Sunday December 13 2020 Forecast (8:19AM)

189 Comments

DAYS 1-5 (DECEMBER 13-17)

A temperature / dew point match and calm wind means that many wake up to a dense fog this morning, except portions of the South Coast where the temperatures are a little higher and there are only patchy areas of fog. Those areas are in the warm sector, while areas with the more widespread fog in place remained in the cooler air – i.e., the warm front never got through there. A frontal boundary from the west pushes through the region this morning and introduces a drier air mass to the region, which will be evident as fog dissipates and the wind picks up from the west during the day. But this air mass is not really that cold at all so it will be a nice day, temperature-wise. For areas in the cool air still, we call this frontal passage a “warm occlusion”, because the air behind the front from the west is milder than the air that was north of the warm front that did not make it through those areas. South of the warm front, areas that are in the warm sector will have that front pass as a cold front, though the air behind it will be milder as it passes those areas due to time-of-day, diurnal warming. Colder air will gradually filter into the region during tonight and we should have just enough clear sky to at least get a chance to view the peak of the Geminid meteor shower. This meteor shower can produce up to about 60 meteors per hour if you are viewing with clear sky and away from light pollution, so in our area the rate of visible meteors will likely be under that with at least partial cloud cover. The clouds come quickly back in overnight and into Monday while on the frontal boundary just gone by, a wave of low pressure will come rippling along rather quickly to the northeast. This low pressure area will come close enough to bring a period of snow and rain to the region during Monday, although it will be a fairly short-duration event that is not too heavy. It does have the potential to produce some minor accumulation of snow, and based on the track and marginal temperature profile expected, the greatest chance to see this accumulation will be along the I-95 and I-90 areas in general. This system exits Monday evening and a reinforcing cold front slides rather quietly through the region, but its impact will become rather noticeable as the cold air behind it arrives during Tuesday as high pressure to the north brings fair weather. This cold air is going to be around for a while, and plays a role in our next storm threat, currently timed for Wednesday night and Thursday. This will take place as low pressure tracks northeastward from lower Mississippi Valley toward the Ohio Valley, then quickly redevelops near the Mid Atlantic Coast, tracking just south of New England. The precise track of this low pressure area and the precipitation distribution to its north will determine how much snow falls in our area. With this threat at the end of our day 4 and well into our day 5 forecast, it’s far too soon to discuss specific snowfall amounts, but not too soon to say the system has the potential to produce a significant snowfall for at least a portion of the region. As always, this will be fine-tuned through the meteorological process as we get closer to the event, and you can see my thoughts in the daily comments section and of course each morning update.

TODAY: Widespread fog especially Boston area west and north to start, gradually dissipating toward midday. Mostly cloudy to partly sunny. Highs 55-62. Wind SW to W increasing to 5-15 MPH, gusts up to 25 MPH.

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

MONDAY: Mostly cloudy. A period of snow/mix/rain, but favoring snow with accumulations of a coating to 2 inches. Highs 32-39. Wind N to NW 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: Sun followed by increasing clouds. Highs 28-35 Wind N up to 10 MPH.

WEDNESDAY NIGHT: Thickening overcast. Snow arriving. Lows 18-25. Wind N to NE 5-15 MPH.

THURSDAY: Overcast with snow, ending late. Significant snow accumulation possible. Highs 23-30. Wind NE to N 10-20 MPH, higher gusts possible.

DAYS 6-10 (DECEMBER 18-22)

Dry, cold weather expected behind storm with Canadian high pressure December 18-19. Next unsettled weather threat comes later on December 20 with rain/mix/snow possible, followed by a return to dry weather December 21-22 and a shot of seasonably chilly air.

DAYS 11-15 (DECEMBER 23-27)

Pattern still looks somewhat active, a little milder to start, then colder again. Can’t rule out a couple rain/mix/snow threats which I’ll bring into focus as we get closer to this time period.

189 thoughts on “Sunday December 13 2020 Forecast (8:19AM)”

      1. Never heard of it but I looked it up.

        Also known as Saint Lucy’s Day (12/13).

        Thanks Vicki! Same to you.

