Good evening from SCW,
It’s hard to believe that we’re going to see snow in just over a day given that it’s 55 degrees in Hartford right now, but snow is indeed in the forecast just in time to mess up Wednesday’s commute.
Models & Analysis
As the system that brought rain to the state today gets pushed out tomorrow evening by a cold front (after more rain tomorrow), that cold front will stall out just south of us, and at the same time, another wave moves up along the front and bring snow on the northern side of the front. These anafrontal events can occasionally be prolific snow producers, but have a well-earned reputation as one of the “fraud five” in weather forecasting; things that are often modeled and rarely occur. That said, as we’re getting close to go time on this one and all signs still point to some snow, it’s time to look at the details.
Here’s a look at the setup on the GFS. You can see the main system moving out to the northeast, but there’s still trailing energy left to our southwest that extends out along the frontal boundary and brings precipitation with it. As we’re on the cold side of the front, it would be mostly snow here.
It’s hard to believe that we’re going to see snow in just over a day given that it’s 55 degrees in Hartford right now, but snow is indeed in the forecast just in time to mess up Wednesday’s commute.
Models & Analysis
As the system that brought rain to the state today gets pushed out tomorrow evening by a cold front (after more rain tomorrow), that cold front will stall out just south of us, and at the same time, another wave moves up along the front and bring snow on the northern side of the front. These anafrontal events can occasionally be prolific snow producers, but have a well-earned reputation as one of the “fraud five” in weather forecasting; things that are often modeled and rarely occur. That said, as we’re getting close to go time on this one and all signs still point to some snow, it’s time to look at the details.
Here’s a look at the setup on the GFS. You can see the main system moving out to the northeast, but there’s still trailing energy left to our southwest that extends out along the frontal boundary and brings precipitation with it. As we’re on the cold side of the front, it would be mostly snow here.
If you’re a snow lover, this depiction is pretty much the best-case scenario for the event. You’ve got ample precipitation, good timing (most of the snow falls at night), and the cold front in the perfect place to allow for temps to drop enough for snow while not being too far offshore which would keep precipitation to the southeast of us. There’s also a strong band of lift oriented along the axis of the front, which will provide the best chance of a period of higher rates. The model consensus right now is that band is positioned right over us, which supports some of the higher totals that guidance is suggesting.
That said, there’s a lot that can go wrong here. If we see the front shift in position slightly, we could see a solution where most precipitation is offshore (should it shift SE) or we don’t cool off in time and just see more rain (should it shift NW). Even as modeled, temps are borderline; we’ll be close to 60 degrees tomorrow and so we’ll need to cool off quickly if we want to see accumulating snow tomorrow night. Heavier rates will help cool the column, but in order to get those heavier rates, we’ll need strong atmospheric lift; if that fails to materialize as forecast or sets up differently than modeled, we’d just see light snow that wouldn’t amount to much of anything. This is shown well here on the GFS – the area of highest lift (the center of the purple contours) is in SECT away from the short, and the simulated radar shows the heaviest precipitation focused right there.
That said, there’s a lot that can go wrong here. If we see the front shift in position slightly, we could see a solution where most precipitation is offshore (should it shift SE) or we don’t cool off in time and just see more rain (should it shift NW). Even as modeled, temps are borderline; we’ll be close to 60 degrees tomorrow and so we’ll need to cool off quickly if we want to see accumulating snow tomorrow night. Heavier rates will help cool the column, but in order to get those heavier rates, we’ll need strong atmospheric lift; if that fails to materialize as forecast or sets up differently than modeled, we’d just see light snow that wouldn’t amount to much of anything. This is shown well here on the GFS – the area of highest lift (the center of the purple contours) is in SECT away from the short, and the simulated radar shows the heaviest precipitation focused right there.
Finally, here’s a look at the 18z 3km NAM, which is closer to the “worst-case” scenario; just about everything that I explained that could go wrong does and the result is just a coating to an inch in eastern areas and nothing elsewhere. Notably, the 0z run of this model corrected back somewhat towards the GFS, so I think this is an outlier solution and am not considering it very much in the forecast, but I wanted to show it as an example of the negative bust potential here.
Forecast & Timing
Here’s our forecast snowmap for this event.
Here’s our forecast snowmap for this event.
If everything were to work out perfectly with this event, models suggest a third to a half of an inch of QPF is about the upper ceiling with this event, which would suggest a 3-5” forecast. However, I think that’s overdone for several reasons. It’s likely that some of the QPF that the models predict to be snow will be lost to “white rain” while the column is cooled, especially if we see lower rates. I also think that we will still see some shifts with the frontal position in the final hours leading up to the event, either way you shift the front, it’s likely that we’d lose some snow accumulation, whether it’s from lack of QPF, minimized forcing, or warmer temps. And finally, there’s the old saying “Fool me once, shame on you. Fool me twice, shame on me”. Past performance is no indicator of future results, but we’ve been burned by these anafrontal events before and they have a nasty history of negative busts.
All in all, by mid-morning Wednesday, we’re expecting one to three inches of snow across the state. We had discussed adding a 2-4” band in interior southern areas up into the NE hills where we think the highest likelihood of good rates is, but we decided to play it conservatively for now and upgrade totals a bit tomorrow if needed once we get a better understanding of where we may see that band of heavier forcing and therefore higher totals set up.
As far as timing goes, rain should change to snow overnight tomorrow from NW to SE, and by daybreak it should be snowing across most of the state. Snow will taper off from NW to SE through mid-morning, but snow is likely for at least the start of the commute in all areas and through it in some.
Impacts
I expect widespread school delays and possibly some cancellations depending on how quickly the storm moves out and how districts choose to handle the event. Roads will be passable but expect slow going across most of the state for the morning rush, so if you can work from home Wednesday, it might not be a bad idea to do so. I don’t expect any power or other infrastructure impacts from this system. Overall, I would say that this is a moderate impact event; totals are relatively low, but snowfall rates could approach 1” per hour in some areas for a short time during the morning commute, which will cause slow going and the potential for school delays. Bring this event in six hours earlier and I would call it low impact, but timing is everything in operational meteorology.
We’ll be back tomorrow with a final call map, until then we’ll be on our social platforms for questions and comments; use the buttons below to join us. Thank you for reading SCW!
-SA
All in all, by mid-morning Wednesday, we’re expecting one to three inches of snow across the state. We had discussed adding a 2-4” band in interior southern areas up into the NE hills where we think the highest likelihood of good rates is, but we decided to play it conservatively for now and upgrade totals a bit tomorrow if needed once we get a better understanding of where we may see that band of heavier forcing and therefore higher totals set up.
As far as timing goes, rain should change to snow overnight tomorrow from NW to SE, and by daybreak it should be snowing across most of the state. Snow will taper off from NW to SE through mid-morning, but snow is likely for at least the start of the commute in all areas and through it in some.
Impacts
I expect widespread school delays and possibly some cancellations depending on how quickly the storm moves out and how districts choose to handle the event. Roads will be passable but expect slow going across most of the state for the morning rush, so if you can work from home Wednesday, it might not be a bad idea to do so. I don’t expect any power or other infrastructure impacts from this system. Overall, I would say that this is a moderate impact event; totals are relatively low, but snowfall rates could approach 1” per hour in some areas for a short time during the morning commute, which will cause slow going and the potential for school delays. Bring this event in six hours earlier and I would call it low impact, but timing is everything in operational meteorology.
We’ll be back tomorrow with a final call map, until then we’ll be on our social platforms for questions and comments; use the buttons below to join us. Thank you for reading SCW!
-SA
