Wednesday May 19 2021 Forecast (7:31AM)

38 Comments

DAYS 1-5 (MAY 19-23)

Is there ever such thing as a “high confidence forecast” beyond a few days? It’s rare, if it exists at all. Yes you can look at a pattern and know with some confidence that there may be a storm threat, or some stretch of heat or cold, or various things like that, but as far as getting specific beyond a few days, it really can’t be done beyond “educated guessing”. I’m not going to cite anyone else’s forecasts but my own here. A few days ago I felt fairly confident that a place like Boston would fail to reach 80 yesterday, but have no problem today. Well, it turns out that they were one of the warm spots at 84 yesterday, but today if they even get close to 80 I’ll be wholly surprised. What I have talked about for days now is not to count out the influence of the ocean, and while it did not show itself to have much influence on Boston’s temperature yesterday, it’s very likely to do so the next 2 days. And this won’t be true for just Boston, but for all coastal areas, and even inland for some distance, as we are going to have a set-up with high pressure at the surface and aloft, but with the highest of the surface pressure to the northeast of New England, that opens the door for easy-developing onshore wind, since it’s already getting a bit of a push from air that naturally wants to flow away from high pressure. This will be another lesson for the reader / listener not to get numbers mentioned a few days in advance too solid in their minds, because there is always the chance that adjustments will be needed. Or at the very least one needs to keep in mind what the seasonal potentials are. Here in New England, especially near the coast, that should be easy to do in the spring. Yesterday, somebody asked me which day would be sunniest this week. My initial answer was Wednesday (today), although now it looks like Thursday ends up sunnier. Yes, even the sky condition can be that difficult to pin down exactly 24 hours in advance. What I did warn them about though was to expect the beach to be significantly cooler than their inland home if they were planning a visit to the coast. And we won’t even talk about the water temperature… 😉 Anyway, the same ridge of high pressure that is giving us this classic spring weather in New England this midweek will contribute to a slightly different kind of classic late spring weather late this week. With the upper level ridge axis to our west, and a northwesterly air flow aloft, this allows disturbances to drop out of Canada and come across the region. We’ll see two of them, one late Friday into Saturday, and another one on Sunday. While it remains fairly dry both dew point wise and in terms of rain threat into Friday (there may be a few showers around later Friday), we will see the humidity uptick itself to a somewhat noticeable 60-ish during the course of the weekend, and a few opportunities for passing showers on Saturday with the first disturbance. The second disturbance on Sunday will feature a fairly strong surface cold front dropping southward out of Canada, and this may trigger some thunderstorm activity along with the shower threat at some point that day or evening. We’ll have to fine-tune the timing and magnitude of that threat as we get closer to it.

TODAY: Partly cloudy. Highs 68-75 coast, 76-83 inland, but turning cooler from east to west midday on. Wind N under 10 MPH shifting to E 5-15 MPH.

TONIGHT: Mostly clear. Lows 50-57. Wind E to variable under 10 MPH.

THURSDAY: Mostly sunny. Highs 69-76 coast, 77-84 inland, but turning cooler at least coastal areas afternoon. Wind variable to SE 5-15 MPH.

THURSDAY NIGHT: Mostly clear. Lows 55-62. Wind SE to S up to 10 MPH.

FRIDAY: Partly sunny. Chance of a shower late in the day. Highs 68-75 South Coast, 76-83 elsewhere. Wind S 5-15 MPH.

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

SATURDAY: Variably cloudy. Possible showers. More humid with dew point approaching 60. Highs 65-72, coolest coast. Wind variable 5-15 MPH.

SATURDAY NIGHT: Mostly cloudy. Chance of showers. Areas of fog forming. Lows 55-62. Dew point middle to upper 50s. Wind variable up to 10 MPH.

SUNDAY: Partly sunny. Chance of showers and thunderstorms, especially afternoon/evening. Moderately humid with dew point lower 60s. Highs 75-82. Wind SW 5-15 MPH, higher gusts, may shift to NW late.

DAYS 6-10 (MAY 24-28)

An area of high pressure from eastern Canada brings dry and cool weather May 24. Milder weather returns after this with a mostly dry pattern into the middle of next week and maybe a shower threat by the end of the period.

DAYS 11-15 (MAY 29 – JUNE 2)

Unsettled weather potential for part of the May 29-31 Memorial Day Weekend and maybe again by the end of the period as our region will likely be near a boundary between air masses.

38 thoughts on “Wednesday May 19 2021 Forecast (7:31AM)”

  1. Good morning and thank you TK.
    It will be interesting to see how the East wind affects the temperature here in JP.
    I am thinking we make 75 -80 before falling back to lower 70s upper 60s. We shall see.

    2. I think eastern Marshfield might be at its mildest for today. We have a northerly breeze, but for our section of town, that´s right off the ocean. Its very nice out, you can feel a difference from yesterday already.

  5. Logan is up to 72 with a NE wind at 10 mph.
    East to NE wind all over Eastern Ma.

    We’re up to 69 here in JP where it appears to be struggling
    to rise. Will keep a close eye on it.

  6. Thank you, TK.

    Although it wasn’t humid yesterday (and there was a northwest wind) it was the first hazy day of the season. We’ve had a lot of bright blue sky days this spring. Yesterday had more of a summer look: lighter, milkier blue.

  9. Logan holding at 70. This makes 7 days in a row where Logan
    had a high temperature of 70 or above. Pretty nice stretch of weather for sure. Last night Harvey said May is running
    2.8 degrees above average. Very nice indeed considering what it could be. 🙂

    We are up to 75 here in JP. Not sure we’ll reach 80, but I am NOT complaining. Absolutely delightful today!

  10. Yesterday was Logan’s 1st 80-degree reading of the season. This is 2 weeks later than the long term average (May 4), but earlier than last year (May 22) and 2019 (May 20).

    Since 1872, Boston has failed to reach 80 before the end of May 9 times – the last time it happened was in 1997.

    The 1st 85-degree reading happens on average in May 18.. Last year it was June 4, and in 2019 it was May 20.

    The 1st 90-degree reading happens on average on June 8. Last year it was June 20, and in 2019 it was July 5.

    2. If I had to wager, I’ll go with Logan hitting 90 later than average in 2021.

          1. Just to add a little on 90-degree days:

            The latest that Boston ever had it’s 1st 90-degree day of the year was 1906, when it occurred on August 6.

            Boston has never had year without hitting 90. They had just 1 90-degree day in 1888 (june 23) and 2 in 1904 (June 25 and 26) and 1992 (May 23 and August 11)

            1. Awesome info! I remember the 1906 stat, but if I ever knew the others, I’d forgotten.

              1. I recall June 18, 1993. It was a double day. My birthday and a horse show. It was in 90s and a struggle to keep both pony and his young rider cool

  12. Sea Breeze days like this I can handle.

    It is 76 Here in JP, some 5 or 6 miles from Logan.

    Logan is sitting at 68.

      1. Here in Dorchester, where sea breezes can be brutal, feels quite comfortable. Hardly noticeable really.

  16. SAK, thank you very much for the temperature information.

    I assume the information does not include data from the summer of 1816, after the eruption of Mt. Tambora.

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