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Breaking Down Thunderstorm Chances for New England This Week

Thunderstorms will have the chance to pop up across New England over the next three days. The most activity is expected on Thursday as a cold front sweeps New England, but the remnants of disturbances riding over the ridge into northern New England will help kick start some storm activity today and tomorrow as well.


TUESDAY


The best forcing for storms to pop up will be across northern New England, closer to the low pressure system crossing southern Quebec. This system will be weakening as it passes New England, but enough energy should be left, combined with the bump in heat and humidity, to produce storms from mid-afternoon through the evening. Southern New England will remain under the influence of high pressure to the south and east. Generally, the farther north you go in New England, the better the chance of seeing a storm.


HRRR showing expected weather this evening:


The threat for severe storms is on the lower end overall, but the ingredients will be there for some storms to become potent. CAPE values (the measure of instability in the atmosphere; a higher CAPE value=more instability for thunderstorms to develop) are expected to reach 600-1,000+ across the northern tier, particularly in Vermont. This, along with limited shear, lift and moisture will be able to create storms with heavy rainfall and small hail. These ingredients will be just plentiful enough for a couple marginally severe storms.




While today's thunderstorm activity will be focused across the northern tier, some storms may drop southward toward the Massachusetts border later in the evening into the first part of Tuesday night. This would come as several hundred units of CAPE will likely be present down to northern Massachusetts this evening, which is enough to produce at least some thunder. A question for evening/early night thunderstorms will be if enough daytime energy can remain for thunderstorms to survive.


HRRR showing potential weather later this evening. Guidance is split on whether storms will be able to fire south of Lake Winnipesaukee:


WEDNESDAY


A bulk of the activity on Wednesday is likely to remain west of New England on Wednesday, as any storms push east into western New England, they will weaken as they will run into less favorable conditions.


Still, with daytime heating and increasing humidity, a spot shower or storm could survive or develop in New England. It's a low risk overall, but the Storm Prediction Center does have all of New England in the zone for (non-severe) thunderstorms. The best chance for a storm will be across western New England. Overall, don't count on seeing a storm on Wednesday.


GFS showing potential weather Wednesday late-afternoon. That area of more widespread activity to the west will break down as it pushes toward New England, but a couple isolated storms may fire ahead of the line through Wednesday evening:



THURSDAY


On Thursday, a cold front will cross New England. This will provide the focus for another round of activity. The four main ingredients for storms will be at its highest across the region with ample lift with the cold front, increased moisture and more elevated shear.


The big question will be instability and timing. The day may start off with mid-level clouds. If these clouds linger as the front approaches, it will limit instability significantly and make it more difficult for storms to develop and strengthen. The other uncertainty is the timing of the cold front. Some guidance is pointing toward the front passing before peak afternoon heating.


Weather map for Thursday morning showing the front already crossing New England:


As of now, eastern New England would be more likely to see strong to severe storms as forcing from the front is more likely to happen later in the afternoon. Western New England may see storms more toward the morning to midday, which would cut down on the potential for stronger storms there. Overall, we need to keep watching the trends to determine the extent of storms for Thursday. Depending on the timing of the front, storm activity could trend higher or lower for New England.




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