Saturday December 12 2020 Forecast (7:38AM)

138 Comments

DAYS 1-5 (DECEMBER 12-16)

We’ve an active weather pattern on our hands and a few other things to talk about too! We start our weekend with the approach of a warm front which will lead to thickening cloud cover after much of the region starts the day with fog. Areas of rain will follow the thickening cloud cover, arriving from southwest to northeast later this morning through the afternoon hours. While it won’t likely rain the entire time, a few of the episodes may be moderate. The low pressure area parenting this warm front will track northwest of New England tonight and north of the region Sunday. The warm front will probably not get through the entire area, with northern MA and southern NH staying coolest through Saturday night. The cold front trailing this low pressure area will cross the region during Sunday morning (as a warm occlusion in areas that the warm front has not passed). This front may produce a few rain showers, but the balance of the day is expected to be rain-free and rather mild by December standards. A secondary cold front will sweep across the region behind the departing low from northwest to southeast Sunday night, delivering a batch of colder air to the region. Let’s hope for some clear sky Sunday evening as we experience the peak evening of the Geminid meteor shower, with up to 60 meteors per hour visible away from city lights. If the sky is clear enough, look into the east northeast sky between 8PM and 11PM for peak activity, radiating out from the left side of the Gemini Constellation. During Monday, a wave of low pressure will be moving rapidly east northeastward and will pass southeast of our area. Model guidance has trended a little further north with this system, and it may indeed have some impact on the region Monday, spreading its precipitation shield at the very least into southeastern portions of the forecast area. Will forecast a minor snow accumulation event for this and make adjustments if necessary on tomorrow morning’s blog update. Temperatures will be marginal for this event and rain will likely be involved as well, at least for parts of the region, if the precipitation shield does indeed make it far enough north. Regardless of the details, behind this system will come colder air as high pressure builds across eastern Canada. We’ll have dry weather Tuesday and at least into Wednesday as we eye the approach of another storm system that threatens the region with snow as early as Wednesday afternoon…

TODAY: Areas of fog. Becoming Thickening overcast. Periods of rain midday on. Highs 40-47 southern NH northern MA, 48-55 to the south. Wind N-NE 5-15 MPH southern NH and northern MA, variable to SE 5-15 MPH elsewhere.

TONIGHT: Overcast with areas of fog and occasional rain in the evening. Mostly cloudy with continued areas of fog and rain showers overnight. Lows 37-44 southern NH and northern MA, 45-52 elsewhere. Wind NE up to 10 MPH in southern NH and northern MA, variable to S 5-15 MPH to the south.

SUNDAY: Mostly cloudy to partly sunny. Chance of rain showers early. Highs 53-60. Wind SW 5-15 MPH, gusts up to 25 MPH.

SUNDAY NIGHT: Partly cloudy. Lows 28-35. Wind NW 5-15 MPH.

MONDAY: Cloudy. Chance of rain and/or snow, favoring southeastern MA, eastern CT, and RI where accumulations of up to a few inches of snow are possible. Highs 35-42. Wind N 5-15 MPH.

MONDAY NIGHT: Clearing. Lows 20-27. Wind NW 5-15 MPH.

TUESDAY: Mostly sunny. Highs 30-37. Wind N 5-15 MPH.

TUESDAY NIGHT: Mostly clear. Lows 17-24. Wind N under 10 MPH.

WEDNESDAY: Increasing clouds. Chance of snow by late day or at night. Highs 28-35. Wind NE 5-15 MPH.

DAYS 6-10 (DECEMBER 17-21)

Potential snow event into December 17, details to be determined by storm track. Dry, cold weather December 18-19. Next threat of precipitation comes later December 20 into December 21.

DAYS 11-15 (DECEMBER 22-26)

Minor precipitation event possible around the middle of the period, otherwise a quieter and seasonable pattern seems likely.

138 thoughts on “Saturday December 12 2020 Forecast (7:38AM)”

  1. Good morning and thank you TK.

    Here is a repost of a couple of posts I made a bit eariler.

    JpDave
    DECEMBER 12, 2020 AT 7:19 AM
    Things are looking up for both Monday and Wednesday/Thursday.