    1. I got bread milk eggs and tp last night before the general public really catches on to the idea of snow.

      1. Amazing how t.p. is now part of blizzard preparation. Given the ongoing pandemic I stocked up on that weeks ago.

  3. Thank you TK!
    Vicki I echo your comment on the fog. It’s coming through the forest in rays as the fog hugs the snow covered ground, glistening on wet branches. Nice winter scene.

      1. Ch7 last night said it had the potential of over 6 inches it was a young lady who was the meteorologist.

  5. Thanks TK
    Bernie Rayno tweets on Midweek storm potential
    I am confident in cold air injection, my focus is strength of upper low. GFS (7am thu) flip flopping with a weaker further S UL, Euro remains very consistent while CMC looks like the GFS yesterday. At this pt I am taking GFS with a grain of salt. like a blend of Euro and CMC.

    The area from i-81 in N VA, SC and NE PA, N NJ to coastal RI, CT toward the Cape is the THUMP zone. likely over 12″. There is also going to a be fairly large 6-12″ which will include PHL, NYC and maybe Boston.

    1. Nope. Been up for quite a while. I have been pissing and moaning over the models and what might happen.

      Currently re-watching the movie “Yesterday”.

      I am liking the look of the NAM at 84 hours.

      https://m2.pivotalweather.com/maps/models/nam/2020121312/084/ref1km_ptype.conus.png

      Ordinarily a system in this position would bring rain. Not so, this time. Bigger danger of slipping Eastward South of us.

      We shall see. Waiting on the piss-ass Gfs at the moment.

  9. He saw the 00z and 6z GFS and has thrown in the towel 🙂

    However the over night Euro was a nice hit region wide and the CMC continues to advertise a big hit as well. Hoping Bernie is right that the GFS is out to lunch.

    1. Me throw in the towel over the GPS? ha.
      Did you look at the EURO? A decent improvement in
      the 0Z run over yesterday’s 12 Z run, although very sharp
      cutoff to the snow as one heads North.

  12. Thanks TK.

    No big changes to my thinking. Monday continues to look like a minor event at best. For Wednesday-Thursday, I’m a little surprised to see most of the guidance not only holding steady but actually trending north, the GFS obviously the exception. Still would not be surprised to see the consensus shift south a little in the days ahead. But hard to argue against the idea that most indications are that a major snowstorm is likely for SNE this week.

  13. Thanks, TK…

    As JJ mentioned above, I watched Bernie’s Periscope last night and he had a 12-18″ zone for PA, NYC, Long Island and southern coast of CT, RI, MA and the Cape.

    1. Even the Euro shows that sharp cut off South to North.
      Wouldn’t take much to shift that in either direction.

  15. I know folks like #’s, so I’ll oblige a bit…
    No, not snowfall accumulation #’s for midweek. I maintain it’s far too soon for those, but here’s a breakdown of confidence that I have, as of the writing of today’s blog.

    On a scale of 1 to 10, lowest chance rated as 1, highest rated as 10, this is how I feel about the potential of the following scenarios for the Wed night & Thu storm threat…

    Out to sea (complete miss, nobody gets any snow): 1
    South Coast measurable snow, traces or no snow elsewhere: 3
    Everybody snows, greatest accumulation southern half of region, lighter accumulation northern half: 5
    Everybody snows, everybody has to perform some kind of snow removal (or have it done for them): 7
    Everybody snows, widespread big hit: 3
    Storm comes too far north, big hit N & W, rain/snow line becomes involved: 1

    That’s the most detail you’re getting out of me for a while. 😉

  16. 12Z GFS woefully pushes the system DUE EAST far enough]South of the region to spare most of the area
    a heavy snowfall.

    Kuchera Snow

    https://m3.pivotalweather.com/maps/models/gfs/2020121312/108/snku_acc.us_ne.png

    Surface maps

    https://m3.pivotalweather.com/maps/models/gfs/2020121312/090/prateptype_cat.us_ne.png

    https://m3.pivotalweather.com/maps/models/gfs/2020121312/096/prateptype_cat.us_ne.png

    https://m3.pivotalweather.com/maps/models/gfs/2020121312/102/prateptype_cat.us_ne.png

    The 500 mb flow just flattens out. Not only is it shunted Eastward, but it weakens greatly at the same time.

    https://m3.pivotalweather.com/maps/models/gfs/2020121312/102/prateptype_cat.na.png

    The 12Z is a COLLOSAL fail of a promising system.

