Measuring Snow

[wxwise]

Hello,

Is there a standard ratio for how many inches of snow it takes to equal 1 inch of rain??? I am trying to prepare for winter up hear in Canada and would like to know how I can measure the snow using my Oregon Scientific WMR-968 rain guage. In that case, is there any way of measuring snow period???

Please give me some tips when it comes to measuring snow.

Thanks,

Doug

Dorchester Weather

[frozen_north]

Hello,

Is there a standard ratio for how many inches of snow it takes to equal 1 inch of rain??? I am trying to prepare for winter up hear in Canada and would like to know how I can measure the snow using my Oregon Scientific WMR-968 rain guage. In that case, is there any way of measuring snow period???

Please give me some tips when it comes to measuring snow.

Thanks,

Doug

Dorchester Weather

Its widely accepted that 1mm of rain will be about 1cm of snow. So I guess that 1 inch of rain wil equal 10 inches of snow.

To measure the snow you would catch it in the rain gauge just like rain but then you would melt it down. When melted you would measure it with the rain gauge and that will give you the rain equivalent to how much snow fell.

[johnholmes]

it depends on the dryness or wetness if that is the right term for the snow falling. Dry snow has much less water in it so maybe 10x the amount can fall for the same water equivalent.

I should know a quick rule but cannot remember it at the moment, sorry.

John

one I recall suggested that 30 cm of FRESHLY fallen snow is equivalent to about 25mm of rainfall.

[Nick F]

I go by the guide of 10cm of snow is equivalent of 1cm/10mm of rain.

[Terminal Moraine]

I've done a bit of research into this over the years and, as John states, the amount of snow to a given number of mm of water varies greatly according to the 'dryness' of the snow; this is largely a function of the temperature at which the snow falls.

The general rule of thumb that 25cm of snow equates to 25mm of rain applies if the temperature is at or just below 0c when the snow falls, if the temperature is much lower, say -5c, then it can take up to 45cm of level snow to equal 25mm of rain.

At the other end of the scale I've measured 20mm of 'rain' from a 10cm cover of very wet snow which fell at a temperature between 0c and 0.8c.

The best way to find the rainfall equivalent is to take two or three cores of snow with the top of an old rainguage in an area where the snow is undrifted and generally representative of the average depth. Melt the snow and measure the resultant liquid and take an average of the number of samples.

T.M

[johnholmes]

I've done a bit of research into this over the years and, as John states, the amount of snow to a given number of mm of water varies greatly according to the 'dryness' of the snow; this is largely a function of the temperature at which the snow falls.

The general rule of thumb that 25cm of snow equates to 25mm of rain applies if the temperature is at or just below 0c when the snow falls, if the temperature is much lower, say -5c, then it can take up to 45cm of level snow to equal 25mm of rain.

At the other end of the scale I've measured 20mm of 'rain' from a 10cm cover of very wet snow which fell at a temperature between 0c and 0.8c.

The best way to find the rainfall equivalent is to take two or three cores of snow with the top of an old rainguage in an area where the snow is undrifted and generally representative of the average depth. Melt the snow and measure the resultant liquid and take an average of the number of samples.

T.M

exactly TM, I remember that well from my old met assistant days when it used to snow!

[acbrixton]

Hence too the unfair ridicule heaped on the old British Rail for blaming the "wrong type" of snow for the malfunctioning of their new rolling stock in February 1991: the sliding door mechanisms of such trains became blocked by the dry powdery snow that fell in the London area at unusually low temperatures of -4/-5c. The rolling stock had been designed to cope with the far more common wetter/denser snow that falls at or arounf 0c.

Regards

ACB

[osmposm]

Hence too the unfair ridicule heaped on the old British Rail for blaming the "wrong type" of snow for the malfunctioning of their new rolling stock in February 1991: the sliding door mechanisms of such trains became blocked by the dry powdery snow that fell in the London area at unusually low temperatures of -4/-5c. The rolling stock had been designed to cope with the far more common wetter/denser snow that falls at or arounf 0c.

Very true, ACB - the powdery snow clogged up the recesses into which the doors opened, and the exceptionally low temps even froze the rubber seals together. The snow also blew into electrical circuits, shorting some of them out, and was sucked into air intakes, blocking them and overheating the motors. And finally, some air brakes failed as the moisture in their systems condensed and froze.

And for those who don't understand why the trains weren't built to resist such a possibility - well, it's the same reason the South of England doesn't have large fleets of snow blowers standing by to clear deep drifts on the roads. The probability of such events is extremely low, and the cost of providing systems that can cope with them is extremely high. And it is we, of course, who would bear that cost. How many Brits own a set of snow tyres?

Woops, sorry - gone WAY off topic...