Friday December 18 2020 Forecast (7:14AM)

74 Comments

DAYS 1-5 (DECEMBER 18-22)

Even though our departed storm is heading into the Canadian Maritimes, it continues to have an impact on the region this morning in the form of extensive cloud cover, and even more of an impact from Plymouth County MA to Cape Cod where ocean-effect snow & freezing drizzle has been ongoing, keeping things on the treacherous side where they already saw a wetter snow with rain followed by a flash freeze with a fluffier snow yesterday. Regionwide, conditions will improve today as drier air moves in and clouds break apart and eventually clear from northwest to southeast. High pressure moves in tonight setting up a strong radiational cooling night over the fresh snow pack, and hangs around to give a nice day on Saturday. The next disturbance from the west arrives Saturday night with clouds and takes the day Sunday to pass through with some rain and snow shower activity, but this will be a minor system with minimal impact. A weak ridge of high pressure brings fair weather for Monday, but an upper trough quickly swinging through the region Monday night and Tuesday will ignite a storm offshore. At this time the guidance has this system just too far offshore to be of an impact, precipitation-wise, but we should watch it carefully, given recent guidance performance in advance of such events. Either way, this system will help drag in more Canadian cold later Tuesday.

TODAY: Cloudy start including periods of light snow and/or freezing drizzle from Plymouth County MA to Cape Cod, gradually ending by about midday. Clearing with sun returning from northwest to southeast midday/afternoon. Highs 26-33. Wind NE-N 5-15 MPH morning shifting to N-NW this afternoon.

TONIGHT: Clear. Lows 3-10 except 10-17 urban centers and coastal areas. Wind NW under 10 MPH.

SATURDAY: Mostly sunny. Highs 30-37. Wind W 5-15 MPH.

SATURDAY NIGHT: Variably cloudy. Lows 20-27. Wind SW up to 10 MPH.

SUNDAY: Mostly cloudy. Periods of light snow/mix/rain. Highs 33-40. Wind variable 5-15 MPH.

SUNDAY NIGHT: Mostly cloudy early, then clearing. Lows 21-28. Wind W 5-15 MPH.

MONDAY: Partly cloudy. Highs 35-42. Wind W 5-15 MPH.

MONDAY NIGHT: Mostly cloudy. Lows 23-30. Wind variable 5-15 MPH.

TUESDAY: Mostly cloudy start with a chance of snow/mix favoring Cape Cod, then cloud/sun mix with a risk of a passing snow shower. Highs 35-42 but temperatures likely falling in the afternoon. Wind N 10-20 MPH, gusty.

DAYS 6-10 (DECEMBER 23-27)

Dry, cold December 23 as high pressure moves in then crosses the area. December 24 & 25 bring the next chance for some unsettled weather with early indications for low pressure tracking northwest of the region bringing a warm front / cold front combo through with some mix/rain with the warm front, a surge of milder air, and then rain showers with the cold front, followed by a sharp temperature drop and perhaps some snow showers. Caveat: I don’t necessarily trust the guidance depiction of this event yet, so changes to this outlook are possible. Dry/seasonable later in the period.

DAYS 11-15 (DECEMBER 28 – JANUARY 1)

One or two precipitation events possible during this period, favoring December 28 & 30. Shot of cold air arrives early period then some moderation follows. Low confidence outlook with much re-analysis needed.

74 thoughts on “Friday December 18 2020 Forecast (7:14AM)”

  4. Thanks, TK!

    You all know I `kill’ for this weather, especially during the heatwaves. I’m going to get outside – now that I no longer have to quarantine – and enjoy it by going on a long run along the Charles. There’s something about winter that reinvigorates me. I take after my mother in this regard. My mother passed away last year this week. It was during one of winter’s only cold spurts. I’ll reflect on her life as I take in the winter air today.

  5. Thanks TK
    Great tweet from Ryan Hanrahan why some parts of NH saw 40 inches of snow.
    About 40″ of snow in parts of New Hampshire today from an epic snow band that set up. The snow was exceptionally fluffy with 20:1 snow to liquid ratios. The reason? Very strong lift in the -12c to -18c that produced large numbers of dendrites – flakes that pile up quickly!

