DAYS 1-5 (APRIL 24-28)
Today is an unsettled weather day. First, a warm front will send a thick batch of mid level clouds west to east through the region this morning, with areas of light rain, which may take a while to reach ground level due to dry air in place. Eventually these clouds start to thin out but are joined by scattered to broken lower clouds in a south to southwest air flow in the warm sector between the warm front and an approaching cold front, the latter of which will set off a scattered to broken cluster or line of showers and possible embedded thunderstorms from mid through late afternoon, west to east across the region. While some of these may be briefly heavy, they won’t last, and breaks / clearing behind them make the region a candidate for rainbows before the sun goes down. Rainbows or not, what is a certainty is the shot of chilly air that arrives tonight, initially with wind, that will then diminish overnight. This leads to the threat of near to slightly sub-freezing temperatures in normal cold spots. Any early vegetation / plants will be vulnerable to minor freeze damage. While Thursday will be a “below normal” temperature day, high pressure building in will keep the wind in check, and along with that higher angle late April sunshine, it won’t feel too bad out there. Another great day follows on Friday with high pressure in control, but that day will be warmer inland and cooler along the coast as a coastal sea breeze will develop. A quick reminder on the classic sea breeze mechanics: Clear (or mostly clear) sky allowing sun to heat land with a weak pressure gradient in place, so no prevailing wind. The sun-heated land then heats the air near its surface, causing that air to rise, which then has to be replaced, and is done so by the cooler, more dense air from the ocean, which then flows inland to fill the void left by the rising warm air. This is your sea breeze, and will reach its peak while the sun is strongest on Friday, then start to fade as the sun sinks and the sea breeze circulation breaks down. This leads to a fairly calm Friday night under a clear sky, another chilly one. Saturday’s air mass will end up warmer, but we’ll have to overcome a cold start to the morning and we’ll see a fairly significant temperature rise from dawn low temperatures to afternoon high temperatures. Coastal areas once again will be cooler Saturday with an onshore component to the wind, which will be southeast to south ahead of an approaching warm front. That front will send clouds into our region Saturday night that eventually thicken up enough for a light rain threat, but that rain will be limited as again we’ll have plenty of dry air in place. Sunday’s weather will be mild, and while we may have a variable amount of clouds around at times, it looks like we will avoid any rain threat with nothing to trigger the warm and slightly more humid air in place to develop them – so a very nice weekend overall despite a Saturday night interruption, and this is better than it looked like when this time period was in medium range. Another good reason to check updated forecasts as we draw closer to any given day or time period.
TODAY: Clouds thicken this morning with a few periods of light rain likely. Clouds break at times this afternoon for partial sun, but another passing shower and possible thunderstorm can occur during mid to late afternoon. Highs 57-64, coolest South Coast. Wind S 5-15 MPH, shifting to W at day’s end.
TONIGHT: Partly cloudy evening. Clear overnight. Lows 28-35 except 35-42 urban centers / Cape Cod & Islands. Wind W 10-20 MPH early, diminishing.
THURSDAY: Mostly sunny. Highs 48-55. Wind NW 5-15 MPH.
THURSDAY NIGHT: Clear. Lows 30-37, coldest interior valleys. Wind calm.
FRIDAY: Sunny. Highs 55-62, coolest coast. Wind variable up to 10 MPH with developing coastal sea breezes.
FRIDAY NIGHT: Clear. Lows 33-40. Wind variable under 10 MPH.
SATURDAY: Sunny to partly cloudy. Highs 56-63 coast, 63-70 inland. Wind SE-S up to 10 MPH.
SATURDAY NIGHT: Clouding up. A period of light rain likely. Lows 47-54. Wind S up to 10 MPH shifting to SW.
SUNDAY: Variably cloudy. Highs 63-70 most areas except cooler South Coast. Wind SW 5-15 MPH.
DAYS 6-10 (APRIL 29 – MAY 3)
April 29 forecast hinges on the position of a frontal boundary to our north which may drop down as a back-door cold front and cool it down significantly, while inland pop up showers are possible that afternoon. General shower threat April 30 as trough and front swings through west to east. Trend is for mostly fair weather and below to near normal temperatures during the first few days of May, though clouds may be abundant for at least part of that time frame. Not a high confidence outlook there so check updates.
DAYS 11-15 (MAY 4-8)
Low confidence / high uncertainty spring forecast. Doesn’t look too wet though or with much in the way of significant temperature departure from what is typical for this time of year, but there is a lot of uncertainty in details. Much fine-tuning to come.