Monday Forecast

185 Comments

7:29AM

DAYS 1-5 (DECEMBER 16-20)
High pressure positions itself north of our area today, delivering cold air which will be a factor in the visit of our next low pressure system, which will be Tuesday, bringing snow/ice/rain to the region. While most areas start as snow (possible snow/rain start immediate South Coast), mild air aloft will help flip the precipitation to rain/ice mainly south of I-90 (rain favoring the coast, freezing rain & sleet interior), while areas to the north of I-90, while possibly mixing with or turning to sleet for a while, will be mostly snow. This is not to be a big storm, in terms of precipitation amounts, but it will impact travel around the region during Tuesday. This system exits Tuesday night and a potent upper level disturbance and accompanying arctic cold front will cross the region Wednesday with a snow shower and snow squall threat. While this will not likely be a widespread snow event, it can have temporarily but significant local impact. Exact timing and placement of snow showers/squalls will not be able to be determined until the day itself, the time period most likely to see activity is early afternoon to early evening based on current expected timing. The Montreal Express visits us on Thursday which will be one of our coldest days so far this “winter” (it technically won’t be winter yet). The cold remains in place though easing very slightly on Friday as high pressure builds in, but it will feel nicer than Thursday due to a lack of wind.
The forecast details…
TODAY: High clouds increase. Highs 30-37. Wind variable up to 10 MPH.
TONIGHT: Cloudy. Snow develops pre-dawn west to east except snow/rain immediate South Coast. Lows 25-32. Wind light variable.
TUESDAY: Overcast. Snow to rain South Coast, snow to mix I-95 corridor which may include sleet and/or freezing rain, snow NW of I-95 area. Snow accumulation a coating to 1 inch South Coast including Cape Cod, 1-3 inches most of southeastern MA and RI to near Boston, 3-6 inches from I-95 area northwestward. Highs 30-37. Wind E to NE 5-15 MPH.
TUESDAY NIGHT: Mostly cloudy with lingering snow showers evening. Clearing overnight. Lows 22-30. Wind N 5-15 MPH.
WEDNESDAY: Variably cloudy. Afternoon snow showers/squalls likely. Highs 33-40. Wind W 10-20 MPH shifting to NW late.
WEDNESDAY NIGHT: Variably cloudy with evening snow showers possible. Clear overnight. Lows 10-17. Wind NW 15-25 MPH, higher gusts. Wind chill 0-10 at times.
THURSDAY: Mostly sunny. Highs 18-25. Wind NW 10-20 MPH. Wind chill near to below 0 at times.
THURSDAY NIGHT: Clear. Lows 5-12. Wind NW 5-15 MPH. Wind chill near to below 0 at times.
FRIDAY: Mostly sunny. Highs 23-30. Wind N up to 10 MPH.

DAYS 6-10 (DECEMBER 21-25)
Near to below normal temperatures December 21-22 weekend while we watch low pressure passing to the south and trough connecting to a weaker northern stream system passing through the region. This brings a chance of at least some light snow (and possible coastal mix south) later Saturday into Sunday – not likely a big storm. If enough onshore flow is involved, ocean-enhanced snowfall bands cannot be ruled out. Generally dry overall with seasonable to slightly below normal temperatures for the remainder of the period, however with a risk of a few passing snow showers from a weak disturbance sometime December 24 and/or 25.

DAYS 11-15 (DECEMBER 26-30)
A little more activity in the subtropical jet stream may send some moisture with a rain/snow threat later December 26 or December 27, with fair and colder weather returning for the balance of the period.

185 thoughts on “Monday Forecast”

    1. Thanks TK. Interesting how you and SAK pretty much think alike on your forecasts. Did SAK attend U. Lowell as well?

  4. Thanks TK!

    The very wintry December for SNE continues. Much of the negative monthly temperature anomaly has actually been removed due to warmer weather in the past 7-10 days (that anomaly may at least temporarily grow again later this week). But temperature’s aside, the snow just keeps coming. I have not looked over SNE in too much detail with this storm, but to me it has the look of an over-performer, if not in terms of snow totals then at least in terms of impact due to potential icing after the snow. I don’t see temperatures going above freezing in a lot of the area throughout the event, so 0.5-1″ of QPF is going to cause a lot of problems.

    Also, get ready for some whiteout snow squalls on Wednesday before the polar plunge.