    Now, the CMC is next, followed by the UKMET and then the Euro. We shall see if they follow suit.

  17. Thanks TK !

    What a morning, its like spring down here.

    I know the GFS shows mostly a miss from the storm´s precip shield, but am I seeing a hint at a moist flow for Boston points South and East that might cause its own indirect lighter snows ??

  18. Well, I didn’t include the ICON, which is ready.

    Icon “true” snow

    https://www.tropicaltidbits.com/analysis/models/icon/2020121312/icon_asnow_neus_37.png

    Surface maps

    https://www.tropicaltidbits.com/analysis/models/icon/2020121312/icon_mslp_pcpn_frzn_neus_30.png

    https://www.tropicaltidbits.com/analysis/models/icon/2020121312/icon_mslp_pcpn_frzn_neus_31.png

    Once again, a very sharp cut off South to North.

    The models all agree about that sharp cut off and thus they
    all agree about a shift to the East. The question is, which one
    will be correct about how far North the good stuff comes prior to the shift. Ah, that is the question. 🙂

  21. FWIW, the 00z EPS (Euro ensemble mean) strongly supports the Euro operational run.

    EPS 10:1 snow with widespread 12″ amounts looks pretty solid:

    https://imgur.com/P499zl2

    And look at all the individual ensemble members….tucked WAY closer to the coast than the GFS:

    https://imgur.com/vHtOt1E

    EPS probability of greater than 6″ of snow is greater than 95% for most of SNE:

    https://imgur.com/nlCRNXe

    EPS probability of greater than 12″ of snow is also greater than 50% in most places…

    https://imgur.com/6SvaAck

    Far cry from the GFS! Hopefully it holds serve at 12z….

    1. question Mark what weathermodels.com service do you have that shows the EPS probability and where do you find it!!!

  24. I feel that the GFS is off but then again we said the same thing with the last storm. Tonight’s model runs will be important as the energy involved for that system will be in the Pacific northwest. Its currently in the process of moving into the west coast.

      1. I’m Home recovering Mark from a minor knee procedure & I’m not back at work until at least January 12th . So if I get a rare chance to miss a snow storm with no stress involved at all & I can enjoy from the comfort of my home I’m 100% on board . Hope all is well mark

        1. Yes, I saw your earlier post and knew you werent working which I am sure helps you be a little more enthusiastic about the snow. Hope you have a speedy recovery!

  31. Let’s also keep in mind that the energy for the midweek threat is JUST getting to the West Coast today. All we had before was deficient upper air data and limited surface reports from ships.

    By the end of today, sampling on the energy for this system improves dramatically.

  32. Here is a bright little tune from my College days in the late 60s.
    You Can All Join in by Traffic:

    First track on Traffic’s first album released 1968, You Can All Join In. Band members – Steve Winwood, Jim Capaldi, Chris Wood and Dave Mason.

    https://www.youtube.com/watch?v=ZDcmo-5Qht4

    There is something about this tune that I really really like.
    Call me nuts, but it is what it is. 🙂

    1. I like the music. Makes you want to dance and the words are fanciful. It is a bit familiar but I’m not sure why. Thanks.

    3. And look at the GFS now, a few runs later…..having gone from 25″ for Boston to 2″.

      I sure hope they followed that up with another model run that showed a much lower impact to relay the uncertainty.

    4. Well, I’ve pretty much spoken all I can say about how I feel about doing that. I’ve reached the point now where I expect it. I don’t agree with doing it, but I’m not them. Anybody with enough common sense should know that scenario is simply one model run’s output and they don’t need to take it seriously. Is it a waste of a frame on a weather-cast in which much more valuable and usable information can be shown? ABSOLUTELY. But it’s not my weathercast so what they show is out of my control. What I can control is what I talk about here and on social media. For the foreseeable future we are always going to have stuff like this out there, and neither I nor anybody else will be able to enlighten those that see these numbers and make them “official forecasts” in their minds.

