Tremendous Nor’Easter, significant snow possible Tuesday

All of those cold and snowy winter forecasts may finally be validated. All of the latest numerical weather guidance has taken a rapid turn towards showing a significant winter storm — with blizzard conditions — affecting the entire area on Monday night into Tuesday. Although plenty of uncertainty still exists in regards to the details, it is becoming safe to say that a snowstorm or large proportions will be affecting the Northeast.

Currently, the  piece of energy that is forecast to develop into our storm is still in Montana, and it is diving southeastward as we speak. Previous forecasts had this piece of energy moving more progressively, not turning the corner in time to crawl up the East Coast, and thus passing seaward. One potential reason for this was because at the time, the piece of energy was still in the NE Pacific, where our data is quite limited. Once that piece of energy reached British Columbia last night, models were able to get a better idea of just how strong this system is, and have rapidly adjusted their forecast evolution of the feature — now indicating that will become much more amplified.

Thanks to a strong area of ridging in the western half of the US and hints of a blocking pattern in the Arctic and Atlantic, this disturbance is forecast to dive almost due south, instead of east-southeast like earlier guidance. As it does so, it strengthens and buckles the pattern downstream.

Today's GFS model valid for tomorrow afternoon shows the disturbance quickly growing in strength, in an ideal ridge-trough orientated pattern for east coast storm development.

Today’s GFS model valid for tomorrow afternoon shows the disturbance quickly growing in strength, in an ideal ridge-trough orientated pattern for east coast storm development.

By Sunday afternoon, that same piece of energy is now in the Missouri Valley and even some of the energy tries to tap into the Gulf. The energy of the northern branch of the jet stream and of this system in general combined with it tapping into some Gulf of Mexico and Atlantic Ocean moisture will lead to classic ingredients for a significant storm system.

The pattern downstream, while amplifying, is still not nearly as amplified as the pattern to the west. Some may think that based on this image, an impressive storm system would develop but miss us to the south. But notice to the north — in Northwest Canada — that there is another piece of energy developing, and ready to dive into our storm. Previous guidance had these pieces of energy missing each other. But now that the original system is so potent, it amplifies the pattern enough to slow itself down tremendously. This gives the second disturbance much more time to catch up to our storm, since the second disturbance is still in the midst of a fast flow. This is because there is an incredibly strong localized jet stream (jet streak) developing which helps the second disturbance to race southward. This sets the stage for a major phase between an incoming powerhouse disturbance and an already amplified one near the East Coast.

Last night’s GFS model valid for Monday afternoon shows that the second disturbance has caught up with our storm and is already interacting with it. This can be partially attributed to the very strong jet streak diving down from Canada, which helps the second disturbance essentially sprint southward. This interaction helps to strengthen our storm even further and bring it up the coast.

Notice how on the bottom left panel of the above image, we can see that the two disturbances are interacting, which has helped to greatly amplify the pattern in an almost due south-to-north fashion along the East Coast. If you notice the bottom right panel, the second disturbance is associated with an extremely strong jet streak, which gives the disturbance a “boost” and pushes it right into the trough of our main storm. Once these two features interact, explosive storm development just off the East Coast can begin.

Forecast models over the last day have come into agreement on the idea that the developing storm system will be quite significant — a powerhouse Nor’Easter, in fact. The track of the storm system will come down to finite details which we cannot possibly pinpoint at this time. Unfortunately, this will also impact where the heaviest precipitation falls. What we do know, at this point, is that precipitation on the northwest side of the surface low will be enhanced greatly by the jet stream orientation. In addition, intense lift for precipitation and atmospheric dynamics will allow for bands of incredibly enhanced snowfall — with very high per-hour snowfall rates.

What area will be impacted the greatest?

The track of the storm system will obviously dictate which areas are hit hardest. Currently, confidence in a high impact winter storm is highest from New York City eastward. This includes much of Eastern New Jersey, Long Island, Connecticut, and all of New England. Almost all forecast models agree that these areas will be impacted by very heavy snowfall regardless of the storm systems track.

GFS model showing enhanced vertical velocity at 700mb. This indicates strong lift for very heavy precipitation.

GFS model showing enhanced vertical velocity at 700mb. This indicates strong lift for very heavy precipitation.

However, confidence has increased in the past 24 hours that areas to the west of New York City will be impacted as well. Forecast models have trended faster with the mid level atmospheric phasing, leading to a more westerly-leaned track on all guidance. Such a scenario brings the threat for very heavy snow farther west to include the entire forecast area.

As time goes on over the next day or so, new and improved data will help our forecasters be able to pinpoint where the banding will set up and which areas will receive the worst conditions.

What are the potential hazards with this storm system? 

This storm has the potential to produce a myriad of hazards throughout our area. Heavy snow will obviously be the most noticeable and notable hazard to come from such a significant Nor’Easter. Where the heavier snow bands setup, significant snowfall accumulation in excess of 1 foot (12″) will be likely. In addition, very low visibilities and extremely difficult and dangerous travel will become likely.

In addition to the heavy snow threat, the offshore storm system and pressure gradient will create the threat for strong winds near the coast and prolonged Blizzard conditions. Winds in excess of 35 miles per hour, gusting higher at times, could create significant blowing and drifting of snow especially near the area coasts where vulnerability to onshore winds is highest.

What can change at this point?

A whole lot. The track of the storm remains uncertain and forecast models are going to struggle to pin down the exact implications of any wobbles in the storm systems track. Forecasters will be working, over the next 24 hours, to pinpoint the storms track and locate the potential for any changes in either direction (west, east, etc).

The best thing to do is stay tuned, and know that the potential is rising for a widespread significant winter storm on Tuesday. But keep in mind that a slight change in forecast modeling can completely alter the forecast. We’ll be working hard to pin down the details of the storm system over the next 24 hours.

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