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All eyes are on March as we near the very end of the winter season, but in some years March can be quite sneaky and can produce sneaky snows. It’s been a warm February overall for many cities in the East with many expected to finish off as a top five warmest February on record. Based on that, you may think winter is completely over. In the Southeast, it likely is, but in the Northeast and Mid-Atlantic, Mother Nature may have something else up her sleeve.
The models have been advertising a significant pattern change for weeks now, mainly driven by a change in the North Atlantic Oscillation (NAO). Throughout much of the winter season, the NAO has been in a positive state, but as we get into March, the NAO will “tank” to a record low state. Based on the EPS data and other various model guidance, it is expected to drop to between -4 and -5 sigma, which indicates a very strong signature.
With the upcoming pattern for early-March, a very strong ridge is going to develop over Greenland. This is often given the name, ‘Greenland Block.’ It will then drift to the west toward the Davis Strait while a trough builds into the south. This is a highly amplified pattern, has shown on the European model’s 500 millibar heights below. With a ridge, it tends to be warmer than normal and dry whereas a trough delivers active and colder weather. This is one of several huge signals highlighting the potential for several winter storm chances in the Northeast and Mid-Atlantic based on this look.
Often times with a negative NAO, it brings a cold and active weather pattern to the East. Every event is different, however, but one good tool to look at are analogs. With analogs, it compares what happened in the past to what is being a modeled. By forecasting based on what happened historically to what is forecast in the future, this is sometimes an accurate way to predict the weather.
There are some conflicting factors among the analogs. The analog below shows the 500 millibar pattern present this time of the year that often produces significant snow to the I-95 corridor. When you compare it to the model image above, it looks eerily similar.
Even though this analog shows a snowy solution for the Northeast, other analogs such as the one below portrays a very different picture. This one highlights a wet and active weather pattern across the US with the exception of the East Coast, Great Lakes, and Pacific Northwest. This analog is based on the guidance from the American (GFS) model, however, which is not as accurate as the European model. The European model shows a wetter/snowier pattern compared to this, but not anomalously active.
Now when we take a look at what the actual model guidance is showing opposed to how the forecast compares to past similar events, it shows several chances for snow with the first significant chance around the weekend of March 3-4. What you’re looking at below is the low pressure locations generated from the European model’s ensemble guidance. There are 50 members in the ensemble guidance, and is generated from slightly altering the environmental conditions. This shows the potential different scenarios based on a slightly different atmospheric setup. Each different ‘L’ that you see represents a different possible location of where this likely coastal storm will be.
To wrap all of our thoughts up for the early-March outlook for the Northeast and Mid-Atlantic, there is definitely some uncertainty regarding this outlook. What we do know is that the weather pattern will likely be active based on this pattern change. One of the big questions we still have is how cold will it be. Both the American and the European models are in pretty good agreement on where it will be cooler and warmer than average. Notice how in New England, it will be right around average–if not above average. In the Mid-Atlantic, it is expected to be colder than average.
Don’t put the snow shovel away yet because there is a good chance more snow is on the way as we get into March in the Northeast and Mid-Atlantic! Maybe Washington, D.C., which has barely received any snow this winter, will receive significant snowfall.