Wednesday Forecast

227 Comments

7:54AM

DAYS 1-5 (JANUARY 3-7)
A “Scandinavian Heatwave” hits today as the temperatures reach the middle to upper 20s. This will end Boston’s record-tying streak of days below 20 that belongs to this year, and 100 years ago. As we are enjoying are balmy respite, a storm will be brewing down the coast. The track of this storm has presented a forecasting headache for many, but after riding a veritable roller coaster of information and speculation, it comes down to an update in which I’m not going to make a whole lot of changes to the forecast issued on the last blog. Significant snow will occur Thursday for much of the region, though it is not likely to be of epic proportion anywhere, just a solid snowfall, except starting as rain east of a line from near Plymouth MA to Newport RI including all of Cape Cod before changing to snow during the course of the storm. Based on the current expected track I’m expecting the following…
Snow accumulation: 8-12 inches in a wide swath from eastern CT and western RI to Worcester to Metro West of Boston to southeastern NH but with pockets of 12-16 inches possible favoring interior eastern MA mainly to the southwest of Boston and possibly along the North Shore communities, 4-8 inches of fluffy snow to the west of this area, and 4-8 inches of wetter snow to the east of this area lowering to 2-4 inches Outer Cape Cod and Nantucket as these areas start as rain first.
Visibility: Blizzard conditions are likely especially along the coast from near Boston and its immediate southern suburbs northward to the North Shore of MA and NH Seacoast, extending down through the South Shore and eventually Cape Cod after rain changes to snow – blizzard conditions are defined as very low visibility due to falling and/or blowing snow with winds sustained or frequently gusting to 35 MPH or greater.
Wind: Gusts as high as 45 MPH inland, 55 MPH coast, and 65 MPH or greater Cape Cod (see detailed forecast for more).
Coastal impact: Moderate to significant flooding likely especially at the time of high tide, especially northeast and north facing shores. Also, ice shoves are possible where ice has formed along the shore due to persistent very cold.
Timing of storm: Snow (rain Cape) arrives between 4AM and 7AM from south to north, peaks early to mid afternoon, ends early evening.
After the storm comes a blast of arctic air equal to or more intense than the one just-departed for Friday and Saturday.
Other notes: There could be a few surprises including a track wobble, dry slots, and synoptic bands of heavier snow, so please check the comments below and the Facebook page if you have access to it for updates.
Forecast details…
TODAY: Mostly sunny. Highs 22-29. Wind S under 10 MPH becoming variable.
TONIGHT: Increasing clouds. Snow developing south to north 4AM through dawn except rain much of southeastern MA and southeastern RI. Temperatures remain stead interior but rise to 30-37 coast with warmest Cape Cod. Wind variable under 10 MPH becoming N.
THURSDAY: Overcast. Snow except rain changing to snow far southeastern areas. Snow will be heavy at times in bands. See above for details of snow accumulation and other storm impacts. Highs 25-37, mildest Cape Cod, in the morning, with slowly falling temperatures during the afternoon. Wind N increasing to 15-30 MPH interior and 25-40 MPH coast with higher gusts (see above for peak expected gusts).
THURSDAY NIGHT: Snow ending south to north evening. Clearing overnight. Temperatures fall to 15-22. Wind N to NW 25-35 MPH, higher gusts. Blowing and drifting snow where dry snow fell and a flash freeze where wetter snow fell.
FRIDAY: Mostly sunny. Temperatures fall to 5-12. Wind NW 25-35 MPH, higher gusts. Wind chill falling well below 0 at times. Blowing and drifting snow where dry snow fell.
SATURDAY: Partly cloudy. Isolated snow showers. Lows -5 to +5. Highs 5-15.
SUNDAY: Mostly sunny. Lows -15 to 0. Highs 10-20.

DAYS 6-10 (JANUARY 8-12)
Potential unsettled weather (snow/mix) at the start and end of this period. Fair in between. Temperatures below normal overall but variable.

DAYS 11-15 (JANUARY 13-17)
Potential unsettled weather early in the period (favoring snow but possible mix). Variable temperatures remaining below normal overall.

