Thursday December 19 2024 Forecast (7:32AM)

105 Comments

DAYS 1-5 (DECEMBER 19-23)

The rain is gone, the mild air has made its exit, colder air is on the way, and there’s snow on the way for most of the region. First, the wave of low pressure that brought a brief but decent slug of rain to the region has exited to the east and we’re in for a fair weather day with a sun/cloud mix. This morning, some temperatures away from the immediate coast and urban areas have fallen close enough to freezing so that lingering wet ground may have converted to black ice on some surfaces, so use caution if heading out early until the temperature can rise sufficiently to eliminate that hazard. Otherwise – a nice day today! But changes come quickly. On Friday, low pressure organized off the Mid Atlantic Coast as high pressure filters cold air in from the north. The low pressure area will pass close enough to southeastern New England Friday night to throw its precipitation shield across much of the region. This will result in a period of accumulating snow, which will be least well northwest of Boston due to further distance and lighter precipitation amounts. A mix with rain over Cape Cod will be a limiting factor there. Between these areas, a general 1 to 3 inches snowfall appears quite probable. I can’t rule out enough synoptic “boosting” and/or ocean enhancement to produce a few pockets above 3 inches. A more definite call on that will appear in tomorrow’s update. As low pressure pulls away it’ll pull in an arctic air mass for the weekend. Saturday can see additional snow showers as a disturbance at high levels drifts through. This day will also be rather breeze behind the departing low pressure area. High pressure will bring more tranquil weather Sunday, which continues Monday as well. The winter solstice occurs at 4:20 a.m. Saturday.

TODAY: Sun/cloud mix. Highs 38-45. Wind N 5-15 MPH.

TONIGHT: Mostly clear. Lows 21-28. Wind N 5-15 MPH.

FRIDAY: Increasing clouds. A few snow flurries possible NH Seacoast and eastern MA coast in the afternoon, except very light rain/snow showers South Shore to Cape Cod. Highs 35-42. Wind N to NE 5-15 MPH.

FRIDAY NIGHT: Cloudy. Snow likely, except rain/mix parts of Cape Cod. Snow accumulations 1 to 3 inches except under 1 inch west of I-495 and over Cape Cod. Lows 25-32 except slightly colder well north and west and slightly milder Cape Cod. Wind NE 10-20 MPH coast, 5-15 MPH inland.

SATURDAY: Variably cloudy. Snow showers likely. Temperatures slowly fall to 22-29. Wind N 10-20 MPH, higher gusts. Wind chill readings often under 20.

SATURDAY NIGHT: Partly cloudy. Lows 11-18. Wind N 5-15 MPH.

SUNDAY: Mostly sunny. Highs Highs 22-29. Wind NW 5-15 MPH.

SUNDAY NIGHT: Mostly clear. Lows 10-17. Wind variable up to 10 MPH.

MONDAY: Mostly sunny. Highs 24-31. Wind variable up to 10 MPH.

DAYS 6-10 (DECEMBER 24-28)

A weak low pressure area from the west can bring some light snow or snow showers (rain or snow showers South Coast) early to mid period, followed by fair weather later in the period. Temperatures undergo gradual moderation.

DAYS 11-15 (DECEMBER 29 – JANUARY 2)

Pacific-dominated air flow brings milder weather but minor precipitation threats as we wrap up 2024 and welcome 2025.

105 thoughts on “Thursday December 19 2024 Forecast (7:32AM)”

  4. Good morning and thank you TK.

    Most interesting to watch this all evolve.

    I am curious to see what the 12z suite shows and if models can agree on amounts

    HRRR is cranking.

    Reply

  5. Its hilarious to go back into the archives around mid/late December, every year, and read the comments.

    Without fail, the “its not going to snow this winter” thought appears, every time.

    The funniest one is to read them in mid/late December 2014 and well, we know what happened in February 2015.

    As Aaron Rodgers once uttered …… R E L A X 🙂 🙂 🙂 🙂

    And yeah, it might end up being 3 lean snow winters in a row, but its impossible to know that is going to happen right now.

    Reply

  6. Winter does not start until Saturday morning. People on X already declaring winter over with what they call A TORCH coming after Christmas and lasting through New Years

    Reply

  11. From Bernie Rayno
    there has been an increase of precip on the backside of the storm Fri night 06z vs 00z on the ECMWF. Model trends are tricky though. The old forecasting saying is the “trend is your friend” but I would also add the “trend can also lead you down the road of despair”

    I am thinking the zone is NYC to Downeast Maine (from coastal storm). Lots of snow showers in the wake of the storm Friday night across interior NE as another shortwave sharpens the trough

    Reply

    1. There can be some single digits in the metro area, but I think the urban center (right downtown & waterfront) will stay over 10.

      Reply

      1. Oh, for sure!

        I think there will at least be Ocean Effect Snows. How much? all depends.

        But, will the synoptic snow get up here? remains to be seen.

        Reply

  20. Hey folks,

    TK and I were chatting and I am suggesting a get together in January. Was thinking of Legacy Place as it’s a good location right off the highway and sort of in between north and south.

    Are folks interested? If so please email me hkasrawi@gmail.com. Once we get a sense of the numbers we can pick a location and will send it out by email vs. just posting it here.

    Reply

  23. Thanks TK. Agree all the way around on your forecast. Think “gradual” moderation like you said is apt for 12/24-28. It’s going to take the warmer air awhile to overcome the cold CAD wedge. But there may eventually be some “winter warmth” there by the end of the year. Definitely not a pattern conducive to significant snow chances.

