. We don't currently expect heavy wet snow, but along the coast it's always tricky, and with higher end winds that means if we see more paste down there we will have big power outages. This is definitely something to watch. ​The greatest risk for widespread outages is in southern and coastal CT, especially SE CT and our friends in Westerly. 

When checking the reports, this is exactly what happened. While some towns had 20+% of the community without power, many many others were just fine with more scattered to isolated outages. While there was fear of a high end power outage event, we didn't feel that was going to happen on a widespread basis around the state and the overwhelming majority of communities kept their power. I think at the peak we had about 15,000 customers or so without power which is very good in the whole scheme of things. 

Proud of this part of the forecast. 

Grade: A

Overall Impact
Not much to say here. We said a bona fide blizzard was coming and it did. It was an upper echelon storm, with part of SE CT getting 24-30" of snow, and high winds in every part of the state, which rarely happens. Bridgeport tied #2 all time in biggest snowstorm. 

Impacts on the roads were extreme and Monday things did grind to a halt. There were widespread school cancellations on Monday and Tuesday. Roads were impassable for a time and thanks to the plow crews out there we're digging out at a good pace now. Snow was not on the wetter side so we didn't get those "tens of thousands" of power outages. That's a line I wish I didn't use, but overall, the impacts were spot on. This was probably the worst winter storm statewide since about 2018. We expected this so be a high impact to locally extreme impact event and it was. 

Grade: A

Overall Grade
Taking everything above, this was a very good forecast. To be sure, not the best, and the other blockbuster storm overall probably was a better forecast. Going back, I'd probably use a 12-24" snow forecast zone, and would have anticipated the possibility that the trajectory of the storm would have snow break out from south to north rather than SW to NE, but when that's your nitpick rather than "man, I thought we'd have 200,000 outages" or "you know, a 16" floor really undersold the potential here", that's a good day in the office. 

Grade: B+

A​s 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 and trusting SCW.

​-DB

Good evening from Southern Connecticut Weather. 

This has been one heck of a roller coaster ride, and we're just getting started. On Monday, in my forecast for the week ahead, I first used the term "explosive"

"What significantly adds intrigue is the AI version of these models. The AI has done very well in identifying medium range patterns this winter, and here, with more ridging in the west leading to better amplification of a storm this coming weekend, the result is explosive. 

The AI GFS has been fairly consistent in developing a big storm that tracks over southern New England. This would bring a very significant storm with all precipitation types. 

The AI Euro, which has also been excellent at identifying patterns and storm tracks so far this winter, also has an explosive setup. This model keeps the low off the coast, bringing another blockbuster storm to the region. 

So what's right? Well, at this stage there's nothing to worry about or get excited about, yet.

It's too early to say what models have a better handle, but with the AI version of these models and legacy model ensembles showing the potential for a significant storm, I currently lean more toward a storm than a miss like last weekend. This one is worth watching." 

From there, many of the models did the equivalent of sticking a finger in the air and waiting to see which way the wind blows. Well maybe not that bad, but the lack of any kind of consensus had us with "zero concern". 

Then something remarkable happened. 

Once there was a definitive trend, it was an all-timer of a trend. We went from miss to glancing blow to a blizzard in the meteorological equivalent of a snap of the fingers.  

Now we have stabilized the trend and it's time for a final call. 

Above: the final call snowfall map. We are going with a general 16-24" statewide. Honestly, a good 12-24" forecast would have worked perfectly but my tired eyes wouldn't have been able to handle all the grief I would have gotten haha. 

In all seriousness, however, we are going with an 8" range because we know from history that extreme banding can do extreme things. The Connecticut River Valley in northern CT is most likely to end up with the least amounts. Eastern CT, including SE CT, is most likely to reach the upper end of the forecast. 

Overall Setup
I'm not going to spend too much time on the setup, but I do want to show you the trend gifs of how this changed.

Overall, our main piece of energy dives down from Canada and the Midwest. A ridge in the western U.S. and just enough upstream blocking will allow for disparate pieces of energy to phase, triggering truly explosive development once the phased energy moves off the coast. 

As I said yesterday, previously guidance had projected a flatter ridge out west and more confluence to our north which would work in tandem to kick our storm out to sea or deliver a glancing blow. Those models were wrong in the medium range, and corrected massively in the short term. The exception here was the AI models, which did an exceptional job sniffing out this potential accurately. 

