Once More Unto the Breach, Dear Friends

Yes, the rumors are true, a storm system is on the way for the weekend, and there is the potential for some significant snowfall. Nothing is definite yet though, so let’s separate the truth from the exaggeration. First, we’ll set the table for what’s going to happen.

Low pressure will move out of the Gulf of Mexico and up the East coast Friday into Saturday while rapidly intensifying. (You’ll hear the word bombogenesis used for sure.) Before that happens, a cold front will move across the Northeast on Friday, producing some snow showers. These are unrelated to the storm system, and could drop an inch or less on the region. That front will likely dissipate south of New England as the approaching coastal storm overwhelms it. Meanwhile, behind that front, a large high pressure system will build into southeastern Canada, locking cold air into place.

Friday’s cold front will drop less than 1″ of snow on most of the region. Image provided by WeatherBell.

OK, now that we have the basic setup, let’s delve into a few things that we’ve heard or read today and how truthful they are.

Statement: An historic blizzard could set records across the Northeast this weekend.
Truth: Yes, some models are showing a rather extreme storm system with the potential for extraordinary snowfall totals. But, it’s still 4 days away, and a lot can change. This is far from a given. We’ll explain below.

Statement: This will be all snow for the entire region.
Truth: Again, given that there is still some uncertainty in the track, a mix or change to rain can’t be ruled out, especially for Cape Cod, and possibly eastern Massachusetts of Rhode Island. Again, read on for more details.

Statement: Significant coastal flooding is likely.
Truth: This one rings true. With a New Moon on Tuesday (we were that close to a Duran Duran song), tides will be running astronomically high. Add in strong east to northeast winds pounding the shoreline for 2 and potentially 3 high tide cycles, yes, coastal flooding is likely, especially the normally vulnerable locations.

OK, now let’s get into what could happen on Saturday. A rapidly intensifying storm system will head up the East Coast, producing strong winds and heavy snow ahead of it. While most of the models are fairly similar to each other with a track close to the “benchmark” (40N/70W), this is far from definite. The storm could end up farther offshore, which would limit the how far inland the heavy snow extends. The storm could also track closer to the coast, which would allow milder air to move in and change the snow to rain, how far inland the change could occur would be determined by the track obviously. This is the type of the detail that won’t become clearer for another day or two at best.

Our friends at the National Weather Service office in Norton, MA explain the potential error in the model forecast nicely.

One factor in determining that track? The upper-level energy responsible for the storm is just moving into from the Pacific tonight. Why is that important? Let us explain. Every day around the world, we send up weather balloons twice a day to sample the upper atmosphere. This is done at 00UTC and 12UTC everywhere (7am/7pm in EST). This data is then fed into the models. The upper-level energy that will create our storm has been over the Pacific for the past several days, where there is little data. In the past, we would get observations from planes as well to supplement the balloons, especially over the water, where there are no balloon launches obviously. Well, since the pandemic, air traffic is less than half what it used to be, so there are a lot less of those aircraft observations. So, we are basically at the mercy of the balloon data. Once that upper-level energy moves over land, as it is doing now, it will be into the balloon network. The models should now start to have a better idea of its structure and converge on a solution.

The kink in the flow near the British Columbia coast and the one over northern Alberta will eventually combine to create our weekend storm. Once they’re over areas with more data, we’ll have a better idea how strong they are. Image provided by the University of Wyoming.

Complicating things is the fact that some models show the system being captured by the upper-level trough of low pressure, or even getting stuck underneath a “cutoff” upper-level low pressure system. (It’s called that because it becomes cut off from the jet stream.) This would potentially allow the low to stall out south of New England for a while, prolonging the impacts to the region. How strong the storm gets (also up for debate) could determine whether or not this scenario occurs, but will also impact how strong the winds will be and in turn the amount of coastal flooding that may occur. Right now, the timing of the system looks to be generally between midnight Saturday morning and midnight Sunday morning, but obviously, this is far from definite.

The models still do not agree on the strength or location of the storm Saturday afternoon. Images provided by Pivotal Weather.

As for how much snow will fall? Well, we’re not even going to attempt to put any numbers down yet. There is still FAR too much uncertainty. In addition to all the factors we talked about above, another one is temperature. Some models keep the cold air locked into place, with temperatures in the teens and 20s for much of the region during the storm. This would result in a much fluffier snow, making it a little easier to clean up, but also allowing it to pile up a lot quicker. If the warmer air does move in, especially near the coast, then temperatures could be near or even above freezing in spots. The general rule is that 1 inch of liquid precipitation equals 10 inches of snow. This holds true at temperatures close to freezing. With temperatures in the lower 20s, that 1 inch of liquid could result in 20 inches of snow. Most of the snow maps you may see online are ones that use the 10:1 ratio only, so in colder scenarios, like this one could be, they will underestimate the amount of snow.

If you really want, there are plenty of people all over Facebook, Twitter, and the web, who are more than happy to share all of those various model forecast maps, no matter how far-fetched they may seem. We’re not going to do that. We’ll just say that the potential is there for this to be a significant snowstorm.

Given all of this, we are issuing an Extreme Hype Watch for the StormHQ viewing area. An Extreme Hype Watch is issued when conditions are favorable for media hype of an event to reach extreme levels within the next 48-72 hours. If conditions warrant, a Hype Advisory or Extreme Hype Warning will be issued as the event draws nearer. We’ll hazard an initial attempt at amounts when we publish our Weekend Outlook Thursday afternoon. In addition, well do another full blog post on Friday.

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