  5. WxWatcher, you had mentioned that the NWS is running a new HRRR in parallel.
    Is it called: HRRRV4 – High Resolution Rapid Refresh V4
    I noticed that it is now available on the College of DuPage Site.
    And if that is it, then can that one be trusted over the regular one?
    Your comments would be most appreciated.

    Many thanks

    1. FWW, the regular shows a change to rain even somewhat N&W of Boston while V4 keeps it all frozen in Boston with mostly snow and some sleet.
      Interesting.
      Will compare the 12Z runs when the V4 is complete as it is running behind
      the regular version which is just about complete.

    2. Yep, that’s the one! As you mentioned, COD now has some products from it, as does Pivotal Weather. And it does run a little behind the operational version and does not run every hour (I’m actually not sure if it is intended to run one-hourly or not when it goes operational).

      In terms of trusting it, it is free from the errors impacting the operational version. However, like any new/upgraded model running in a parallel capacity, it is subject to close monitoring and tweaking by the developers. So far I have been quite happy with its performance, but it’s a small sample size.

      1. THANK YOU!
        This is good news.
        Now concerning tomorrow’s event, the V4 is more robust for snow, at least with the 6Z run. Still waiting on the 12Z run. We shall see.

      3. Oh and I see that the HRRRV4 runs out 48 hours or at least it
        did on the 6Z run. 🙂

        I press the LIKE button.

  8. JPD…
    The regular HRRR would have the changeover too far NW due to 1-2 degrees too long warm initialization on bare ground.

  9. Although it is not really that cold out, today packs a bite due to the comparison
    with the recent warm weather.

    2. BTW pretty sure JMA called for “colder” a week ago. Was all over that. I think models were showing mostly rain at the time too.

  21. A violent day of weather is underway over the Southeast US. At least two strong tornadoes on the ground right now, one in Mississippi the other in Louisiana. More are likely through the afternoon. One of those tornadoes going on now, the one in Louisiana, is tossing debris to ~25,000 feet, likely an EF3+.

  22. Will have to monitor initially how far/fast the mid level warmth makes it north for sleet/frz rain line and then, in the middle of the event, how far north and west the coastal front makes it for boundary layer issues, before slowly collapsing back to the south and east.

    A less intense southerly jet should ease how fast the warm layer aloft proceeds north, but that may be offset by less intense precip in this event.

    I’m sure we can recall a week or 2 ago, where the very intense precip helped to keep the column cool enough in that part of the area where the column above was marginally cool (very close to 0C).

      1. oh my goodness, that would be 3 before December break.

        I hope not 🙂 🙂 🙂

        June, for length of daylight and the warm, but not oppressively humid temps is my favorite month of the year and I don’t want to be inside missing most of it.

  23. [12:45pm Monday 12/16] – Winter Weather Advisory expanded to include the Connecticut coastline and all of northeast NJ with the exception of Hudson County.

    This tells me they are going with the colder solution if all the shoreline is now included.

    1. Perhaps, but Connecticut, NYC and northeast NJ can have cold surface winds, but because of the geography of the northeast relative to storm track, we can still have issues in eastern and southeastern Mass.

  24. Hate to throw yet another wrinkle into this, but the latest Hi-Res models indicating
    that the bulk of the precip may actually passs South of the Boston Area.

    1. Which one? Euro high res has most snow north of the city. Not seeing anything pointing to is being that far south.

  32. If the icing could be kept to under a quarter inch then you could avoid major problems. A quarter inch icing or greater then were talking tree damage power outages.

  41. I say KANLOOEY!!!

    informal : to suffer complete failure, destruction, or ruin especially in a sudden or spectacular way
    One of several prize prospects of the mid-80s, he tried a comeback with the Rangers after his career went kablooey.
    — Kevin Sherrington
    … went public … just a few months before the technology-stock bubble went kablooey.

  43. Interesting that the 18z GFS has come WAY north for the 12/23 storm. Still a miss by quite a bit but the 12z run had the storm over FLA and the precip staying south of NC. 18z brings the storm off the Carolinas with rain/snow as far north as VA and the southern Delmarva.

    May not mean anything but 7 days away with this one so still plenty of room for changes…

    1. Eric F’s snowmap actually looks similar if you were to project Ryan’s further out.

      He’s got 3-6″ N and W of a Hartford – Providence – Boston line.

