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  • Chasing Snow
    ... is a blog dedicated to winter weather and skiing in New England.

    Bryan K. Woods, Ph.D. founded Northeast Mountain Sports and publishes this blog dedicated to skiing and winter weather. He received a B.S. in Meteorology from UMass Lowell and his Ph.D. in Geology & Geophysics from Yale. He is an expert in mountain meteorology with multiple peer-reviewed publications. He worked for five years as a Senior Staff Scientist at Atmospheric and Environmental Research, Inc and its parent company Verisk Analytics. He is currently a Principal Engineer at HERE Technologies, the Open Location Platform company.

    Bryan lives in Chelmsford, MA with his wife and ski tuning bench. He spends his winter weekends in North Conway, NH or elsewhere skiing. He is actively involved in the Eastern Inter-Club Ski League (EICSL) as its Secretary, and a Board member of the Makusue Ski And Sport Club in North Conway, NH and ACE Ski and Board Club in Chelmsford, MA.

    Click on the post titles in the feeds below to view recent posts. Or bookmark the blog directly.

  • Recent Weather Updates from "Chasing Snow"

    • By Weatherman in Chasing Snow
      Model trends today have been to the west, which is no real surprise. In this highly amplified flow the models tend to damp down such extremes in the long range. The way we initialize models (data assimilation) there are terms in the equations to penalize extreme solutions and force everything back to average. The result is often suppressing storms in highly amplified regimes like this one.
      The track looks to be just offshore with strong snow banding just to the west of the track. This bring heading snow bands to eastern coastal regions of New England from eastern Massachusetts into most of Maine. The White Mountains of New Hampshire into Maine will see a localized maximum as is common in coastal storms. For those of you in Vermont -- tough luck but that's no surprise. Your bread and butter are the lighter snow of upslope wrap-around. I don't mean that there won't be any snow -- there will be some upslope -- but when in these cold regimes it is the light and fluffy stuff that just serves as a top dressing. For skiers, it won't give you any float, it won't serve to reinforce the base, and it won't stand up to skier traffic. It will end up blown into the woods.

      If you look careful at the precipitation map above, you'll note the cellular pattern in the precipitation. This is the result of embedded convection within the snow band. In these intense snow storms, there can be pockets of elevated air that become unstable and rise upward like in a thunderstorm. This is in contrast to overrunning (stratiform) precipitation where moist air rides mostly horizontally from the south up cover cold air. The overrunning results in precipitation. Those same dynamics are at play here, but mesoscale (mid-scale) dynamics are at play that causes that overrunning area to have more energy than the air below it, resulting in overturning.

      A sounding from the model forecast above taken in southeast Massachusetts (where the red dot is) shows this. For the untrained eye, there are three things to see.
      Note the profile of "equivalent potential temperature" in the lower right. This is the temperature that the air would have if it was brought down to the ground and all the water vapor condensed. This should continue upward if the profile is stable. If it decreased with height, the air will want to convectively overturn and result in precipitation. Note the elevated unstable later around 800 mb pressure level, and a near surface instability area as well. This same unstable layer shows up in the Skew-T sounding in the middle of the page. The diagonal solid dash lines refer to lines of constant potential temperature, which are just subtly different from equivalent potential temperature -- just discounting the events of moisture. The green line is the dew point temperature, and red line is the air temperature. Where the red and green liens meet, the air is saturated. In the saturated layers, note the negative omega values in the bar plot in the lower left -- in dynamics omega is vertical velocity of an air parcel with respect to pressure. Negative omega means decreasing air air pressure and upward motion. Where the air is saturated is becomes buoyant and accelerates upward. Once the instability relaxes the upward motion slows. You can see this upward motions in the negative omega values in the two layers. The presence of these two unstable layers are likely due to two different mechanisms at play. The elevated, and stronger, unstable layer is the broad scale up-lifting. As snow falls from the upper layer into the lower, it will seed additional precipitation from the lower saturated level. This is a common situation with terrain-based enhancement and is know as seeder-feeder snowfall.
      S0o where does that leave us? The responsible NWS is showing a broad moderate snowfall, and that's the appropriate forecast at this time.

      Note that these maps don't accurately show expected terrain enhancements. The White Mountains will once again make out well from this storm. The global GFS guidance picks up on it, and the high resolution 3 km NAM really latches onto it.

      As previously discussed, convective dynamics are at play in this storm, and the global models do not have sufficient resolution to catch this. So give more credence to the NAM forecast in the lower plot.
      It's also worth noting that skiers may miss the real news worthy story. You'll hear talking heads on TV tossing around the B-word. That's a result of the strong winds being driven by the intense cold already in place that we're feeling when we go outside. The NAM is showing a taste of that.

      The heavier, wet snowfall in southeast Massachusetts couple with those strong winds could result in power outages. Those would be a big deal in this regime. We'll be returning to extreme cold on the backside of this storm. Those who lose power could be facing freezing pipes within hours of power loss. Temperatures will be diving sub-zero again across New England on Friday into Saturday. If you lose power, watch your pipes!

