We’re tracking what will likely become a highly-impactful nor’easter tonight into Friday, bringing damaging winds, flooding rains, significant storm surge, and feet of snow. There are two pieces of energy that will contribute to this coastal storm: one over the Great Lakes region and a second over the southern Appalachians. Once these two piece of energy come together and phases just off the Northeast coast, our nor’easter will quickly blossom and deepen. Over the course of the next 24 hours this system will “bomb” out, undergoing a process called bombogenesis. This is when a low pressure system drops at least 24 millibars within 24 hours. With this particular system, pressures will begin at around 1000 millibars Thursday night but will fall down into the 970s by Friday evening. With wind gusts climbing upwards of 75 mph in some places, this hurricane-like storm will bring heavy rain, snow, damaging winds, catastrophic flooding, and rough surf to a large portion of the Northeast.
Snow will be a big story across portions of the Northeast, specifically from the eastern Great Lakes through central New England. Even though there is still some uncertainty among the model guidance, mainly in central and southern New England, we are getting a better grasp on what will take place. Snow will be falling by Thursday evening across portions of eastern Lower Michigan, northern Ohio, western Pennsylvania, and western New York as well as the Appalachians in West Virginia. This snow will be falling at a moderate to heavy rate, so travel is not advised for any of these locations, especially as winds pick up with our storm rapidly deepening. Thundersnow cannot be ruled out for some places with such strong dynamics in play.
Into the overnight hours of Thursday, our coastal storm will begin to get its act together as the two pieces of energy phase and form a nor’easter. Rain will transition over to snow across much of the interior Northeast, with a quick changeover to heavy, wet snow leading to dangerous conditions for travel. Snow is forecasted to fall Thursday night across much of Pennsylvania, with the exception of the greater Philadelphia area, as well as most of New York State besides the Lower Hudson Valley, New York City, and Long Island. However, as we head later into the morning and afternoon tomorrow, these areas will see a period of moderate snow, including the Appalachians in West Virginia, and the Berkshires by daybreak Friday. The rain may briefly changeover to snow for an hour or two in portions of the Mid-Atlantic, including Washington, D.C. and Baltimore between 6am and 10am.
On Friday, snow will clear out by 10am across the Mid-Atlantic while rain possibly changes over to snow across New Jersey and the DelMarVa by the end of the day. This will be brief, lasting for only a few hours in the afternoon and evening. Because temperatures will be in the upper 30s, no accumulation is expected. That will not be the case further north however. In the New York City area up through Boston, this is where the forecast becomes most volatile. There is a range of outcomes but our snowfall forecast below reflects what we think is the most likely scenario.
It’s important to note how elevation will play a role in this forecast with higher totals expected in the Berkshires due to colder air, a longer time period of snow, and enhanced lift. We’ll see rain will changeover to snow across most of southern New England into the immediate northwestern suburbs of New York City as the day progresses. The immediate coast of New England will likely deal with all rain during this event due to the intrusion of mild ocean air. Even though surface temperatures will be marginal in this region throughout this snow event, we still believe accumulating snow is likely due to how heavy it will be. For the remainder of the Northeast, a moderate to heavy snow is forecasted to fall on Friday across central and eastern Pennsylvania, most of New York State, and into the southern Green and White Mountains of northern New England. The snow will mainly fall Friday morning in western New York and central Pennsylvania before drier and colder air infiltrates.
By Friday night, we’ll have our full-blown nor’easter. This event will become confined to southern New England and the Mid-Atlantic coast by this juncture. Snow is expected to continue to fall throughout most of southern New England and down into New Jersey through the night. By midnight, drier air will invade and break up this precipitation shield, allowing for the snow to be more scattered. The snow will finally come to an end early-Saturday morning while southeastern Massachusetts experiences a few hours of heavy snow early-Saturday morning. All of this precipitation will clear out by dawn Saturday morning as our nor’easter begins to pull out to sea, although a few isolated snow showers may swing through the Cape throughout the day Saturday.
Rain will also be a big story due to the risk for flooding. Flood Watches span from southern New England through New Jersey and eastern Pennsylvania. A widespread one to three inches of precipitation is forecasted to fall in southern New England, and for some cases (the coast and southeastern Massachusetts), this will be an all-rain event. A few areas may receive over three inches, especially in Cape Cod. The soil is saturated in this region due to a super wet February, so it won’t take much for flooding and river flooding to occur.
