Thunderstorms are a part of summer, and we have two days ahead with a risk of them. Today, a cold front will cross the region. This front will help lift the warm and humid air at the ground, and that lift will build cumulus clouds into cumulonimbus ones. These types of situations can bring strong to severe storms, but they will be widely scattered. There have been a few showers overnight and early this morning over western New England, but the highest risk of storms this afternoon will be to the east.
When thunder roars, go indoors
The map below is the predicted radar for 3 p.m. These types of forecasts give me a general idea of the upcoming situation. Notice the reds and yellows on the radar, those are the thunderstorms. Now this map won’t be correct, but it will be close. What you can expect are scattered storms with the heaviest concentration between 2 p.m. and 6 p.m. The best chance of seeing severe weather will be east of a line running from roughly southwestern Maine, the MetroWest area of Boston, then onto Hartford. This doesn’t mean those of you west of that line won’t see storms, that’s just the area of highest risk.
It will be warm and a bit muggy today with highs getting into the lower 80s. The warmer we get and the more sunshine we see during the day, the better chance the air will have to warm up and give us the storms.
Cooler air arrives tonight
Once the sun goes down this evening the threat of storms will quickly diminish. The front will push off the coast and cooler air arrives. You’ll notice the lack of humidity tomorrow.
Wednesday brings another chance of storms, for a different reason. Tomorrow, although it will be cooler at the ground, it will also be much cooler aloft, and there will be a strong jet stream pushing over our area. The combination of cold air above us, and a strong jet, will help ignite more storms in the middle of the afternoon. Because the air will be so cold above us, hail may occur.
Hail could also happen today, but I think the likelihood is a bit greater tomorrow, even if the storms aren’t as widespread then.
What is a severe thunderstorm?
In order for a thunderstorm to be classified as severe it must contain one of two things: either hail that is one inch in diameter or larger, or winds of 58 miles per hour or greater. The amount of rain and lightning have nothing to do with whether a storm is classified as severe, although each of those is certainly a part of a severe storm.
I’ll be updating the situation on Twitter today @growingwisdom.