Friday Forecast

60 Comments

7:35AM

DAYS 1-5 (DECEMBER 13-17)
The pre-Christmas express is rolling in the form of a fast-moving active weather pattern. We’ll have passing trains on two tracks during the next 5 days. A low pressure system from the south, “the inside runner” will blow through here tonight and Saturday with a rain event, the heaviest of which will occur Saturday morning, leaving plenty of wind in its wake Sunday as drier air moves in behind it. The “Ohio Valley Express” will be up next in the form of a weaker but somewhat colder system that will arrive late Monday evening and be gone by late Tuesday. While the exact track of this one is still somewhat in question, the area is likely to at least start as snow and end as snow showers. What is uncertain yet is what happens in between. At 4 days away I’m leaning toward a flip to rain South Coast and mixing elsewhere. Either way this does not look like a big storm, in terms of precipitation amounts, but will likely impact a couple of commutes.
The forecast details…
TODAY: Limited sun early, otherwise becoming cloudy. Highs 37-44. Wind E to SE up to 10 MPH.
TONIGHT: Overcast. Areas of fog. Occasional light rain evening. Steady light to moderate rain overnight. Temperatures rising slowly through the 40s. Wind SE 5-15 MPH, higher gusts along the coast.
SATURDAY: Overcast. Areas of fog. Rain, moderate to heavy at times morning. Scattered rain showers afternoon. Highs 51-58. Wind SE 10-20 MPH with higher gusts morning, becoming light variable afternoon.
SATURDAY NIGHT: Mostly cloudy. Rain showers likely. Slight chance of thunderstorms. Temperatures steady 51-58 evening. Lows 40-47 overnight. Wind S 10-20 MPH, higher gusts, shifting to W overnight.
SUNDAY: Mostly cloudy with a risk of rain showers early morning, then sun/cloud mix. Highs 43-50 occurring morning. Wind W 15-25 MPH, gusts 35-50 MPH possible.
SUNDAY NIGHT: Clearing. Lows 22-29. Wind W 10-20 MPH with higher gusts, diminishing overnight.
MONDAY: Sunshine followed by increasing high clouds. Highs 30-37. Wind variable up to 10 MPH.
MONDAY NIGHT: Thickening overcast. Snow arriving late evening or overnight – some accumulation possible. Lows 20-27. Wind light variable.
TUESDAY: Cloudy with snow to mix north, snow to rain south, ending as snow showers late. Additional snow accumulation possible for some areas. Highs 33-40. Wind variable 5-15 MPH.

DAYS 6-10 (DECEMBER 18-22)
Polar jet stream dominates with cold weather. A risk of a few snow showers December 18 and possibly a period of snow around December 19 or early December 20 from a clipper system. Uncertainty for the end of the forecast period as we may need to watch a system to the south over the December 21-22 weekend for possible impact with snow/mix at least for southern areas.

DAYS 11-15 (DECEMBER 23-27)
Much of this period looks dry and seasonably cold with occasional snow shower risks from passing disturbances but this is only low to moderate confidence.

60 thoughts on “Friday Forecast”

  2. Good morning and thank you TK.
    Not feeling bullish for a White Christmas.
    Still time, so we shall see. 12/22 could still pan put. long way to go on that one.

  4. Thanks TK!

    Noticed you mentioned a slight chance of thunderstorms for tomorrow night. While it usually overdoes these things, the 12z 3km NAM is quite robust on an instability burst tomorrow evening. Plenty of shear of course. Any convection would be elevated (above the low level inversion) but I could at least see some isolated thunder tomorrow. SPC has general thunder in their outlook.

    Definitely a soaking rain event… but possibly our last heavy precip event for awhile? The early next week event looks moderate at best on QPF and from there the signals look rather dry to me.

      1. A little hard to say this far out. But I do think the second half of this month will certainly favor a drier pattern than we’ve seen and probably drier than average, and that may carry into January.

  5. 12Z NAM has a similar theme for Tuesday, namely a start as snow with a change/mix to sleet and then RAIN. What else is new?

  10. 12z EURO looks a bit sharper at 500mb at hr 96. Accordingly, low looks a bit stronger and tracking a bit further west.

      1. There won’t be any snowcover left anywhere by tomorrow inside 495 with the possible exception of north-sloped wooded areas.

  14. MJO forecasts today tilt just a tiny but toward phases 8 & 1 but are still technically “too weak to be determined”.

    1. The biggest mistakes made were everyone getting out at once during the worst of it. Had they stayed in place and let the road crews work, getting home would have been easier (not easy, by definition, but easier than it turned out that day).

      There were a whole lot of people very angry because “where are all the plows?” … Well, they are stuck in the same back-up that you’re in. 😉 Logic that very few people recognized.

      1. I remember that. And I remember suggesting someone special to leave much earlier. My guys always put the company first. 🙂

  17. According to Eric tomorrow’s highs:

    Boston 57F
    Bedford 47F

    Considering all rain well into NNE with strong southerly winds somewhat surprising for a “wintry” type coastal front thatclose between the city and suburbs.

      1. Nobody said anything about a guaranteed white Christmas. The odds are still roughly climatology, maybe a couple percentage points over.

        1) We need to lay down a snowcover of some kind from the system early next week.

        2) We probably need 1 or 2 other shots at something.

        3) We need cold enough air to keep it in place but air not so dry that most of it sublimates.