    Most models are now on board for accumulating snow on Monday. Anywhere from an 1 or 2 upwards of 4 or 5 inches.
    Imho, “could” be 6+ inches for a sneaky nice one. We shall see.

    Then, the main event, Wed/Thurs.

    Here is a very nice write-up from the Norton NWS office.
    Please note what they say about Monday’s system possibly having an effect on the Wed/Thurs system:

    Southern stream system that clips Southern New England Mon phaseswith Northern Stream energy Tue, developing an intense cycloneover/near Newfoundland with both GFS/EC lowering MSLP down into the940s mb! Per WPC, the record MSLP for Atlantic Canada is close to940 mb. Models sometimes are too strong at day 5 time range but even
    the GEFS and ECENS mean is around 964 mb! What is significant hereis that this intense cyclone downstream will place cold confluentflow over the maritimes and may shunt upstream storm track farthersouth of New England for the mid week system. Thus uncertaintyrevolves around how far north will this southern stream systemtrack.

    Here is a GFS look at a 936 mb low just North of NewFoundland.

    https://www.tropicaltidbits.com/analysis/models/gfs/2020121206/gfs_mslp_pcpn_frzn_namer_16.png

    https://www.tropicaltidbits.com/analysis/models/gfs/2020121206/gfs_z500_vort_namer_17.png

    https://forecast.weather.gov/product.php?site=BOX&issuedby=BOX&product=AFD&format=CI&version=1&glossary=1&highlight=off

    Hopefully, that feature at least allows the good stuff across
    SNE even it does not penetrate into NNE.

    REPLY
    JpDave
    DECEMBER 12, 2020 AT 7:27 AM
    6Z GFS Kuchera snow for Wed/Thurs

    https://m3.pivotalweather.com/maps/models/gfs/2020121206/138/snku_024h.us_ne.png

    Mark posted the 0Z Euro,UKMET and Cmc totals.

    FWIW here is the 6Z ICON

    https://www.tropicaltidbits.com/analysis/models/icon/2020121206/icon_mslp_pcpn_frzn_neus_40.png

    Pretty tight to the coast, possibly bringing rain to the Boston Area. Given the above discussion, I think this solution is unlikely, but I suppose everything is on the table.

  2. Before we jump to Wednesday (I am thinking more late Wednesday and / or Thursday) we may want to place some focus on Monday. Which while progressive is a moisture laden system that with a slightly cooler temp profile could drop some impactful snow on SNE. As it stands now, I think immediate coastal and valley areas will not see much of any notable accumulation on warmer surfaces. I do think areas of elevation where the snow falls hard enough could see a light accumulation of up to a few inches of snow on all surfaces in a short period of time. How that system evolves as it bombs out near the Canadian Maritimes will have a great deal of influence on the track of the later system, which is still over the Pacific and I think too much of the current model trend is linking position and intensity for the Wednesday / Thursday system to that energy in the eastern pacific. Where and when the southern stream energy and long wave northern trough interact will be your major determining factor in what the regional weather outcomes are and no model can reasonably prognosticate where that will happen, until pacific energy comes ashore and we see the evolving impact of the rapidly deepening system that departed our area later Monday and will be raging well to our Northeast.

  3. Dave – that is an excellent NWS write up discussing the later week system.

    Something I didn’t mention, but I think is understood – Cold air should be abundant for the later week system regardless of intensity and track. Only potential marginal profiles could be immediate south coast and the Cape and the Islands.

    1. As always, many thanks for your input and thoughts.
      No matter that system Well NE of us, there is still a reasonable
      chance that a good slug of precip can still make it into SNE, yes?
      The caveat being that the bulk of it “could” be shunted to our South.

    1. I don’t expect them to suddenly make this thing look bigger than it will be. I think they have a decent handle on it, at this range, given what they have to work with.

  6. JMA…
    In general agreement with your thoughts.

    Overall pattern next 2 weeks (continuing from what started last weekend) is what I was envisioning when I wrote my winter outlook in November.

    1. Meteorological analysis would lead one to be very leery of this system (not for a big storm, but for something to deal with).

