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The fourth nor’easter of this month alone, named Winter Storm Toby, is set to slam portions of the Mid-Atlantic and New England with heavy snow, gusty winds, and coastal flooding over the next 48-72 hours. We're going to discuss the timing and the details of this storm. We'll also get technical to deliver the science behind this forecast.
Timing:
Precipitation Begins: As sleet or snow between 12am and 6am Wednesday (uncertain given the slow advance of precipitation shield)
Snow peaks in intensity: All of Wednesday afternoon and evening
Snow ends: Between 10pm Wednesday and 4am Thursday
Temperatures:
Tuesday night: Lows between 26F and 31F
Wednesday: Gradually rising from 26-31F to 29-33F by end of day
Wednesday night: Lows between 22F and 28F
Winds:
Tuesday night: Gusts up to 35 mph
Wednesday: Gusts up to 40-50 mph
Wednesday night: Gusts up to 35-50 mph
Main Threats:
Moderate to heavy snow all day Wednesday
Difficult travel, especially in the afternoon and evening
Isolated power outages due to gusty winds and snow
Minor coastal flooding along coast
Forecast Discussion:
We're going to be dealing with yet another nor'easter that produces widespread snow to the area. A classic transfer of energy from a weakening low pressure approaching the southern Appalachian Mountains to a new and developing low pressure just off the Carolina coast will occur Tuesday night. Our nor’easter will then track toward the north while hugging the New Jersey and DelMarVa coasts before taking an eastward turn toward the 40/70 benchmark and moving very close to these coordinates (40°N, 70°W) Wednesday night. This is a slow moving storm, which will allow for greater impacts. Even though this storm will feature a slower forward speed compared to the previous nor’easters this March, the storm will not rapidly strengthen into a “bomb cyclone.” This is good news because coastal flooding won’t be as terrible as it could have been and winds will not be as strong. However, many areas from the Mid-Atlantic coast up through New England can still expect minor to moderate flooding. While no bomb cyclone, our storm will start off with a pressure between 990 and 995 millibars Tuesday night near the Outer Banks of North Carolina, and then bottom out between 980 and 985 millibars by Wednesday night as it nears the benchmark.
Now let's chat about the actual impacts: the precipitation will begin as either sleet or snow sometime Tuesday night as the northern shied of our developing nor'easter slowly expands into the area. At this time, I don't know when exactly the precipitation will begin due to the slow forward progress of the storm. By the time you wake up Wednesday morning, however, it should be snowing. This will likely be an all-snow event all-day-long on Wednesday, even at the coast. The morning commute should be fine if traveling I-95 between New York and Boston while from New York through Washington, D.C. it will become messy. For the evening commute, however, it is expected to be a mess for the entire I-95 corridor. Temperatures will be marginal (near freezing to as low as the upper 20s), so the road treatments should keep the major roads in fairly good shape. The secondary and even some of the primary roads will become snow-covered, especially inland.
By the evening hours, snow will be falling from coastal Maine through eastern Virginia. The fact that this storm is impacting the entire Northeast megalopolis during a weekday will make this a high-impact event. Snow will be falling at a moderate to perhaps heavy intensity (0.5-1.5 inches per hour) for a very widespread area. This is because of large scale ascent or rising of the air. Instead of thin mesoscale snow bands that set up, like with the past storms this winter, the model guidance is hinting at a larger but lighter band that sets up compared to very heavy, discrete bands that lead to large snowfall variations. Temperatures will be at around -15°C in the dendritic growth layer of the atmosphere, which will allow for a fluffier snow and large snowflakes, allowing for snow to add up pretty quickly. Then by Wednesday night, the snow will persist in the evening before tapering off early-Thursday morning.
In terms of snowfall, I'm currently forecasting 6-10 inches for the entire area. Snow may have a tough time accumulating initially, but by the mid to late-morning the snow will be adding up. There is still time for the track of this storm to shift slightly, which would lead to an increase or decrease in forecast snowfall amounts. This will not only make for travel issues but schools will either declare an early dismissal or closure. It really depends on the timing of the start of snow. At this time, widespread school closures in southwestern Connecticut is likely.
For the latest developments on Winter Storm Toby, be sure to stay updated with Jackson's Weather. We'll have LIVE updates as new model guidance comes in on our Twitter feed, which you can view below.