Tuesday September 29 2020 Forecast (7:48AM)

56 Comments

DAYS 1-5 (SEPTEMBER 29 – OCTOBER 3)

Discussion…

Things are on track, forecast-wise, it seems. We’re in the middle of a 3-day unsettled and humid stretch, and while we did not see a whole lot of shower activity yesterday, and won’t again today, I cannot rule out passing showers at times in a few areas later today. But our main window of opportunities for the most widespread and significant showers will be from about midnight tonight to noon Wednesday, as a wave of low pressure pulls a cold front eastward trough the region. From tonight through Wednesday morning we’ll also have a period of moderate to strong wind gusts which could result in local tree damage with some isolated power outages. While we remain on the eastern side of an upper level trough through the end of this week we will remain vulnerable to additional unsettled weather, and my target date of October 2 for the next round of unsettled weather remains a go, with a chance of some rainfall on Friday, mainly during the afternoon based on current timing. This should be long gone so that the start of the weekend will feature dry weather. The first 3 days of October (Thursday-Saturday) will also feature a cooling trend as the mild and muggy air we have now will be replaced with a Canadian airmass arriving indirectly via the Great Lakes and Midwest.

Details…

TODAY: Low clouds break for sun into midday then more clouds at times during the afternoon with a risk of a passing shower, but mainly rain-free. Highs 73-80. Dew point above 60. Wind increasing to S 10-20 MPH.

TONIGHT: Mostly cloudy. Areas of fog evening. Isolated showers evening. Numerous showers overnight, including a slight risk of thunderstorms. Lows 61-68. Dew point 60+. Wind S 10-20 MPH, gusts 25-40 MPH.

WEDNESDAY: Cloudy with widespread showers and a slight chance of thunderstorms morning, maybe lingering to early afternoon eastern coastal areas. Clearing follows and the day ends sunny. Highs 70-77. Dew point starts above 60 but falls to the 50s by day’s end. Wind S 15-25 MPH with gusts 30-45 MPH morning. SW 10-20 MPH with a few higher gusts afternoon.

WEDNESDAY NIGHT: Clear. Lows 56-63. Wind SW to W 5-15 MPH.

THURSDAY: Partly sunny. Highs 67-74. Wind W 5-15 MPH.

THURSDAY NIGHT: Variably cloudy. Lows 50-57. Wind variable up to 10 MPH.

FRIDAY: Mostly cloudy. Chance of rain or showers, favoring the afternoon. Highs 62-69. Wind variable 5-15 MPH.

FRIDAY NIGHT: Mostly cloudy with a chance of rain evening. Clearing but patchy fog overnight. Lows 53-60. Wind variable up to 10 MPH.

SATURDAY: Sun and passing clouds. Highs 59-66. Wind NW 5-15 MPH.

DAYS 6-10 (OCTOBER 4-8)

A wave of low pressure may bring some additional unsettled weather with a rain or shower chance later October 4 to early October 5. A cold front from passing low pressure to the north brings a shower risk October 7. Temperatures variable, but a sharper cool shot is possible by October 8.

DAYS 11-15 (OCTOBER 9-13)

A shot of cooler air to start this period followed by a warming trend again. Generally dry weather with just minor shower risk around October 10-11.

56 thoughts on “Tuesday September 29 2020 Forecast (7:48AM)”

  1. Good morning and thank you TK.

    Latetst 3KM NAM and HRRR both showing wind gusts to 44 Knots in Boston, 44 knots = 50.6 mph.

  3. Tk how strong do you think the wind gets at home . We have some big Halloween displays out including a new addition 12’ high Skelton which I think is secure but I told my son about the upcoming winds .

  5. Thanks TK.

    For rainfall through tomorrow, I’ll go with a general 0.75-1.25″ for most. Some locally higher totals in the 1.5-2″ range are possible. Obviously not a drought buster, but much needed especially for short term relief.

    The wind potential looks a little more significant this morning. NWS Boston has gone with a Wind Advisory for most of the area, a good call IMO. Some 40-50mph gusts are likely, with a few 50-60mph possible especially in any heavier convective cells. Pretty solid storm system, our first of the season.

  7. Looking at the dew-points along the east coast, I´m thinking there´s a few hour window in eastern Mass, ahead of the cold front and east of the storm track, where the dew-points will rise to or just above 70F.

      1. Agreed ! We´ll probably get rain from convective showers that will unfortunately, mix some of the impressive low level jet down though.

  8. 12Z 3KM NAM only has 0.53 inch for Boston.
    Regular NAM has 0.62
    HRRR has 0.49

    Helpful, but NOT enough. 1-2 inches would be much better,
    so I hope WxWatcher is correct.

      1. How about the nested NAM? That and the HRRR agree, so either they are both garbage or the HRRR stumbled onto
        an acorn and made a good forecast for a change.

        1. Just because they agree on 1 or 2 parameters doesn’t mean that both are the same. To be honest, all the models are garbage lately, but the HRRR has been garbage for a long time and never been fixed. I posted last winter about the significant issues it was having, especially with temperatures. Until v4.0 comes out (currently scheduled for “late fall”), I would avoid that model completely.

