Good evening from Southern Connecticut Weather.
'Tis the season! Our first significant winter weather event is looking more likely, with all of the guidance trending toward a moderate impact event this weekend. It is very important for all of you to remember that we’re still in the lower confidence range on snowfall. This discussion seeks to give you the information we have right now and provide some clarity on what we (think we) know and what we don’t know. Let’s get down to business.
'Tis the season! Our first significant winter weather event is looking more likely, with all of the guidance trending toward a moderate impact event this weekend. It is very important for all of you to remember that we’re still in the lower confidence range on snowfall. This discussion seeks to give you the information we have right now and provide some clarity on what we (think we) know and what we don’t know. Let’s get down to business.
Overall Setup
As I alluded to in my two week outlook (which is looking great by the way!) the pattern is changing. Colder air is filtering into the east and that has opened the door for a system to develop deep in the south that is bringing snow to Mexico and Texas today, and will deliver snow in the southeast tomorrow. By Saturday, that system is rocketing up the coast, and now looks to get close enough to deliver more than a glancing blow to the region on Saturday.
As I alluded to in my two week outlook (which is looking great by the way!) the pattern is changing. Colder air is filtering into the east and that has opened the door for a system to develop deep in the south that is bringing snow to Mexico and Texas today, and will deliver snow in the southeast tomorrow. By Saturday, that system is rocketing up the coast, and now looks to get close enough to deliver more than a glancing blow to the region on Saturday.
18z GFS depiction of the overall setup above (not a forecast obviously) and the GEFS precipitation total plot below. The trend has been toward more precip getting into the area.
Saturday Timing—High Confidence
Right now, I have the greatest confidence in the timing of the system. The low currently to our south will move fairly quickly up the coast on Friday and Saturday. Much of the guidance is in agreement that snow starts in Connecticut on Saturday morning. Mid-morning in southern areas and late morning in the rest of the state. The heaviest snow should come during the afternoon and evening hours. This is when the roads are likely to be worst and we see delays at airports. As the storm departs, snow will begin to taper off and should be gone by early Sunday morning.
Things could shift back and forth by a few hours, but I don’t envision a scenario where say, snow starts tomorrow or Sunday.
Advisory to Low End Warning Level Snow Accumulation—Low Confidence
Of course, everyone cares about how much snow falls in their backyard. This is unfortunately the lowest confidence part of the forecast. It has the lowest confidence because the guidance has yet to stabilize with the trend toward a more impactful event. Last night, it looked like this system would be a glancing blow at best. Tonight, after the morning and afternoon runs of all the guidance, it looks much more significant.
The keys here are
So here is the map again.
Right now, I have the greatest confidence in the timing of the system. The low currently to our south will move fairly quickly up the coast on Friday and Saturday. Much of the guidance is in agreement that snow starts in Connecticut on Saturday morning. Mid-morning in southern areas and late morning in the rest of the state. The heaviest snow should come during the afternoon and evening hours. This is when the roads are likely to be worst and we see delays at airports. As the storm departs, snow will begin to taper off and should be gone by early Sunday morning.
Things could shift back and forth by a few hours, but I don’t envision a scenario where say, snow starts tomorrow or Sunday.
Advisory to Low End Warning Level Snow Accumulation—Low Confidence
Of course, everyone cares about how much snow falls in their backyard. This is unfortunately the lowest confidence part of the forecast. It has the lowest confidence because the guidance has yet to stabilize with the trend toward a more impactful event. Last night, it looked like this system would be a glancing blow at best. Tonight, after the morning and afternoon runs of all the guidance, it looks much more significant.
The keys here are
- How closely the area of low pressure gets to the region. We’re likely threading the needle here. If we see ticks west, that introduces more snowfall statewide and creates a higher impact event. If it comes too far west, we have to worry about mixing in SE CT. Right now, I think that is a low probability. If things are overcorrecting and we see a significant shift east tomorrow, that would reduce totals across the board.
- How strong the system is. This probably matters a bit less than track, but I think there is room for this to amplify more than currently modeled, which could bring more precipitation to the region.
So here is the map again.
Overall, I think we’re looking at 2-4” in Northwest CT where they are furthest away from the heavier snows. Beware the deformation banding though—last year NW CT ended up with more snow than forecast because of banding over the region. I think 3-6” is most likely in central, southern, and eastern Connecticut. This is a forecast that does not have mixing in CT. I think the storm stays far enough offshore and temperatures stay low enough to prevent mixing issues.
This is a first cut of a forecast. It is my best guess right now. These numbers could go up or down, and my guess is that there is a higher chance they go up than down so stay tuned for our final call tomorrow.
This is a first cut of a forecast. It is my best guess right now. These numbers could go up or down, and my guess is that there is a higher chance they go up than down so stay tuned for our final call tomorrow.
Moderate Impact—Moderate Confidence
Impact is often directly tied to snowfall, but there are other factors that make a storm a serious one or more run of the mill. I have moderate confidence in impact by taking in the totality of factors. There will be delays but not as many as there would be during the work week when more are on the roads. This also doesn’t look like a “snow blitz” where very heavy snow falls. In an effort to provide you with a better graphical breakdown of impact, I'm rolling out a SCW Impact Scale. This will be refined over the course of the season, so please provide feedback if it is helpful or not. Moderate impact is more run of the mill in my opinion.
Impact is often directly tied to snowfall, but there are other factors that make a storm a serious one or more run of the mill. I have moderate confidence in impact by taking in the totality of factors. There will be delays but not as many as there would be during the work week when more are on the roads. This also doesn’t look like a “snow blitz” where very heavy snow falls. In an effort to provide you with a better graphical breakdown of impact, I'm rolling out a SCW Impact Scale. This will be refined over the course of the season, so please provide feedback if it is helpful or not. Moderate impact is more run of the mill in my opinion.
Overall, there is growing confidence in a moderate impact event statewide on Saturday. There is low confidence in snow totals right now, but we think this is a good forecast given the current guidance trends and overall setup.
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Thank you for reading SCW.
- DB
As 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
