Tips for predicting good Skating after a rain event 12/11

[Evan Perkins]

The whole region is currently experiencing heavy rainfall which is expected to continue through tonight. Many of our ponds and small lakes are frozen throughout Vermont and New Hampshire. Ice thickness varies .probably in some places!It's only an inch thick under snow and in other places several inches thick. Given the forecast, I'm sure many of us are hopeful that there might be some good skating this weekend in accessible places.

     There are three major factors that I use to try to predict (using a basic weather app) where good ice may have formed after a rain event

     -temperature 

     -rain/snow

     - wind 

    How the temperature, precipitation and wind interact with the existing surfaces that were present before the storm dictate What kind of ice conditions might arise after.

 When the rain turns to snow as it often does is a major factor in what kind of ice conditions you might expect. If the rain turns to snow when it is still above freezing outside, and the snow is not heavy those snow showers will often fall on wet ice, and melt, resulting in a smooth surface when the ice refreezes. If the snow falls on ice when it is above freezing, and it is windy out, it is possible that snow may be blown into slush bands or slush piles, which, if they have enough time above freezing will melt and smooth out. but , if they remain as a the temperature goes below freezing they will permanently freeze Those bumps and texture into the ice. if it snows as the temperature is going below freezing, that snow will often freeze to the surface of the ice and create a texture, what kind of texture depends on how much moisture is on the surface of the ice. If it is windy and it snows while the temperature is dropping below freezing, particularly if it is dramatically dropping below freezing, this often creates some thing I refer to as the spackle, which is a very rough irritating substance to Skate through. The snow is plastered in regular patterns across the ice sometimes forming tripping hazards. It is snow that is generally going to create texture, ranging from slightly texture to orange peel to slush bumps to spackle.

    If the rain stops before it goes below freezing, and it never snows the other major factor that you have to think about is wind. If it is perfectly windless as you go below freezing after a rain event, this is often when you get really smooth ice conditions after a refreeze. The exception to this is if the temperature goes below freezing, but does not get very cold very quickly in this case sandwich ice will be formed,( ice freezing over puddles on top of the ice pack ) and then because it does not get very cold the water in those puddles will have time to drain out leaving shell ice . Shell ice is Ice that is suspended over a pocket of air over the ice pack. This can create a tripping hazard. 

   In the same scenario as above where the rain stops before it goes below freezing and it does not snow, but it happens to be very windy, (in the 10 to 25 mile an hour plus range) it is often the case that the wind will actually clear the standing water off the ice by blowing it into drain holes and cracks, thereby eliminating much of the hazard of shell ice . Also, in this situation, the shell ice is often easier to see because it will often freeze with a texture on top as the wind blows it as it freezes.

    There are obviously other scenarios beyond what I have described above, but these are the most common occurrences. the other very common occurrence is that it just snows a little bit too much after the rain and the ice gets covered with snow, making it hard to read and slowing its ability to freeze and therefore eliminating Skating all together, let's hope we avoid that after this storm .

   In summary, you can use the Weather app to watch the radar as the temperature goes below  freezing to see whether there is any snowfall over the bodies of water  You are interested in skating in a few days. You can also use the weather app to pay attention to how windy it is in a given location to try to predict how that might affect the surface. Knowing how windy it is when it goes below freezing is the most important data point. 

   I hope this helps folks to know where to go looking for Ice.if we get lucky after the storm, there could be good skating as of Saturday morning, and in a limited set of circumstances on Friday on Lakes, that already had thick ice, as long as folks are careful watching out for sandwich ice .

     As always, it would be great to hear reports from folks on Friday if they see bodies of water that are free of snow and have an ice surface on them. Even partial reports just describing whether snow fell or not, or that you saw a frozen pond from the car while driving by our super helpful so that we can get enough information out for folks who only have the weekends to skate..

     Of particular note to folks in the Burlington area, all of Missisquoi Bay was frozen over as of the radar on December 7, that ice is unlikely to melt during the storm and there's a good chance it could refreeze. If one were to venture onto that Ice it would be wise to avoid any current hazards from the Missisquoi river or the channel going down into the inland sea.  Happy Skating, Evan

[Evan Perkins]

As a follow up to my previous email, after a heavy rainfall like this, it is important to note that any areas with current are likely to have underthinned if they have not melted the ice completely . Since much of the ice that is present is opaque snow ice ,under thinning is particularly hard to see. If you wait to skate until the freezing degree temperatures have been present long enough to grow a supportable surface that shouldn't be an issue unless there is still continued current under thinning in the spot.  The other major hazard that occurs during large rainfalls like this is the melting out of shorelines . you might have a pond with 4 inches of ice by Saturday morning, but the shoreline may be too thin to cross to get to that ice because they completely melted out due to runoff. Carrying a long board with you, can help to create a portable bridge when scouting ice under these conditions. And it's always fun when the person who brings the bridge Takes it home with them while other people are out on the ice,.having Used the bridge to get there  :)  .