Showers & Thunderstorms May Lead To Localized Areas Of Flooding Tonight, Especially Near & South Of The Mass Pike

This Afternoon is going to feel very warm and downright tropical as a frontal boundary slowly slides towards us. This will put our area in a very moisture packed afternoon & combined with an unstable air mass means any thunderstorms that begin to develop by this evening will be capable of producing extremely heavy downpours leading to the threat for flash flooding, especially across areas near and south of the Mass Pike.

How warm and tropical is it going to be? High temperatures this afternoon will be near 90 Degrees and dew point temperatures will be between 74 and 78 Degrees. Low temperatures tonight will be near 70 Degrees along with dew point temperatures of around 70 Degrees.

It remains uncertain as to when exactly the slow moving showers and thunderstorms will begin to develop. Some of the weather forecast guidance are forecasting thunderstorms to start developing between 5 pm and 8 pm today and then continuing through all of tonight. Other weather forecast guidance doesn’t show any thunderstorms developing until just after midnight tonight and lasting through the early morning hours of Wednesday.

Given that the atmosphere is going to be unstable and extremely moisture packed, it’s going to take very little in the way of a trigger to set off thunderstorms. This means that I think that the weather guidance that are showing the delay of thunderstorms developing until after midnight tonight are wrong.

My thinking is that we’ll see thunderstorms begin to develop, mostly across areas near and south of the Mass Pike during the early evening hours, perhaps between 6 pm and 9 pm. Thunderstorms are then expected to push northward into the remaining parts of Western and Central Mass during the 9 pm to midnight time frame. Thunderstorms are then expected to last across the entire area through the after midnight hours of tonight before ending towards sunrise Wednesday morning. It should be noted that the coverage of thunderstorms will be the most widespread near and especially south of the Mass Pike with more scattered activity across areas north of the Mass Pike.

The thunderstorms will be moving in the same direction as the mid and upper level winds (from southwest to northeast), which means that these storms will be slow moving. Training thunderstorms will also be a threat, which means multiple thunderstorms may affect the same areas for several hours. This all means that thunderstorms will have the potential to cause localized flash flooding, especially in urban areas and low-lying areas. Given that the thunderstorms look to be most widespread across areas near and south of the Mass Pike, this is where I think the greatest threat for localized flash flooding will be.

I do want to emphasize one last thing – Not everybody is going to see thunderstorms, but those that do will be impacted by thunderstorms that produce 1 to 2 inches of rain per hour leading to localized flood issues.

Finally, strong or severe thunderstorms are not anticipated.

I will be keeping close tabs on the thunderstorm potential & will post updates as needed.