The best way to see the change is by looking at the Euro legacy model, which has struggled. Here are approximately the last 2.5 days of runs. In the medium range it has nothing to a glancing blow, then you suddenly see it has a storm, and then eventually it agrees with the blizzard idea. 

The Forecast
Timing
This may still be the toughest part of the forecast. I want to outline it very clear so everyone can understand the evolution of the storm. Let's start with the general start time: 

• There may be light snow in the morning as we see some pre-storm convergence over the area. This should be light and not impact any morning activities around the state. 
• The storm truly arrives between 4-8pm from west to east
  • If you are in western CT, expect a start time between about 4-6pm
  • If you are in central CT, expect a start time between about 5-7pm
  • If you are in eastern CT, expect a start time between about 6-8pm
• It looks like conditions will quickly deteriorate, meaning that you should expect moderate to heavy snow within an hour of the time it starts where you are. That is the time to get off the roads. 
• The worst of the storm looks to be from about 8pm on Sunday to 8am on Monday
  • The worst wind will occur between about 12am Sunday and 12pm (noon) Monday. Wind will gradually diminish as the storm pulls away.
  • The worst coastal flooding will coincide with the strongest wind gusts. Expect moderate flooding in the Coastal Flood Warning zone between 11pm Sunday and 5am Monday. 
• Snow will continue through the day on Monday with snow transitioning to light snow around 4pm and snow fully exiting the state by around 10pm. This could be a few hours earlier if the storm moves a bit faster than expected. 
• It is going to take a long time to dig out. Expect blowing and drifting snow and power outages to impact Tuesday and maybe even Wednesday for school and work. 

Snowfall Accumulation

Above: the 18z GFS showing 700mb frontogenesis (banding) evolution over the storm. There is a huge signal for intense snowfall rates early Monday. 

As you saw above, our forecast is for a general 16-24" of snow across the state. This is heavily dependent on how close the storm tracks to us, which will determine how much moisture gets pushed into the state. As of now, the numbers are extremely impressive. 

Above is the GFS, which took a step back at 18z in the CT River Valley, but still has 1.5 to over 2" of moisture coming from the storm. That would easily put everyone in the 1-2 foot range. 

The National Blend of Models below has something similar. 

You will note though that there is this shadowing effect in the CT River Valley. This happens when you have massive easterly flow downsloping into the valley, limiting the amount of moisture wrung out. All this could be overcome with banding over the area, but watch out in places like Hartford and Windsor Locks. The risk is higher for a "bust" here. 

Elsewhere, there's always the risk of subsidence (read: dry slotting) when you have extreme banding. Anything lower than 12" would be a bust in my book, and while the forecast is for 16-24" statewide, someone could very well end up with a lollipop of 30" if they get under extreme banding for longer than anticipated. Most probably end up in the 16-22" range, but we have ranges for a reason here. The bigger the storm, the bigger the range due to the unpredictable nature of banding. 

Above: the AI GFS, which has by far been the best so far, showing how heavy banding moves into the state from our rapidly intensifying low pressure.

Folks, this is a blockbuster event. Thundersnow and snowfall rates that meet or exceed what we saw in the other huge winter storm this season is entirely possible. 

Wind & Power Outages

This storm is not going to be like anything we've seen recently.

Above you can see the high resolution NAM from earlier predicting incredibly strong sustained winds offshore and strong wind extending inland. The wind offshore will not fully translate on land. As we've already said, this is a blizzard. Don't get caught up in whether inland CT gets warnings officially, this is a blizzard if the winds verify. That means consistent winds over 35mph (need 3 consecutive hour observations of it), and visibility less than a quarter mile. Winds should easily top that. 

Now I know this is the scariest part of the forecast for a lot of people, and I wish I could say our analysis suggests that wind won't be a problem, but I can't. 

Snowfall consistency and ratios will probably oscillate with the banding, but remain in between true paste and pure fluff. With that in mind, the combination of snow on power lines and trees and high winds will be highly problematic. 

We have two things working against us here. First, we have a rapidly intensifying low pressure. Visible satellite sometime Monday will reveal our storm looking more like a hurricane than any of the weak low pressures we've had this season with pressures expected to potentially drop into the 960s. That's incredibly powerful. 

