Powerful storm will develop off the East Coast Tuesday and Wednesday
Critical questions remain on exact storm track and resulting impacts to Northeastern U.S.
Heavy snow possible in parts of eastern New England and likely in Atlantic Canada
Light accumulating snow probable elsewhere in the Northeast
Coastal flood, high wind threats in coastal New England Wednesday
Precursor disturbance brings light snow to the Midwest Monday and Tuesday
Our Current Forecast
Winter Storm Ingredients
Winter Storm Ingredients
- Ingredients: A northern upper-level disturbance moves into the Northeast in the morning while the southern disturbance spins up new low pressure off the Florida coast. By early evening the two systems begin merging into a stronger low-pressure center just off the Mid-Atlantic coast. This low pressure intensifies explosively Tuesday night as it moves northeast to an area off the coast of Cape Cod.
- Impacts: Light to moderate snow from the Great Lakes and Ohio Valley into the central Appalachians and Mid-Atlantic states during the day, ending Tuesday night. For the I-95 corridor the snow may mix with rain, at times. As the merger occurs and the coastal low strengthens, there is the potential for snow and wind to spread through New Jersey, the New York City area including Long Island, and into New England Tuesday evening and Tuesday night. The strength of the winds and the amount and westward reach of snowfall are all uncertain at this time and will depend on the exact track/intensity of the low pressure system. Snowfall amounts in New York City could range from a dusting to several inches, depending on the track of the low, with the highest totals over eastern Long Island.
- Cities: New York | Philadelphia | Baltimore | Washington
Midwest Snowfall Forecast Valid from the time shown on the map until 48 hours later.
Midwest Snowfall Forecast
- Ingredients: Low pressure is likely to reach its peak intensity, likely below 970 millibars, over the ocean somewhere between New England and Nova Scotia in the daytime hours before being shunted northeastward across the Canadian Maritimes on Wednesday night.
- U.S. impacts: Potential, albeit still highly uncertain, for heavy snow and strong, potentially damaging wind across eastern New England, particularly southeast Massachusetts and Downeast Maine. Even slight changes in the track of the low-pressure center could have huge implications for the forecast. Some computer models are showing the potential for blizzard conditions in parts of eastern New England while a few models bring no rain or snow at all to much of the New England coast. High surf, beach erosion and mainly minor coastal flooding are also possible.
- Canadian impacts: Regardless of the exact track, a major blizzard appears likely across portions of the Canadian provinces of Nova Scotia, New Brunswick, and Prince Edward Island, potentially expanding into Newfoundland later in the day. Depending on the storm track, some areas may change over to rain after a burst of heavy snow.
- Cities: Providence, R.I. | Boston | Portland, Maine | Halifax, N.S.
- Winter Alerts: SE Mass. | Downeast Maine
What Should You Do?
If you have travel plans on the East Coast Tuesday and Wednesday – especially to, from, or within New England and Atlantic Canada – it's time to start thinking ahead.
While there is still considerable uncertainty in the forecast, there could be significant impacts to travel. Even the threat of strong winds and snow could prompt airlines to alter flight schedules.
If your travel plans are especially sensitive to weather disruption, you may want to consider moving your flight or your road trip outside of the storm's expected time frame just to be safe. If you are comfortable waiting for more clarity in the forecast, we should have a better grip on the forecast details later Monday.
Given the uncertainty still involved in the forecast, it is probably still too early to cancel or postpone local events, gatherings, or plans with friends and family that don't involve long-distance travel, unless they're in southeast Massachusetts, including Cape Cod, Martha's Vineyard, Nantucket Island, as well as eastern Maine.
Of course, it's never a bad idea to check your preparedness in case a major storm of any kind strikes your community. Although winter is almost over and you may not use them this time, items such as batteries could be useful to have on hand for the Atlantic hurricane season, which begins in just over two months.
Meteorology 101: Why Uncertainty Exists
Computer model animation from last Thursday, showing disturbances in the upper atmosphere from then through this coming Tuesday. Image credit: WSI
NOAA's NCEP ensemble is a set of closely-related models run simultaneously to show the range of possible outcomes. In this model forecast produced Sunday morning, the individual L's show the forecast location and intensity of the low-pressure center, valid 8 a.m. EDT Wednesday, from each individual member of the ensemble. The white lines show the forecast surface pressure from averaging all the members together.
Atmospheric disturbances responsible for spawning a potential future East Coast winter storm are usually thousands of miles away several days in advance of the storm. Sometimes, the future disturbances haven't even formed yet or break apart from a larger weather system.
Furthermore, while disturbances cross the Pacific Ocean, we often have to rely on little more than satellite data and ocean buoy data to analyze them. All of this complexity and imprecision in the data generally leads to larger and larger forecast errors as the major weather-forecasting supercomputers try to calculate the state of the atmosphere further and further into the future.
This is why the output from various computer models can vary wildly from run to run days in advance of a storm.
As the ingredients for a storm move over North America, we can measure them with weather balloons, surface weather observations, and other methods that provide more detailed data that improve predictability. Now that the seeds of this storm have moved over land, the computer models are now ingesting that more robust data.
The animation above and to the right is a previous computer model forecast of upper-atmospheric disturbances (light green, yellow, orange shadings) in the atmosphere from last Thursday to this Tuesday over North America and the North Pacific. Without getting into details, you can see that the atmosphere above us is complex. How these impulses track, interact and break apart dictate how future weather conditions will evolve.
The second graphic shows a forecast of the location and value of this storm's lowest pressure as predicted by a suite of closely related computer models called an ensemble. Even 72 hours in advance of the storm, this particular model simulation still displayed a significant range of possibilities while generally agreeing on a storm center being located off the New England coast.
Another typical uncertainty, particularly with early spring storms, is how much cold air is available for the storm to tap and produce wintry weather. In this case, it appears the air mass will be plenty cold enough, so that is not a major factor.
Check back with weather.com and The Weather Channel for updates on this East Coast winter storm.
50. Florida: 4 inches
Milton, Fla., just northeast of Pensacola, had 4 inches of snow on the ground on March 6, 1954. It all fell in one day, making it the state's heaviest one-day snowfall as well. Image: Snow in Ocala on Jan. 9, 2010. (iWitness Weather/SONBON)