227 thoughts on “Wednesday Forecast”

  6. Thanks Tk . Early thoughts on pembroke & I should take all precautions with the wind correct.

      1. And snow number ( tentatively) . With me home this will be the most prepared storm for the house .

  9. What seems so different now from when I was growing up ( I’m 51 ) is that now any snow at all seems to cause a general shut down of everything. Businesses don’t open deliveries don’t happen etc. I don’t ever remember my father not going to work because of weather. I suppose many people can work from home now whereas that simply wasn’t an option in the 70’s….

    1. I was a kid in the 80’s…my Dad use to walk a half mile to the bus stop and take the bus to Boston. I literally can’t remember snow ever stopping him. I am sure I am not 100% correct, but have no memory of it.

      1. I guarantee snow stopped many people in the 80s and before. I don’t think we were highly tuned in on when our parents got days off vs when we got days off. I read a lot of old newspapers and have seen mention of various shutdowns ahead of predicted blizzards and heavy snow and even icy conditions.

  16. Early in the game, but the HRRR and RAP are coming in well east of the NAM guidance. I expect east will be the trend on most of the 12z mesoscale models.

  18. Looking at the 13z RAP, one thing we should really watch for is the direction of motion of this thing above about 35 degrees north. If you watch the RAP through about 16-18 hours, it begs the question, how in the world will this thing tuck in close enough to give us heavy snow? But then the last few hours of the run the trajectory changes from NE to more NNE and almost N. I think the low center will be quite far off the Outer Banks around midnight tonight, quite a bit farther than the NAM shows. If it continues on a NE trajectory from there, the western edge totals and even totals into I95 will be cut down dramatically, and indeed there is a notable cluster on the 9z SREF plumes which goes for this, which didn’t go for it before. If the trajectory is more N-NNE after 35N, then we get a crush job.

  19. Question regarding recent runs of NAM. At what point does its “convection feedback” issues stop being relevant in terms of the immediate forecast? Or does that predilection for CF always remain, regardless of the time range of the forecast?

    I guess what I am getting at is, when do/should we start “believing” in the NAM? Or do we just take it as just one piece of the forecasting puzzle?

  20. I think this will turn into a nowcasting situation where you got to look for any wobbles on approach. A wobble west look out a wobble east less snowfall.

  23. WBZ not buying any shifts west. They’re sticking with the same snowmap with boston at 8-12 and 12+ confines to a small area along the south shore

    1. I just have a feeling the jackpot will be Down here someplace say between Hingham & Duxbury any town along that stretch with blowing & drifting snow .

  27. The 12Z NAM is in. Now it has shifted a bit to the East.
    Now shows all snow for Boston. Here is the Kuchera snow map

    https://imgur.com/a/rdyFq

    However, the 3km NAM still has a brief period of rain for Boston

    https://www.tropicaltidbits.com/analysis/models/nam3km/2018010312/nam3km_mslp_pcpn_frzn_neus_28.png

    3KM NAM 10:1 snow

    https://www.tropicaltidbits.com/analysis/models/nam3km/2018010312/nam3km_asnow_neus_41.png

    12KM NAM 10:1 snow

    https://www.tropicaltidbits.com/analysis/models/namconus/2018010312/namconus_asnow_neus_14.png

    Still close for rain/snow in Boston

    2. So in other words you are saying PISS ALL OVER IT!!
      It’s a throwaway. If it’s that bad, why run it.

      1. It’s not always that bad.

        And of course if it is right, we’ll all buy it next time and get burned.

  29. Thank you, TK.

    Rather unbelievable that we could be talking about some rain mixing in in Boston after this long stretch of cold, but that is the unbelievably variable weather we often experience.

    It is `mild’ outside, and some melting of sidewalk snow will occur today with the southerly wind and a rather strong sun. I know I sound like Charlie from Attleboro, but today’s sun and relative `warmth’ felt like a sign of spring. I’m guessing some locations overshoot in terms of temperature today with 35F a possibility along the south coast.

    2. they are trying to figure out what will dominate., if the further one to the east dominates much less for us.

  32. JP can we see where low is now comparing with NAM and Hrrr? Wouldn’t that give us an idea of how models are handling the placement?