        This all comes out to about maybe a 25% shot for Metro Boston at this point.

          1. Nothing unusual. 🙂 We’re already basically over December’s normal for snowfall. Anything else is a bonus. Whether there’s an inch of snow or more on the ground at 7AM December 25 (which would make an official white Christmas) depends on the factors above. There are many many years we could pretty much put the shot at near 0% even with just under 2 weeks to go. This is definitely not one of them.

  20. Thank you, TK.

    Goodness, it’s gray. Loved yesterday. But man, I’ve had (we’ve had) too much gray, too much rain. I realize we’ve had gloomy periods before. But, this extended period of mostly gloom is really getting to me. I guess it’s too much to ask for 2 days of sun. Yes, we had that last weekend. But, it’s really been hard to find a 2-day stretch of sun for a rather long time. Don’t care if it snows or not. Just give me an extended (is 3 days asking too much?) period of cold and sun. I apologize for the complaining.

    1. There’s something about a slate grey sky that I have always loved. It reminds me of impending exciting weather, especially snowstorms. Yes in this case no snowstorm but I’m always excited to watch an event play itself out. I’m curious about the potential for thunderstorms tomorrow evening.

      I also love weather changes. I like inside runners and Great Lakes cutters just as much as cold track storms. I love going through the various air mass sectors, and this upcoming event is going to do that for me, so that’s why I loved the sky today. It was also beautiful this morning with filtered sunshine and a gorgeous moon set.

      1. As you know, I feel the same. Oddly, After reading your post Joshua, I had to stop and think whether we saw sun the last few days. I honestly can’t answer that.

        I sat out last night late …it was a beautiful sky

        1. Wednesday late morning on was sunny (with passing “marshmallow clouds being friendly”). Thursday was also sunny. And there was limited sun this morning as well. 🙂

          Hope you got the song reference. 🙂

  21. For Tuesday:

    Ch. 7 = snow to wintry mix
    Ch. 5 = snow-rain-snow
    Ch. 4 = wintry mix (kitchen sink)
    NBC10 = snow ending as drizzle (1-3”)

    NBC10 has “light” snow next weekend.

  23. From the NWS 430 pm package…

    “Another low pressure system looks to impact the area by early Tuesday. GEFS
    Ensemble shows PWATs 1 to 2 standard deviations above normal and
    even 2 to 3 standard deviations above normal for parts of Eastern MA
    coast. With the cold air in place, it should start off as snow
    before changing to mixed precipitation or rain away from the
    interior. However, if the low pressure tracks near the 70W/40N
    benchmark, it is not out of the question this could remain mostly
    snow and bring impactful snowfall to the I-95 corridor. But since we
    are still 4 days away and given the spread of model guidance,
    confidence is low and all solutions remain on the table.”

      1. It’s also not out of the question that a potent upper level disturbance and weaker surface reflection bring a brief snow threat on Wednesday or Thursday next week too. Sometimes these can end up more impressive than what precedes them.

  24. TK, I like the variability, too. And, you’re right, there are some really nice benefits attached to slate gray skies. For example, photography is made easier. In fall, the gray skies `bring out’ the colors of the leaves. They enhance the colors, if you will. I’m just a little sick and tired of the gray and rain. That’s all.

  25. Just drove with my youngest backroads to Sutton schools to pick up her son at teen night out. So far roads are just wet. The temp in Sutton center area is right at 32. At least one of the sidewalks into the school was thin ice

    Very foggy.

    1. That’s absolutely correct. There were pockets of cold air trapped well into last night with some icy patches. Some locations would be above freezing while just down the road would be below.

      There were also some icy patches in locations where the air temperature (at 5 feet) was slightly above freezing, because we were in a situation where the ground temperature was now below freezing.

      This is where a person can be mislead by seeing a temperature of say, 33, or 34, and automatically thinking there can be no ice. But micro-meteorology will tell you otherwise. 😉

      At least by now it’s long gone as its warmed adequately since late last night. 🙂

  26. Not looking forward to the commute tomorrow I need to be in work at 5am should be pouring at that hour

  28. For model users!!! I’ll also re-post this on the update.

    Don’t use the HRRR or RAP from now until the upgrade in the spring. In case you haven’t noticed, both have been producing increasingly poor forecasts due to initialization problems, and the NWS has elected to not fix these issues since the models are due to be upgraded in the spring. However they are going to continue to run the models, knowing the output is bad. This was confirmed by a colleague who contacted them directly. So just a heads up, avoid those for short-range info right through the winter season. No big deal. Not like anything important happens in winter anyway. 😉

    1. Oh lord.

      GFS looming toasty in the long range and the EURO is showing the SE ridge flexing at the end of the run. Not what I thought would transpire the rest of the month.

      1. That probably won’t happen until January, or at least the last few days of December. It’s also not really a new pattern emerging, but an interruption to the current one more than anything. I do think, however, January when it’s over will end up closer to normal with a thaw embedded, with near normal snowfall (basically the same as describe in my winter forecast).

  29. Ensemble Mean MJO forecast from GFS (which of the medium range models has the best handle on the pattern at the moment – that can change any time though), takes MJO from extremely weak phase 2 across “the circle of nothingness” and puts it in extremely weak phase 8. This adds a few ounces to my left turn on the phase diagram theory. 😉 We’ll see how it looks over the next few days. Just one element to consider, but I feel it plays a role in this pattern more so than last year’s pattern despite the weakness of it.

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