Summer heat gives way to showers
After strong sunshine and offshore flow brought Boston its second 90-degree day of 2016 on Wednesday, today will begin a string of cooler, potentially rainier days ahead. Sunshine will return for the start of the day today, but scattered thunderstorms are likely to develop across southern New England this afternoon as surface warming creates an unstable air mass. Though storms are likely to develop somewhere in the region, it is difficult to forecast their specific locations in advance, and the scattered nature of their spatial coverage means that any particular point (for instance, the Institute) might or might not see a storm at some time today.
A back-door cold front will sweep down from the northeast during the day on Friday. The frontal passage will usher in a cooler maritime air mass, resulting in a roughly 10-degree (°F) drop in temperatures compared to today. The cool ocean air will stick around for the remainder of the weekend, and the lingering presence of the frontal boundary will give rise to showers and thunderstorms on each of the next three days. The best chance for rain will be on Saturday, before the frontal disturbance exits the region on Sunday, paving the way for a sunny start to next week.