The second is the pressure gradient. There will be a very strong and sprawling high pressure to the north that will clash with our storm. That will produce big amounts of wind. 

This is the GFS pressure anomaly below. Note how strong our low is (blue) and how strong our high is (1049mb in Canada). That's a massive gradient. 

So what does that mean for us?

In northern CT, our forecast is for maximum wind gusts of 40-50mph. 

In southern CT, especially coastal sections, our forecast is for maximum wind gusts of 50-65mph.  

Scattered to locally widespread power outages are anticipated. 

Locally widespread means that some towns may have significant parts without power, while another town does not. We don't currently expect heavy wet snow, but along the coast it's always tricky, and with higher end winds that means if we see more paste down there we will have big power outages. This is definitely something to watch. ​The greatest risk for widespread outages is in southern and coastal CT, especially SE CT and our friends in Westerly. 

Overall Impact
A high impact event is a lock, but the real question here is whether we see extreme impacts.

A bona fide blizzard is coming, and while we get those from time to time, the combination of high end snow, wind, and timing--especially since a lot of people still have significant snowpack from the last big storm just a few weeks ago, has me wondering if this is going to be an upper echelon storm.

The impact will be extreme on the roads. The only saving grace here is that the worst is overnight Sunday into Monday morning. The state will grind to a halt on Monday. The combination of drifting snow and high winds will make roads impassible statewide for a time Sunday night into Monday, and clean up will make Tuesday and even potentially Wednesday bad. 

Power outages as mentioned above will be scattered to locally widespread. We're not expecting October 2011, so let's put that to rest, but there will likely be tens of thousands of outages, especially is snow is on the wetter side. 

I also cannot emphasize enough how much high amounts of snow removal can impact the body and make generator use dangerous. Make sure you are using proper techniques when shoveling and do not take shoveling related cardiovascular issues lightly. If you use a generator, make sure you have it properly ventilated. 

This is a serious storm. Do I think it'll be like 1978 or 2013, no, but this could easily be the worst winter storm for us in over a decade.

With the totality above, we expect this to be a high impact to locally extreme impact event. 

Stay tuned and stay safe. 

A​s 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

Good evening from Southern Connecticut Weather. 

Whew. It has been a season. Normally, we would see one high end winter storm at best in a given season, but after a gargantuan trend in the last 24 hours across guidance, it is increasingly likely that another big event is coming. 

We didn't talk in much detail about this storm over the last week because there was no need to, other than provide our basic updates. The hype was out of control, and nothing that happens from here on changes that because the guidance was not anywhere near on board until now. Our aim is to provide you with information that can be backed up with solid analysis. 

Well, here we are. The third system in our active pattern may very well realize its explosive potential, and that means a possible blockbuster storm for our region. 

This is our first call forecast. It is meant to give you everything you need to know right now so you can begin planning. There will be a final call forecast issued tomorrow or very early Sunday depending on the timing of the storm. 

Let's get to it. 

Above: the first call snow map. We are initially calling for 8-16" of snow with the lightest amounts in western CT and perhaps the CT River Valley in north central CT. 

Overall Setup
Explosive is the word. We actually said that some time ago, but it wasn't until the last 24 hours that the true potential for this storm began to come into focus. 

The expectation continues to be that energy dives down from Canada and the Midwest in the wake of our current storm today. A ridge in the western U.S. is absolutely critical here, as is blocking upstream that will slow the flow and allow for explosive development once the energy moves off the coast. 

Previously, the guidance had a flatter ridge out west and more confluence to our north which was working in tandem to potentially kick our storm out to sea or deliver a glancing blow at best. Now, as we get closer in time to our event, the models are latching onto the idea of the opposite occurring. The result is...explosive. 

Above is the 18z GFS depiction of the 500mb evolution from Saturday to early Tuesday morning. Note the energy diving down aided by the big western ridge, and watch the energy intensify and wrap up right south of New England as it rolls by. That is a big winter storm signal. 

The GFS has led the way overall with this system, sniffing out this potential before the Euro model could. Once again, the AI versions of both models showed the potential early, and now are converging on a higher end solution for New England. 