  34. My daughter and I headed to the grocery store after dropping her four year old at pre-school. We both commented how warm it feels when you get past the 20 degree mark. And she is NOT a fan of cold. It amazes me how well we can adapt.

    The grocery store was surprisingly empty.

    2. True. I also think bodies adjust to temperature, particularly during long spells of cold or heat. No, we’re not amphibians, but we do acclimate. Even I acclimate in summer to 90s, heat and humidity. The first few days are bad, but then my body adjusts or gets accustomed to it and it becomes bearable. So, when the temperature then dips into the 80s I feel refreshed. A simile exists in winter. 20s feel `balmy’ after an extended period of sub-20 weather. Next week’s 30s will feel like Bermuda, and if we can believe the extended long-range there are some 40s (perhaps even 50) on the way for later in the month as a southeast ridge builds and the current pattern comes to an end.

  37. I always forget to mention, Plymouth State runs its own proprietary version of the WRF model. I’ve linked the output from its latest (0z) run. Note in the accumulation maps how it tries to show two separate maximum bands with a shadow in between. Pretty cool. May be a little hot on QPF; JP Dave will like it though 😉

    http://vortex.plymouth.edu/WRF/wrf_over_d2.html

  39. Noting the east shift as expected on the 12z RGEM. 12z GFS held serve or ticked west just slightly, but as mentioned yesterday we’re more into hi-res territory now. Based on the RGEM, and latest runs of the RAP and especially HRRR, I think what we really need to watch for is a late shift east.

      2. I asked earlier and got a no way but could rain be the big story here now from Boston / south . What a roller coaster

        1. It’s a roller coaster for anyone who reacts to each individual model’s take. 🙂 🙂 🙂

          I’ll still stick with previous experience on these bombs that the cold air rushes towards the storm’s center quicker than the models show.

  44. Don’t get hung up on shifts at this point, a powerhouse storm near the benchmark is pretty good spot for majority of the area to get snow. So many models and small changes that impact outcomes.

  45. Looking at the 850mb signatures (temp, vertical velocities, etc) on the 12z GFS and the 00z EURO, I see the 10am to 2pm timeframe as the window in Boston and at the coast to get the multi-inch snow rates per hr. Prior to that, the temp could be slightly near or above 32F, the precip rate may not be consistently heavy and thus, the snow wont pile up in the early morning hours.

    But, in that 10am to 2pm timeframe, the lift is best, the column above cools dynamically, I believe the cold air rushes back at the surface and its this time frame when 80% or more of the accumulating snow occurs.

  47. Sit back and watch a beautiful storm form, goes-16 should have some spectacular views. Storm is starting to get it’s act together and will undergo explosive development soon.

    1. I’ll be watching. I just have to figure out how not to work tomorrow. I can hardly claim a dangerous commute 🙂

  49. Having the center of low pressure west of (or east of, or any direction of) model forecasts at this point with this system is pretty much insignificant. There are probably multiple low centers right now.

  52. Good read

    EE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
    INGEST…

    12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    ~~~~~~~~~~~~~~~

    …EJECTING NEGATIVE TILT TROUGH ALONG THE EASTERN SEABOARD WITH
    RAPID DEEPENING OF SURFACE CYCLONE TODAY INTO THURSDAY…
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    ~~~~~~~~~~~~~~
    PREFERENCE: BLEND OF THE 12Z GFS, 00Z ECMWF, 06Z GEFS, 00Z EC ENS
    CONFIDENCE: AVERAGE

    MODEL TRENDS CONTINUE TO BE TO GRADUALLY NUDGE THE POSITION OF THE
    EVOLVING CYCLONE FURTHER WEST. THIS HAS BEEN APPARENT ON THE 12Z
    GFS AND NAM…AND IS PRETTY CONSISTENT ACROSS THE SPECTRUM OF
    AVAILABLE MODELS. OVER THE PAST THREE CYCLES (02/00Z TO
    03/00Z)…THE ECMWF ENSEMBLE HAS NUDGED THE POSITION OF THE
    SURFACE LOW ON THURSDAY MORNING ABOUT 60MI TO THE WSW INDICATING A
    WESTWARD AND SLIGHTLY SLOWER TREND OVERALL…AND THIS TREND
    MAGNITUDE IS SIMILAR TO OTHER MODELS.

