Tuesday July 27 2021 Forecast (9:17AM)

82 Comments

DAYS 1-5 (JULY 27-31)

Some up and down temperatures and weather as we head through the final 5 days of July, but if you are on vacation this week, overall it’s a pretty decent week, which started out yesterday with smokey sunshine, a bit of heat, but manageable humidity. As high pressure sits offshore today the humidity will up-tick as the temperatures stay quite warm, but a cold front moving this way is set to bring a significant change. If you have outdoor plans, such as the beach, today turns out quite decent as most of the cloud cover and the shower / t-storm threat holds off until the end of the day and especially this evening. The thicker plume of wildfire smoke (from Canada and the western US) has moved on and we are left with some thinner smoke today, and then the plume will be pushed south of the region by tomorrow. We may see it come back marginally at times later this week, but not to the extent we had it yesterday. We will probably see two rounds of showers and thunderstorms, one with a pre-frontal trough, with activity concentrated mostly north of I-90, but some still possible to the south, and another round with the actual cold front, a little more spread out along the boundary as showers with embedded thunderstorms a little bit later in the evening. If there are going to be severe thunderstorms, they will most likely occur with the first batch, favoring areas north of I-90 in the 6PM to 9PM window, with damaging wind gusts as the main threat. The cold front will still be crossing southeastern MA and RI when we get to Wednesday morning so the day may start with a lot of clouds and a few showers around, especially in those locations, but during the day we end up with a fair amount of sunshine taking over on a drier and cooler north to northeast air flow, as high pressure moves toward the region from Canada. This high slips right across the area Wednesday night, which will be tranquil with a lighter wind and pleasantly cool mid summer air, but watch for some fog to form over inland locations at lower elevations where the temperature can easily fall to match the dew point, even with the dew points being down somewhat. I’ve been talking about Thursday as a day with an unsettled weather threat, and that is still the case, but as it stands now the warm front that comes along first doesn’t look like it will have a lot of support for activity, so just expecting a varying amount of cloudiness but a generally rain-free daytime, with most of the shower and potential thunderstorm activity holding off until evening or night with an approaching and passing cold front. The humidity will come back up a bit during Thursday as the warm front leads an air mass into the region from the southwest but behind the cold front comes another shot of drier air for Friday. With some upper level energy set to cross the region on Friday I can’t rule out some pop up showers or thunderstorms, but they should be generally isolated. A small area of high pressure is expected to bring nice weather to the region for the final day of July on Saturday.

TODAY: Lots of sun filtered by smoke into afternoon giving way to more clouds later in the day. A shower or thunderstorm possible mainly southwestern NH and central MA by late afternoon. Highs 81-88 except cooler South Coast especially Cape Cod. Dew point rising through 60s. Wind SW 5-15 MPH.

TONIGHT: Mostly cloudy. A couple rounds of showers and thunderstorms, most widespread north of I-90 and more scattered to the south. Patchy fog overnight. Lows 62-69. Dew point falling slowly through 60s. Wind SW to variable 5-15 MPH shifting to N overnight.

WEDNESDAY: Lots of clouds and a chance of showers southeastern MA and RI until mid morning, otherwise partly to mostly sunny. Highs 72-79. Dew point near 60 then falling through 50s. Wind N to NE 5-15 MPH.

WEDNESDAY NIGHT: Clear evening. Partly cloudy overnight. Patchy ground fog forming late. Lows 55-62. Dew point near 50 then rising through 50s. Wind variable under 10 MPH.

THURSDAY: Variably cloudy. Only a slight chance of a passing shower. Highs 76-83. Dew point rising into 60s. Wind S 5-15 MPH.

THURSDAY NIGHT: Mostly cloudy. Chance of showers/thunderstorms evening. Patchy fog. Lows 60-67. Dew point falling to near 60. Wind W 5-15 MPH shifting to N.

FRIDAY: Partly cloudy. Isolated afternoon showers and thunderstorms possible. Highs 76-83. Dew point near 60. Wind NW 5-15 MPH.

FRIDAY NIGHT: Partly cloudy with a chance of showers early, then clearing. Patchy ground fog forming late. Lows 56-63. Dew point falling to middle 50s. Wind W under 10 MPH.

SATURDAY: Sunny. Highs 77-84. Dew point upper 50s. Wind W 5-15 MPH.

DAYS 6-10 (AUGUST 1-5)

August arrives, typically the month with perhaps the weakest upper level steering on average, and we’ll start it with a continuation of but probably also a weakening of the west to northwest air flow driving the pattern. This does allow seasonal humidity to spike ahead of drier intrusions from Canada. Current timing indicates these disturbances will be passing by about every other day, so we could see shower and thunderstorm threats about August 1, 3, and 5, but with most of the 5-day period being rain-free. Temperatures would be variable but not feature major swings, and would average out to fairly close to normal in this pattern. As always, day-to-day details can’t be determined this far in advance.