  10. I learned the best lesson of all with our last storm. Tom and then TK pointed out that every single thing verified except the amount. Pretty darned good IMO. I really enjoy that we have learned to look past just the totals. And I love the links everyone posts for that reason. We can watch and enjoy the transition from beginning to end. It doesn’t get much better

  11. https://imgur.com/a/I1QmlKy Just for showing and wondering what people think about this map for snowfall. I will of course keep the other type of map as well for New England but I am thinking of expanding my snow maps to the Northeast region. PS I took this map out from GIS. My other maps have used google maps.

  18. In the latest “misinformation” photo, there’s a post going around social media of a photo claiming to be the northern lights seen from Australia (not Austria, but Australia).

    Perhaps they meant the “southern lights”? Or maybe it’s just a fake. Let me know what you think if you should see it out there…

    Somebody sent a fake photo to Ch 5 who aired it, unbeknownst to the on-air met who was asked to comment on it. He handled it very well, then said “Let’s just move onto the weather…” It was a photo supposedly taken here in eastern MA of a spectacular display of the northern lights very high in the sky. We all know that DID NOT happen. I wish people would keep things real. 🙂

    2. It is social media. Half the people post this stuff just to get a reaction. I try really hard not to make their day

    1. Oh yeah the accuweather ad sales team wastes no time getting into the forecast decision room. It’s a site you can’t go to without wanting to jump as
      Soon as you click

  24. Thanks TK.

    For SNE, I would say the “danger” of both of these systems for you guys would be that they miss to the south. I’m not overly impressed by Monday from a snow perspective. Seems to be a case where it would be very tough to get the right overlap of enough moisture and enough cold air together for anything noteworthy. But still a little time to watch it.

    For mid-next week, definitely a better chance for somewhere in the Northeast/mid-Atlantic to get hit hard. With such a strong high to the north, don’t be surprised if that one gets shunted a little further south. Maybe like an NYC or even Philly jackpot, but there may be plenty to go around with that one. I could see good “fluff bomb” potential with that one. High ratios, high winds, high totals… somewhere. And still very early on that one as well so the usual day 5-6 uncertainty applies. There’s not a 1:1 correlation between how consistent the models are that far out and how confident we should be in the forecast.

        1. It seems we either have “too much” or “too little” cold air around here for a good snow event. Frustrating either way.

  26. Thanks TK.

    Good first ski day of the season here at Killington. Snow is nice and soft and the rain has held off. Interestingly, the only places we encountered natural snow on the ground on the way here was within 3 miles of my house in CT and then about 10 miles south of the mountain.

    Models continue to look great for the midweek system. Need to stay the course with these model runs for another 36 hours before we can start to gain some more confidence that this might actually happen.

  30. Well here is the confirmation!@)(@#&!*@(&#(*!&#*(@!&

    Euro shunted South.

    https://m3.pivotalweather.com/maps/models/ecmwf_full/2020121212/120/prateptype_cat_ecmwf.us_ne.png

    https://m3.pivotalweather.com/maps/models/ecmwf_full/2020121212/126/prateptype_cat_ecmwf.us_ne.png

    https://m3.pivotalweather.com/maps/models/ecmwf_full/2020121212/138/sn10_acc.us_ne.png

    Pissah! Just what I wanted. Figures! Still time for a shift, but I am not liking this development one bit.

  33. Things could still change, but this morning’s NWS discussion
    looks to be coming to fruition. I figured once I read that discussion. Just our rotten luck.

    Perhaps we could get an ocean effect snow storm instead. Wouldn’t that be something? Things have to line up just so for that to happen. I have seen it happen a couple of times with
    the low center well to the South. Again, set up would have to be perfect and probably won’t happen.

    1. I think it’s just a tad too early to verify something that hasn’t even developed yet. 😉

      1. I did say looks to be. Since when is that confirmation? just saying. I know it’s 5 days off and things can change.

        I am simply expressing my disappointment in this particular run which fwiw, was fully supported by the UKMET.

        I do not like the smell of this.

        It will be ocean effect snow that saves the day if there is
        saving to be done. 🙂 🙂 🙂

        Let’s see what the 0Z runs have to say.

        1. I would love to see one of those ocean-effect major snowstorms. It’s been a while. We had one (I want to say December 1977) that we got about 10 inches here and next town over had only 2.

