Finally after weeks of boredom we may actually have something of importance occur weather-wise.  The jury is still out this storm but the potential for is there for a long-duration precipitation event across the Adirondacks, Green Mountains, and White Mountains from Friday through Saturday night.  While track and storm strength are still up in the air, I have high confidence in at least some accumulating snows across the mountains of northern New England and northern NY.

Here’s the synoptic overview: Late this week, as an upper level trough digs through the Ohio River Valley, the baroclinicity caused by the cold air and low pressure of the trough to the west and the mild air with higher pressures to the east over the western Atlantic, will cause a surface low pressure system to form off the mid-Atlantic coast.  It will track up the eastern seaboard and will likely get captured by the big upper level trough that takes on an obscenely negative tilt as it reaches the northeast.  The interaction between the upper level trough and the surface low along the eastern seaboard will determine where and just how much precipitation (in both liquid and solid forms) will fall.  At this time, it appears that the upper level low, which slows and cuts off from the flow at the base of the upper trough, will be strong enough to yank the surface low back NNW into ME after it passes Cape Cod.  This track will allow for marginally cold air to work into the system on its western side and cause rain to change to snow first across the Adirondacks on Friday, the Greens on Friday Night, and eventually the Whites on Saturday.

This potential storm will have two phases to it with regards to precipitation: 1) Synoptic scale precipitation and 2) Meso-scale upslope precipitation.  Synoptic scale precipitation is caused by the interaction of large areas of low and high pressure systems and occurs over a wide spatial area.  Meso-scale upslope precipitation occurs on a much smaller scale and in our neck of the woods only effects localized mountain areas, particularly across the northern Adirondacks, the northern Greens, and portions of the northern Whites.

The synoptic precipitation will likely be mostly in the form of rain as the low works its way up the coast and a moist southeasterly flow off the Atlantic pumps in mild, maritime air ahead of the storm.  Actual rainfall amounts are going to be hard to pin down because most of the computer models don’t show this coastal storm getting its act together (and getting captured by the upper level low) until it is physically passing Cape Cod and moving into the Gulf of Maine.  This causes a couple of concerns… if the storm is even a few degrees of latitude too late in developing, it could miss us all together synoptically speaking (the Canadian GGEM has been showing this as a possibility) but would still bring some upslope snows to ski resorts like Whiteface, Jay Peak, Stowe, and Bretton Woods.  However, the majority of the global models including the GFS, the European ECMWF, and UKMET do show this tracking close enough to the coast to bring us rain on Friday, then mountain snow Friday night and Saturday as cold air wraps around the western side of the storm.  Accumulations from the synoptic portion of the storm look minimal with maybe up to 3” above 2,500ft by very early Saturday morning.

By Saturday morning, the low will have passed our latitude, hopefully bombing out in the process.  The term “bombing” out refers to rapid deepening of a surface low in a very short period of time.  In truth, the term “bombogenesis” is for a storm that deepens by 24mb or more in 24hrs and while we won’t see that sort of explosive development, we could witness a quick 12mb drop in 12hrs on Friday night.  This will tighten up the pressure gradient around the low and the wind field at all levels will increase markedly.  As the low tracks into the state of ME or the Canadian Maritimes, winds will pick up across the summits out of the NW.  H85 (~4,500ft) wind speeds on all models increase to 40-50kts out of the northwest, while advecting cold air into region.  Our low pressure system is now vertically stacked from the surface to 500mb (~20,000ft) up in southern Quebec and this is allowing it to cyclonically wrap moisture from the Atlantic back into northern New England.  This moisture when combined with colder temperatures and strong NW winds will produce upslope snow across the northern Adirondacks, northern Green Mountains, and northern Whites.  I have decent confidence in at least a moderate upslope event for the Green Mountain spine ski resorts north of I-89.  I am not sold on the Adirondack or White Mountain resorts quite yet because they are a little more fickle when it comes to upslope (ie. The planets need to align just a little more than they do for the Greens to get upslope) but regardless they should both see at least some accumulation on Saturday.

Given the overall look to the synoptic pattern and with the potential for a decent upslope event on Saturday, I think there is a moderate to high risk of 6-12” falling across the northern Green Mountain spine including Bolton Valley, Stowe, Smugglers Notch, and Jay Peak by Saturday night or early Sunday morning.   Elsewhere, I’d say that Whiteface in the Adirondacks, MRG and Sugarbush in the Greens, and Wildcat, Cannon, and Bretton Woods in the Whites stand a moderate to high chance of seeing 3-6” of snow with locally higher amounts.  I’m a little uneasy about throwing numbers out still 4 days away from the event, but that’s the type of system I’m looking at right now.  It might not be prolific but it’ll likely be the first widespread snow of the season for the ski resorts.


