Tuesday May 18 2021 Forecast (7:15AM)

DAYS 1-5 (MAY 18-22)

A disturbance will cross the region from northwest to southeast today bringing some cloudiness especially this morning, and allowing for the development of a few isolated showers with the sun’s heating this afternoon. Upper level high pressure builds over the region with mainly dry weather at midweek. Look for sea breeze development both today and Wednesday. The wind may end up turning onshore more regionally during Thursday (timing uncertain) as a weak back door cold front moves into the region. There’s a little more uncertainty in the forecast for late week (Friday and Saturday) as the axis of the ridge is far enough west to allow a reinforcing back-door front into the region from the northeast and a couple disturbances to come through the region with chances for showers. There will be some fine-tuning needed on that part of the forecast.

TODAY: Variably cloudy. Isolated afternoon showers. Highs 73-80, coolest coast. Wind variable up to 10 MPH with coastal sea breezes developing.

TONIGHT: Clearing. Lows 50-57. Wind variable under 10 MPH.

WEDNESDAY: Mostly sunny. Highs 80-87 except 70s in some coastal locations and 60s on parts of Cape Cod and the Islands. Wind variable up to 10 MPH with coastal sea breezes developing.

WEDNESDAY NIGHT: Partly cloudy. Lows 55-62. Wind variable under 10 MPH.

THURSDAY: Partly sunny. Chance of a shower late in the day. Highs 77-84 but may turn considerably cooler at least in eastern coastal areas by late. Wind SW to variable 5-15 MPH possibly shifting to NE by later in the day especially in southeastern NH and eastern MA.

THURSDAY NIGHT: Variably cloudy. Possible showers. Lows 55-62. Wind variable to NE 5-15 MPH.

FRIDAY: Variably cloudy. Possible showers. Highs 63-70, coolest coast. Wind NE 5-15 MPH.

FRIDAY NIGHT: Variably cloudy. Possible showers. Lows 53-60. Wind variable 5-15 MPH.

SATURDAY: Variably cloudy. Possible showers. Highs 65-72, coolest coast. Wind variable 5-15 MPH.

DAYS 6-10 (MAY 23-27)

Frontal boundary likely in the region with possible showers and thunderstorms as higher humidity May 23. Front pushes to the south with cooler weather and potential rain due to a wave of low pressure May 24. Drier/cooler weather follows from high pressure in eastern Canada mid period then milder with possible unsettled weather again later in the period as the next disturbance approaches / arrives.

DAYS 11-15 (MAY 28 – JUNE 1)

Trends on medium range guidance say we sit in between warm high pressure to the south and cool high pressure in Canada and this leaves us vulnerable to shower activity and variable temperatures. Not a very high confidence forecast with re-evaluation to come.

Monday May 17 2021 Forecast (7:43AM)

DAYS 1-5 (MAY 17-21)

Deeper into May we go, and as we start this new week off we’ll be talking a little bit of spring and a little bit of summer preview. First, we have the continuation of the active pattern today, this time a weak cold frontal boundary moving down from the north which will help trigger more cloud development and a few showers and possible thunderstorms, somewhat similar to what we saw yesterday. So it will start bright and sunny across most areas (except a few cloud patches) but we’ll see lots more clouds pop as the day goes on. Some areas will get wet, and many will not, but those that do will not see it linger very long. And yes once gain a few locations may see rainbows later in the day if the timing and placement of a departing rain shower or thunderstorm is just right. Things will settle down tonight. On Tuesday, we transition toward a preview of summer, but we won’t be fully there yet. It’s still going to be a little bit chilly aloft, so we’ll see some clouds pop again, and again some of them may build enough to produce a shower or thunderstorm in some locations, so if you do have plans to be outside, keep an eye on the sky (and the radar if you can), especially during the afternoon. Wednesday, high pressure aloft and a surface high centered to the west will combine to produce the sunniest and warmest day of this week. Areas away from the direct influence of the ocean should easily break 80 for a high temp, but with the gradient wind not all that strong, there is always the chance for some sea breeze development near the coast. While the upper level pattern says “warm” for later this week, the high pressure ridge being centered far enough west is an unlocked door for cooler air to slip down from the Canadian Maritimes via the Gulf of Maine, and by Thursday we’ll have to watch for the potential arrival of a back-door cold front. While at least inland locations should warm nicely, that warming may be thwarted closer to the eastern coastal areas, and then depending on how far southwest that expected boundary pushes will determine how cool the remainder of the region trends through Friday. There should also be some cloudiness with this air mass change, but any rainfall should be limited to just a few showers, if that. Back-door fronts don’t often produce much precipitation unless they are combined with tropical moisture, which we won’t have, or a stronger disturbance coming along in the jet stream, which we also won’t have. Keep in mind that there is still the possibility that a back-door front never quite does make it all the way into or across the region, but given past history, I’ll lean toward it doing so for now and adjust the forecast if necessary going forward this week…

TODAY: Lots of sun to start then lots of clouds popping up during the day. Isolated to scattered showers and thunderstorms developing this afternoon. Highs 69-76, coolest near the coast. Wind variable to N up to 10 MPH with some coastal sea breezes.