  47. I have seen plenty of times over the years where these storms creep north so that fact that no storm is being shown here is nothing to get discouraged about at this time.

    1. JJ, this is looking like the real deal for an ice storm for central and southern CT. Maybe even extending into northern CT if some of the latest runs are correct. Hoping for more snow/less ice but not liking the looks of this.

  49. The cold air at the surface doesn’t want to give way and that spells trouble. I think the majority of CT will stay below freezing for this entire storm system. The immediate shoreline may get above freezing. Then the attention turns to Wed pm with the potential for those snow squalls. Just like the summer when it comes to thunderstorms not every town sees one but those that do it will pack a punch.

    2. That’s ripped right from the 18z GFS. 12z GFS and Euro didn’t look quite that warm….more like low 40’s.

      1. Can you guys please post links or exact wording. My guess is this is the ten day which we know is not what he thinks but what he is required to post. I know Pete well enough to know he would NOT say more than potential

  52. As Ryan Hanrahan said on air the longer it snows the less ice will deal with the quicker the change from snow to ice the more ice will deal with.
    #MESSORAMA

    1. I agree with cold at the surface. Just west of the coastline and all inland locations. Quite cold, maybe in the mid-upper 20s. (Maybe a dramatic coastal front between Boston western suburbs and Logan)

      Less certain how it plays out aloft.

  54. Low dew points and big opportunity for some further cooling when precipitation commences much later, especially inland.

    Think this is going to create a big area of mid 20F temps away from the coast, which will be heavy, dense air that will drain to the CT coastline, especially if the low center kind
    of jumps from PA to south/southeast of Long Island. Hopefully, the column want have an above 32F layer for too long in those areas and/or the precip shuts off.

  55. So, seems a 4-6 am arrival for snow. The worst timing. Anything is better, from 3 hrs earlier to 3 hrs later. The superintendents make their decisions sometime in that 5am timeframe and I hate when the wintry precip sets in then. I think it makes for a most difficult decision.

    1. It is nice to have a decision to make plans off of. Now, we’ll see how the weather and that decision get along.

      1. And see if they actually change the decision. Guess they could happen? Really not sure how they decide that.

        1. Good question.

          I know the superintendent down here always says …. “after consulting with the Marshfield Police dept and the DPW, …… “

  57. Good points above. Along the coast ANY Easterly component to the wind will switch
    things to rain when it warms above. Inland is a different story.

  59. Interesting that the 22Z HRRR has 1/2 inch Kuchera snow for Boston by 8AM,
    while the 23Z HRRR has 1.1 inch at the same time, 8 AM.

        1. Another somewhat long event …..

          Initial burst of snow/sleet ….

          Perhaps some cold rain for a while in the middle.

          The temp drops back below 32F sometime later tomorrow with some light wintry precip possible into the first half of the night.

            1. We are so well known for our snow removal people ask did the storm miss this place . Spotless , safe ,attention to detail & pride in workmanship at the highest level .

    1. Am I dreaming that TK offered us caution with HRRR the other day, needing some upgrade that is not coming til spring ??

      1. I was just about to mention that. In fact this morning he cautioned that the hrrr was likely warming too fast due to the warmer initialization. So, we shall see.
        hrrrv4 holds onto cold much longer.

  64. I stand firm that this ends up being mostly snow/ice and sleet vs plain rain. We shall see how it plays out. All I know if why delay 2 Hours? It won’t be any better at 9:30-10 am.

  66. 0z hrrr v4 holds onto snow/ sleet longer than hrrr, but boston accum is still less than 3 inches. nams almost set.

  67. oz Nams push snow even farther North.
    reg under 1 inch for boston. 3km a bit morevthan that. mobile, cannot conveniently post maps.

    1. That is a lot of ice. Worse ice storm in awhile for CT if that verifies and the models unfortunately have been fairly consistent in that regard.

      One thing I will say is that the actual “ice accretion” on branches and power lines should be less than those numbers which are the actual amount of freezing rain that falls. A portion of that rain will run off, especially if it is coming down hard.

      Nonetheless, it seems likely that some areas may top 0.5″ of accretion which will surely start to bring some branches and power lines down.

