Relief arrived yesterday afternoon as a backdoor cold front pushed west-southwestward introducing cooler air from ME and the Maritimes. Before that happened, some areas of Metro West such as Millis, Dover, Townsend, East Bridgewater and Holliston got their 6th day of temperatures at or over 90 degrees! Coincidentally, there was also a drop in the dewpoints by a few degrees just adding to the more comfortable conditions. This switch came with a price, however, as scattered showers and storms were generated releasing torrents of rain in spots. Hard-hit areas were located in the Merrimack Valley region of NH into MA plus places strung out near and just south of the MA Pike. As examples, Brookline, NH received 1.3″, Haverhill 1″ and Franklin got 2.22″ of rain in less than 90 minutes. Some more showers and boomers are possible anywhere today especially over southwestern and western New England closer to that frontal boundary which is parked over central CT to southwestern RI. As the front returns as a warm boundary tomorrow, more showers and stronger storms will be generated and that activity will probably last through Wednesday night into Thursday morning.
With the so-called marine layer spread out over much of the region, it is a rather murky start to the day with a low overcast, spotty mist and areas of fog especially at some coastal locations. The dilemma of the day is to determine the scope of clearing. Generally speaking, with the strength of the strong July sun, the chances are usually high that a burn off will occur when there are no other overlying layers of clouds. In today’s case, there are other clouds above so I will predict that it will be a mainly cloudy day with some brightening episodes and perhaps a few breaks and splashes of sunshine eventually. Consequently, the temperatures will rise to maximum readings ranging from near or slightly over 70 at the coastline up to the middle to upper 70s farther inland with a few spots near or a bit over 80 from the Blackstone Valley westward. The wind will be light in from the northeast to east under 10 mph for the most part. After some 60s tonight, it will warm up to the lower to middle 80s tomorrow as the wind becomes south-southwesterly with that warm frontal passage.
My eyes are watching a mass of refreshing air flowing from the Canadian Rockies toward the northern Plains States. It is associated with a sprawling zone of high pressure which could be ours this weekend IF all goes well. As the Bermuda high pressure heat pumper has weakened and shifted southeastward, the pattern is changing and the jet stream should propel this package of pleasant air across the Great Lakes into the Northeast. The new ridge of high pressure will become elongated in a northeast to southwest axis northwest of the Boston area. A cold frontal boundary pressing eastward will push the showery weather off the coast during Thursday morning. Its momentum will decrease as its grinding into the area so the driest air will certainly overspread areas across the northwestern half of New England. It will be come less humid over the rest of the area but the real driest air may not make it to southeastern MA especially on Cape Cod. Nevertheless, I am expecting some improvement down there too. It presently appears that a tongue of moisture riding up over the departing frontal boundary will essentially remain just south of Cape Cod but that is a very close call right now. Any slight deviation in the steering currents will change that scenario for the better or for the worse. For now, I will postulate varying amounts of cloudiness of the high and mid-level variety over southeastern MA and southern RI area through the weekend. In the drier air north and west, a development of some small puffy clouds each day will partially cover the blue sky. With a weak upper level trough aloft, there is just a slight risk of a few spotty sprinkles or showers well inland each afternoon from Friday through Sunday. The temperatures will max out near or slightly over 80 farther inland with lower to middle 70s along the coast. This scenario would make for a delightful weekend for all outside activities. The caveat is that it is not etched in stone due to the closer proximity of that stalled out frontal boundary south of New England.
Looking way ahead, as our weekend high pressure system merges with the Bermuda high, it will become energized and eventually turn into a heat pumper again as the winds in all levels turn southwesterly and drive the heat from the Plains to the Midwest to the Northeast later next week. Based upon this evolution, the 90s will be returning on July 17th or 18th. We shall see.
We are monitoring the progress of Tropical Storm Chantal. The storm will likely become increasing ragged as it eventually crosses the mountains of Hispaniola. After that, re-strengthening is likely on its way to the Bahamas. For more detailed information, logon to the National Hurricane Center.
Todd Gutner returns today and he will post his blog early this evening and I shall return early tomorrow morning.