TONIGHT: Lots of clouds and a lingering shower possible early, then clearing. Lows 47-54. Wind N to variable under 10 MPH.

TUESDAY: Sunny start, then a sun/cloud mix with isolated afternoon showers and thunderstorms possible. Highs 72-79, coolest in coastal areas. Wind variable up to 10 MPH with coastal sea breezes developing.

TUESDAY NIGHT: Clearing. Lows 50-57. Wind variable under 10 MPH.

WEDNESDAY: Mostly sunny. Highs 80-87 except 70s in some coastal locations and 60s on parts of Cape Cod and the Islands. Wind variable up to 10 MPH with coastal sea breezes developing.

WEDNESDAY NIGHT: Partly cloudy. Lows 55-62. Wind variable under 10 MPH.

THURSDAY: Partly sunny. Chance of a shower late in the day. Highs 77-84 but may turn considerably cooler at least in eastern coastal areas by late. Wind SW to variable 5-15 MPH possibly shifting to NE by later in the day especially in southeastern NH and eastern MA.

THURSDAY NIGHT: Variably cloudy. Possible showers. Lows 55-62. Wind variable to NE 5-15 MPH.

FRIDAY: Sun/cloud mix. Highs 63-70, coolest coast. Wind NE 5-15 MPH.

DAYS 6-10 (MAY 22-26)

Frontal boundary hanging in the region May 22 means clouds and possible showers, then this front should push back to the north allowing a warmer May 23 but still with a chance of showers and thunderstorms as a cold front approaches. There’s a chance of some wet weather about May 24 if this front slows down and allows a wave of low pressure to move across the region. Drier weather should be back in place by later in the period.

DAYS 11-15 (MAY 27-31)

Overall pattern looks dry and mild, but ocean’s influence likely keeps coastal areas cooler some of these days.

Sunday May 16 2021 Forecast (8:09AM)

DAYS 1-5 (MAY 16-20)

A weak trough of low pressure will cross the region during the day today, and while the majority of the day and possibly all of the day will be rain-free in most of the region, there will be some varying amounts of cloudiness and some scattered shower activity developing with the passage of the disturbance. A cold front will cross the region from north to south Monday, another focus for some shower activity, and possibly even a thunderstorm. This leads to a stretch of fair weather starting Tuesday through midweek, along with a warming trend with high pressure building over the region both at the surface and aloft. However this opens the door to sea breezes, and by the end of the period we will have to keep an eye out for one of those can-be-sneaky back-door cold fronts that are often not picked out by medium range guidance.

TODAY: Variably cloudy. Isolated to scattered showers and possible thunderstorms midday-afternoon. Highs 70-77 except cooler in some coastal areas. Wind SW up to 10 MPH except light sea breezes developing in coastal locations.

TONIGHT: Variably cloudy. Lows 48-55. Wind W under 10 MPH.

MONDAY: Variably cloudy. Scattered afternoon showers and thunderstorms. Highs 66-73 except cooler in some coastal areas. Wind N up to 10 MPH with coastal sea breezes.

MONDAY NIGHT: Partly cloudy. Lows 46-53. Wind variable under 10 MPH.

TUESDAY: Mostly sunny. Highs 65-72 coast, 73-80 inland. Wind S up to 10 MPH with coastal sea breezes.

TUESDAY NIGHT: Mostly clear. Lows 50-57. Wind SW under 10 MPH.

WEDNESDAY: Mostly sunny. Highs 78-85 except 70-77 South Coast and 63-70 Cape Cod. Wind SW 5-15 MPH.

WEDNESDAY NIGHT: Mostly clear. Lows 53-60. Wind SW under 10 MPH.

THURSDAY: Partly cloudy. Highs 77-84 except cooler in coastal areas and possibly cooler all areas later in the day. Wind SW to variable 5-15 MPH may turn NE later in the day.

DAYS 6-10 (MAY 21-25)

High pressure aloft likely remains dominant early in the period but more high pressure at the surface to the north likely means cooler than previous days. Watch for low pressure from the west which may bring a shot at wet weather later in the period (May 24-25).

DAYS 11-15 (MAY 26-30)

Overall pattern looks dry and mild, but ocean’s influence likely keeps coastal areas cooler some of these days.

Saturday May 15 2021 Forecast (7:45AM)

DAYS 1-5 (MAY 15-19)

It’s time to make a few adjustments to the forecast, and they are generally good ones if you want more days with nice weather. Not that I had a forecast of bad weather every day – far from that. But today the shower threat comes out of the outlook as the atmosphere looks stable enough to prevent them. We’ll just see some cloud patches and otherwise lots of sun, with once again warmest weather away from the immediate shoreline. Sunday and Monday will be the days that feature the chance of pop up showers, and even a few thunderstorms, as we’ll have a couple disturbances drifting across the region with colder air aloft and a more unstable atmosphere. But neither of these days will be “rainy”. You will just have to watch for developing and passing showers especially during the afternoon hours each day. Anybody who does experience a shower or thunderstorm can see a briefly heavy downpour, but these will be isolated. When we get to Tuesday and Wednesday, high pressure dominates at the surface and aloft and you can expect fair weather, and that hint we started to see of rather warm weather last week for this period of time will indeed come to be, with many areas not having hit 80 yet doing so by Wednesday. There will be exceptions, of course – probably Cape Cod and the Islands…

TODAY: Sunny to partly cloudy. Highs 73-80 but cooler some coastal areas. Wind variable up to 10 MPH with light sea breezes in coastal locations.