Thursday night, a light to moderate rain is forecasted to fall across the Mid-Atlantic, mainly north of Washington, D.C. and the DelMarVa into most of New England. As we get into Friday, snow will become more prevalent, therefore decreasing the aerial extent of the rain. Rainfall intensities will increase due to the rapidly-intensifying coastal storm. Rain on Friday is expected from New Jersey up through southern Maine. Keep in mind, snow is expected to takeover this area of rain across most of this region by the end of the day. That leads us to Friday night, which is when rain will solely be focused on southeastern Massachusetts.
Wind will be another significant threat posed by this storm. This will be the most widespread threat, affecting all of the Northeast and Mid-Atlantic. Winds will begin to ramp up Thursday night as our coastal low develops with widespread gusts between 30 and 50 mph. The highest gusts at this time will be found in the Appalachians where gusts may top 65 mph at times Thursday night through Friday night. We expect winds to really peak during the day on Friday for most of the region. Winds will be very strong throughout the day from the Appalachians through the Washington, D.C. area and up through the I-95 corridor. These major cities could see gusts up to 65 mph at times, leading to significant problems. The last time this happened was during Superstorm Sandy in 2012. Obviously we’re not expecting a storm quite of that magnitude, but the winds will affect similar areas. By the end of the day, concerns really heighten for southeastern Massachusetts, where the worst of this storm is expected to occur. Winds may gust as high as 85 mph due to the hurricane-force low into Friday night.
No doubt this level and extent of wind will lead to widespread power outages, not only for southern New England but across a large portion of the Northeast and Mid-Atlantic. Winds will remain strong into the weekend as we deal with a tight pressure gradient between the departing coastal storm and high pressure incoming from the west. This will keep widespread gusts of up to 40 mph around.
Our map below shows the extent of power outages expected due to the wind, rain, and snow. A very large portion of the Mid-Atlantic and Northeast will be dealing with scattered to widespread outages, with places as far as extreme northern New England and the southern Mid-Atlantic even at risk.
The last major threat with this storm will be the coastal flooding. The worst of the flooding will occur along eastern Massachusetts and into Cape Cod Bay. Minor to moderate flooding is also possible from Maine through Delaware, including towns across Long Island and the Massachusetts islands. A town or two may reach major flood stage, which has prompted some mandatory evacuations. For all of these areas, because this storm will practically stall just off the southeastern New England coast Friday, three to four high tide cycles will likely be impacted by some sort of flooding between Thursday night and Saturday night. The full moon presence also won’t help, already creating above-normal tide levels.
Again, our highest concern is for southeastern MA, where evacuations are currently underway. The National Weather Service office in Boston has been using very strong wording this Thursday, urging people to evacuate if you are told to do so and that life-threatening flooding is possible:
[COASTAL FLOODING] Take this storm seriously! This is a LIFE & DEATH situation for those living along the coast, esp those ocean-exposed shorelines; moderate to major flooding; locations becoming inundated, cut off for periods of time; expect structural damage, homes destroyed pic.twitter.com/vGLB09BFbW
— NWS Boston (@NWSBoston) March 1, 2018
In the Boston Harbor, they recorded their highest water level back in January of this year from a nor’easter of similar magnitude. For context, this is what Marshfield, MA, which is south of Boston, looked like during that January storm:
One more look at this amazing picture from Karen Crandell Morse in Marshfield MA on Jan 4th. Look at that wave in the background. This will be much worse! pic.twitter.com/W0jcSPj1kE
— eweather (@Eweather13) March 1, 2018
Based on the setup and how prolonged the event will be, new records may be broke. Three to four feet of storm surge is forecasted along the entire eastern Massachusetts coast, and some locations will reach major flood stage. On top of that waves of up to 20 feet are likely along the coast – Not a good combination at all. If you do not evacuate as you are told to do, you could become trapped by the flood waters and your life could be at risk. Also remember not to drive through flooded roadways.
Please stay safe during this storm. We’ll have live updates for you, monitoring the progress of this storm on Twitter.