Forecast discussion: We had milky sunshine by the afternoon here in Boston on Friday, as some moisture from the northwest spilled over the capital city. We will see more moisture work its way into Southern New England for the weekend, but this time it will come from the east.
The weather map shows a strong frontal boundary off the coast of South Carolina. This boundary will slowly push back to the west and be offshore of our area. This in turn will help keep a lot of moisture and precipitation over the state. At this time, eastern Massachusetts will see heavier rain and isolated thunderstorms during the early part of Saturday. Then, the boundary will move slightly eastward, giving the Cape and Islands a higher risk at seeing heavier rainfall. The boundary will slowly push back to the west Saturday evening, increasing the chances for us to see more widespread rainfall across the region.
As we head into Sunday, the showers and thunderstorms will slowly push off to the east. There may still be an isolated shower or thunderstorm in the area by the afternoon, but the best chance will be for the Cape and Islands, along with parts of southern Bristol and Plymouth Counties. The cold front will move further into the Atlantic by Sunday night, allowing for some drier air to move over Massachusetts for Monday.
As we head into the work week, there is still a slight chance for a passing shower or thunderstorm by Monday afternoon. Otherwise, a weak high pressure ridge will give us partly sunny skies. A weak cold front will pass through New England on Tuesday, and with any sunshine, this could help create some showers and an isolated thunderstorm during the afternoon.
By the time we reach Tuesday, an upper level trough which has stayed to the west of New England will begin to weaken. This will allow for a surface high pressure system will finally bring mostly sunny skies back to eastern Massachusetts by Wednesday. We will remain with mostly sunny skies into next Friday.
Finally, the National Hurricane Center issued its first advisory on Tropical Storm Bertha at 11 p.m. Thursday night. Right now, Bertha has maximum sustained winds of 50 mph. Watches and Warnings are out for much of Puerto Rico and the Virgin Islands. The system is forecast to pass over southwestern Puerto Rico by Saturday afternoon, before passing east of the Bahamas Sunday afternoon. The system is expected to reach about 70 mph but remain well offshore of Florida on Monday. However, swells and seas will be increasing along the southeastern side of the Atlantic.
72 hour forecast:
Tonight: Cloudy with isolated sprinkles and a low of 67.
Saturday: Mostly cloudy with scattered showers/thunderstorms by 10 a.m. We will have a high of 73 with northeast winds of 6-9 mph.
Fenway Park Forecast (4:05 p.m. vs. Yankees): Isolated showers/thunderstorms, 72.
Saturday night: Scattered showers/thunderstorms with patchy fog and a low of 61. Winds will come from the north-northeast at 6-9 mph.
Sunday: Scattered showers/thunderstorms until noon, then the southern part of the state will see scattered activity. The northern part will see partly sunny skies with a high of 74.
Sunday night: Precipitation ends after midnight in the whole state, with clearing skies. We will see a low of 64.
Monday: Partly to mostly sunny with the slight chance for an afternoon shower or thunderstorm. We will see a high of 80.
Monday night: Partly cloudy with a low of 66.
Tuesday: Partly sunny with possible afternoon showers. Highs 81-84, lows 64-67.
Wednesday: Partly sunny. Highs 79-82, lows 63-66.
Thursday: Mostly sunny. Highs 79-82, lows 62-65.
Friday: Mostly sunny. Highs 79-82, lows 63-66.