Incredibly humid air not only made for an uncomfortable Sunday night following two Sunday evening tornado touchdowns – one in Falls Village, CT, and the other in Sandisfield, MA – but also has led to areas of fog for our Monday morning. The fog will burn off and humidity will very slowly decrease over the course of the day, limiting the heat index value but not stopping a rise in temperatures to around 90 degrees by afternoon. Aloft, there’s really no significant trigger to touch off thunderstorms, so a storm-free day is expected Monday for most of New England. Of course, to our south a storm continues to churn as Isaias continues to slowly move northward toward the Southeast U.S. coast. The sooner Isaias makes landfall in the Carolinas – and the longer the storm spends over land as it moves north – the better the outcome for New England. In fact, by the time Isaias arrives to New England and makes a pass over Western New England, it’s likely to carry heaviest rain along and to the west of the storm track – mostly Western New England into Upstate New York – and a shrinking and weakening wind field that may only deliver 40 to 45 mph wind gusts to New England, focused mostly at the coastline. Nonetheless, the National Hurricane Center continues advisories for the expectation of Tropical Storm conditions from Long Island Sound to Block Island, RI, where an extra line and fender wouldn’t hurt for boat owners. The quick shot of a southeast and southerly wind and rain later Tuesday into Tuesday night won’t linger as what will become the remnant of Isaias trucks northward into Canada on Wednesday, starting a process of more comfortable air filtering into New England that should stick around for the end of the week, with high temperatures hovering in the 80s all the way through the end of our exclusive First Alert 10-day forecast.
Fresh air has taken hold of New England for a day here on our Wednesday – the dew point temperature, measuring the amount of moisture in our air, has dropped significantly, indicating less humid air has arrived. The difference in air was palpable as soon as the early morning hours Wednesday with most communities 10 to 20 degrees cooler than Tuesday morning at the same time. Although sunshine will warm the dry air to around 90° by Wednesday afternoon, the lack of humidity negates any worry of heat index beyond the actual temperature. The presence of dry air means we all have a greater than 90% chance of staying dry, save for the Islands of Massachusetts where a few leftover morning showers accompany the still-ongoing change of air. In fact, while humid air will briefly ease on the Cape and Islands, it quickly returns from the south Wednesday night, not only putting the South Coast back into soupy air overnight, but also resulting in areas of fog for Southern New England and a few overnight rain showers in Central and Southern New England. By Thursday morning to midday, all of New England is back into humidity, with a truly tropical feeling in place for Southern New England and scattered afternoon showers and thunder expected to develop in that moist air and fueling some potentially strong thunderstorms. This time around, humidity is short-lived with a cold front following the Thursday afternoon storms and delivering less humid air as soon as Friday, with showers ending from northwest to southeast but possibly lasting at least in scattered form into Friday morning for Southeastern New England, particularly the Cape and Islands. By Friday afternoon, the less humid and comfortable air will be in place, leading to an incredible start to the weekend. The only weekend weather concern our First Alert Weather Team has right now is an increasing chance of showers or thunder by Sunday afternoon or evening as humid air will be pressing northward again, attempting a return to New England that eventually succeeds by Monday. In fact, the first half of next week we not only will have our eyes turned to humid air progressing on a southerly wind, but that same south wind both at the surface and aloft will mean we’ll be watching the moisture associated with what is, as of this writing, Potential Tropical Cyclone Nine and seems likely to be classified as Tropical Storm Isaias soon. This storm is expected to be near or over Florida this weekend, and represents at the very least a large swath of tropical moisture that may be able to enhance showers and thunderstorms even here in New England next week, before another approaching cold front dries us out for the second half of next week in our exclusive First Alert 10-day forecast.
After a handful of communities joined the Century Club by topping out at or over 100° Monday afternoon, the temperature will be a few degrees cooler…but we won’t notice the difference with increased humidity creating a heat index around 100° for the metropolitan areas of Southern New England. Farther north, a round of morning showers combined with more clouds will keep temperatures cooler than Southern New England, but that same disturbance aloft – driving a cold front at the surface – will trigger scattered afternoon thunderstorms in Southern New England, particularly from 2 or 3 PM onward. Not everyone will see Tuesday afternoon thunder, but with temperatures in the 90s and dew point temperatures around 70 indicating plenty of moisture in the air, any storms that develop will have the potential to grow strong off the heat and humidity with torrential downpours, lightning and locally strong or damaging wind gusts. Storms won’t reach Cape Cod until night, when most of them will be weakening as the cold front driving them slows…slowing so much that humid air is unlikely to be completely replaced on the Cape and Islands and immediate South Coast, though the rest of New England will feel a huge difference with much more comfortable air Wednesday, even as temperatures still rise to 90 degrees. Another disturbance and associated cold front drops into New England later Thursday, prompting a few more thunderstorms but also ushering in a fresh shot of even more comfortable, cooler air for Friday and the weekend – a splendid-looking weekend. Humidity will return early next week with a developing southerly wind flow – we’ll need to watch that flow of air because as of this writing there’s a tropical disturbance way out in the Central Atlantic that may strengthen as it churns west, and could represent a healthy slug of moisture, a piece of which could migrate north early next week to enhance showers and thunderstorms Monday and Tuesday, but another cold front is expected to once again sweep in more comfortable and drier air around the middle of the week, at the end of our exclusive First Alert 10-day forecast.
Monday’s record high temperature of 98° in Boston was set in 1882 and isn’t an easy one to surpass, but after 138 years our First Alert Team thinks that record will likely fall Monday afternoon, as we predict Boston’s temperature to top out at 99°. Of course, some towns in Southern New England are likely to hit the century mark as humidity actually drops during the midday and afternoon, with the slightly drier air able to warm just a bit more than humid air would, giving the extra boost to break records. Physical stress on the human body increases during hot stretches with time, as the cumulative effects of hot days and warm nights don’t give the body a chance to recovery for those without air conditioning, which is why it becomes important to check on those who are vulnerable Monday and Tuesday. For all of us, heat safety tips can make a difference: staying hydrated, wearing lightweight, light colored clothing, taking breaks and finding air conditioning when possible. Keep in mind cars heat to dangerous temperatures very quickly and pets need water and shade on days like today. No thunderstorms are expected in Central or Southern New England Monday afternoon or evening, owing both to the less humid air temporarily in place and the lack of warm/cool clash, even high in the sky – it’s just hot all the way up. In Northern New England, cooler air aloft will afford scattered thunderstorms Monday afternoon and evening. Tuesday is forecast to be just a few degrees less hot, but humidity will rise again and heat index values will rise to near or over 100 degrees, making the day just as impactful as Monday. The chance of thunderstorms increases Tuesday – first a round of showers may quickly run west to east for a part of Central New England during the morning, then scattered strong thunderstorms are possible Tuesday afternoon to early evening as a weak cold front passes through by Tuesday evening and delivers less humid and storm-free though still hot air Wednesday. Another disturbance Thursday brings a chance of isolated to scattered thunder in the afternoon ahead of another shot of comfortable air that should lock in a pleasant summer weekend. Humidity and chance of thunder builds again first thing next week in our exclusive First Alert 10-day forecast.