7:25AM
DAYS 1-5 (JULY 18-22)
Not time for a heatwave yet. Patience! First we have this marine-cooled day to get through, and then, Friday through Sunday will produce a heatwave for many, but possibly not all. With a lower launching pad and marine air to warm-up, Friday may fall shy of 90 in some locations, including Boston. No guarantee but we’ll watch to see how it pans out. While we have a northeast to east air flow at the surface today we still have some tropical moisture riding up over a boundary to our south and that will create a shower and thunderstorm risk today as well, but it won’t be a widespread heavy event, just more scattered activity and favoring areas to the south of I-90. This moves out tonight, and a southwesterly air flow arrives Friday, bringing in the heat and humidity, although as stated, it may struggle to heat up too quickly at first. But that’s splitting hairs. After today, whether a particular area is in the upper 80s or lower 90s Friday, with high humidity, it will feel quite hot. The heat peaks Saturday then eases ever-so-slightly Sunday, almost unnoticeable. We may get the dew points down a little over the weekend because of a downsloping west wind, but that will be compensated by the higher air temperatures. Another thing we have to watch out for in this pattern are nocturnal thunderstorm complexes, or the remains of them, from the Great Lakes area. One or two of them may make a run at New England, but the first indications are that one would cross far southwestern New England while dying, not impacting the WHW forecast area, early hours of Saturday, and another one may visit northern New England Saturday night or early Sunday, again not impacting southeastern New England directly. A surface boundary (weak cold front) getting closer to the region later Sunday may trigger a few showers and thunderstorms as we break the heat Sunday night. This should push through the region by early Monday but still may be close enough with some cooler air aloft to trigger a few showers during Monday. That day will also be decidedly cooler than the weekend, back to more seasonable warmth.
Forecast details…
THURSDAY: Mostly cloudy. Episodic showers and a chance of thunderstorms, favoring areas near and south of I-90 in southern MA, eastern CT, and RI. Moderately humid. Highs 70-77. Wind NE to E 5-15 MPH.
TONIGHT: Variably cloudy. Areas of fog. Humid. Lows 63-70. Wind light SE.
FRIDAY: Partly sunny. Very humid. Highs 81-88 Cape Cod, 88-95 elsewhere. Wind SW 5-15 MPH.
FRIDAY NIGHT: Partly cloudy. Humid. Lows 72-79. Wind WSW up to 10 MPH.
SATURDAY: Mostly sunny. Humid. Highs 92-99, hottest Merrimack Valley, except 84-91 South Coast and Cape Cod. Wind SW 5-15 MPH.
SATURDAY NIGHT: Partly cloudy. Slightly less humid. Lows 74-81. Wind light W.
SUNDAY: Mostly sunny morning. Party sunny afternoon. Moderately humid. Highs 90-97, cooler Cape Cod. Wind W 5-15 MPH.
SUNDAY NIGHT: Variably cloudy. Scattered showers/thunderstorms possible. Moderately humid. Lows 63-70. Wind W 5-15 MPH, higher gusts.
MONDAY: Partly sunny. Isolated showers and possibly a thunderstorm. Less humid. Highs 80-87. Wind NW 5-15 MPH.
DAYS 6-10 (JULY 23-27)
With upper level high pressure having pushed back to the west we’ll see a more seasonable temperature period. The very start of the period may feature some cloudiness as a disturbance passes, but much of the time should be rain-free. We may have to eye some tropical moisture from the southwest by the very end of the period that would at least make it more humid, and possibly increase the shower risk.
DAYS 11-15 (JULY 28-AUGUST 1)
Near to above normal temperatures expected with a couple opportunities for showers and thunderstorms as we go down July’s home stretch and arrive at August.