    1. I bet even JPD would have to say “uncle” on that amount. 😀

      And btw, Florida received 2 feet (24.0”) yesterday! 🙂

          1. OK, I was fooled on that one, pondered on it for a few seconds, but had no time to go and look it up. Good one Philip!

            Love this blog…

    2. JJ my brother and SIL are in Bow. They were well behind what we had but got clipped by some of that and ended up with two feet

  9. If that low pressure center on the 12z GFS could shift to the east and offshore for Christmas Eve into Christmas Day we could get quite a dumping of snow. Western NY and western PA the winners on that run.

    1. I’m not holding my breath on that storm . Most all of us will be having a white Christmas so that’s good . Probably picked up another 1.5 “ last night

  10. I am worried that many could see their snow start to disappear before X-Mas, not liking the setup I am seeing for snow, I see rain chances but not snow. I don’t like the positioning of the trough next week and I don’t see the Monday/Tuesday event phasing in time for any meaningful event.

      1. It seems we always get snow 1-2 weeks too soon before Christmas Eve/Day. The 12/25/2017 event was pure “atmospheric luck”more than anything else. Everything had to come together just right for snow and it did, at the last minute.

    1. I remember one Xmas Eve a few years back we had a really deep snow cover in pembroke . We had significant fog that night & woke Xmas morning it was pretty much gone & it was a decent snow cover , fog destroys snow .

      1. As a kid, I hated watching snow melt. I have a few recollections of what your describing above SSK, times when there was a deep snow pack and then, poof !!

        1. I did also. I was terrified sant wouldn’t be able to come if we didn’t have snow. Oddly, neither my kids nor my grandkids seem bothered by no snow

    2. Probably “just enough” left for the true definition of a White Christmas. Maybe 2-4 inches remain on the ground most areas?

      It should remain cold/cool through next Wednesday.

  12. Somewhat joking, a bit serious, given what we’ve been through this year …..

    Celebrate Christmas Day by Dec 23rd, probably a high chance of a white Christmas to that point.

    But, if we get one of those intensifying storms thru NY State, we know the drill, the temps get to 55-60F for a few hrs, the dps get to nearly the same, it pours rain for an hr or 2 (remember ravens vs pats) and that’s gonna be a big snow eater.

  13. Well, as TK offered in his discussion above, maybe the evolution of how the Dec 22nd disturbance works out can alter the following low on the 24th/25th.

    Hopefully so, because the current projection shows quite a surge of several hrs of real warmth in and around Christmas Eve.

  17. My view on a white Christmas is probably well into the minority. I’m more interested in seeing family than snow. And if we toss in warm weather, it may well mean, unlike thanksgiving when it poured, that people can see family they might otherwise not see outdoors. Just my opinion and I sure don’t expect many agree and understand that.

    1. And it teaches me NOT to read up which I rarely do. I see the warmth may bring rain. Can’t seen to win on outdoor distanced gatherings. Oh well….,time to change

    2. There should not be a lot of traveling hooefuy because there begging people to see anyone for the holidays if they live outside your house . Sadly we have canceled everything .

      2. I absolutely know that and it makes sense. We have not even tiptoed outside of what we should be doing since a few weeks before the March 13 shutdown. But You can see people in yard.

        Both my oldest daughters family and all in this house will have been in full self quarantine 16 days by Christmas and through to New Years. It’s just my son and family I won’t see. We talked tonight and we will do zoom. I’m hoping zoom will waive the 40 minute limit for Christmas also.

  18. Thanks, TK…

    Just finished my last Friday class for 2020. Two days in-person Monday and Tuesday next week, then a 12-day break.

    Severe Thunderstorm Warning for Christmas Day? 2020…wouldn’t surprise me in the least.

  20. Thanks, TK.

    For some reason I can’t bring up the radar when I go on the NWS site. Some other weird stuff comes up. Anybody know what’s going on?

    We got 14 inches of snow in Sudbury.

    1. I want to say I read that they just rolled out a new radar system just yesterday.

      I really liked the old one.

      This new one has a drop down box up in the left corner with multiple options and maybe after some time, I will come to like it, but as of now, I do not !! 🙂

      I really liked the old one.

