Rain totals will likely reach and exceed 2 inches across most of Southern New England, with isolated totals reaching 4 or 5 inches through Wednesday night.Boston Globe
Forecast rain, flood risk
What’s concerning is just how much rain could fall with this system. With plenty of moisture in the air, the atmosphere is really primed for heavy rain as storms interact with it and wring out brief torrential downpours. A single storm cell Tuesday afternoon dumped nearly 2 inches of rain in Hartford in less than an hour. Some areas in the Berkshires have picked up over 2 inches with this storm already, and over 4 inches in Southern Vermont.
There’s an elevated risk for flash flooding as multiple, repeat storms with heavy downpours pass over towns and cities from I-495 to roughly the New York border (including the Mass Pike, I-84, and Route 2). A flash flood warning had already been issued for southwest Connecticut this morning.
The flood risk will be highest starting Wednesday morning for Western Mass., Connecticut, and Southern Vermont. Flood watches remain in effect for much of New England through Wednesday evening, including west of I-495 and northern Rhode Island.
Right now, a low to modest flash flood risk exists for Greater Boston and all of Eastern Massachusetts, Rhode Island, and spilling into Southern New Hampshire and Maine for much of Wednesday.
Storm timeline and region-by-region breakdown
The slow-moving nature of the system means that rainfall totals are going to vary widely from town to town — some areas will be hit with rain multiple times, while others could see the strongest downdrafts dump lots of rain. Here’s the breakdown into Wednesday:
It’s going to take a while, but eventually the showers and even thunderstorms and downpours rotate into Boston, most likely starting Wednesday morning around the start of the workday. The heavier downpours in Boston peak after 10 a.m. through the afternoon, making the evening commute quite wet. Flash flooding is possible with water collecting rapidly on streets and other low-lying areas.
Central and Western Mass.
The action began in the early hours of Tuesday afternoon, with the chance for scattered to steady showers packing heavy downpours lasting through much of Wednesday.
Scattered showers and thunderstorms will continue across the region, with a bit longer breaks in between the rain during the afternoon. A couple of storms could spark more flash floods for this region.
Southeastern Mass. and Cape Cod
Showers and pockets of heavy rain ramp up by early Wednesday afternoon. A few spots stay dry to start, but the rain takes over, with some heavy downpours at times.
A flash flood risk will be in place with the heavier downpours, mainly during the late morning and through much of the afternoon.
After a dry Tuesday while the weather held north and west, showers and general thunderstorms will push in overnight and last through most of Wednesday.
Scattered showers and thunderstorms will spread across the state in the morning and become a bit more isolated during the afternoon and evening. Some heavy downpours at times could lead to flash flooding, mainly in the late morning.
New Hampshire and Maine catch a break for once and wind up on the lower end for rain totals and flooding risk from this storm. There’s still going to be some rain for folks, like with heavy rain at times across the southern third of Vermont. Even southern Maine, including the Portland area, may see heavy rain at times.
On Wednesday, scattered to steady showers persist over Vermont and New Hampshire while pockets of rain push into Maine. The storms with heavier downpours will likely concentrate over Southern Vermont, New Hampshire, and Maine.
Scattered pockets of heavy rain persist over Connecticut early Wednesday morning. With little break in the action, scattered to steady showers and thunderstorms pop up in the afternoon and linger into the evening. The flood risk continues for most of the state.
These maps break down some of the forecasting details, including flooding threat, expected rainfall totals, and storm progression:
Repeat storms will increase the flood risk across Western and Central Mass. on Wednesday morning.Boston GlobeFlood watches blanket much of New England for Wednesday.Boston GlobeForecast accumulated precipitation showing batches of rain moving through New England through early Friday.Tropical TidbitsThe Blend of Models reveals rain totals exceeding 2 inches in Western and Central New England through Thursday morning.Pivotal
Temperatures and humidity
Wednesday will remain on the cooler side with temperatures hardly breaking into the 70s across New England. The air will be very thick and humid with near tropical-like conditions as dew points reach the upper 60s.
Highs on Wednesday will be cooler than normal, held to the low and mid-70s.Boston GlobeThe air will feel near-tropical on Wednesday, with dew points rising to the upper 60s.Boston Globe
Thursday: Showers and thunderstorms linger
Because the area of energy moving through the jet stream will not be moving quickly, the chance for showers will linger into Thursday. The core of the storm passes directly over Southern New England, keeping rain chances in place throughout the entire day. There may be a few extended dry periods at times, but showers and thunderstorms will lurk, so best hang on to that umbrella.
Thursday’s storms should be light enough to avoid any flash flooding.
The start of the weekend should bring more sunshine. However, the weather pattern remains active, and we could see more rain by Monday.
The forecast across Boston for the next seven days.Boston Globe
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Ken Mahan can be reached at [email protected]. Follow him on Instagram @kenmahantheweatherman.
