Powerful storm develops just off the East Coast Tuesday and Wednesday
Heavy snow possible in parts of eastern New England
Some accumulating snow possible elsewhere in the East
Coastal flood, high wind threat in coastal New England Wednesday
Precursor disturbance brings light snow to the Midwest Monday and Tuesday
The feel of winter is going to carry over into the first week of spring if you live east of the Rockies. Not only are temperatures going to plunge below average, but we also expect a powerful storm to develop just off the East Coast, bringing the potential for a nasty winter storm for parts of the Northeast and Mid-Atlantic.
The Current Forecast:
Ingredients: Two upper-atmospheric disturbances will be moving east – a northern disturbance over the Midwest and a southern disturbance over the Gulf of Mexico.
Impacts: The Midwest disturbance will bring some light snow to the Plains and Midwest. Light accumulations are expected
Monday in eastern South Dakota, eastern Nebraska, southern Minnesota and most of Iowa.
Monday night will bring light accumulating snow east of the Mississippi River into much of the rest of the Midwest and as far east as West Virginia. No winter weather will be associated with the Gulf disturbance.
Cities: Omaha |
Des Moines |
Chicago |
Indianapolis
Tuesday:
- Ingredients: The northern disturbance moves into the Northeast in the morning while the southern disturbance spins up new low pressure off the Florida coast. By afternoon 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: The northern disturbance brings light to moderate snows from the Great Lakes and Ohio Valley into the central Appalachians and Mid-Atlantic states through midday. As the merger occurs and the coastal low strengthens, there is the potential for snow and wind to spread along the I-95 corridor from the Mid-Atlantic into the Northeast Tuesday afternoon and Tuesday night. The strength of the winds and snowfall amounts are uncertain at this time and will depend on the exact track/intensity of the low pressure system.
- Cities: Cincinnati | New York | Philadelphia | Washington
Wednesday:
- 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 afternoon or evening hours.
- U.S. impacts: Potential for heavy snow and wind across eastern New England, particularly southeast Massachusetts and Downeast Maine. Again, snowfall amounts and the strength of the winds are uncertain. That said, some computer models are showing the potential for blizzard conditions in parts of eastern New England. High surf, beach erosion and coastal flooding are also possible.
- Canadian impacts: A major blizzard appears likely across the Canadian provinces of Nova Scotia, New Brunswick, and Prince Edward Island, potentially expanding into Newfoundland and Labrador later in the day.
- Cities: Providence, R.I. | Boston | Portland, Maine | Halifax, N.S.
Meteorology 101: Why Uncertainty Exists
Computer model animation of disturbances in the upper atmosphere Thursday through next Tuesday. Image credit: WSI
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.
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.
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.
What Should You Do?
If you have travel plans on the East Coast Tuesday and Wednesday, it's time to start thinking ahead. While there is still some uncertainty in the forecast, it appears more and more likely that there will be some impacts to travel.
If your travel plans are especially sensitive to weather disruption, you may want to consider moving your flight or your road trip to either before or after the storm. If you are comfortable waiting for more clarity in the forecast, we should have a better grip on the forecast details by Monday morning.
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.