We start today off mainly dry before a few showers run through late morning to mid afternoon. Those showers will be more widespread west of 495 and isolated inside 495, including at Gillette. So if you’re heading to the Pats game, plan on a passing shower or two, but many dry stretches out there too. Temps average in the mid 60s with an increasing breeze this afternoon.
The greater concern runs from this evening to early Monday morning as a developing area of low pressure off the mid-Atlantic coast comes charging north, into New England. The contrast of cold air crashing in from the west and tropical air streaming south to north along the East Coast, will help ignite a potent storm. Not only do we have the contrast of airmasses, but also a jet configuration which allows for good venting of the storm aloft. That’ll allow the storm to rapidly strengthen, quickly lowering it’s pressure and increasing the rain/wind. Additionally, there will be a hybrid/tropical-ish like low (what NHC calls Philippe now) that tries to pivot around the main low, perhaps passing close to, or over the Cape between 3-6am Monday.
The wind is a main headline with this storm as a rapidly deepened storm is accompanied by a viscous low level jet. Check out the map below, winds about 2,500 feet up are pushing 90mph where you see that purple color! Where you see the blue is the hybrid low that will contain very powerful winds that could increase the risk of gusts to hurricane force (74mph) on the Cape around 3-6am.
A lot of times, cooler marine air near the surface creates an inversion that limits how much strong wind mixes down to the ground. However, when you start introducing/infusing tropical air, that inversion is either weaker or can erode. So the concern is the a portion of these very strong winds will be able to mix down to the ground overnight, especially in any tropical downpours that get going. It’s not to say all of that wind comes down, but the threat for gusts near/past 65mph at the coast is there, especially across Cape Ann and Cape Cod. Additionally, strong winds will be felt inland too, with gusts 40-55mph. The combination of strong wind gusts, a saturated ground, and leaves on the trees, will likely create issues with tree damage and at least scattered power outages across New England. Have those cell phones charged and set a back up alarm for Monday morning in the event you lose power tonight! We’ll also have to watch that potential of near hurricane force gusts on the outer Cape/Nantucket between 3-6am with that potent hybrid low.
We’ll catch some lulls in the winds mid Monday morning before gusty winds return late morning/early afternoon on the back side of the storm. Those winds will be out of the west.
Rainfall really ramps up here tomorrow evening and overnight with a quick 1-3″ falling, producing localized street flooding. The heaviest rain likely fall between 10pm – 4am.
With that in mind, a flash flood watch has been posted for the area by the National Weather Service. While some small streams may overflow their banks, main rivers across the eastern half of the state will likely avoid significant flooding. There’s a higher risk of river flooding in western and central New England.
In terms of coastal flooding, despite the howling winds, we have a few things going for us. 1) Tides and astronomically low. 2) Wind changes direction from SE to S to SW to W. 3) It’s a fast moving system. The combination of all 3 factors limit storm surge to 1-3′, which considering the tides astronomically low and winds peak at low tide, we’ll catch some splashover but no significant coastal flooding is expected.
Halloween still looks good for the little ghosts and goblins!
Have a good Saturday and check back for updates on the storm this weekend!
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