The warm and humid conditions we’ve had for much of the region over the past several days are going to continue today, but changes are coming, and the change may not be that quiet.
A weak cold front is going to approach the region today. The front may never make it across the area before it washes out, but it will help to trigger some strong to severe thunderstorms across parts of the region today. Right now, it looks like the most likely area for strong storms is from southeastern Connecticut into Rhode Island and southeastern Massachusetts. The most likely time for the storms in this area is from 11am to 3pm,, though some storms may continue through about 7pm.
The ingredients appear to be in place for some strong to severe thunderstorms to develop across the region. There are several different indices that meteorologists look at to help determine the risk for severe weather. We won’t confuse you with most of them, nor will we bore you with how they are derived. Most of these indices are indicating that the risk for today is real and significant. One of the parameters that we will share you you is called CAPE. That stands for Convective Available Potential Energy. It’s a measure of how unstable the atmosphere is, and how much “juice” is available to fuel the storms. It’s measured in joules per kilogram, and a value over 1000 means that the atmosphere is moderately unstable. If the values reach 2500 there is strong instability, and values over 4000 are indicative of extreme instability. as you can see in the map below, values of 2000-4000 (or more) are expected early this afternoon.
Any storms that do develop this afternoon will likely contain heavy downpours, strong winds, and hail. There is even a risk for an isolated tornado. With the heavy rain, flash flooding is also a risk. So, if you’ve got plans that involve outdoor activities, make sure you keep an eye to the sky.
So, things will be better on Sunday, right? Not so fast my friends. We’ll have an upper-level low pressure area dropping southward from Canada. So, not only will it be cooler, we’ll have some more showers and thunderstorms developing. We don’t expect most of these to become severe, but with cold air aloft, we’ll have some of these storms produce small hail across the area. This is similar to what happened last Saturday, when another upper-level low moved through. There were numerous reports of small hail across the region. So again, if you’ve got outdoor plans on Sunday, keep an eye to the sky.