  1. Greg
    wrote on November 24th, 2009 at 3:23 pm  
  2. Danielle
    wrote on November 24th, 2009 at 4:00 pm  

    There is no mention of Southern Vermont. Is that because nothing is going to happen down here?

  3. St. Bear
    wrote on November 24th, 2009 at 4:14 pm  

    It might be my computer, but the left edge of your website is cut off from view. I can’t see the first 2 or 3 letters of every line.

    • Greg
      wrote on November 24th, 2009 at 5:55 pm  

      I think I got this fixed St. Bear. Thanks for the open eye. I think you were using IE7 right?

      Any trouble with seeing the banner at the top? It’s a rotating picture of some cool skiing with the words famous internet skiers .com… in case you aren’t seeing anything. thanks again!

  4. billski
    wrote on November 24th, 2009 at 4:52 pm  

    Mother Nature loves her averages, or so a famous prognosticator once said. Once this gets crankin, meybee we’ll be sliding till May???

    St. Bear – Scott has always been a little edgy ;)

  5. Scott
    wrote on November 24th, 2009 at 6:47 pm  

    Danielle… this is something that AJ and I are trying to work on (ie. how to incorporate all mountain areas into a forecast). It is hard to try and produce a detailed forecast though over a large geographic area and be accurate at the same time. I generally try to focus on the regions that’ll see the highest impact from the storm, which right now looks like the northern Green Mountains. Southern Vermont definitely has the chance to see some accumulation but the highest risk areas for heavy snowfall are definitely the northern mountains. At this point, I think southern Vermont could get 1-4″ in the higher elevations (say above 2,000ft).

  6. Scott
    wrote on November 24th, 2009 at 6:50 pm  

    18z American models (NAM and GFS) continue the heavy snow threat for Friday night and Saturday. I’m really thinking the upslope snow behind the storm will be the big story…we could be snowing 1″/hr for a while on Saturday along the Green Mountain spine while valley areas are mostly cloudy with flurries or sprinkles.

    • Greg
      wrote on November 24th, 2009 at 8:39 pm  

      you know what time it is?


  7. Lionel Hutz
    wrote on November 24th, 2009 at 9:01 pm  

    I have to agree with scott that the upslope is the event to keep your eyes on.

  8. Jens
    wrote on November 24th, 2009 at 10:44 pm  

    Any ideas on how this might work out in the Mtns of Maine?

    • Greg
      wrote on November 25th, 2009 at 12:19 am  

      I’ll leave the door open to our more knowledgeable weather forecasters, but it seems to me that since the big snows of this event will primarily be restricted to upslope events, the Mtns of Maine don’t stand as high a chance as the Greens to pick up a high amount. Based on what Scott wrote above, he seems to think 2-3″ for the higher terrain at this time from the synoptic portion of the storm friday night/early saturday, and then an extended period of favorable upslope snow conditions saturday into sunday which would favor the Greens more than Maine. Of course if the big (synoptic) features of the event change drastically… e.g. the Canadian Model turns out to be correct, I can see Maine doing very very well for itself. Scott?

  9. LES POW
    wrote on November 25th, 2009 at 8:19 am  

    Nice to see a chance of snow.. Cant get excited because what falls will melt and and there is more possible torches in the extended.

  10. Chris
    wrote on November 25th, 2009 at 10:52 am  

    Thanks for the write up guys… will be happy to see some white stuff. Hoping for that 6-12 for Stowe/Smuggs..

  11. Im_a_crappy_skier
    wrote on November 25th, 2009 at 11:32 am  

    Awesome right-up. I’m not real savvy on all these meteorological concepts. But I like the way it sounds and I generally just like to hum along. I’m routing for this thingy though, bigtime! Hopefully it can open the door to some cold air in the catskills so “huntah” can start making the white stuff.

    • Greg
      wrote on November 25th, 2009 at 11:41 am  

      Hey Im_a_crappy_skier: you (and others) might just want to check out the wording in the Burlington, NWS forecast discussion today (visible by clicking on “BTV NWS Weather Discussion” in the text products part of the weather page).

      They’re basically zeroing in on the same event our weather guys have been seeing, and talking about it in perhaps simpler terms

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