If you haven’t heard yet, the threat for a fourth March nor’easter — yes, a fourth coastal storm in the month of March — is becoming increasingly likely. The model guidance has been hinting at this threat for nearly a week now, but this set up seems to be the most complicated, and it now appears that there will be two separate low pressures that form within a border area of low pressure. Whether it’s a nor’easter or not is still uncertain because it depends on if there is the presence of a northeast wind. Either way, the impacts will be the same nor’easter or not.

Since we are looking out several days in time through the middle to end of next week, the model skill is pretty low, especially because the energy associated with this storm system is still over the eastern Pacific Ocean. Weather forecasters have no tools to use to sample the atmosphere over the open ocean compared to over land. Weather balloons are often used over land in the United States, which can put better data into the computer models and that could lead to better forecasts. Since the energy is still over the Pacific, we are purely relying on the model guidance at this time, which tends to be showcasing erroneous model outputs.




If you are an avid weather geek and you’ve been looking at what the operational GFS (American) and ECMWF (European) models have been showing run-to-run, you can tell that they don’t have much of a clue as to what will happen. These two models are not in agreement at all. They are also painting a different picture as to what will happen with this storm with each new model run. Now it is worth noting how the GFS model has been somewhat more consistent with the general set up of the storm track and where the precipitation will set up. This particular model is expecting an area of low pressure to move in from the west and into the Appalachians while a weak low develops off the Mid-Atlantic coast on Tuesday. Then on Wednesday, ย that weak, offshore low will head out to sea while the interior low moves offshore and develops into a possible nor’easter, bringing snow to a very large area. By Thursday, that second low will head toward Canada while a third low pressure may form and continue the risk for snow, especially in the morning, to New England. Keep in mind, this is not an official forecast overall. We are explaining this to show the differences between the modeling and the uncertainty that exists.

Meanwhile, the ECMWF model is honing in on two separate coastal storms that will develop within a border area of low pressure: one on Tuesday then a second on Wednesday that will develop right on the heels of the first. This model has been fairly consistent on the formation of these two different lows, but have been varying in terms of the track of these lows with the different runs that have come in. Again, this model is changing from run-to-run, which we’ll explain in more detail later on in this article.




The way the upper-level energy has been trending with the is toward a more organized and stronger storm system. In the GIF below, you’ll see the trend in the model guidance from the last 8 model runs of the GFS model, showing how the upper-level energy has evolved in showing a more compact and organized storm system, but a slower-moving storm. Maybe there is only one coastal storm that develops given this evolving set up but we have no idea at this time given the extremely-high uncertainty.

Now let’s take a look at the ECMWF model: this model has been more volatile with big changes in each new model run. Friday morning, it showed a full-fledged snowstorm for the I-95 corridor. Then in comparison to the afternoon run on Friday, it didn’t show much in terms of land impacts. It’s all dependent on how the upper-level energy sets up. This is such a complex forecast and every detail is crucial to whether there will be another high-impact snowstorm for the northeast. Below is a model comparison between the 0z (early morning run) and 12z (afternoon run) model runs from Friday. Notice the difference in the location of the energy just north of New York State? In the 0z run, it was further north, allowing for a nor’easter to form and move up the coast, thus bringing widespread snow to much of the Northeast. Then there’s the 12z run, where that piece of energy was further south, thus forcing the low pressure out to sea.

These subtle differences is what us forecaster’s are currently dealing with. It’s a matter of whether there will be a high-impact snow event, a minor storm with rain and snow, or a fish storm with minimal impacts. There is another tool that we look at, which is the ensemble guidance that the GFS and ECMWF models produce. Basically with the ensemble guidance, it slightly alters the current environment to show different scenarios in how a storm may evolve. Note that the model guidance tends to follow the operational model run. Below, we’re showing you the different possible storm tracks from theย 12z (afternoon run) model suite. Each ‘L’ on the maps represent a possible location of the area of low pressure.

Now to wrap up our thoughts, here’s the main points on this impending fourth and potentially fifth nor’easters:

  • At least one coastal storm will form.
  • Impacts from this large-scale storm system will occur in the Tuesday through Thursday time period.
  • The exact impacts remain highly uncertain.
  • The track of the storm or storms is shifting with each new model run.
  • Snow is possible for the entire I-95 corridor.

 

At this time, monitor the forecast from WeatherOptics. We’ll keep you updated as the confidence in this forecast hopefully increase. For now, we leave you with a general overview graphic below.

Keep in mind that if you are in a colored in area, you may not receive any precipitation at all, but the point of this graphic is to highlight where the chance exists for the different precipitation types. We wish we can tell you in more detail with what will happen with this storm, but for now, we’re in the wait and see period.



Author

Jackson is Head of Content at WeatherOptics and produces several forecasts and manages all social media platforms. Previously, Jackson forecasted local weather for southwestern Connecticut, founding his website, Jackson's Weather, in the March of 2015. He is currently studying Meteorology and Broadcast Journalism as the University of Miami.

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