Weather report
An area of warm, humid air will hover over much of southern New England in the afternoon and evening, setting the stage for potentially severe weather that could produce severe thunderstorms with strong wind gusts. wind, hail and even an isolated tornado.
A tornado watch was issued until 8 p.m. for northeastern Massachusetts and western and central Massachusetts, but not for Boston. Monitoring also covers New Hampshire, Vermont and southern Maine. A tornado watch over such a large area of New England is quite unusual, but not unprecedented.
A tornado watch means weather conditions are favorable for thunderstorms capable of producing tornadoes. This doesn’t mean a tornado will occur, but it’s best to be prepared for one. When a warning is issued, you should immediately seek shelter by heading to the lowest level of your home or building, such as a basement. If there is no basement, position yourself in the center of a small interior room on the lowest level – closet, interior hallway – away from corners, windows, doors and exterior walls.
Higher level energy will move through the region this afternoon and evening. This energy will help to raise the atmosphere and is why showers and thunderstorms are likely to develop in the afternoon and evening.
The greatest instability will be west of Interstate 495 and in western sections of northern New England. These are the areas where severe weather is most likely.
Severe weather is much less likely east of I-495 and unlikely throughout Greater Boston. However, there could still be showers and thunderstorms with some gusty winds this afternoon and evening. The greatest threat occurs between 5 p.m. and 9 p.m. in the Boston area, and earlier, before 5 p.m., north and west of Boston.
One way meteorologists measure the amount of energy available in the atmosphere for severe storms is by using something called CAPE, which stands for “available convective potential energy.” The map above shows the location of this afternoon’s largest CAPE or instability in the atmosphere and gives a rough idea of a thunderstorm’s lift.
Note that the strongest forecast storm energy is to the west and north of the coastline. This is why I am less concerned about bad weather in Greater Boston.
In terms of precipitation potential, any time you get this type of setup there can be some heavy downpours that can deliver over an inch of rain in a short period of time, but in general most areas will remain under a half inch of rain.
Once the threat of severe weather subsides this evening, it will remain warm and humid overnight before drier air arrives on Monday. Tomorrow you will notice lower dew points throughout the day and there is little to no chance of showers and mostly sunny skies. Hot weather continues Tuesday and Wednesday with an additional risk of showers and thunderstorms midweek.
Boston