    CONFIDENCE IN THE WESTWARD TREND IS INCREASED SLIGHTLY BY THE
    LATEST GOES-16 WATER VAPOR LOOPS WHICH SHOW THE BASE OF THE
    EJECTING WAVE IN THE SOUTHEAST TODAY GENERALLY STAYING NORTH OF
    THE GULF OF MEXICO…AND THE 12Z NAM AND GFS INITIALIZING A LITTLE
    TOO LOW WITH 500MB HEIGHTS IN NERN NEW ENGLAND AND THE CANADIAN
    MARITIMES (20M TOO LOW MAINE TO NOVA SCOTIA). A SLIGHT NORTHWARD
    TREND IN THE EJECTING WAVE…AND A MORE AMPLIFIED UPSTREAM
    RIDGE…WOULD TEND TO FAVOR A SLIGHTLY SLOWER/DEEPER SYSTEM THAT
    IS IN CLOSER PROXIMITY TO THE COAST. THE 12Z NAM AND GFS DID MAKE
    SOME MINOR ADJUSTMENTS TO THE NORTH WITH THE EJECTING WAVE.

    THE 12Z NAM CONTINUES TO PRODUCE THE MOST PRECIPITATION IN THE
    COLD SECTOR AS THE LOW PUSHES UP THE COAST…AND THIS IS A TYPICAL
    BIAS IN THE MODEL. IT IS ALSO FURTHEST WEST WITH THE SURFACE
    LOW…ALTHOUGH THE MODELS OVERALL HAVE CONVERGED OVER THE PAST
    COUPLE MODEL CYCLES. REMAINING DETAIL DIFFERENCES WOULD AFFECT
    SOME SENSIBLE WEATHER IMPACTS ALONG THE PTYPE AND PRECIP
    GRADIENTS…SO TRENDS OVER THE NEXT COUPLE MODEL CYCLES WILL STILL
    BE IMPORTANT TO MONITOR.

    A USAF RECONNAISSANCE PLANE IS SCHEDULED TO SAMPLE THE LOW OFF THE
    SOUTHEAST ATLANTIC COAST THIS EVENING AS THE LOW IS LIKELY TO BE
    RAPIDLY DEEPENING. THESE ADDITIONAL OBSERVATIONS MAY HELP NARROW
    THE MODEL SPREAD A LITTLE FURTHER…PARTICULARLY AS ENSEMBLE
    SENSITIVITY ANALYSIS SHOWS THE ULTIMATE LOW TRACK AND TIMING IS
    SENSITIVE TO CONDITIONS OFF THE COASTAL CAROLINAS THIS EVENING.

    OTHERWISE…THE 12Z GFS…06Z GEFS…AND 00Z ECMWF AND EC ENS MEAN
    APPEAR TO OFFER SIMILAR SOLUTIONS WITH THEIR MASS FIELDS AND VERY
    SIMILAR LOW TRACKS AND INTENSITIES. THEREFORE A BLEND OF THESE
    MODELS IS PREFERRED FOR THIS SYSTEM. HOWEVER…STORM STRUCTURE
    WILL PLAY A ROLE IN QPF DISTRIBUTION AND BANDING. FOR MORE ON
    THAT…PLEASE REFER TO THE QPF AND HEAVY SNOW DISCUSSIONS FROM WPC.

    2. Did they give a reason for both days, Captain? I figure they know their student population and school best so am just curious.

    1. many of the models that are showing wide spread 12+ are not taking to account the banding of the deepening low pressure.

  58. Are the models accounting for very cold ocean water? I’m not sure. This is why I’m skeptical about a change to rain in Boston. My guess is ocean water away from the coast is around 41F, while it’s closer to freezing at the coast (hence all the ice formation).

  59. I have a feeling these higher QPF’s number might very well verify, storm will be juicy and how many times does a 950-960 mb storm not drop at least a foot or more when near the benchmark in January. Just watch that radar down south.

    4. Mark, does the euro have 2m wind projections on your site? I’m curious how strong the winds are being projected and how far inland

  63. Matt, i agree with you re: banding. This storm will be so intense and wrapped up there’s bound to be some areas that get stuck in a band and some areas outside of bands. It’s impossible to determine where those will set up. Someone will get shafted.