          1. I sure wouldn’t mind. I have seen a few, but they are few and far between.

            I remember one, sometime in the late 60s or so.
            Major storm stayed South, but we were in a NE fetch with arctic air in place. I don’t remember exactly how much snow fell, but I was living in Millis at the time
            and was out in Framingham and both of those locations had substantial snow. Can’t say exactly, but
            say somewhere in the order of 6-10 inches.

            There was another in the early to mid 70s, perhaps 4-8 inches, widely variable location to location.

            1. And one more December 1987 or 88? Wasn’t huge, but we were having a Christmas party and I had to run some errands in it. It was really snowing hard for awhile, but not for too long. About 4 inches.

  35. The drum that’s been banging for a lot of this year and especially last winter is showing something blockbuster that peters out as we get closer. I’m very much looking forward to see how this wed/thursday storm turns out – I’m not a big fan of snow from a shoveling/my back standpoint… but I’m more looking forward to seeing if this sets a tone for the winter like the last one and these high runs get diminishing returns the closer we get to the day – or if it keeps cranking and we do see a big event when it comes to pass. Not being a fan of snow has made me less of a prisoner of the moment lol

  36. Looking at those CMC and GFS ensembles there are still more low centers NW of the mean than SE. Still plenty of uncertainty there.

  38. The word fetch was mentioned above. I would like to illustrate that with some model frames

    https://m3.pivotalweather.com/maps/models/ecmwf_full/2020121212/108/sfct_b.conus.png

    https://m3.pivotalweather.com/maps/models/ecmwf_full/2020121212/114/sfct_b.conus.png

    https://m3.pivotalweather.com/maps/models/ecmwf_full/2020121212/120/sfct_b.conus.png

    https://m3.pivotalweather.com/maps/models/ecmwf_full/2020121212/126/sfct_b.conus.png

    https://m3.pivotalweather.com/maps/models/ecmwf_full/2020121212/132/sfct_b.conus.png

    Even after the system departs there is a still a NE fetch off of the relatively warm ocean (about 46) with a nice big HIGH to the North pumping in cold air over that warm water.

    I know it is not as simple as that, but I could envision quite an
    ocean effect event in Eastern MA with this system.

    Even if it passes to the South, I will be watching for this
    possibility.

    1. Here is a nice discussion of Lake Effect snow.

      http://www.theweatherprediction.com/winterwx/lesnow/

      Of course in our situation one has to substitute ocean here. One thing I found interesting was the unidirectional wind shear. Best if wind shear is less than 60 degrees through 700 mb (about 10,000) feet.
      This is the first time I have seen this. This may be a limiting
      factor as I do not see unidirectional shear to that height.

      Oh well, I’ll be watching just the same. When the hi-res models get in range, they are better at picking this up.

  39. Thank you, TK.

    Mark, enjoy Killington.

    My brother-in-law skis there frequently. He also climbs NNE mountains in mid-winter. He lives in Vermont, and has become a mountain man. This includes a large beard, and a massive pick-up truck.

  40. NWS 3:30 PM Update

    Wednesday into Thursday…

    We continue to monitor the potential for a winter storm still on the
    map but still a lot of uncertainty on how it all plays out given it
    is still a Day 4/5 forecast. Abundant southern stream moisture and
    antecedent cold air are in play for potential significant, plowable
    snowfall (6+ inches), but the northward extent of heavy snow threat
    remains highly uncertain at this time range. Given we are still 96
    hours out from possible onset of the storm, it is important not to
    focus on any specific deterministic model outcome given the
    windshield wiper effect or potential for model flip flopping. After
    all, the system responsible for the storm remains over the Pacific
    Ocean and it will take another day or two before it is better
    sampled by the upper air network in the US. Until then, there will
    likely remain considerable spread in the surface low track and
    timing among ensemble guidance.

    What we do know is that deep cold air is likely to be in place
    thanks to the Monday system with 850mb temperatures around -10 to –
    12C, which would suggest an all snow event. The current negative NAO
    regime also favors downstream blocking, which tends to help keep the
    cold air locked in place over New England. Nonetheless, if the storm
    tracks closer to the coast, portions of southeast New England,
    especially towards the immediate south coast could see rain mixed
    in. If the low tracks to far south of the 70W/40N benchmark, then
    the northwest zones could get shut out of any significant snow.
    Downstream ridging over north Atlantic will likely also be a factor
    to how amplified this system becomes and how close it tracks to
    Southern New England.

