DAYS 1-5 (JULY 29 – AUGUST 2)
Heat and humidity dominate today (peak day) into tomorrow (final day) before a change to cooler weather, along with some additional rain, before a drying trend. That’s the one-line synopsis of the next 5 days. Here are the details… You wouldn’t know it, but what used to be a cold front pushed through our region early this morning. But this front is far from its source region with a very modified air mass behind it. The only change is to shift the wind from predominantly southwest to more of a west northwest direction, and take the dew point down up to a few degrees. Hardly noticeable just walking out the door, but somewhat significant to today’s forecast. The west northwest wind will likely be strong enough to prevent any coastal sea breezes, except being a direct sea breeze where it comes across water before reaching land again (Outer Cape Cod, for example). While places in examples like that will be modified cooler, a west northwest wind is one of the hotter summer winds for our region, and that will be the case today, with the non-modified areas, a vast majority of our region, exceeding 90 for high temps. And despite the tiny dew point decline, it will still be quite humid as they even recover that mini-loss, if not during the day today, by sometime this evening. In short, a hot day. I am now reluctant to call for any isolated showers and thunderstorms today as it looks like they just don’t have the trigger to fire up. I would not be totally surprised if one did, but I think the chance is so remote that other than this discussion they don’t get included in the detailed forecast that follows it. Next up, Wednesday. The outlook for this day is a little different than I had a few days ago, when I thought the set-up and timing of things would be slightly different. It’s going to be another hot and humid day, and with the approach of a cold front we will have to watch for the development of showers and thunderstorms. I expect these to be mostly from mid afternoon into the evening, and while I am not expecting widespread coverage, there can be individual storms or small storm clusters that can be quite strong, possibly severe (primary threat being straight line wind gusts). Keep an eye out for those, also knowing that some places will end up seeing little or nothing. Places that do get hit can be impacted significantly, at least for a brief time. Temperatures are a little tricky. I think upper 80s to middle 90s is a safe bet for high temps in most of the region, with typically cooler conditions for the South Coast / Cape Cod with a “mostly” southwesterly air flow. However, the air flow at the surface is not going to be that strong, and this does allow for the possibility of the wind becoming more south to southeast along MA’s eastern coast, including Boston, which could hold the maximums down a little in those locations. The cold front moves through in the evening but doesn’t get far. It comes to a stop just to our south and southeast early Thursday, and provides a running board for a wave of low pressure set to move along it later Thursday through early Friday, producing a swath of rainfall here. Reliable guidance has been starting to paint this as a moderate to heavy rainfall event for at least a portion of the region – fine tuning to come still. Current expected timing for most rain is later Thursday to early Friday. Later Friday into Saturday, drier and cooler weather is expected.
TODAY: Clouds mainly I-90 southward early depart, otherwise sunshine. Highs 90-97 except 80s some coastal areas and some 70s Cape Cod / Islands. Dew point declines slightly from near 70 to middle 60s. Wind W to NW 5-15 MPH.
TONIGHT: Mostly clear. Lows 68-75, warmest urban areas. Dew point 60s. Wind variable under 10 MPH.
WEDNESDAY: Sun / cloud mix. Scattered to clustered showers and thunderstorms mid afternoon on, with a few strong to severe storms possible. Highs 88-95, however cooler in some coastal areas. Dew point middle 60s to near 70. Wind SW up to 10 MPH, with a potential SE shift in eastern coastal areas. Wind can be variable, strong, and gusty near any storms.
WEDNESDAY NIGHT: Variably cloudy. A shower or thunderstorm possible in the evening. Patchy fog overnight. Lows 63-70. Dew point 60+. Wind shifting to NW up to 10 MPH.
THURSDAY: Mostly cloudy. Showers likely, especially in the afternoon. Highs 73-80. Dew point 60s. Wind N to NE up to 10 MPH.
THURSDAY NIGHT: Cloudy. Showers likely. Areas of fog. Lows 62-69. Dew point 60+.
FRIDAY: Cloudy with showers early, then a slow clearing trend. Highs 72-79. Dew point 60+. Wind NE to N up to 10 MPH.
FRIDAY NIGHT: Clear. Patchy fog. Lows 57-64. Dew point not far from 60. Wind N up to 10 MPH.
SATURDAY: Sunny. Highs 76-83, coolest coast. Dew point near 60. Wind variable up to 10 MPH with coastal sea breezes.
DAYS 6-10 (AUGUST 3-7)
High pressure will be dominant with fair weather and typical summertime temperatures across the region for this 5-day period.
DAYS 11-15 (AUGUST 8-12)
High pressure focus shifts off the Atlantic Coast heading toward mid month, with a pattern that would feature higher humidity and a slightly better chance to see some shower and thunderstorm development at times.