        2. greatest concern is charlie hole and Merrimack valley right now usually the two areas that get skunked

  64. Tom, if you’re out there, you seem to be tuned into the tides. Are we in a cycle of higher than usual tides?

    2. Yes this month at the beginning and end of the month and also last month and then they go down a bit in coming months.

          1. Great. We love it here. My daughter is a Junior at the high school and loves it. How is the family?

    4. 12.1 ft tomorrow a bit after noon time.

      Depends how fast the ramp up in wind is up to about 2pm.

      If the storm was 5 to 8 hrs ahead of its current pace, I think there would be big problems.

      Id put max surge somewhere in that 2 to 5 pm time slot, not exactly lined up with the high tide.

      So, many hours of splashover with moderate coastal flooding and the tide will appear not to lower quickly for 3 to 4 hrs after high tide. But, thank goodness, the max surge is not perfectly aligned with the highest water tomorrow.

  68. Some point forecast numbers for tomorrow…

    Boston Logan: 12.1″
    Providence: 11.2″
    Worcester: 9.7″
    New Bedford: 8.0″
    Springfield: 4.2″
    Jackpot: Wrentham (hey, why not?): 15.8″ 🙂

    I like the idea of a broad 10-15″ zone for most of eastern MA and RI. There will probably be areas that come in higher and lower due to banding. But most should be in that range.

  69. Lean colder on next weeks storm. Maybe not a big QPF producer, but I’m already seeing people lock in a big thaw for next week and beyond. Yes, we are definitely, finally, going to break this Arctic pattern. However, even if the upper level pattern supports warmth, I don’t think we’ll get too warm at the surface. More seasonable. May lead us into additional icy mix opportunities next week and beyond.

  70. To continue to address possible coastal mix/rain ….

    I keep seeing 850 mb temps over Boston and Marshfield remaining at -2 to -5C and cooling even a bit more near the storm’s closest passage.

    I think the concern should be that the western storm track shift has increased the threat of wet or higher density snow to a larger portion of the viewing area. So now, it may not be just the traditional south shore coastal spots, but may also include the north shore, Boston’s western and southwestern suburbs and interior SE Mass.

    Hope that the crashing coastal front mid storm can make the snow more powdery and that the cooling boundary layer can help to add a bit of stabilization to the surface winds and decrease them slightly in the wet snow zone.

    High stakes with arctic airmass coming in Friday into Saturday.

    1. I do NOT want any wet snow. Wet snow with the crash in temperatures
      spells serious trouble. Even if snow slowly dries out, anywhere cars and pedestrians stomp down that wet snow, it will become ICE. Bad news.
      KEEP IT DRY!!!

  71. That storm threat for next Tuesday 1/9 on the Euro trended way east and colder with the 12z run. Now delivering 6″+ FWIW NW of a Hartford to Lowell line. Still a rainy solution verbatim but it has a much colder look.

    Euro then has another snow threat next Friday 1/12.

      1. Kids are loving it down that way….maybe not so much the parents.

        My son in law said some florida schools are closing because of the high of 40….they don’t have heat.

  75. It would appear that the HRRR wants to slow things down a bit with
    snow now arriving around 6AM. I hope this doesn’t screw up school systems.

  77. Max wind gusts from each model
    EURO Regular. Around benchmark 950mb
    https://weather.us/model-charts/euro/massachusetts/gusts-3h-mph/20180104-2100z.html
    EURO control 950mb around benchmark
    https://weather.us/model-charts/euro/massachusetts/m0_gusts-3h-mph/20180104-2100z.html
    German 957MB around bench mark tad further east than EURO
    https://weather.us/model-charts/german/massachusetts/gusts-mph/20180104-2200z.html
    US model 959 MB Furthest east
    https://weather.us/model-charts/standard/massachusetts/gusts-1h-3h-mph/20180104-1700z.html
    Conus HD 946MB Benchmark storm
    NAM32KM 954MB
    NAM 12KM 954MB
    NAM 3KM 947MB
    HRDPS 951MB
    RGEM 950MB
    canadian 958.
    Mean MB pressure between models 952 mb. This will be a strong storm. winds aloft are 60+ for many in south eastern New England. The coast is gonna get clobbered.