DAYS 11-15 (AUGUST 6-10)

A weakening of the westerly flow aloft and more high pressure off the US East Coast allows warmth and humidity to become a little more dominant. There will still be a few opportunities for showers and thunderstorms, and we have to watch the boundary between the warm/humid air and cooler/dry air in Canada, which for now I think will be mostly to our north. Should it end up further south, we look at going into a wetter pattern, but not expecting this to set up like that at this time.

82 thoughts on “Tuesday July 27 2021 Forecast (9:17AM)”

  1. Good morning and thank you TK.

    Here is a repost of something I posted a short time ago:

    JpDave
    JULY 27, 2021 AT 9:15 AM
    SPC has upgraded our area to slight risk today.

    https://www.spc.noaa.gov/public/cwa/images/BOX_swody1.png

    REPLY
    JpDave
    JULY 27, 2021 AT 9:16 AM
    …NY/New England…
    Surface-based thunderstorms are expected to develop by midday over
    parts of western NY and/or adjoining ON, along and south of the
    front. Activity should increase in coverage and move mostly
    eastward across central/eastern portions of NY and south-central New
    England through the afternoon, its movement aligned with an
    instability gradient and boundary-layer moist axis. Damaging to
    locally severe wind gusts will be the main concern. Confidence has
    increased that enough large-scale lift (related to the MCV) and
    diurnal low-level destabilization will occur to support maintenance
    of the threat eastward into New England. The 15% wind area has been
    extended accordingly

    REPLY

  3. Thank you, TK. Looking for a spot to pit down lawn treatment. Seems tomorrow after rain stops looks good

    Meanwhile, what a morning. Lower humidity is noticeable today. So far blue sky here not yet filtered by smoke.

    1. Per visible satellite looks like most of the smoke is in NNE at this point. I can see some in my sky but definitely hazier look to the north and a bit bluer to the south.

  7. If you are like me and not a fan of the heat you are rooting for the CPC 6-10 and 8-14 day outlook to be right as it has below normal temps for New England.

    1. I’ll join your cheering party. I don’t mind heat but can stay outside a whole lot longer when it isn’t HHH

    2. I think their 6-10 will verify. The 8-14 may need to be adjusted up a little bit, but that will depend on what happens with high pressure in the western Atlantic.

    1. It’ll be heading back up but it’s only a relatively minor factor. The convection today will develop west of here and move in. At that time other dynamics are really what will be in control. I don’t think the city will end up seeing all that much anyway.

  13. I love Tim Kelley. He’s focusing on tomatoes and the fact that the air quality alert expires at noon rather than the anchors’ insistence that we’re in dire straits with wildfire smoke. 😉

    Keeping it real Tim, keeping it real!

  14. Thanks TK.

    I do have to totally disagree with your opening statement above regarding yesterday, “bit of heat, but manageable humidity”.

    Comfort-wise, yesterday was AWFUL!!! on both counts. At least it didn’t rain. 😉

    1. Upper 50s to lower 60s dew points? Awful? Hardly…
      I was outside all day yesterday – it was quite nice.

      Most of today will be rain-free.
      Most of this week will be rain-free.
      We’re in a much different pattern now.

      This pattern also lacks very high humidity except for very brief periods of time.

      1. Those dewpoints felt more like upper 60s to lower 70s to me, if anything. I left work then to the grocery store then my medical appointment then home. I never felt comfortable at all. Sweating the entire time I was outside. When I got home I turned my fan on full blast!!!

        I hadn’t seen such hazy/smoky skies since I was a kid. Maybe the lack of breeze made it feel worse for me.

        1. The smoke-fest we had in the mid 2000s was worse than this one. The sun disappeared in an otherwise clear sky before 5PM in early July a couple of times.

          And those dew points were definitely not close to oppressive levels. The entire region was in the upper 50s to lower 60s yesterday with a slight downward trend as they day went on.

          1. I sure didn’t think yesterday was close to oppressive. We were in higher 60s all day but the lower 60s (63 now) to me are noticeably different. I don’t recall smoke in mid 2000s so this is worst I remember. In ten years, I won’t remember this Either so it would be worst remember then also 🙂 🙂 🙂

            If I don’t recall, I’m careful to word comments carefully 😉

            1. I guess even though it felt “awful” to me, in reality it definitely wasn’t. When dewpoints drop even a little, I usually notice right away. I don’t understand why my body didn’t react to that and felt totally opposite. Oh well. 🙂

  15. We´re camping Aug 3rd thru 10 in south coastal Mass without electricity (no A/C 🙁 )

    I can see a projected warmer, different pattern on today´s 00z and 12z GFS just in time for that week.

    Its a guarantee it will be either hot, humid or both during this time period. 🙂 🙂 🙂 🙂

  17. Boston Harbor buoy water temp at 72.9F with a light SE wind. Logan also with a light seabreeze.

  18. I wonder if we need to watch an old washed out front in the SE about a week from now …….. then, as the pattern seems to transition to flow up the east coast …….. could something stir off the SE US coast and then have flow that might send it our way ?????

