Wednesday December 2 2020 Forecast (7:33AM)


The big storm system that brought our wind & rain Monday and our continued windy weather yesterday will still have somewhat of a hold on the region in the form of a gusty breeze and passing clouds during today. Our air, a modified polar air mass indirectly from Canada via the Midwest, will feel more typical for early December. As a low pressure trough makes its way eastward, there will be an area of snow showers from the Great Lakes across New York, extending into the Berkshires, and a few of these, in the form of very light rain and/or snow showers, may sneak eastward far enough to survive into the WHW forecast area during the afternoon & early evening. That disturbance will be long gone by Thursday, which will be the “pick of the week” in terms of nice weather – sunshine, not too breezy, not too cold. And then things change. I’ve been trying to work out the timing of the threat of unsettled weather later this week for some time, and it still appears we’ll see the return of clouds and a rain shower threat Friday as a cold front moves into the region. The dilemma has been the weekend – would a storm develop and move in to impact Saturday, both days, Sunday, or would no storm impact the region at all? The answer seems to be revealing itself with gradual consensus developing between various model guidance to show that low pressure won’t waste that much time getting formed on the trailing portion of the front that passes through here, to our southwest, and then heads in this direction for the weekend. What still isn’t clear is the timing. The most likely scenario at this time seems to be a rain event beginning sometime Saturday, and ending, mostly as a mix or even snow for parts of the region during Sunday, pending the arrival of colder air. So as you see, there are still details to work out as we get closer.

TODAY: Sun and passing clouds. Chance of a brief light shower of rain or snow, favoring the hills well west and northwest of Boston later in the day. Highs 40-47. Wind SW to W 10-20 MPH with higher gusts.

TONIGHT: Partly cloudy with a brief sprinkle of rain or flurry of snow possible early, then clearing. Lows 28-35. Wind W 5-15 MPH.

THURSDAY: Mostly sunny. Highs 45-52. Wind W to SW 5-15 MPH.

THURSDAY NIGHT: Increasing clouds. Lows 35-42. Wind SW 5-15 MPH.

FRIDAY: Mostly cloudy. Chance of rain showers. Highs 45-52. Wind SW 5-15 MPH shifting to W.

FRIDAY NIGHT: Mostly cloudy. Lows 38-45. Wind variable under 10 MPH.

SATURDAY: Mostly cloudy. Chance of rain. Highs 45-52. Wind variable 5-15 MPH, higher gusts possible.

SATURDAY NIGHT: Cloudy. Chance of rain. Lows 35-42. Wind variable to NE 10-20 MPH, higher gusts possible.

SUNDAY: Cloudy with a chance of rain/mix/snow morning. Variably cloudy with a chance of mix/snow showers afternoon. Highs 38-45 then falling. Wind N to NW 15-25 MPH, higher gusts possible.

DAYS 6-10 (DECEMBER 7-11)

With the storm threat focus shifting to the weekend, the early portion of next week looks mostly dry and seasonably cold at this time, but we still may have to keep an eye on potential offshore low pressure. With low confidence I say that the next threat of precipitation is around December 10 from a system tracking west to east along the boundary of cold to our north and warmer air to our south.

DAYS 11-15 (DECEMBER 12-16)

Signal for another disturbance bringing a precipitation threat in the December 12-13 window followed by drier but colder weather. Again a low confidence forecast at this time.

47 thoughts on “Wednesday December 2 2020 Forecast (7:33AM)”

  1. Good morning and thank you TK.
    My eyes may be deceiving me but I think I see the weekend system tracking a little more to the East of yesterday’s runs. That at least increases the chances of some back end snow. Time will tell.

  2. Looking at an image of 6z EURO on twitter and it goes bonkers with a 978 low pressure system offshore with the snow line coming into western CT and MA at 5pm Saturday.

  3. The 12z NAM goes bonkers with snowfall from CT River Valley west. 980 low pressure coming over the south shore.

  4. Well, at the very least it is getting interesting and not a total
    bore for the weekend event. πŸ™‚

  5. I got to see more model consistency before I get excited for back end snow. The 6z NAM had nothing then BOOM double digits snowfall totals CT River Valley West.

  6. 12Z GFS is chugging away. What will it show? What will it show?
    I am liking the 500MB flow at 66 hours better than previously,
    Will it translate? who knows.

  7. Thanks TK.

    For model watchers…

    The HRRR was upgraded as of the 12z run this morning. The synoptic hour (0z, 6z, 12z, and 18z) runs will now go out through 48 hours. Several changes/improvements have been made to the model, so it will be interesting to see how it performs this winter.

  8. I’d watch the weekend system pretty closely. It’s a really difficult forecast as TK has alluded to with the struggles in the guidance. But this storm could crank pretty quickly once it starts to come together. Just a matter of where that happens. You need the northern stream trough to dig hard and capture the southern stream system to get the real “bomb” solution and draw in some colder air. Otherwise the southern stream system will be all on its own, like the GFS shows. Which would still likely yield some rain, but less cold air getting drawn in and a less impressive evolution overall with a slower rate of deepening. If pressed, I would say I prefer something closer to the NAM/Euro, but that is not a high confidence forecast.

  9. Generally the models have been horrible, but we are now in a 72 hour window where their output can’t be ignored. As prognosticated here ingredients have been trending favorable for winter weather impacts 12/5-12/25

    That said, other than the maps you all have posted, I have looked at no guidance since the 00z suite. I remain weary of ECMWF precip amounts. Just last week I noted it’s modeled 4-6β€³ of rain from our early week system would be more like 1-3β€³ so details to be worked out, but it is going to be a fast forecast adjustment. You all got more than a watcher cooking.

  10. Not sure the NWS has received the memo yet or perhaps they have and this is how they interpret it:



    * A few showers possible Fri
    * A storm brings mostly rain Sat/Sat night, possibly ending as snow
    higher terrain
    * Improving conditions Sunday, then mainly dry and turning colder
    early next week

    1. they probably won’t change much until Thursday afternoon as there has been just to much variation in the models though the ensembles mean have been some what more constant. Have to watch that ULL and digging trough to see if the ULL over the central plains can get ahead of the digging trough to form what the EURO is showing.

        1. The 18z EURO was slower, a tad weaker and further west (traveling over SE New England instead of off the coast. The temperature profile is marginal at best.

    1. Indeed they are. This is what us mets are dealing with, more so than usual, and this will continue. Get used to it. πŸ™‚

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