      So is it safe to be confident that Boston will get 25.1 inches of snow yet? 😉

  36. Philip, I saw your comment above and tried to find the photos of Macs sister as st lucia with her crown of lights (real candles back then) and Mac and Cam as star boys. They were living in Sweden at the time. I’d say Mac and Cam were about 5 or 6 and Jenny 3 years older. We celebrated it with our kids and then grandkids. My 13 year old grandson taught himself to sing the song in swedish when he was about four and a half. Ans then retaught himself this year

    It is a lovely holiday.

    1. Most any day set aside this time of year is lovely. Thanks again Vicki! 🙂

      Although wearing a crown with real candles lit…Yikes!!! 🙂

      2. Is the qpf is 2 inches and it is all snow, how can the 10:1 snow
        be 18 inches??? something wrong there.

        With the temperatures, I expect the Kucera ratio
        might be 11,12 or 13:1 overall. We shall see.

        But even a true 10:1 would be 20 inches for Boston.

        Cut it in half and we still have 10 inches, a very resepectable snow fall.

  38. question Mark what weathermodels.com service do you have that shows the EPS probability and where do you find it!!! I am guessing you have the commercial use version sense I can not find it.

    1. I don’t have a subscription, I just pulled those EPS maps from someone else’s posts on the American Weather forum.

      1. got ya I was wondering as I use to have access to those but I think they took them out. Had them last winter, this winter.

  40. The new Euro looks too juiced up on the whole to me, but it’s distribution of QPF and snow seems pretty reasonable. Small shift south in the axes of both versus prior runs. I think that’s the right direction.

      1. Yes, there will be a fluff factor. 10:1 snow maps, as they are often are, will be misleading for this event. Whereas in most cases so far the 10:1 maps have been too high, in this case they are going to be too low especially on the northern side of precipitation.

  41. Comparing the 00z Euro to the 12z, they look nearly identical. Maybe a slight 5-10 mile south tick with the heavier snow totals but it is ever so slight. Really nice hit there for CT.

    12z run on the left and 00z run on the right:

    https://imgur.com/fk9NmAm

  46. This should be the coldest snow event of the season so far with temps in the 20s and likely a fluff factor.

    No sloppy 30-35 degree slop this time around!

  47. Snow ratios could be as much as 12:1/ 18/1 for areas along and west of I95 in New England 10-1 southeast but with more precip. Like its been pointed up above, Euro is probably a bit to much moisture.

  50. 18Z NAM is complete.

    At 84 hours
    Surface

    https://m2.pivotalweather.com/maps/models/nam/2020121318/084/ref1km_ptype.us_ne.png

    500 mb

    https://m2.pivotalweather.com/maps/models/nam/2020121318/084/500wh.us_ne.png

    200 mb

    https://www.pivotalweather.com/model.php?m=nam&p=200wh&rh=2020121318&fh=84&r=us_ne&dpdt=&mc=

    Kuchera snow to this point

    https://www.pivotalweather.com/model.php?m=nam&p=snku_acc&rh=2020121318&fh=84&r=us_ne&dpdt=&mc=

    Given all of this, I think it translates to a huge hit for this particular model. We shall see what the 0Z runs shows as it
    will give us 6 more hours of snow. 🙂

      1. Agree Hadi. Look at the 500 mb and 200 mb flow.
        That system should slide “just” South of the SNE coast.
        No way South like some models were showing.

  51. C’mon GFS, at least have the decency to spread the snow
    a little farther North than your 12Z run. I know you can do it.

  52. Yes, that’s a beautiful surface map at hour 84 on the NAM. Looks like a replication of the CMC solution. Caveats being this is the NAM at hour 84 and the NAM’s qpf is often overdone. But regardless, a major snow event either way!

  53. 18Z RDPS at 84 hours

    Surface
    https://www.pivotalweather.com/model.php?m=rdps&p=prateptype&rh=2020121318&fh=84&r=us_ne&dpdt=&mc=

    Kuchera snow to this point
    https://m2.pivotalweather.com/maps/models/rdps/2020121318/084/snku_acc.us_ne.png

    500 mb
    https://m2.pivotalweather.com/maps/models/rdps/2020121318/084/500wh.us_ne.png

    200 mb
    https://m2.pivotalweather.com/maps/models/rdps/2020121318/084/500wh.us_ne.png

    Looks like another big hit, perhaps with heavy snow shield “slightly” farther South than the NAM, but Not South of Boston. Boston should still be within the heavy zone.