      So where to ski this weekend? Nowhere? Everywhere? Good luck. It's going to be damn cold. But the White Mountains will have the deepest snow pack in place, with depths in the high terrain approaching three feet. Secondary maximums are evident in the higher terrain of Vermont, but are not quite as deep, especially counting the water content of the snowpack which is helping to pad the New Hampshire numbers.

    • By Weatherman in Chasing Snow
      Please don't panic. Life will go on. But this Saturday it is going to rain. Vermont will get the worst of it. As is usually the case with these inside runner storms, the frozen precipitation will hold on the longest over the White Mountains of New Hampshire and into Maine. They made actually see a net positive gain in snow depths (base builder event) especially at places like Wildcat, Sunday River, and Sugarloaf that sit on the north side of the White Mountains. The high terrain can act as a protective barrier keeping the cold air locked in place for longer. It won't stay snow there, but it will contribute positively to the water load in the existing snow pack rather than melting it.

      The good news is that this may not ruin the whole Christmas week. For those of you with travel plans on Christmas day, please keep an eye on the forecast. Right it looks like a storm is brewing which will refreshen our snowpack bringing widespread snowfall to the higher terrain.

      So after a rain and then a snow storm, what is the net-net gain? The White Mountains look to come out nicely. It should be a great Christmas week for skiing in New Hampshire.

    • By Weatherman in Chasing Snow
      It's all about the base. Starting tomorrow we'll be seeing a storm system composed of two phases. The first phase will be a quick hit of light to moderate snowfall falling throughout the day.

      Late Friday night into Saturday morning we'll see a lull in the precipitation, followed by the onset of freezing rain on Saturday afternoon and evening. It's remarkable how consistent the models have been with this freezing rain for days now. Typically models don't handle freezing rain well as they generally lack the resolution, especially vertical resolution, to capture the dynamics of entrenched cold air damming. This gives us confidence that significant freezing rain is expected, but I don't expect significant impacts. Because the freezing rain will be preceded by a snow event, the snow will act as a spongue and prevent significant glazing.

      When the storm is over, expect moderate accumulations of snow with a breakable crust across northern New England.

      Expect subzero cold to move in for the middle of next week. It'll make skiing unpleasant for long periods, but is not unexpected at this time of year. The larger topic of interest is a potential storm looking toward next weekend. It's too early for details, but I can't help but get excited.
    • By Weatherman in Chasing Snow
      The stars have aligned over the last 24 hours as the weather model guidance has decided that it's time for winter to get started. This a much more sensical solution as all the pieces were in place. The first development is that model guidance has shifted on-shore with Saturday night's snowfall. The result is a plowable snowfall across southeast New England, with light snow over the White Mountains of New Hampshire and western Maine. Accumulations in Vermont won't be meaningful until later in the week.

      Another storm is expected on Tuesday which will track across New England and bring a mixed bag of precipitation. Right now it looks like a solid base-building snow event for the White Mountains on New Hampshire. Details are still sketchy this far out, but the model runs have been more consistent than usual for this range of a forecast bring snow to the mountains and rain to the coastal plain. The latest GFS model forecast below illustrates that the rain-snow line will be a question in play, but just inland of the line it's looking like several inches of mixed precipitation or wet snow.

      After these two systems pass, the cold sticks around for the foreseeable future. Stay tuned as much snow events are likely.
      10:45 PM Update:
      With the latest round of guidance coming in, we're finally at the point where the high-resolution models are in range. And terrain enhancement in the White Mountains is looking good. I'm upgrading this to a Powder Day Watch. Carrying wider skis with you this weekend is recommended. Something in the 95 - 100 mm width range is recommended for Sunday. About 6" of fresh is expected for first chair at Wildcat on Sunday.

    • By Weatherman in Chasing Snow
      Temperature Outlook
      Cold air is moving into the Northeast today, and it will be here to stay for the foreseeable future. The long range forecast is for below-average forecast at least the next two weeks. Snowmakers will be working overtime. Below are the surface temperature anomalies for the next two weeks.

      This Weekend
      This weekend looks tranquil with a low chance of very light snow -- not enough to do anything but look pretty. A wave low pressure should stay just offshore. There is still model disagreement with whether light snow will reach coastal areas, but it should stay far enough out to miss ski country. Below is one of the more snowy model solutions.

      For those of you attending our season kick-off and demo day at Bretton Woods on Saturday, expect highs in the 20s and calm wind. The snow should be hardpack after this week's rain. Hopefully a couple of grooming cycles will allow them to recover.

      No Snow?
      While the ingredients are in place, right now there's no sign of significant snow over the next several days. Anything beyond early next weeks remains uncertain, but nothing stands out at this time. The 10-day forecast shows only light accumulations, with the possible exception of the higher terrain of northern Vermont. There they could see a total of several inches of light, fluffy snow, but nothing of the quality needed to build a base.


Northeast Mountain Sports

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