Forecast discussion: Over the last few days, it has felt more like late spring more than the middle of summer in Boston. A low pressure system along a frontal boundary kept showers and periods of rain over the state for the last eighteen hours. The low is now moving away from Cape Cod, moving towards the Gulf of Maine this evening. Any showers will come to an end by midnight.
As we head into the weekend, skies will begin to slowly clear, thanks in part to a high pressure ridge over western New York. We will feel warmer temperatures thanks to the sun, and the dewpoint temperatures will also rise as well, making the air more uncomfortable and oppressive. I am predicting high temperatures in the middle 80’s with lows only falling into the upper 60’s for Saturday.
As we approach Saturday night, a cold front now moving into the western Great Lakes will bring the threat of some showers before sunrise Sunday morning. From there, the front will be slow moving, so I am expecting showers, periods of rain at times, and isolated thunderstorms to remain over the state into Monday evening. A new high pressure center will help bring back mostly sunny skies for the middle of the week.
By Thursday, a low pressure system forming over the Carolinas will slowly move northward. It will bring a weak warm front and lots of moisture. We should see the first raindrops fall by Thursday afternoon, with a slight break from the precipitation Thursday night. Scattered showers will begin to fall again by the morning commute on Friday, with more widespread showers arriving in the afternoon.
Meanwhile, Tropical Storm Dorian is centered at 17.8N 45.8W as of 5 p.m. EDT, or about 1135 miles east of the Northern Leeward Islands. Maximum sustained winds are at 45 mph and is moving west-northwest at 20 mph. Right now Dorian is weakening due to some wind shear and drier air from the north and west. This is due to an area of high pressure in the upper levels of the atmosphere. The computer models all suggest Dorian will weaken over the next 5 days, and possibly become an open tropical wave before that time period. If the tropical remains a weak tropical storm, it will weaken into a depression and be just east of Cuba by Tuesday afternoon.
72 hour forecast:
Tonight: Partly to mostly cloudy and becoming more humid with a low of 63.
Saturday: Partly to mostly sunny and warmer with a high of 86. Winds will come from the south-southwest at 9-12 mph.
Saturday night: Mostly cloudy with a low of 68. Winds will shift to the southeast at 4-7 mph before sunrise. Patchy fog is possible after midnight.
Sunday: Cloudy with showers/thunderstorms by mid-morning and a high of 82.
Sunday night: Showers with possible periods of rain and a low of 70.
Monday: Lingering showers before ending during the evening commute with partial clearing before sunset. We will see a high of 83.
Monday night: Partly cloudy with a low of 67.
Tuesday: Mostly sunny. Highs 81-84, lows 64-67.
Wednesday: Mostly sunny. Highs 82-85, lows 67-70.
Thursday: Cloudy with showers and possible periods of rain developing by the afternoon. Highs 83-86, lows 68-71.
Friday: Scattered showers through the morning, with more widespread showers by the afternoon. Highs 83-86, lows 70-73.