    1. Cool and thanks Matt. That’s some pretty powerful winds. We would NOT want to combine that with heavy wet snow. No we do not. Let’s keep the snow dry.
      Problem is, no matter what the track is, somewhere in SNE will get those
      winds with the wet snow. Power outages are almost assured.

    1. Thanks HADI.

      I just sent copies to management here. We almost certainly will be closed
      tomorrow and I believe they will notify staff by about 4PM.

  85. Latest 18Z HRRR simulated radar for 12Z tomorrow morning.

    https://imgur.com/a/rFJQ4

    LOOK at the wall of snow heading up here. Those would be tremendous snowfall
    rates. Certainly 1 inch per hour, but more likely 2-3 inches per hour.

    can you say WHITE OUT????

  86. I’m struggling to post a SC radar.

    However, even this early in its evolution, the storm has some inland banding fairly west of the coastline. And in between the heavy coastal precip and the inland band of heavy snow, is a sliver of much lighter precip.

      1. perfect !!!!!

        Look over I95, somewhat light to moderate.

        But, at the precips western edge, is a pretty intense band of snow.

        1. My pleasure Tom. The RadarScope is a for fee radar
          service app that I purchased for my smart phone’
          It was cheap, only $9.95. TK recommended it to me.
          You should seriously consider it for your phone. It is a way cool app. It has radial velocity modes and different radar modes. Worth the money 10 times over.

  87. When there is a storm brewing or in progress, there is no better place in the world to be than this blog. Thank you a million times over TK for providing this forum for us!!!

    1. Thank you, TK…..and thank you, JPD and so many of the others who truly make the anticipation fun!

      For one, and I know there are more, I am thrilled beyond belief that you are getting your storm, JPD!

    1. Oh, I’ll get to sleep. I am just afraid I’ll be up way too early.
      I would like to be up and ready to go for the first flakes, IF they are
      around 6-7AM. IF first flakes are at 2-4 AM, I’ll catch some later flakes. 😀

  94. 18z is showing what I was concerned about….. very powerful storm, but when the heavy precip is about to change to snow from Boston to Providence points southeast it shuts off. Thats why the numbers were cut in half basically or more so

    1. what do you mean about to change to snow? It will be ALL snow. No Rain.
      Yeah, I know I was crying chicken little this morning. But it is what it is.

      I do not share you concern.

      1. sorry was looking at an earlier model whoops, I have a bunch of them on top of my screen lol. My brother says I am crazy. lol

      1. Power outages a guaranteed Tom . The only thing that concerns me with that is the pipes freezing

    1. 950 something. Can’t count the isobars and other sites, with the damn 24 hour increments, can only see 24 and 48 hours, pre and post blast.

  98. Harvey sticking with 10-15 from Boston down through the south shore. Just listened to Rob Gilman & he is extremely concerned with down this way high tide , Hurricane force winds etc

  100. Blog posts coming fast and furious!
    I’d like to second a comment from up there somewhere:

    This is an awesome place to be, especially before a storm.
    Sort of like a pre-game show before a Patriots’ Super Bowl!

    Mil gracias, TK for maintaining this fun place and your keen expertise and everyone for joining in the fun!

  102. My Sister and Brother-in-law were scheduled to leave Logan at 6am tomorrow for Miami but got on a 5pm tonight which is on-time. They are then off to the Bahamas tomorrow with a high there in the mid 60’s. Better than here but chilly for there.

  103. When will the snow/storm shut off and when will the frigid temps/winds kick in?
    If there are power outages, will there be a window between extreme weather situations that crews can repair lines, etc?

    2. Best I can tell, Highest temps are reached around 9AM with the temperature
      steadily falling thereafter and the coldest of coldest on Friday AM.

  108. I was thinking of beach volleyball tomorrow. Nahant Beach? Anybody wanna join me? I’ll watch from my car. But I probably won’t be able to see anything. 😛

  109. I’VE POSTED A NEW BLOG. Please go there. I will also post SAK’s latest blog update there too.

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