  55. 18Z GFS has the 500 mb flow just FLATTEN out causing the system to move straight Eastward WELL South of SNE
    AND at the same time weaken dramatically!!

          1. Oh yeah I’m not doubting it since nature has probably run nearly every permutation over time. Just Can’t recall and racking my brain over last years.

    2. We’ve seen this before. It’s usually not right when it’s the only one. Rarely, it is. That said, its solution is not out of the realm of possibility. SO I would not just toss it.

  56. I don’t see any reason to call the GFS unrealistic. As I like to say, it’s not the only option, but it definitely is an option, and one that I think has some potential merit. That is a very strong high to the north of this storm.

    1. Have you noticed that high pressure forecast errors have been instrumental in outcomes? Maybe I’m paying more attention to it but it seems like the GFS in particular (and the ECMWF to some extent as well) have both had issues forecasting placement and strength of high pressure in eastern Canada in recent months. I wonder if this is also a data input issue at least partly related to decreased data from aircraft.

      1. Yes, I wouldn’t say I’ve been keeping close track but in a more subjective sense it definitely seems like that has been a problem spot. And in an already sparse area for observations I’m sure the loss of aircraft data isn’t helping. The GFS may well be too suppressed, but I get the sense that if you take a consensus of all the 12z guidance, there’s not a lot of room for the precip shield to go further north, but a good deal of wiggle room to the south.

  57. I have always loved AJ Burnett I love all ch5 Mets . I loved how he just said I absolutely will not throw numbers on this today . Said south of Boston has good potential of removable snow & said tomorrow’s storm will be a big indication of what will happen as you know that already .

    1. I know I’ve stated this here before but AJ was one funny guy to work with in the office in the private company I worked for. 🙂 Great sense of humor..

      1. You know tk I can see that from tv as he just seems like one of those guys you love to be around . Like I said his forecasting style tonight is how it should have been presented on a Sunday night for a Wednesday night potential. He’s actually been on a lot lately which I like .

  58. NWS’s snow map from 3:10PM (for tomorrow’s system) is one I agree with and reflects the thoughts in this morning’s blog post.

  61. This suckers going to end up out to sea. These storms hardly ever materialize for us. The cape will get snow

    1. You are right about they never seem to be a big hit. We are certainly due for one that’s for sure .

  62. We should start to get some clues after the 0z runs later. Energy for this storm is coming onshore from the Pacific tonight. Either the GFS caves or we see the other models start to back off a bit. IMO this is probably going to end up somewhere in the middle.

  63. If I did the model mood swing (example, compare today’s 18z GFS to yesterday’s 18z GFS), I’d need a dramamine IV. HAHA! I’ll stick with the approach that works, and doesn’t result in 500 forecast “adjustments”. 😉

    Current thinking: No change from this morning’s update.

      1. It is a lovely celebration. Not religious but just a day when Christmas prep is complete and time to sit back and enjoy. Mac and I had some fun parties on this date.

        1. As an aside. We have a small neighborhood. My immediate next door neighbor has friends in Sweden and we have shared Glogg when gathering was permitted. As I discovered this year that family of another neighborhood a few houses down came from Norrköping, Sweden, where Mac and family lived. Small world indeed

  65. I meant to post this earlier but I’ve been multi-tasking like 3 people this weekend. 😉

    Now (8PM) to about midnight is Geminid meteor shower peak, and we have some clear sky currently in MA and southern NH (less so to the south unfortunately). Max potential is up to 60 meteors per hour away from light pollution. It’s not too cold for December so it’s not a bad night to try to catch a few. Radiant direction is from the ENE (constellation Gemini).

  66. Thank you, TK, for your detailed forecast.

    Vicki, thanks for sharing the video.

    My perspective – for what it’s worth – has been and continues to be that the Wednesday night storm will mostly graze us. Some light snow in the Boston area (perhaps a couple of inches of fluff), with heavier bands over the Cape and the South Coast. We’ll see what happens. Always fun to study the different models.