So what would this mean? As the energy dives south and reaches the coast, it will trigger a coastal storm. Because there is some modest but well-timed blocking, that will trigger high end intensification of our storm as it moves northeast. The combination of a strong pressure gradient and rapidly developing storm will make this a very windy event, very different from any winter storm this season.  

The big question remains just how far northwest this storm gets. A bona fide blizzard is squarely on the table.

Above: the 18z GFS surface depiction of the storm. This would suggest heavy banding across the state and blizzard conditions somewhere in southeast New England, if not most of the region. 

Below: the hot off the presses 18z Euro AI. You may not see pretty colors, but the result is all the same. Blockbuster event. 

Now these are just surface depictions, and you have to do a whole lot more to come up with a forecast than look at that, but everything at this moment points to a high end event across much of the northeast U.S., with more time for this to trend.

Because we haven't seen things stabilize yet, we need to be on the lookout for 1) a further northwest trend that makes this even more impactful or 2) last minute shifts southeast (as does happen with coastal storms) that makes this less of a blockbuster and more of a run of the mill major storm. 

The Forecast
Timing
This is tricky still and expect some possible shifts, but we have more consensus now. Currently our expectation is that snow begins from SW to NE on Sunday, most likely in the late morning to early afternoon timeframe. If I had to put a number on it, I'd say between 11am-2pm. The worst of the storm would most likely occur however during the overnight period through most of the day Monday. That's when you can expect the heaviest snow and strongest wind. 

Snow Accumulation
We're still in somewhat uncertain territory given the ongoing trend, but everything has pointed upward. In fact as I was writing this I took the numbers up. 

My current expectation is a general 8-16+ inches of snow across the state, with the highest amounts in eastern CT, and lowest in western and north central CT. This is subject to change as we gather more information on the amount of moisture the system will throw into the state. The plus is there because it's quite possible the numbers go up for the final call, but let's not discount the last second shift southeast either. 

Bottom line: expect a high end event but the final totals are not in stone yet. 

Wind & Power Outages
The forecast here is very different from what we've seen in other recent winter storms. Here, we expect both a strong pressure gradient and an explosively developing storm to produce significant wind. The wind could very well be prolific in eastern New England, but for now we want to hedge a little more conservative on wind here. 

In northern CT, our current forecast is for maximum wind gusts of 35-45mph. While that's enough to meet the wind minimum for blizzard conditions, we need three consecutive hours of it for a blizzard to verify. It's unclear if that will be the case, especially in NW CT. 

In southern CT, especially coastal sections, our current forecast is for maximum wind gusts of 45-55mph. Here, blizzard conditions are more likely to verify, especially in SE CT. 

We don't currently expect heavy wet snow, but along the coast it's always tricky, and with higher end winds that means scattered power outages are possible. This is definitely something to watch. 

Overall Impact
Folks, this is one to take seriously. The trend has rapidly moved toward a high impact event and a bona fide blizzard is on the table. As much as our first blockbuster storm was impactful, this could be even higher end due to the potential for very strong winds. That's not said to make anyone panic, but based on the information we now have, it's time to prepare. We will be watching the track trend over the coming day, and will be with you every step of the way. 

Stay tuned. 

A​s 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

Good evening from Southern Connecticut Weather! 

System #1 was good for providing much needed rainfall, but was a bit of a dud when it came to wintry precipitation, even by the low bar our forecast set. 

Our next system is on the way, and while the setup is fairly similar to System #1 we do expect this one to be more impactful. This forecast will be quick and to the point. Let's dive in. 

Above: the snowfall map for our coming system. In far northern CT we should see all frozen precipitation, which should lead to minor snowfall and a glaze of ice. In most of CT we expect minimal snow with a glaze of ice/sleet possible. Along the coast, while we may start out with some mixed precipitation, or end as snow on Saturday, this is a rain event. 

Overall Setup
Much like System #1, this storm is the result of energy being ejected from a sprawling low from the Midwest. Unlike System #1, there should be colder air in place at the start, and with a stronger storm we should be able to keep some marginal cold in place over the region. 

This means that we will have a mixed bag event in what is a southwest flow event. That means that warmer air from the southwest will move over the region, flipping the column aloft from below freezing to above at some level. While temperatures throughout the column will be too warm for accumulating snow or ice in coastal CT, the level of cold available will determine how much snow and mixing occurs in interior CT. 