    1. WOW !! If that day 8-10 (500 mb) flow on today´s 12z EURO ever verifies, the Eastern US coastline better hope nothing comes to life in the tropical Atlantic between now and then.

  20. Thanks TK!

    Enjoy the (mostly) lower humidity pattern while it lasts. As the western Atlantic high builds back in, it continues to look to me like we’ll revert to a warm and more humid pattern, likely for much of August. No threats from the tropics that I can tell for the next couple weeks at least, but even without that the pattern may again become more supportive of excessive rainfall heading towards 8/5 and beyond…

      2. It would be very unlikely to pull off two record or near record wet months in a row. But it will probably be the type of pattern, like we saw in much of July, capable of producing multiple heavy rain/flash flood events. I think on the whole though, it will be a little more progressive than what we saw in July, and that we’ll still get occasional relief from cold fronts, like TK has been talking about.

        In short, it won’t be anything unusual for summer, but will probably bias more towards the humid side after this drier interlude.

  21. Sunday is August 1st and when that happens to me it’s five and half weeks left of a weather pattern that could deliver sustained heat and humidity. Once we get past September 10th the heat and humidity don’t have the staying power just like when March 1st hits the cold doesn’t have the staying power.
    WxWatcher you seem to be on the same page as meteorologist Steve DiMartino

    https://twitter.com/nynjpaweather/status/1420097158976622596

    1. It’s something we’ll have to keep an eye on. Any time the western Atlantic high strengthens, we have to be on alert. As I’ve been talking about for weeks, there’s still a seemingly never ending tendency for ridging in the West, even now. It’s shifted east just enough, combined with (more importantly) the breakdown of the western Atlantic high, to open the door for this overall drier interlude. But shift it back west just a little with the Atlantic high building in, and you again set up the “moisture funnel” effect over the East Coast, since there will remain troughing downstream of the Western ridge, near the Great Lakes.

    1. Tough call, but I don’t see that activity falling apart as it moves east. Seems to be coming through early enough to not totally lose the daytime heating. I’d say good chance for a storm over most of eastern New England in the 7-9PM range, maybe weakening right towards the coast.

          1. Thank you, mama. Front one may slip north of me. Maybe one behind it. Or will it’s power be zapped.

  23. I don´t have a great deal of experience reading wind velocities on a dopplar radar.

    With that said, I think the dopplar radar I am looking at is showing 50-60 mph winds not too far west of Shrewsbury and if the storms maintain intensity, then on a line later for Marlborough, Framingham and Needham.

      1. This (the gusty winds) would be lined up for Boston and its western and southern suburbs in perhaps an hour.

        The next line of storms may be lined up for Sutton. It might be interesting to see what the outflow boundaries from the leading line do to the second line.

  24. Indeed, JJ, while we’re in what is on average the warmest 7 to 10 day period of the year, summer’s grip will start to loosen within 5 or 6 weeks. It can still get warm (even hot) in mid to late September. But, like the cold in its counterpart, March, September heat generally lacks staying power.

    About 4 weeks until some leaves start to turn in Aroostook County, Maine.

    1. I am chuckling while typing this …………..

      I will remember to post next January 27th about winter´s eventual demise 🙂 🙂 🙂 🙂 🙂 🙂 🙂 🙂 🙂 🙂 🙂 🙂 🙂 🙂 🙂

    1. yup, ch 5 interactive radar shows on that leading line, the thunderstorms have dropped a bit SE and built back a bit on the SW side of the line.

      You should have very heavy rain quite soon.

  28. Haha. My eight year old grand just said this is a boring thunder storm. We only got to count once to see how far away the storm is

  29. Windy, thunder, massive lightning strike just now quite close to my building, very heavy rain – 1921 record is possible by the end of the month, perhaps.

  33. Heavy rain has subsided, but it’s still raining. Thunder is now more distant. Apparently there’s enough rain in the forecast to postpone the Red Sox game.

    1. Looking at that, it actually looks to me like we are looking at a cross section view of the shelf cloud & gust front, rather powerful, stirring up the water. Doesn’t look like rotation but we’d need a clearer view to be certain. Great capture either way!

          1. Yes. Gustnado is very possible. You can get turbulent funnels / rotation on those gust fronts that are not true tornadic development (wrong side of storm) but can spin. Wonder if any other video exists of this.

  36. WxW thank you for your thoughts today!

    I’d also like to give kudos to SPC & NWS Boston for good forecasts on this activity today.

    On a weather page I belong to there were people complaining that a watch wasn’t needed, simply because the storms didn’t hit their locations. I try to help them understand more about the process of outlooks, watches, warnings, etc, but it seems to me they are not interested in learning, only complaining. Oh well.

    Great job by the professionals today. 🙂

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