May is a big severe-weather month for much of the country — there’s actually more tornadoes in May than any other month. After some overnight thunderstorms around Greater Boston and Worcester, there’s another risk for storms this afternoon and evening, as a cold front pushes the early taste of heat and humidity out to sea.
The risk of severe weather this afternoon is small, but it’s certainly not zero. This isn’t the type of setup that would likely produce any tornadoes, but it is the type of setup that can produce very gusty winds, torrential rain, and hail. If the hail is large enough or the winds strong enough, then the storm can certainly be categorized as severe.
Temperatures Monday reached 80 degrees in Boston for the first time this year, which is actually a couple weeks later than average. Those averages are made up of years where the first heat arrives in April and other years where it doesn’t arrive until late May or even June. In other words, it’s not really that notable that this is our first 80-degree day.
The warm and humid air mass causing the high temperatures will be pushed out to sea by a cold front this afternoon or evening. As the cooler and drier air bumps up against this warm and humid air, it will create cumulonimbus clouds — large, tall clouds with dark bottoms — and along with them, the risk of showers and storms.
I expect most of the storm activity to be done midway through the evening, and when you get up tomorrow morning, the air will feel completely different — much drier with a bright blue sky. Temperatures the rest of the week will be seasonably mild.
A line of storms will sweep eastward Monday afternoon and evening. (COD Weather)
Tracking the front that is bringing our weather, you can see it snaking across the Appalachians and then taking a left-hand turn up through the Southern plains states. It’s there were most of the severe weather will occur today.
There is a high risk of severe weather across portions of Texas into Oklahoma Monday, and the Weather Service has elevated the risk to its highest level in two years. These types of outbreaks don’t occur every season and there’s actually been some school closings across that part of the country in anticipation of today’s severe weather.
The storms in the southern plains will likely be accompanied by tornadoes. These are ranked in categories on an enhanced Fujita scale, which runs up to an F5. It’s not out of the question that parts of the Southern plains could see an F3, F4, or even an isolated F5 tornado later today.
This area of the country is more sparsely populated, so these storms can move through big open spaces without doing a lot of property destruction. There are some major cities, however, including Oklahoma City, which will be under storm watches today. There’s no doubt that this is going to be an eventful afternoon in many parts of the country.