TONIGHT: Clear to partly cloudy. Lows 52-59. Wind S under 10 MPH.

SUNDAY: Partly sunny. Scattered afternoon showers and thunderstorms. Highs 70-77 except cooler in some coastal areas. Wind SW up to 10 MPH except light sea breezes developing in coastal locations.

SUNDAY NIGHT: Partly cloudy. Lows 48-55. Wind W under 10 MPH.

MONDAY: Partly cloudy. Isolated afternoon showers and thunderstorms. Highs 66-73 except cooler in some coastal areas. Wind N up to 10 MPH with coastal sea breezes.

MONDAY NIGHT: Partly cloudy. Lows 46-53. Wind variable under 10 MPH.

TUESDAY: Mostly sunny. Highs 65-72 coast, 73-80 inland. Wind S up to 10 MPH with coastal sea breezes.

TUESDAY NIGHT: Mostly clear. Lows 50-57. Wind SW under 10 MPH.

WEDNESDAY: Mostly sunny. Highs 78-85 except 70-77 South Coast and 63-70 Cape Cod. Wind SW 5-15 MPH.

DAYS 6-10 (MAY 20-24)

While high pressure aloft, centered west of the area, brings generally dry weather early to mid period, the region will be vulnerable to the passage of a back door cold front and influence from high pressure in far eastern Canada, which would cool the region down especially in coastal areas. The transition out of that cool-down toward an attempted warm-up could bring some rainfall by the end of the period.

DAYS 11-15 (MAY 25-29)

Trend back to drier. Any warm up may be thwarted by another cooler air mass from eastern Canada. Too early to really pick out details but the general pattern from the previous period will still be in place as it appears.

Friday May 14 2021 Forecast (7:35AM)

DAYS 1-5 (MAY 14-18)

Yesterday’s diurnal development of cumulus clouds did occur as expected, and the heaviest clouds were along a sea breeze boundary not far from the eastern coastline. Some larger clouds were also seen initially over the hilly terrain of southwestern NH and central MA in the late morning and midday with the help of the hills forcing the air upward. None of the clouds really built up enough for any showers yesterday, and any that did try to produce a few drops did not see them reach the ground due to the dry air in place. Today, we have a similar set-up but with a little more “oomph” available. This means that some of the clouds may pop enough to produce showers. Watch hilly areas and near any sea breeze boundary for the best chance. Also, if these occur late enough in the day, rainbows are possible as any showers exit to the east. Then sun must be below 45 degrees for most to be able to see a rainbow, with the bow being lower to the horizon when the sun is higher and taller rainbows occurring as the sun sinks toward the horizon. Anyway something to watch for! The weekend will be ok – not perfect, but not bad! We will have a couple disturbances coming by with more clouds, but still some sunshine, and both days run risk of seeing a few showers pop up. A frontal boundary and disturbance passing by to the south may bring more cloudiness early next week but any rainfall should stay to the south.

TODAY: Mostly sunny start, then partly sunny midday and afternoon with isolated to scattered afternoon showers. Highs 70-77 but cooler in some coastal areas. Wind NW up to 10 MPH but with some coastal sea breezes.

TONIGHT: Partly cloudy. Lows 48-55. Wind variable up to 10 MPH.

SATURDAY: Partly cloudy. Isolated to scattered afternoon showers. Highs 67-74 except cooler some coastal areas. Wind variable up to 10 MPH with sea breezes.

SATURDAY NIGHT: Partly cloudy. Areas of ground fog forming. Lows 48-55. Wind variable up to 10 MPH.

SUNDAY: Partly sunny. Scattered afternoon showers. Highs 60-67 coast, 68-75 inland. Wind variable up to 10 MPH becoming SE to S.

SUNDAY NIGHT: Partly cloudy with a chance of showers during the evening. Clearing overnight. Lows 46-53. Wind N up to 10 MPH.

MONDAY: Increasing clouds. Highs 60-67, coolest coast. Wind N up to 10 MPH shifting to E.

MONDAY NIGHT: Mostly cloudy. Lows 48-55. Wind E under 10 MPH.

TUESDAY: Mostly cloudy to partly sunny. Highs 62-69, coolest coast. Wind variable to SE up to 10 MPH.

DAYS 6-10 (MAY 19-23)

Trends indicate a mainly dry stretch with high pressure in control with temperatures not too far from seasonal normal.

DAYS 11-15 (MAY 24-28)

A shot of some rainfall early in the period then back to mainly dry weather again. Temperatures variable, but no significant lasting departures from normal expected.

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