DAYS 1-5 (SEPTEMBER 6-10)
A hazy look to the morning sun today is due to a wildfire smoke plume aloft that moved in last evening but will be pushed off to the east during the day. Mid summer warmth and humidity dominates today’s weather with offshore high pressure, but an approaching cold front and one of the better set-ups for thunderstorms of the summer, coming quite late in the season, will have us on the look-out for strong to severe storms later in the day. We’ll first need to watch for the development of individual storms ahead of what will eventually be a cluster / line of storms. These first individual cells, if they occur, have the ability to become super-cells, and those can produce larger hail, strong winds, including isolated tornadoes. I don’t say this in the thought process that everybody will see this today. Their occurrence will be isolated, but better to be prepared for the potential in case you happen to be in one of the locations hit by one. Whether or not these occur, there’s a higher likelihood for the aforementioned cluster or line of storms to develop and charge eastward late in the day to the very early evening. Potentials with this include damaging wind gusts and also some hail. Any storms can produce torrential rainfall and dangerous lightning, of course. Many outdoor plans happen on this particular day (Hampton Beach Seafood Festival, an air show in Portsmouth NH, numerous other things). It’ll be important to keep a close eye on the weather for any of these that coincide with the time(s) of storm threats – follow radar, watch the sky, monitor any statements from NWS. The thunderstorm activity is likely to be most powerful north and west of Boston and show a weakening trend as it approaches the coastal plain more due to the later timing of arrival there and the loss of solar support, but a couple stronger cells can always survive further south and east, so people in those areas should also be weather-aware into the evening. Once that threat is by us, the cold front responsible is not going to be in much of a hurry to get through the region, and its slow movement allows additional moisture and a weak wave of low pressure to come up from the south and keep our showery weather going into Sunday. I’m still expecting that most of this activity will take place through Sunday midday and we’ll see a drying trend follow that, and clearing at night. Additionally, the warmth and humidity of today will be replaced by significantly cooler air and a more gradual dry-out, held up by the showers. High pressure from Canada delivers pleasant, cooler and dry weather early next week. By Wednesday, a shield of clouds from low pressure passing offshore will likely limit the sun, and the South Coast may be close to some of that rain, but my early idea is that it will stay offshore.
TODAY: Hazy sun then eventually a sun/cloud mix. Isolated thunderstorms possible by mid afternoon. More widespread showers and thunderstorms likely, especially north and west of Boston, later in the afternoon, progressing eastward into evening. Any storms can be strong to severe. Highs 81-88 except 73-80 South Coast. Dew point rises toward 70. Wind SW 5-15 MPH, higher gusts, and can be variable with powerful gusts near storms.
TONIGHT: Variably cloudy. Occasional showers / chance of a thunderstorm. Patchy fog overnight. Lows 63-70. Dew point 60+. Wind SW 5-15 MPH.
SUNDAY: Mostly cloudy. Occasional showers, favoring morning and midday. Highs 67-74. Dew point falls toward 60. Wind variable to NW up to 10 MPH.
SUNDAY NIGHT: Clearing. Lows 48-55. Wind NW 5-15 MPH.
MONDAY: Sunny to partly cloudy. Highs 67-74. Wind NW 5-15 MPH.
MONDAY NIGHT: Mostly clear. Lows 45-52. Wind NW under 10 MPH.,
TUESDAY: Mostly sunny. Highs 67-74. Wind NW to N up to 10 MPH.
TUESDAY NIGHT: Partly cloudy. Lows 48-55. Wind NE under 10 MPH.
WEDNESDAY: Mostly cloudy. Highs 66-73. Wind E up to 10 MPH.
DAYS 6-10 (SEPTEMBER 11-15)
High pressure dominates the weather with dry conditions expected. Temperatures near to below normal.
DAYS 11-15 (SEPTEMBER 16-20)
There has been a trend on medium range guidance, not surprisingly, for a continued dry look and dominant high pressure in the waning days of astronomical summer, and my outlook continues to lean dry with near to below normal temperatures for this period.