Yesterday’s Nor’easter will seem downright quaint by the time Tuesday morning rolls around. Just a couple of days ago, forecasters were not even clear if we’d get any precipitation Monday going into Tuesday. Now, words like “historic” are being used to describe what will undoubtedly be the biggest snowstorm of the season so far. When all is said and done, we could be looking at widespread snow totals on Tuesday of 18″ to as much as two feet of snow. During the peak of this much stronger Nor’easter, high winds and blowing snow could lead to an extended period of blizzard conditions near the coast.

The Setup

Forecast models that up to just 2 days ago were displaying significant differences as to how this system would transpire are now in close agreement on a classic setup for a strong Nor’easter, and a powerful, high-impact blizzard for the Northeast.

A relatively weak clipper-type low will be moving across the Midwest during the day today. By Monday evening, a secondary low will form from the remnants of this first system. This second low will rapidly intensify as it tracks on or just west of the 40ºN 70ºW benchmark early Tuesday morning.

As the low bombs out (dropping more 30mb in less than a day), its forward progress will be slowed by a high pressure to the north. This high pressure over Quebec is a key difference between the setup of the storm on Saturday and this coming Nor’easter. In contrast to Saturday’s storm, this high pressure will allow a relatively deep layer of cold air to take hold prior to the arrival of this storm. As the low pressure continues moving northeast, the pressure gradient between the rapidly intensifying low and this high pressure will allow for strong winds to affect the area from first from the east, then northeast and finally north.

This combination of a slow moving, strong low pressure with ample cold air and moisture available will translate to widespread snowfall totals of over a foot, and close to 2 feet, primarily for the Hudson Valley and points east. This will primarily be due to the influence of a mesoscale deformation banding feature is expected to form north of the storm center, then slowly wrap around the storm as it moves northeast. Because the forward motion of the storm will be so slow, the banding feature (which could contain snowfall rates of 2-4″ per hour) could be sitting nearly stationary over large portions of the region for a prolonged period of time – thus leading to what could be record breaking totals.

With the wind expected to pick up during this event, there is a blizzard watch in effect for coastal areas of the region, where wind sustained winds (25-35mph) could lead to near zero visibilities while heavy snow falls.

Snowfall Totals

As you can see from below, almost the entire region is expected to pick up more than 12″, with eastern areas possibly picking up near 2 feet!

Looking at probabilities of snowfall totals below, you can see that there’s now at least a 70-80% chance a good portion of the NYC region receiving more than 8″ of snow.

This storm will also have ample moisture to draw off of, with the liquid water equivalent of between 1.5″ to over 2″ across a good part of the region. Using the standard 10-1 ratio of snow to liquid water, this would translate to between 15-20″.

Timing

Snow will begin Monday, with increasing intensity through the day. Winds  from the northeast will also pick up during the day Monday with high temperatures only in the mid-upper 20s. Anywhere between 1-3″ of snow could fall across NYC.

The heaviest snow will be taking place overnight Monday into Tuesday morning, where parts of the area could pick up another 9-13″. Again, the heaviest snow will be occurring within the mesoscale banding feature, where intense snowfall rates of 2-4″ an hour for a prolonged period of time could even be accompanied by thundersnow. Winds will probably peak during this overnight period.

Snow will continue to fall during the day Tuesday, with another 4-8″ of snow possible. High temperatures will again only be in the upper 20s.

Rest of the Week

Wednesday – snow finally ends Tuesday night with conditions clearing by Wednesday, but high temperatures again struggling to reach the upper 20s.

Thursday – a slightly warmer day with high temperatures in the low 30s.

Friday – there’s a chance at some more precipitation (but much lighter) from a weak low pressure system moving through Friday.