      Not looking good in your area JJ

    2. When I see those numbers, it tells me the NAM thinks there’s going to be a cold, low level northerly flow the entire system in those areas. That ice makes it pretty far east into southern New England. The NAM must think the coastal front is going to be restricted to far SE mass immediate coastal areas.

  75. As much as I love the weather, I’m not up on advisory/warning criteria.

    Can a winter storm warning be posted for an impactful ice storm?

    I’d think after seeing so many warnings, the public might think a winter weather advisory indicates something not too hard to handle. Of course, if those ice amounts around the populated areas of coastal Connecticut, that’s going to be a high impact event.

    1. Tom, NWS can issue an Ice Storm Warning. I thought the threshold was 1/4″ of ice accretion or more expected.

    1. No word on schools from this area that I’m aware of.

      Hoping all who are on the roads in the morning safe travels

    1. It’s been trending that way last few runs and with the storm onset only a few hours away, I would lean more ice/less snow most areas unless you are NW of 495 in eastern MA or north of the Pike in west/central MA

  78. Tom, both the NWS Upton and Norton mention in their discussions that they expect 0.1-0.2″ ice accretion with as much as a 1/4″ or more in a few areas. So it seems they are expecting most areas to remain under the threshold.

    It will be interesting to see with the latest guidance if they contemplate upgrades to warnings in portions of interior CT.

  79. That track makes me suspicious on seeing that much snow north. But who the hell knows. Seems like an awful day tomorrow either way.

  80. Take a look at this Tom. You called it.

    Sure looks like Southeast convection undid the forecast. NNE/SSW oriented line favored transport of latent heating towards the Northeast. Watch the last several runs gradually bump heights up locally. Rather than a more zonal, flatter system this has now become more amplified.

  81. Eric is moving to TK land

    A little more sleet/freezing rain, a little less snow. Going to nudge the 3-6″ range to the north. Good trend for ski country, ugly day for us in SNE. #wbz

  82. I’m not sure off the top of my head, but I think the ice storm warning criteria for SNE is 0.5”. That’s what it is across our northern zones here at least; there’s a jump in the middle of our CWA where the criteria goes from 0.25 to 0.5. I don’t think it decreases again to the north, but again I’m not 100% sure on that. But in cases of a combination of a few inches of snow and a couple tenths of ice, a winter storm warning can absolutely be issued for that. I am definitely concerned about ice with this event. Not everywhere, but I think there will be a stripe of significant ice impacts.

    1. That’s accumulated freezing rain, not technically ice accretion. The actual ice accretion would likely be a bit less than these values.

  84. Here is a link to all the NWS warning criteria for BOX….

    https://www.weather.gov/box/criteria

    Ice storm warning criteria in SNE is indeed 1/2″ or greater ice accretion which explains the advisories vs. warnings.

    I think still an outside chance that interior southern CT meets the criteria but it may end up a nowcasting situation with any upgrades.

    1. It’s going to be a nasty morning old salty & rain going back to snow tonight I may be here till tomorrow if that’s true

    2. Another loser day? We’ve done incredibly well this month for snowfall by December standards.

      Besides this is not an “solid entity”. A lot of the precip has not formed yet. That will take place as the event happens during the next 12 to 15 hours. It’s just starting. The precipitation is not all in existence already. 80% of it will generate atop southern New England.

  90. My radarscope precipitation depiction mode shows mix up to Quincy/Boston, but
    it is SNOW here, at least for now. 🙂 Light coating on the ground. Temp 28 here. Came down 2 degrees with onset of snow.

    1. It’s also going to stay a touch colder than the models’ overreaction to thunderstorms last night. And the TV guys all bit the bait perhaps a bit too hard.

  93. Tk,

    Thank you for your response the other day. My bad on thank you so late. Heading to FL on Thursday and it looks as though it’s going to rain Saturday and Sunday such a bummer.

    1. There will be some showers/thunderstorms around but a lot of the activity may end up to your north.

  94. Almost 1/2 inch snow so far, and the landscape has returned to postcard December quality. 🙂 Roads are just wet at this point at my location. Snow tapered off for now but will fill back in soon.

    New post!

  95. Warm air is definitely moving in aloft. Snow has changed to mix in Westwood under light precipitation after a coating of snow. If heavier echoes move in, it may drag down some colder air turning the mix back to snow prior to a complete change over but it will be difficult to achieve an inch or two of snow from this system.

Comments are closed.