DAYS 1-5 (AUGUST 15-19)
A frontal boundary, trying to be a warm front, will instead become a quasi-stationary front as it makes a feeble attempt to move northward into our region today. It gets to about Nantucket and Martha’s Vineyard, Block Island and maybe touches a portion of the South Coast, otherwise stays to the south and even moves a bit further south by evening as an initial wave of low pressure goes by from west to east. A swath of widespread showers and some embedded downpours moved into the region overnight and will gradually taper off and exit during the course of this morning. Heavier thunderstorms have been located to the south and will pass mostly off shore, only clipping Nantucket for a while from early to mid morning. A general east to northeast flow will keep it on the cooler side, though it will be quite humid, and with temp / dew point readings nearly the same we’ll see areas of fog and drizzle around even as showers taper off and exit, under a sky that remains generally overcast throughout the afternoon into this evening. Another disturbance will kick off showers and a few heavier downpours and possible thunderstorms especially near the South Coast again tonight, lingering as long as the hours around dawn on Wednesday. Elsewhere, just spotty drizzle and possible sprinkles of very light rain occur. During the day Wednesday, the final disturbance exits, and there will be a slow arrival of drier air, but with the air flow still from the northeast for a good part of the day, the clearing process may be a sluggish one, so I’m only expecting partial sun as the shower chance becomes confined mainly to the higher terrain of southwestern NH and north central MA with a help of a bit more solar heating there. Any of these that pop up are gone by evening and we have a fairly tranquil night with broken to scattered clouds but patchy ground fog forming under light wind conditions and a small temp / dew point spread. On Thursday, our wind flow will shift to southerly ahead of the next approaching trough, and a cloud / sun mix will give way to more clouds eventually, along with increasing shower opportunities due to a combination of an approaching trough from the west and more humid southerly air flow. This is most prominent Thursday night into part of Friday, until a cold front sweeps through from west to east during the day. Any sun on Friday can help enhance the shower activity with some thunder possible as well. Right now I don’t think we’ll see any severe storms. Timing of the front should allow a drying process to begin during the afternoon, first to the west (southwestern NH and central MA), lastly in southeastern areas (Cape Cod). Expect fair weather Saturday with lower dew point air, but still seasonably warm. Pop up showers in response to a trough of low pressure across northern New England should remain north of the WHW forecast area, so overall it looks like a nice beginning to the weekend at this point.
TODAY: Cloudy. Widespread showers until mid morning, tapering to sprinkles and patchy drizzle with areas of fog late morning on. Highs 67-74. Dew point middle 60s to around 70. Wind E to NE up to 10 MPH, a few higher gusts near the coast.
TONIGHT: Cloudy. Areas of fog. Isolated to scattered showers, except a couple periods of more widespread showers / downpours and possible thunder near the South Coast. Lows 63-70. Dew point in 60s. Wind NE up to 10 MPH.
WEDNESDAY: Clouds break for sun at times. Early morning showers possible Cape Cod / Islands. An isolated shower may pop up southwestern NH and north central MA midday or afternoon. Highs 75-82. Dew point falling slowly toward 60. Wind NE to briefly N up to 10 MPH then variable.
WEDNESDAY NIGHT: Partly cloudy. Patchy ground fog. Lows 58-65. Dew point upper 50s to 60. Wind variable under 10 MPH.
THURSDAY: Sun and passing clouds, with clouds becoming dominant later. Passing rain showers possible by late-day / evening. Highs 77-84. Dew point rising through 60s. Wind S increasing to 5-15 MPH, higher gusts possible late.
THURSDAY NIGHT: Mostly cloudy. Showers and possible thunderstorms, especially overnight. Areas of fog. Lows 65-72. Dew point middle to upper 60s. Wind S 5-15 MPH.
FRIDAY: Variably cloudy. Scattered showers and thunderstorms , diminishing from west to east midday through afternoon. Highs 78-85. Dew point 60+. Wind S shifting to W 5-15 MPH.
FRIDAY NIGHT: Partly cloudy. Lows 60-67. Dew point falling below 60. Wind W 5-15 MPH.
SATURDAY: Sun/cloud mix. Highs 78-85. Dew point below 60. Wind W 5-15 MPH.
DAYS 6-10 (AUGUST 20-24)
Fair weather holds for August 20. The August 21-24 time frame will find the region in a minor battle between Canadian dry air and a northwest flow and attempted pushes of warmer, more humid air in from the southwest. This may result in a couple of unsettled episodes interspersed with fair weather, and temperatures that are variable, but not that far from normal.
DAYS 11-15 (AUGUST 25-29)
Trends remain for a more persistent west and northwest flow than previously indicated which may continue to limit or even eliminate a hot weather threat and keep it on the drier side with just brief shower chances.