Forecast discussion: High pressure moving away from Nova Scotia helped give Boston dry weather on Tuesday. By mid-morning, clouds began to increase in the skies. By the late afternoon, skies became completely overcast. The clouds are due to a series of low pressure systems which will bring the risk of some heavy rainfall starting early Wednesday morning.
Our first raindrops will come from a low pressure system passing east of North Carolina. The shower activity will arrive by the early morning, with some scattered showers by the morning commute. By the late morning, the second low pressure system will bring the heavier rainfall, along with some scattered thunderstorms. Also, some thunderstorms may be accompanied with heavy rain, gusty winds, and lightning. Any severe thunderstorms may be along the south coast, as computer models indicate this region will have the greatest chance to see them. Along with a Flash Flood Watch, a Coastal Flood Advisory is in effect for the eastern coastline of Massachusetts. Along with heavy rain, high tide may help create some splash over on some streets along the coastline.
By Wednesday night, the second low will move out to sea, and the first low will begin moving into eastern Canada. We will see some leftover showers into Wednesday evening, before drizzle, mist, and patchy fog take over early Thursday morning. High pressure behind the cold front will help bring drier air into the region. However, temperatures will only be in the upper 70’s entering the weekend. On Sunday, a low pressure system over Quebec will bring the risk of some showers starting early Sunday morning. The showers will end by early Monday morning, but the dry weather appears to be short lived. A quick moving disturbance will help create a new band of showers by Tuesday morning. A weak low pressure system will slowly move in behind the disturbance, helping to create some heavier rainfall by Tuesday afternoon.
72 hour forecast:
Tonight: Cloudy skies with showers developing around 5 a.m. We will have a low of 67.
Wednesday: Showers with periods of heavy rain and scattered thunderstorms. The thunderstorms have the potential to be severe. We will see a high of 74 with south-southeast winds of 17-20 mph. Patchy fog is possible, especially along the coastline.
Wednesday night: Precipitation tapers to showers by 9 p.m. with all precipitation ending by 4 a.m. Patchy fog is expected. Skies will begin to clear by sunrise. We will see a low of 62 with winds shifting to the west-northwest at 10-13 mph.
Thursday: Mostly sunny skies by noon with the high only reaching 78.
Thursday night: Mostly cloudy with a possible shower and a low of 60.
Friday: Mostly sunny with a high of 75.
Friday night: Partly cloudy with a low of 59.
Saturday: Partly sunny. Highs 77-80, lows 60-63.
Sunday: Mostly cloudy with possible showers starting in the early morning. Highs 78-81, lows 62-65.
Monday: Showers end just after midnight, with mostly sunny skies by mid-morning. Highs 77-80, lows 62-65.
Tuesday: Cloudy with showers by the early morning. Precipitation could become heavier by the afternoon. Highs 79-82, lows 65-68.