Today will feature more stifling humidity along with more toasty temps as SW flow continues to bring ever increasing amounts of tropical moisture into the region. Sunny skies this morning SE of the mountains will destabilize the atmosphere and thus when the front starts to sag south this afternoon, we run the risk for thunderstorms. Highs will soar into the mid to upper 80’s for most with some low 90’s in SW NH. That combined with even stickier conditions will result in more dangerous heat and a heat advisory is out for southern NH and York County ME.
Because there is so much moisture, the main threats from these storms will be very heavy rain and intense lightning. A few wind gusts, possibly up to severe levels, are possible but conditions today are not classic high wind conditions. Also, because of very low cloud bases due to all the moisture and a marginal amount of low level turning, an isolated weak tornado can’t be ruled out. This will by no means be a big Maine tornado day, the atmosphere is not set up that way, but an isolated spinup is certainly possible so be aware and make sure you have a plan to hunker down for a few minutes if the need arises. For a detailed analysis of the severe weather threat, please refer back to last evening’s discussion.
This morning, I’ll focus mostly on the heavy rain threat for the weekend as I will be away in the Catskill mountains and unable to post until Monday morning. The biggest day for heavy rain looks to be tomorrow. Deep tropical moisture will be in place across the entire area as the front sits just to our south. The tropical moisture will run up and over the front, cool, condense, and rain buckets over much of the area. A wave of low pressure moving along the front will assist in the heavy rain potential by providing some additional forcing.
This is about as classic a heavy rain sounding as you’ll ever see in Maine. Notice how close the green line (dew point) is to the red line (temperature) all the way into the very upper reaches of the atmosphere (it finally dries out around the stratosphere). This shows that the entire atmosphere, from top to bottom, will be saturated enough for very heavy rain. Throw in the frontal boundary and the wave of low pressure as well as a disturbance aloft and that moisture will have no trouble falling to the ground in the form of heavy rain.
It’s important to note that not everyone will see the heavy rain. It will come in the form of thunderstorms which, of course, hit some folks with all their fury, and leave others high and dry. Despite the convective nature of the precip, over the course of the next several days, most everyone should see a round or two of heavy rain as they rarely set up in the same places day after day.
I will be off until Monday morning when I’ll post next.
Have a great weekend and try to stay dry! Remember, we need this rain!