11:31AM
COMMENTARY
We currently have a good example going on of medium range uncertainty in forecasting. Guidance alone pretty much failed to pick up on this small low pressure area impacting the weekend weather when this period of time was beyond several days in the future. The general outlook was one that would probably have you envisioning a more typical August weekend with warmth, humidity, and maybe a few showers/storms. Well, this is not actually all that far off of that, being cooler due to cloud cover and an onshore flow, but with the humidity and some wet weather, just a little more widespread. We started to pick up on this a few days ago, and even then still had to adjust timing and location as initially it looked like the South Coast would be the wettest place today. The lesson here, even though we can see a lot of things in the future, never take a day 5 forecast and expect it to verify exactly. There is a reason why forecasts, including the one on this blog, is updated daily. Predicting the future is not easy. 
DAYS 1-5 (AUGUST 11-15)
Low pressure will impact the weather for this entire period, but that does not mean 5 days of rain and cool temperatures either. We will witness an evolution in details as low pressure spins to the south of New England this weekend and then backs up to the west early next week, being absorbed by a larger scale southerly flow, then the remains of the low coming back across the region in the form of a trough by the end of the period. What does this all mean for the weather here? Well we’ve already seen some heavy showers in southern areas but the axis of most widespread rain will now shift to one that runs from southeastern NH and northeastern through central MA down through RI & eastern CT, and these areas will be wettest most often through this evening, including some embedded downpours which may result in some road flooding, as well as the chance of a few rumbles of thunder. To the southeast of this, activity will be more isolated, but any downpours that do develop there have the chance to produce a strong wind gust with even some local damage possible. Tonight, that axis will pivot eastward and a more general area of showers/thunderstorms will move back across the entire region before exiting early on Sunday. During Sunday, activity will be much more isolated regionwide, but some breaks of sun can still fuel some pretty serious downpours, so while many areas may get through the day with little or no rainfall, some areas that do see it can pick up quite a bit in a short time. Another surge of energy may increase the coverage of showers/storms on Monday. By Tuesday when our friendly low pressure area has moved back to the west we’ll get into a more tropical-feeling southerly air flow with the possibility of showers and thunderstorms, and Wednesday is the day when it all comes back east as a trough with additional showers and storms possible, but probably more then exception than the rule. Forecast details…
TODAY: Mainly cloudy. Scattered to numerous showers, some heavy. Slight chance of thunderstorms. Most numerous shower activity southeastern NH, northeastern through central MA, RI, and eastern CT. Humid. Highs 67-74. Wind E 5-15 MPH. Slight risk of briefly stronger wind gusts in any isolated downpours/storms in southern areas.
TONIGHT: Mainly cloudy. Areas of fog. Numerous showers with probable embedded thunderstorms, some heavy. Humid. Lows 62-67. Wind light E but briefly strong wind gusts possible in any storms.
SUNDAY: Mostly cloudy to partly sunny. Scattered to isolated showers and possible thunderstorms. Humid. Highs 68-75 coast, 75-82 interior. Wind NE 5-15 MPH.
SUNDAY NIGHT: Variably cloudy. Patchy fog. Isolated showers. Humid. Lows 62-67. Wind light variable.
MONDAY: Mostly cloudy. Showers likely. Chance of thunderstorms. Humid. Highs 68-73 coast, 73-78 interior. Wind variable 5-15 MPH.
TUESDAY: Partly sunny. Scattered showers. Isolated thunderstorms. Humid. Lows in the 60s. Highs from the lower to middle 70s coast, upper 70s to lower 80s interior.
WEDNESDAY: Variably cloudy. Isolated to scattered showers/thunderstorms. Humid. Lows in the 60s. Highs from the middle 70s to middle 80s, coolest South Coast.
DAYS 6-10 (AUGUST 16-20)
While the ridge in the Atlantic hangs a little further east a couple more disturbances will be able to move through from west to east. This would bring a few opportunities for showers and thunderstorms but overall this period would not be all that wet. Seasonably warm and somewhat humid weather will be the rule, though August 16 may be briefly less humid.
DAYS 11-15 (AUGUST 21-25)
A possible quick shot of cooler/drier air to start the period then warmer/humid weather returns with a couple shower opportunities. Heat may try to build later in the period as high pressure again strengthens off the East Coast and backs westward.