      This is a pet peeve of mine with technology. As soon as I get used to something and really like, it gets switched to something new. And the old thing I liked I understood and worked perfectly.

      1. Thanks, Tom. I know what you mean. It was so easy before – just click on radar and you would get it. I always thought things would get easier as technology advanced through the years. Now they make it so complicated. Thanks again! 🙂

  21. It’s too early to really tell where the positioning of the low will be Christmas Eve. A shift of a several hundred miles could make all the difference, given that there’s plenty of cold air on the back side. But, it does look like milder temps will make their presence felt starting on Sunday.

  22. If you think areas that saw over 4 inches of snow will lose it before Christmas, let’s talk about making a bet. 😉

      1. As was pointed out by a colleague before I got a chance to look at anything this afternoon, some members of the 12z GFS Ensemble actually have snow for Dec 25.

        One can’t just look at an operational run and decide all of our snow is going to vanish before Christmas. That’s not forecasting. 😉 Saying that we have a system potential around that time and leaving room for various scenarios due to inherent uncertainty is the way to forecast this one right now.

  23. NWS new radar will get easier to use. It’s going to be an excellent system for moving around & zooming, etc.

  24. TK, I agree with your thinking on next week. I have zero knowledge about meteorology, but I’ve analyzed economic modeling for decades. So, I’ll use that as an analogy. There are many models in operation, each with a distinct range of variables – endogenous and exogenous – that are hard enough to pin down from day to day, let alone week to week or month to month. What we do know about the economy from, say, week to week is the general contour. Getting back to the weather for next week, milder air will begin to play a role on Sunday and throughout parts of next week. However, it’s still to be determined: a. how mild; b. precise positioning of jet stream and therefore lows that travel parallel to it; a myriad of other factors, such as snow depth, interaction between systems, etc …

    1. A co-op observer in Peru VT actually came in higher at 44.8″. If this is verified, it would break the 24 hour record.

    1. Guess that 44″ in VT doesn’t seem so much anymore! Interesting that highway pictured runs along the coast. I had always thought the snow in Japan was mainly confined to the mountains.

  30. Trans Siberian Orchestra has a virtual concert at 8:00. Anyone else attending? I got airplay working and set up surround sound. Good thing grandkids don’t have school tomorrow. It will be loud down here

  31. Yes, Mark, most of the snow in Japan is either in Hokkaido – far northern Province (I think they call them provinces) or the mountains. Certainly, Tokyo is not a snowy city by any stretch of the imagination, at least not normally. My guess is it’s more like Seattle than, say, a Northeast city in the U.S.

    1. Joshua, you made an interesting comment above, including this phrase: “precise positioning of jet stream and therefore lows that travel parallel to it”.

      This got me thinking about how this all works, and also why things differ in the summertime.

      Found this article on Jet Streams: https://climate.ncsu.edu/edu/JetStream
      “The polar and subtropical jets are both westerly, meaning they come from the west and blow toward the east. Both jets move north and south with the seasons as the horizontal temperature fields across the globe shift with the areas of strongest sunlight.

      In the winter the polar jet moves south and becomes stronger because the North Pole gets colder but the equator stays about the same temperature. This increases the temperature contrast and moves the strengthened polar front jet farther south.”

      More good stuff in the article, at least for beginners.

      1. this is part of the reason that the PV will likely weaken as the climate continues to warm as that difference shrinks

        1. With what effect Matt? When the polar vortex weakens does it float about erratically, or does it it just stay further north?

          1. Stronger PV, keeps the cold air locked up near the poles. a weaker PV allows cold air to go to the mid latitudes. When the PV is weaker it floats around more often of course other factors impacts where the throughs form. The warmer the polar regions get the closer they will be to the temperate regions allowing the PV to tend to be weaker. As the climate continues to change, we will see more moisture heavy systems. Many people believe due to the warming climate that we will decrease our snow, but that won’t necessarily be the case for this reason. Climate models from 10/15 years ago have been extremely accurate for our period of time.

        2. In my mind, a tighter vortex is a smaller diameter, but the article above indicates a stronger polar vortex “moves the strengthened polar front jet farther south.” Presumably a larger area?

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