    Big EPO flip coming right around the turn of the year though….

    I think it’s time for NCEP to turn off the NAM. It’s been on “death row” for years now – it’s no longer updated and is slated to be discontinued. The whole reason behind not turning it off is that historically it has still handled situations like CAD better than the global models. But between advances in the globals and development of new hi res, I think we’re there. It’ll be remembered as the NGM of my generation 😉

    Reply

    2. I read somewhere that the NAM was supposed to be gone by the end of 2024 and replaced by some sort of rapid refresh model (Can’t remember the whole name). It sort of made me wonder if the current generation of models will all be replaced because of super-duper computers and AI assisted models.

      Reply

      1. As far as I know it’s not specifically planned for the end of 2024, but could happen any time really.

        To your second point, a very good one: that’s not a matter of if, but when. In a way it would just be keeping with the historical order of things with technology – the “old” is always replaced by the “new”. After all, we’re not using the ETA, NGM, and NOGAPS anymore 😉 but as to the time frame, who knows at this stage.

        The bigger question for me is what the public/private balance will look like in the next generation. In the same way that we have a “GFS” and “Euro” model now, will we be more beholden to the “Microsoft” and the “NVIDIA” models in the future? Very possible. NVIDIA has already published research on the development of a next generation hi res model designed to compete with the HRRR. But we know both NCEP and the ECMWF are involved in AI model development as well. It’s a bit of a space race…

        Reply

  29. There is a little fine line to deal with near the coast.

    The real cold of this cold shot hasn’t fully come in during the handful of hours some light moisture comes in off the ocean.

    So, inland 5-10 miles or more, yes, I can see a coating -2 inches.

    But, it could still be 33-35F near the immediate coast and really struggle to accumulate, so we could be dealing with that localized effect.

    Reply

    1. Agree. Let’s see what the intensity really is, if at all.

      Last night Pete was calling for a coating to 2 inches.
      He was struggling whether or not we would se synoptic or ocean effect snow, but said flakes would be in the air either way. 🙂
      “So far” his forecast looks good. 🙂

      Reply

  33. What is the definition of “synoptic” snow? I have never seen that term here before on the blog.

    In layman’s terms please. Thanks.

    Reply

    1. It is the snow produced by the storm itself and not ocean effect.
      Of course, sometimes there can be both, in which case
      it is called ocean enhancement.

      Reply

  37. A general widespread 1/2 to 2 inches of synoptic snow + an additional 1 to 3 inches of ocean effect snow POTENTIAL in a more banded or swathy structure. This is basically my reasoning for 1 to 3 in the main accumulation area. I could not rule out 4 or even 5 in a case of maximum realization of potential – both synoptic and ocean effect – in isolated areas. If this happens, Plymouth County would be the most likely target.

    The under 1 for Cape Cod was due to mix at the start and wetter overall snow. The under 1 further NW is the combo if being further away from low pressure and missing out any O.E.S.

    Reply

    1. As usual that word POTENTIAL when it comes to snow events while rain events words like EXPECTED are the norm. 😉

      Well, let’s see what happens. 🙂

      Reply

      1. Well you’re confusing amounts with occurrence.
        When we talk about rain amounts, the word potential is used as well.

        The other day, the weak system that arrived kept its snow intact while the rain portion of it was a complete fail.

        Reply

  39. The recent mild spell was not enough to push Boston to the + side for departure, and now it’s about to dive further negative for the month.

    Reply

  41. Upcoming set-up features westerly flow aloft, trending northeasterly flow surface. Interesting interactions sometimes take place. This general idea carries well into next week with the system that’s around Dec 24-25.

    Medium range split flow pattern, but no chance to stay “warmed up” for long here. Especially since there will be blocking high setting up in eastern Canada.

    Took a look at CPC’s long lead update today. That’s a wasted 5 min I’ll never get back. 😉

    Reply

  50. Once again I’ll ask that folks that don’t like snow please don’t come on here and just post all day trying to annoy people. Out of work so trying to enjoy the holidays and a little snow so please kindly don’t make it not fun to come on here. Thanks

    Reply

  51. Taking a look through Xmas whatever falls today won’t melt before Xmas and we have a shot at some robust snow showers the 24-25 so should hopefully assure a white Xmas.

    Reply

  52. Special Weather Statement from NWS Boston

    LIGHT SNOW TODAY THROUGH TONIGHT…

    Minor snow event expected today through tonight, with widespread
    1 to 2 inches, expect for lower amounts near the Connecticut
    River Valley. Locally higher amounts are possible in parts of
    Essex and Middlesex Counties. Motorist should plan on slippery
    road conditions, which could impact the Thursday evening commute.

    Reply

    1. Have you seen some of the wording used on statements and discussions lately? Ugh … writing in understandable form is slowly becoming a thing of the past.

      Reply

    1. Does not appear to be connected to system to the South, so I assume some sort of ocean effect???
      Or sone sort of streamer ou ahead of main system???

      Reply

        1. South Shore to Cape Cod starts with anything from rain to sleet to snow. Not a surprise. Temps there are initially marginal, but the cold will win with time.

          Reply

            1. Yep! We’re going into this thing “coming out of warm” in a relative sense. Early in the season unless you already have solid antecedent cold, you’re going to have at least mixed down that way to start out. But as we go through today we’re cold advecting gradually. The HRRR model has come around now to show this process taking place as well.

              Beware some of the amounts on the NAM – it’s up to its old tricks. Like was mentioned here yesterday, it’s time for that model to go byebyes.

              Reply

Leave a Reply

Your email address will not be published. Required fields are marked *