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Cold Front to Deliver Shot of Rain/Storms to New England Tonight

After a brief bout of high pressure, a frontal system will be moving through New England today through Thursday. This system will initially lift its warm front through New England, bringing higher humidity levels to the region. A weaker cold front will move into New England ahead of the main front this afternoon. This will bring a more westerly flow rather than a Depp southwesterly flow, which will keep dew point levels from really spiking, especially across areas well away from the coast.

This weaker cold front may provide just enough forcing ahead of the main front to allow some isolated showers or thunderstorms to pop up along it in the afternoon. It does look like a vast majority of areas will remain dry and storm-free through this afternoon, but with the arrival of a pre-frontal thought, the ingredients will be there for a couple storms to pop up in southern New England and possibly along the northern New England coastal plain.

WRF-ARW showing potential weather this afternoon, with isolated storms popping up:

As we go into the evening and overnight hours, steady rainfall with embedded thunderstorms will gradually become more widespread. The bulk of the rainfall is looking to arrive for the overnight hours into early Thursday morning. The atmosphere will quickly become moisture-rich for this system, allowing a slug of heavier rainfall.

It is looking increasingly likely that this heavier rainfall and storm activity will be centered over southern New England, with northern New England seeing more of a period of steady rain without much in the way of thunder.

HRRR showing potential weather around midnight tonight:

The severe thunderstorm threat is looking minimal, but not 0%. As usual, instability will quickly begin to wane as we head into the evening and overnight hours, when activity will begin to ramp up. This should keep a majority of storms sub-severe. With that said, shear will increase ahead of the front, and there will be ample lift and moisture. CAPE values may also hang around 1,000+ in the evening to the early part of the night.

This is why a stronger storm can't be completely ruled out, but most should remain below the severe threshold. The Storm Prediction Center does have southern New England along with southern Vermont and New Hampshire in the "marginal" category (level 1 of 5) for severe storms.

With a moisture-rich environment, rainfall rates will be able to become torrential at times, especially within any thunderstorms that can embed with the rainfall. A widespread 0.25 to 0.75 inches of rain is likely across New England through Thursday morning with southern New England seeing the most.

There will likely be localized areas that see much more (1-3 inches) where the thunderstorms set up. This may result in some isolated instances of flooding. The Weather Prediction

Center has all of New England except Cape Cod and the islands in the “marginal” category (level 1 of 4) for excessive rainfall. The system is progressive, which will help to mitigate flood concerns.

The progressive nature of the system will also help clear it out quickly Thursday morning. Most areas will just see a few lingering showers by sunrise Thursday. Eastern Maine will naturally be in the rain later into the morning, but even there, it looks to slow down by the early afternoon hours. 

HRRR showing potential weather around 8am Thursday:

Thursday afternoon, the region does stay under broad cyclonic flow, so a few scattered showers could pop up in the afternoon, but most will stay dry after the morning rain moves out. Heading into Friday and early Saturday, high pressure briefly builds in, bringing dry and comfortable weather. This will quickly be followed by another frontal system later Saturday into Sunday before high pressure builds back in for early next week. We went into detail about our current pattern in yesterday’s article

Looking at the weekend a bit closer, Saturday afternoon through Sunday morning may end up being similar to this afternoon through Thursday morning with showery and thundery weather and embedded steadier rain. Sunday may remain unsettled with scattered showers and storms. All of this will be determined by the timing of another cold front, so we need to keep watching the trends as it pertains to when the most moisture moves through during this time frame.



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