DAYS 1-5 (SEPTEMBER 13-17)
A long-talked about trough and associated frontal system will enter our region from the west today and take until sometime Thursday morning to completely pass across the region. This allows high humidity to continue along with a couple or a few rounds of showers and thunderstorms, generally arranged in broken lines or clusters, the first from late morning too early afternoon, the second later this afternoon to early this evening, and a likely third round in the early morning hours of Thursday over southeastern MA (maybe part of RI) lingering on Cape Cod as late as mid morning Thursday. Any or all of these areas could contain an isolated severe storm or to with the emphasis south of I-90. The perimeters are there for even a storm or two with rotation, so that will be something to keep watch for as well. I also know many are concerned with repeated flooding from today’s and tonight’s activity. While heavier showers/storms can result in some additional/renewed flooding problems, these should be more localized and much shorter-lived than the event that took place Monday. As the front passes, a wind shift to northwest, occurring from west to east, will usher in much drier air, but this progression is not rapid, and it will take until midday Thursday for this new air mass to have reached the entirety of the region. Thursday night will give you that feel of autumn in the air, while it’s still technically summer, the days are waning and it’s only a matter of time. But we haven’t felt much of this yet in the late summer days as we’ve been in such a persistent pattern of higher humidity and frequent rainfall events. Speaking of events, while we’re enjoying a comfortable mid September / late summer day on Friday, we’ll be keeping a close eye on Hurricane Lee, which will be in the process of accelerating northward in the waters between Bermuda and southern New England. The track of this system, as usual, has been the hot topic, but some details need to be remembered. These include Lee’s path over cooler water and its encountering of wind shear, and a slightly slower-than-typical acceleration, all which will contribute to a weakening and an early beginning of the transition from tropical to post tropical system. Transitioning systems also expand in size in terms of their wind field, so this has to be taken into account when developing a forecast for our region. My initial ideas for Lee’s eventual path haven’t really changed that much, nor will they here for this forecast. We see the cyclone wavering along its path due to influences from various weather systems in the western Atlantic and eastern North America. This is typical but maybe a little more apparent due to this particular pattern configuration and Lee’s slightly slower movement. But slower movement is still relative, because the system will be accelerating and expanding as it makes its closest pass to us between Friday night and Saturday afternoon. My best guess is that Lee’s landfall will take place between the eastern tip of Maine and the southern tip of Nova Scotia sometime on Saturday evening. What that means for our region is that we get under the cloud canopy of the storm Friday night into Saturday, and a period of stronger northerly wind (on the storm’s back side), especially for the coastal areas / Cape Cod, where it’s not unreasonable to expect gale-force gusts at this point. Does the rain shield on the western side of the storm make it this far west? Good question. It probably does, to some degree, with the greatest chance of rainfall being on Cape Cod. There will also be a significant amount of dry air in place over our region, which tends to eat away at the western sides of these precipitation areas when the storms are passing by like this one will be. So I’m downplaying the rain chance, based on this, and just focusing on the impacts of cloud cover and wind, and probably the most important of all, for coastal areas – rough surf and rip currents, which have already begun and will continue into the weekend as Lee passes by then moves away. The peak for this will likely be the second half of Friday and a good portion of Saturday, so keep this in mind if you have late-season coastal water or beach plans. Is it too early to call for the potential of stunning sunsets on Friday and/or Saturday during the approach of Lee Friday and the departure of Lee Saturday, allowing the setting sun to sneak under the storms cloud deck? Mark it down – let’s see what happens!
TODAY: Some early sun for eastern areas otherwise generally cloudy. Showers and possible thunderstorms midday on. Any storms can produce downpours and localized flooding. Isolated severe storms are possible mainly south of I-90. Highs 71-78. DP 60s. Wind S 5-15 MPH.
TONIGHT: Cloudy. Showers continue and become most likely in RI and southeastern MA. Areas of fog. Lows 61-68. DP 60+. Wind SW up to 10 MPH.
THURSDAY: Clouds and showers linger in the Cape Cod region for a while in the morning. Otherwise, a sun/cloud mix. Highs 71-78. DP falling 60s to 50s. Wind W 5-15 MPH.
THURSDAY NIGHT: Clearing. Lows 55-62. DP ~ 50. Wind WNW 5-15 MPH.
FRIDAY: Sun, but clouds increasing later in the day from south to north, especially in eastern areas. Highs 68-75. DP ~ 50. Wind NW 5-15 MPH.
FRIDAY NIGHT: Mostly cloudy. Lows 55-62. DP lower 50s. Wind N 5-15 MPH except 15-25 MPH Cape Cod with higher gusts.
SATURDAY: Mostly cloudy through midday including a chance of rain Cape Cod. Sun may shine more, especially western areas, later in the day. Highs 66-73. DP lower 50s. Wind N 10-20 MPH except 15-30 MPH Cape Cod with higher gusts possible.
SATURDAY NIGHT: Clearing. Lows 50-57. DP falling to 40s. Wind NW 5-15 MPH.
SUNDAY: Mostly sunny. Highs 68-75. DP 40s. Wind NW 5-15 MPH.
DAYS 6-10 (SEPTEMBER 18-22)
Next trough brings a chance of some wet weather early next week, before high pressure returns and brings a stretch of dry weather for several days following, starting slightly cooler and drier then with a warming trend as we hit the last couple days of summer
DAYS 11-15 (SEPTEMBER 23-27)
Autumn arrives with the equinox on September 23. The early days of the new season look fairly quiet with a zonal flow pattern, mostly fair weather, a brief shower threat or two, and temperatures near to slightly above normal.