    Quebec City’s been snowy this weekend. Once the travel ban to Canada is lifted, maybe by mid to late February, I may head there for a couple of days. Guaranteed snow, ice, and cold.

  67. Maps from around the dial – except channel 7 who didn’t put one out: https://i.imgur.com/w4Cdase.jpg

    They all gave extremely short shrift to the weather tomorrow talking about it very fast (or in channel 7’s case almost all but ignoring it) in favor of hyping up the other storm. This makes me want it to bust even more, is that so bad? lol

    1. I saw Ch 7. They didn’t believe there would be any accumulation beyond a patchy coating in highest elevations tomorrow, hence no map.

        1. I’m in general agreement with all the ones I saw, and the NWS. I like 2 inches as a max just in case we get a band north of the low. It’s not got a ton of energy with it since we’re in between 2 jets, but once in a while you can still get an enhanced band for a brief time. So I left 2 for my upper limit. Most places will probably end up with under 1.

  68. TK – thanks for the reminder on the meteor shower. The sky is very clear here and on weekends the nearby primary school has no lights, so the viewing conditions are good. I saw a few in a short time.

  70. Round 1: Was outside 5 minutes, saw 4 meteors. That’s a good show!

    Going out for Round 2 shortly.

    1. Ok, you inspired me:
      – I did not go outside, I went to an upstairs window instead
      – A bright light was shining directly toward the window
      – I waited and hoped for less than five minutes, and then, I saw one! It was bright and clear and very fast. Worth the mini-effort!

    2. I meant that a nearby light was shining directly at the viewing window, seemingly ruining any chance of seeing a meteor, and definitely ruining the chance for a good photo. But it was great to see it with my own eyes.

      Reminds me of an icy cold night a while ago, on a quiet dark stretch of Route 128 heading home to Gloucester. There were no other cars at the time, and I saw the biggest meteor, a brilliant blue-green streak against a black night sky, pretty much straight ahead looking through the windshield, so it looked giant to me.

      Wonderful memory of it, I think of it from time to time. To this day it remains the most beautiful color I’ve ever seen in my life, a powerful, icy, fiery blue-green-white.

  71. 00z NAM is just a beauty, 12+ area wide. Perfect track, like the H placement. Fresh cold air, powder snow. Let’s do this.

    1. I would love for this to happen but I’m just not getting excited 4 days out yet . This time tomorrow night let’s see how it all looks

      2. Actually only 3 days. Of course a lot can change but based on what I am seeing all point to a major storm. If you aren’t working why don’t cheer for a big one.

      2. I generally would have just thrown it out by now but after the last storm and the fact that the Icon is going south, it has my eye.

  76. No meteors for me but wow the sky is full of stars so I did a lot of wishing . We did have a thin cloud layer closer to horizon

  77. Here’s what Model Watcher Woods Hill Blog forecast would look like:

    THURSDAY: Overcast with snow, ending late. At least 2 feet (edit) 12 inches actually (edit 2) goes further south so maybe 6 inches (edit 3) wowzers crush job 32 inches. (edit 4) coating perhaps (edit 5) tick up north a bit 16 inches. Highs 23-30. Wind NE to N 10-20 MPH, higher gusts possible, or maybe not go ask a wise fisherman if the sky was red the night prior.

  81. 00z UKMET looking good at 78 hours with low just off Atlantic City and heavy snow well up to the Vermont border.

  82. One thing to be leery of with all these models spitting out big snow totals….this system looks to be hauling. The bulk of the accumulating snows are in and out in 12-15 hours. Going to be tough to pull out widespread 20″ snows in that timeframe unless the snow rates are extremely intense. More likely we are going to see a max swath of 12-18″ in the “jackpot” zone (wherever that ends up) with maybe a few isolated 20″ amounts.

    1. As a point of comparison, Boston was about 10″ at 12z, now down to 9″. Worcester down from 11′ to 8″. Springfield down from 12.5″ to 9.5″. Hartford down an inch to 14.5″.

      These are all 10:1 numbers so add a few inches for Kuchera/fluff factor.

      So no big swing with the Euro BUT it does seem to be in the process of adjusting south a bit.

  85. Mark if it stays in this position it is good for us here in CT. At this point I think the low end in CT would be around 6 inches should a further south track happen.

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