As the storm departs on Saturday, residual moisture may flip everyone back to snow as colder air advects into the state. 

Above: the 18z GFS depicting the surface evolution of our storm. As you can see, the Midwest low effectively ejects energy that spurs a coastal storm, but for us the southwest flow from the primary low in the Midwest warms the column up.

The Forecast
Timing
In writing this forecast, timing has been the most difficult part to predict. Some of the global models have pushed back the start time of the precipitation to the afternoon, but we still think that a morning start time is most likely. The AM commute looks ok, with precipitation moving into the state toward the end of it--between about 9am and noon from west to east. 

While there may be a little mix early in the coastal areas, I don't anticipate that lasting long and things should flip very quickly to rain there. Inland, you will likely start out as a mix of sleet or freezing rain, especially in elevation areas. In the CT River Valley, you will be close to freezing rain and we really need to watch what the surface temperatures are in the morning. If surface temperatures are too warm, you will go from rain to mixing. 

Mixed precipitation continues during the afternoon and evening inland, with plain rain further south. Overnight as the storm pulls away we cool off and whatever moisture is left over should change to snow. This may be how a lot of people verify the snowfall forecast, though the bar is low to begin with. 

The high resolution NAM, which tends to be very good with depicting warmth aloft in these setups, provides a general evolution that we agree with. 

Some guidance does have snow showers lingering on Saturday in the wake of our storm, but for now, we limit the potential of that in this forecast. 

Snow Accumulation
Given the temperature profile, the snow is not the story of this event. It's the mixing. Many inland locations should see a period of sleet and freezing rain, which may lead to minor accumulation in northern CT. It doesn't take much to put down a glaze, though marginal surface temperatures will make accretion of ice less efficient. 

In far NW CT and some towns along the CT/MA border, we expect 1-2" of snow/sleet (yes, sleet officially counts as snow). In most of interior CT, we're expecting a coating of snow at best, though some towns could see a little more. Here icing is the biggest hazard, with minor accumulation possible. A coating of snow/sleet to 2" of the same are possible, noting again that some may not verify snowfall until late Friday/early Saturday. 

Wind & Power Outages
Although we're expecting whatever snow to fall to be on the wetter side, and minor icing, that's not enough for a significant power outage kind of storm. We shouldn't see strong winds with this either. 

Overall, any power outages should be isolated. 

Overall Impact
Despite the overall minor amounts of snow and ice, the timing makes this a much more impactful event than it'd otherwise be. The end of the morning commute may be impacted, especially in western CT with the earlier start time of precipitation, but the evening commute should be impacted for all. As a result, we could see scattered to even widespread school cancellations tomorrow, if not early dismissals, in interior. That alone is worthy of a moderate impact event for interior CT, with a low impact in coastal CT. 

Bonus Discussion
For those of you that read to the end, let's talk about the weekend. 

There's a lot of hype out there about this one, but we've kept our powder dry because a lot of the model solutions suggest a miss. The setup is actually pretty straightforward: in the wake of System #2, energy will dive down from Canadian Plains and Midwest, and spurred by a big ridge over the western U.S. this should force the energy offshore and allow for some level of storm development. 

Above: the 500mb depiction of the 18z GFS. Note the big ridge over the western part of the country. How amplified this is and where it sets up will be big for how explosive this potential is and the track of the storm. 

So far, the majority of guidance has kept this one as either a middling storm that slides east and out to sea once leaving the coast (Euro), while other guidance like the GFS has an explosive system that either provides a glancing blow or direct hit. 

Above is a lot of information, but here are surface depictions of the GFS (top left), Euro (top right) and their respective AI models underneath them. These are Monday morning. For the first time, we've really seen the Euro move toward a more impactful system. Each of the depictions above would bring snow to the state. The AI models have been more bullish on a big system just offshore from the beginning, though not all were hits. 

What does this tell us?

Well, one model run doesn't make a trend, so I need to see a lot more consistency to latch onto what you see above. That said, we're getting into the short range soon, so each model cycle becomes increasingly important. Tomorrow it will definitely be time to talk about the Sunday/Monday potential, especially if the models "hold" tonight. 

For now, there are three scenarios:

Blockbuster Hit--20%

Glancing Blow--60%

Total Miss--20%

Stay tuned.