ABOUT POSSIBLE EAST COAST SNOWSTORM JAN 29 for eastern half of Mid Atlantic & New England

stardate 202201.24 ……1900 est

This event has been showing up on the various weather models since late last week. The operational GFS model from the12z JAN 22 run showed a slow-moving, massive LOW pressure area along the Middle Atlantic Coast which dropped over 30 inches of snow in a band from central North Carolina to Richmond VA into southern Maryland and a large area of 8 to 18 inches of snow throughout most of New England and the Mid-Atlantic region. Obviously, that kind of model output got everybody’s attention.

During the weekend, the various weather models had shifted this LOW to the east, away from the coast and showed a weaker overall LOW. But the new data since Sunday evening, has shown a persistent trend of the LOW becoming larger and more intense as well as tracking closer to the coast.

Let’s start with the basics. In order to get big historic East Coast snowstorms you have to have a blocking pattern in the jet stream across the arctic region and in Greenland / northeast Canada. The blocking pattern in the arctic region is referred to as the negative phase of the AO (Arctic Oscillation). But right now the Arctic Oscillation is positive which is unfavorable with respect to the Big East Coast snowstorm idea. In addition, the development of blocking patterns in the jet stream across northeast Canada and Greenland, which is referred to in the weather business as the negative phase of the NAO (North American Oscillation), is also supportive of Big East Coast snowstorms. But right now the NAO is in the positive phase (not favorable for East Coast winter snowstorms).

What this means is that the when the large area of LOW pressure begins to form along the southeast US Coast on Friday, it will only has a small window where it can take the exact perfect track that will result in a significant East Coast snowstorm for the Mid-Atlantic region.

The general overall outline of events.

A major trough in the jet stream will sweep across the Midwest and head for the East Coast during the second half of the week. As it builds into the East Coast, the Trough will intensify which means that the surface LOW pressure area that develops at the base of the jet stream trough in the southeastern states will become quite strong. To the north, this Trough will drive a new strong cold front Across the middle Atlantic and New England regions. this font will reinforce the cold air on the East Coast for the weekend Nor’easter/ East Coast winter storm. This means that whatever develops along the East Coast on Friday and Saturday, the atmosphere will be cold enough to support mainly snow as far south as southern portions of North Carolina and northwest portions of South Carolina.

With respect to the actual large and powerful East Coast winter storm threat for Friday and Saturday, there are still a lot of details we do not know but some things are coming into Focus about this event.

1. All of the weather models on Monday morning and at midday are now in strong agreement in showing a ruly impressive powerful LOW pressure area developing off the Southeast coast on Friday night. This LOW will track in a NNE or NE direction as it parallels the East coast. Because of the jet stream pattern across North America, additional energy coming down from western Canada into the Plains and the Midwest, there is little chance that this LOW pressure area is going to hug the coast and/ or come inland.

2. This means that the main risk that of what could go wrong is LOW tracking too far to the east and missing everyone on the coast

3 the current midday models show that there was going to be a very sharp cut off on the western side of the Nor’easter as of parallels the East Coast. This means there is going to be a sharp gradient where one location could end up with 6 or 8 in but only 30 miles away the snow amounts could be 1 inch or less. This means is likely that the further West you are with respect to I-95, the less snow your will see. In fact the Appalachian Mountains regions, such as southwest Virginia, the Western mountains of North Carolina, the Shenandoah Valley the western half of Maryland, and the eastern half of West Virginia are likely to miss out on this event.

12z MONDAY operational GFS and amount of Liquid. Note the black line.

12z MONDAY GFS ensemble and amount of Liquid.

4 The midday data also indicates that this is going to be a fast-moving event. It is not going to slow down or stall along the Mid-Atlantic Coast, which is what some of the data suggested last week. The fast movement of the system means that there is little chance that anybody in the ***Middle Atlantic** region will get over 12 inches of snow. However once the LOW reaches southeast New England, where it slows down and stalls, the odds of 1 to 2 ft of snow become quite High for that region.

5 exactly how much snow falls in the I-95 corridor from RIC to NYC, will greatly depend on how close the Nor’easter tracks to the East coast while staying offshore. Theoretically, if the Nor’easter were to track really close to the coast, it could bring ain and or a rain/ snow or mix to the immediate coastal areas from North Carolina to southeast New England. But right now none of the data shows that and we think this possibility is extremely small.

6. The odds are quite high at this early point in time that the snow amounts will be greater than 12 inches for most of New England and this also includes New York City metro area, most of Long Island, and northeast third of New Jersey. Because of the intensity of the LOW the midday models are showing wind gusts over 50 mph. We believe there is a high probability of this event qualifying as a blizzard for New England, New York City and northeast third of New Jersey on Saturday and Saturday night.

Without getting too technical in terms of meteorology there are three possibilities or scenarios which are under consideration.

Scenario #1 — the large and powerful LOW pressure area tracks a tad too far to the east so it parallels the East Coast. In this scenario or option #1, there would be strong wind and high tides but no substantial snowfall anywhere on the East Coast except for perhaps Cape Cod Massachusetts. The massive LOW pressure area would track into southeastern Canada as a massive blizzard on Saturday night into Sunday, January 30th. Based upon the midday data from the operational GFS European and Canadian as well as their respective and sandals this option worst scenario of the low being too far to the east appears to be less likely.

Scenario #2 is a glancing blow. That is to say, the large powerful LOW pressure area tracks fairly close to the coast so that the western fringes of the LOW pressure area brings accumulating snow to the eastern portions of North Carolina, the Southeastern of Virginia, perhaps the coast of Delmarva, eastern Long Island and southeastern New England. There would be strong winds, coastal flooding, and this could be significant winter event for only those areas. But this outcome would NOT be a direct hit or eastern Mid Atlantic as most of the heavy snow would stay off the coast to the east, this outcome would still be a major hit for New England. This is what WxRisk favors right now.

Scenario #3 is the Big East Coast snowstorm outcome. This event would be a direct hit for everyone from central North Carolina to Boston. That is to say, a massive LOW pressure area takes the exact perfect track just off the coast so that there is a significant Middle Atlantic snowstorm mainly along the coast, but a major snowstorm, possibly reaching blizzard conditions, from the NYC to Boston. Based upon the midday data from the operational GFS European and Canadian as well as their respective ensemble, the risk of this scenario Verifying appears to be increasing.

The 12z EURO ensemble is a bit to the west of the op run