DAYS 1-5 (APRIL 23-27)
Mother Nature has been giving us example of “classic spring scenarios” recently, and today / tonight / tomorrow will fit that category as well. We start today with some filtered sun as a canopy of high clouds, the one that provided a beautiful sunset yesterday for many areas, continues to slide across the sky, eventually shifting offshore. Meanwhile, there are some coastal areas, particularly Outer Cape Cod, that can’t see this at all early this morning under a blanket of marine stratus. A wind shift to the northwest should push this offshore as well over the next couple hours, and that northwesterly air flow will also limit how much sea breeze takes place today, but ultimately many coastal areas do end up cooler than inland this afternoon with a light sea breeze. Tonight, high pressure settles right over the region, and with a clear sky, this is the perfect set-up for radiational cooling, when the warmth of the day radiates quickly away from the surface and we chill down quickly. Under this set-up, inland valley locations end up the coldest, so some of the areas that end up the warmest this afternoon will end up the coldest tomorrow morning – classic spring set-up. Thursday, with high pressure still over the region, the light wind will allow for a more prominent sea breeze in the coastal plain, setting up a larger temperature contrast between the coast and interior for high temps. Additionally, with inland areas being the warmest in the afternoon after being the coldest in the morning, we’ll get an example of the large temperature “diurnals” (difference between low temp and high temp) that can occur in the spring. So you see, there can be a lot of weather to talk about even when you have high pressure and fair weather dominating. Moving onward, we’ll see an increase in high and middle clouds later Thursday ahead of a warm front. This front may produce some scattered rain showers across southern NH and perhaps far northern MA at some point Thursday night, and will lead a warmer air mass on a southwesterly air flow into the region on Friday, but of course this air flow is a cooler one for the South Coast, particularly Cape Cod. Additionally, getting the warm southwesterly air flow into all areas for the day is not a complete lock. All it takes is the tiniest wave of low pressure to form on that front just to the north and it gets pulled back, with the help of marine air, southwestward as a back-door cold front. This is a possibility especially Boston northward on Friday, so something to watch for. Looking ahead to the weekend, the next round of unsettled weather is due on Saturday as a cold front sweeps across the region, trailing form low pressure passing to our north. I’m not expecting a wash-out of a day, but as it looks now, I think two rounds of showers will occur, one with a pre-frontal trough, the other with the cold front itself. Timing and details will be fine-tuned as we get closer. Sunday will be a breezy, cooler, dry day with a sun/cloud mix behind the front.
TODAY: Limited sun at first Cape Cod / filtered sun at first elsewhere. Brighter sun all areas midday on. Highs 57-64 I-95 eastward / south of I-90, 65-72 elsewhere. Wind NW up to 10 MPH with light coastal sea breezes.
TONIGHT: Mostly clear. Lows 33-40 interior locations, coldest in valley areas, and 40-47 coastal plain, warmest in Boston. Wind calm.
THURSDAY: Sunny morning. Partly cloudy afternoon. Highs 57-64, 65-72 inland, but a more notable temperature fall in coastal areas after midday. Wind variable up to 10 MPH with coastal sea breezes up to 15 MPH.
THURSDAY NIGHT: Variably cloudy with brief light rain possible northern MA and southern NH. Lows 45-52 evening, with a slow rise overnight. Wind SE shifting to SW up to 10 MPH.
FRIDAY: Sun/cloud mix. Highs ranging from 55-62 South Coast to 68-75 inland areas west of the I-95 belt. Wind SW 5-15 MPH.
FRIDAY NIGHT: Variably cloudy. Patchy fog. Lows 50-57. Wind SW 5-15 MPH.
SATURDAY: Variably cloudy with rain showers likely. Highs 60-67, cooler Cape Cod. Wind SW 10-20 MPH, shifting to W from west to east by late-day.
SATURDAY NIGHT: Clearing. Lows 45-52. Wind W 5-15 MPH.
SUNDAY: Sun/cloud mix. Highs 58-65. Wind NW 10-20 MPH.
DAYS 6-10 (APRIL 28 – MAY 2)
Dry with a warming trend early in the period. A more unsettled pattern arrives to end April and start May with some wet weather possible.
DAYS 11-15 (MAY 3-7)
Continued indications of blocking evolving with increase unsettled weather chances and variable temperatures with an overall cooling trend.