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At what temperature does snow fall as powder?

post #1 of 13
Thread Starter 
Is it possible to tell from a weather forecast if snow will fall as powder rather than as wet snow? Is temperature the only variable?

What air temperature will encourage snow to fall as powder rather than wet snow?

Thanks all.
post #2 of 13
Not sure, but I learned an interesting fact the other day. For Lake effect snow to be produced, the temperature of the air passing over the relatively warm vapors above the Lake must be at least 18 degrees cooler than the water surface temperature.

The early lake snows we get in November are usually very heavy and wet. This year, almost all the storms we've gotten have been low water content snow. Due mostly to the very cold winds and intensity of the systems passing through our area.
post #3 of 13
Quote:
Originally Posted by Steve Robinson View Post
Is it possible to tell from a weather forecast if snow will fall as powder rather than as wet snow? Is temperature the only variable?

What air temperature will encourage snow to fall as powder rather than wet snow?

Thanks all.
no air temperature is not only determining factor, other factors would be humidity, storm intensity, clouds dynamic.

also at what density is snow powder? you may want to define that because there is no official differential between wet snow and powder there is no line there is no classifications.
post #4 of 13
But, there are some Resorts that do studies and document the water content of the snow that falls on their slopes.

I know Steamboat does.
post #5 of 13
post #6 of 13
Quote:
Originally Posted by BushwackerinPA View Post
no air temperature is not only determining factor, other factors would be humidity, storm intensity, clouds dynamic.

also at what density is snow powder? you may want to define that because there is no official differential between wet snow and powder there is no line there is no classifications.
Just like on the news they will say something like "we were 10 inches snowfall behind average last month" followed by "the first day of this month a storm dropped 3 feet, beating the average for the month"
post #7 of 13
Quote:
Originally Posted by slider View Post
Yep! As simple as that.

The only complication is, it's not the temperature on the ground, but the temperature where the snow comes from.
post #8 of 13
Most weather models will predict a precipitation amount in terms of inches of water (doesn't matter what the precipitation type is). From there, the snow:water ratio tells you how much snow you will get out of it (and that ratio is based on temperature aloft, humidity, and many other factors). I seem to recall someone saying they like at least a 15:1 ratio to call it powder, or greater than 20:1 for the high-quality Utah stuff.

This page tracks snowfall history at Alta in terms of inches of snow and inches of water equivalent:

http://alta.com/pages/snowhistory.php

A lot of it's in the 10:1 to 15:1 range, but there are a few 20:1 events this season that were probably wonderful to ski in.

If you want to know more, Google "Kuchera algorithm snow" for a model that can predict the snow:water ratio. It will show all the input variables.
post #9 of 13
Quote:
Originally Posted by skier219 View Post
Most weather models will predict a precipitation amount in terms of inches of water (doesn't matter what the precipitation type is). From there, the snow:water ratio tells you how much snow you will get out of it (and that ratio is based on temperature aloft, humidity, and many other factors). I seem to recall someone saying they like at least a 15:1 ratio to call it powder, or greater than 20:1 for the high-quality Utah stuff.

This page tracks snowfall history at Alta in terms of inches of snow and inches of water equivalent:

http://alta.com/pages/snowhistory.php

A lot of it's in the 10:1 to 15:1 range, but there are a few 20:1 events this season that were probably wonderful to ski in.

If you want to know more, Google "Kuchera algorithm snow" for a model that can predict the snow:water ratio. It will show all the input variables.
here is food for thought total moisture content of a storm will determind how much you float. if its to dry you hit bottom and thats not fun, and dense snow is better to jump in.
post #10 of 13
Another factor is wind and transformation. Along with large temperature swings in the past week or so, we had a storm with high winds which packed the snow. The 15" or so could have been easily better than 2' of champagne if not for the wind. The week before was dry fluff and Friday's freshies were more like skiing in soft ice cream or whipped cream and grippy, but still dry.
post #11 of 13
Exactly right Bush -- the snow density (and thus float) is inversely proportional to the snow:water ratio. The higher the ratio, the lower the float. Of course, I think there are cases where snow packs down under skis (especially wide skis) and increases the effective density underfoot.
post #12 of 13
Quote:
Originally Posted by slider View Post

They it would seem that antartica would be incredible to ski.
post #13 of 13
Quote:
Originally Posted by skibum185 View Post
They it would seem that antartica would be incredible to ski.
Yep. No lift lines either.
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