          1. Yup, understand that. Good to know.
            The nested NAM is fairly decent, isn’t it?

            How would you rank the models? Curious.

            Many thanks

            1. Lately? Their all like the Red Sox. Don’t look at them.

              For really short-range guidance, I have used the LAMP MOS for a very long time in some of my forecasts and find it to be pretty good.

              https://www.weather.gov/mdl/lamp_home

              It’s a version of MOS (based off of the GFS) that gives hourly output out to 25 or 38 hours (you pick which version you want), and is updated every 15 minutes.

    1. Thanks Tk I appreciate the response. I’ve warned him to secure . He also built a big haunted house outside as well out of plywood with cut windows & all . He’s 16 & absolutely loves decorating

      1. Are you having a party? In my neighborhood houses with lots of outdoor decorations imply just that. It’s an alternative to trick-or-treat.

        The CDC though has other ideas.

        1. Nope my son just decorates the outside of the house in a big time way . People stop to see our home for Xmas & Halloween . He does it himself . This year he is working Xmas lights into the mix he hung those all ready. He also does inside

  11. Maybe it’s just because it’s been so quiet lately, but this could actually be a pretty interesting storm, especially for SNE. It’s quite a dynamic and strongly forced system. I don’t expect the rain to be too much of a factor, a good drink of water but much more in the way of positive impacts than negative. I’m more interested in what the peak wind gusts will be. The trend is stronger with the LLJ. I could see a couple gusts in the 60s especially in eastern areas, at least at a place like Blue Hill. I expect at least isolated power outages.

    Instability will be very marginal especially with the time of day, but given the wind fields and lack of a low level inversion, a tornado is not totally out of the question either, again especially over eastern New England in the predawn or early morning hours. Always a low risk in these environments but once in awhile they produce if only from a “spinning shower”.

      1. Because the instability is so limited, there probably won’t be much in the way of thunder, maybe just isolated instances.

          1. Yep, contrary to popular belief thunder is not a requirement for tornadoes, though obviously most tornadoes occur with thunderstorms. If I remember right the 2016 Concord, MA tornado didn’t involve thunder. We’ve had a couple in my area in the past year that occurred with little or no thunder. Many tropical cyclone tornadoes fall into that category as well. And typically these are “weak” (EF0-1) tornadoes.

  12. 12z GFS has quite the cool shot for Columbus Day Weekend. Highs only in the upper 40s and lower 50s on the Friday and Saturday (October 9-10) under mostly sunny skies. We’ll see how much that changes over the next several days.

    1. It would be the first time in awhile that we have had a cool Columbus Day weekend. Lately they have been quite warm/hot. Hope that verifies.

      1. Columbus Day Weekend last year had highs in the middle 50s on the Friday/Saturday, and upper 60s Sunday/Monday.

        Columbus Day itself 2018 was only in the middle 50s with some rain.

        Columbus Day 2016 was only in the middle 50s after 1″+ of rain on the Sunday.

      2. I was about to say we’ve had quite a few cool ones, and recently, but I see SAK already provided the stats. 🙂

        “Hot” Columbus Day weekends are quite rare, actually.

  14. Still not overly impressed with the rain prospects. I like most places under 1 inch, with isolated locations over 1 inch.

    Friday’s event, which I’ve been watching for several days now, looks generally light at this time.

    The event that I had targeted for October 4 about a week in advance looks a little more like an October 5 event now. Will keep an eye on that. The sucky guidance occasionally touts that as being a bit of a producer, but it also was screaming about a 2-3 inch rain event for most of our area for tomorrow several days in advance (which I never bought, by the way). As SAK has repeatedly said, and correctly, ALL the models have been terrible with respect to their expected performances lately. Just yesterday morning, they were still high on a solid shot of rain here Wednesday night and Thursday morning. The sky at that time will be mostly clear and the nearest rain will be a few hundred miles away.

  15. 18z NAM (3km & 12km) are both down to under 1/2 inch for all of Greater Boston, & eastern coastal MA now. Ouch if that verifies.

    #DroughtGoesOnAndOnAndOnAndOnAndOn

  16. Last rain storm we had a couple weeks back brought us about 2 inches. The models predicted we would get .30 or so. Can’t trust any precip models 🙂

    1. The over-achievements have been extremely rare. The vast majority of our systems have come in under to well under model forecasts. You just happened to get lucky on that one. 😉

  18. Thank you, TK.

    I’m beginning to worry about the pilings that are part of our building’s foundation. Serious drought is not good for the pilings. I’m hoping we get more than 1 inch today, 0.20 inch on Friday and the same next Tuesday. But, realistically, I think the amounts will be much less.

  22. This thing has some teeth. Got woken up by the rain here which is unusual for me. High Wind Warning up for portions of southeast New England now. Gonna be a pretty wild few hours. Fairly widespread gusts in the 50s and 60s looking probable.

  23. up to 0.97 inch so far here in JP.
    wind is not so bad. curently gusting to 33 mph at the airport and
    56 mph atop Blue Hill.

  24. my wind equipment is too sheltered for any kind of meaningful measurement. But NOT hearing muxh in the way of wnd outside my window.

    Loagn’s rain looks to be pathetic. 0.32 inch as of 6AM. we shall see what the 7AM obs brings

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