      1. I’m not sure HRRR can pick up stratiform precip that well. I seem to recall it doing this and missing the whole northern part of a precip shield. Since it’s been changed recently I’m curious to track its performance both winter & especially summer (for convection).

  42. I love to see our media sources sending frequent reminders of the midweek event being a day 4/5 forecast. Specifically this afternoon Eric & NWS have done that. Bravo & Awesome. 🙂

  48. The Monday system that is going to absolutely bomb up in Newfoundland …….

    This is an occasion we want north Atlantic blocking to be on the wane towards mid-week.

    If the blocking diminishes, that intense storm can lift out and then things can gain a bit more latitude down around our way.

    If the blocking sustains, that intense storm stays closer to Labrador/Newfoundland and that will suppress the Wed/Thursday system down into the mid Atlantic.

    1. Im pretty sure the 18z GFS allows that intense system to move out and thus, the mid week system is not suppressed.

    2. The high in Canada is about maybe 200 miles further NE on the 18z. That’s the first thing that jumped off the page for me

    2. Rain on the Wed/Thur system???? I think not. What are you smoking? A miss or graze? Sure, I could believe that. Rain? I don’t think so.

          1. I’m not smoking anything Philip I was just playing with old salty . I have no idea what Wednesday will bring I just want a big snow event before I go back to work mid January.

            1. The snow storms as you know mean lots of hours at work for me & stress it would be awesome to just sit & listen to the plows all night in the neighborhood with 0 worries & not worry about how much drops & when I’ll sleep .

    3. Rain very likely for Monday (if it does anything at all) but highly unlikely for Wednesday/Thursday. That one is either heavy snow, light snow (graze) or a miss.

      Monday temps will be marginal at best for snow in eastern sections.

  53. I’m guessing the drought monitor is looking much better in SNE. And, with more precipitation events in our near future we should be done with the deficit soon.

    My guess is rain in Boston on Monday, and a near-miss with light snow on Wednesday night. The cold will be here, but will the strong Arctic high shunt systems to our south and east. We shall see. Shaping up to be our coldest 3-day period thus far this winter later this week, with some teens at night; colder in Southern NH and Western MA.

    1. Boston is now at “Abnormally Dry” which is the lowest level on the Drought Monitor. We are done for all practical purposes. No more of those deep “fall” colors on the map.

  55. May I ask that the rain stop please Anyone here have a connection with a higher power. We have one outdoor outlet that seems to want go blow when rain gets in. On the inside part of that is our verizon plug. It’s been pure joy 😈

    1. Some of the decorations here Vicki don’t like the rain as well . I was down at the panel tonight dealing with it .

    2. I wonder if it’s the same kind that we had the same problem with outside.

      It was a new one in the electrician said that he had no choice but to use those ones because they were the only ones that his higher-ups would use.

      1. I’ve seen on Facebook tonight a lot of the same issue . Here we have so many electric cords & boxes with cords coming out it’s absolutely ridiculous. Has anyone see that Xmas light contest on tv , it’s like that here at my house .

    3. I have had the exact same problem with the lighted decorations we have out on the back deck! We were thinking it was all the rain as well.

  56. If you have LED lights its generally fine but if you have more traditional the rain can cause havoc on the decorations. Generally in heavy rain, we keep the lights off. Snow is different though we put them on when it snows.

    1. Having been around for quite a while I will say as far as the conventional decorations, the ones made after 2000 are far worse off in weather than the ones that are older. Huge difference.

      We have multitudes of light sets that don’t work properly after one season, if they make it even that far, all of which were purchased recently. The ones we have had since the 1970s and 1980s that my dad and older brothers were putting up are still burning nicely, with very few exceptions. 🙂

    1. The difference between the 18z & 00z operational GFS illustrates perfectly what I always say about run-to-run this far out. 😉

      Meteorology not Modelology. I’m thinking of making a t-shirt that says that. 😉

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