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  • Convert 1 inch of rain to ? inches of

    snow? or are there too many variables to do this sort of converson.

  • #2
    Re: Convert 1 inch of rain to ? inches of

    You should be able to get an approximate value without too much trouble.

    I searched Google and found the Specific gravity of snow.

    Freshly fallen Snow, 0.16
    Compacted Snow, 0.48

    The specific gravity means its density as compared to water. So fresh snow has a density 0.16 times that of water.

    rainfall / 0.16 = snowfall
    snowfall * 0.16 = rainfall

    Lets just call this an educated guess though. Seems simple but their may be variables I am not seeing.

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    • #3
      Re: Convert 1 inch of rain to ? inches of

      I was always told that 1" of rainfall was the equivalant of 10" of powder snow! The heavier the snow the higher the moisture content the fewer inches of snow per inch of rain.

      Now where this originally came from I don't know - It was something my grandfather passed on to me - he said that this was the way they measured snowfall back in the old country (Germany)

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      • #4
        Re: Convert 1 inch of rain to ? inches of SNOW

        Originally posted by Jan from Humboldt
        snow? or are there too many variables to do this sort of converson.
        HOW MANY INCHES OF SNOW FOR 1 INCH OF RAIN

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        • #5
          Re: Convert 1 inch of rain to ? inches of

          An average value would be 6.25 inches of snow for 1 inch of water.

          Warmer weather would provide lower values, colder weather would provide higher values.

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          • #6
            Re: Convert 1 inch of rain to ? inches of

            1 inch of rain = how many inches of snow?

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            • #7
              Re: Convert 1 inch of rain to ? inches of

              1 inch rain = 6.25 inches snow

              This is an average value though. Colder areas will have a lower number while warmer areas will have a higher number.

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              • #8
                Re: Convert 1 inch of rain to ? inches of

                so how would i convert 2 inches of rain per hour to mm per hour

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                • #9
                  Re: Convert 1 inch of rain to ? inches of

                  2 inch = 50.8 millimeter

                  2 inches/hour = 51 millimeter/hour

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                  • #10
                    Re: Convert 1 inch of rain to ? inches of

                    Opinions vary greatly, but a common number seems to be 1:10 (one inch or water will result from melting about 10 inches of snow)

                    See Google rather than trying to reverse engineer specific gravity (while admirable, it appears rather on the low side of the accepted average)

                    google . com/search?q=1+inch+rain+%3D+snow

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                    • #11
                      Re: Convert 1 inch of rain to ? inches of

                      well actually dispite what annoymous has said the specific gravity of snow would be a good indicator of how much snow per inch of rain fall. as its a direct weight comparison between snow and water and its a measurement done by volume so its the weight of snow based on weight for a specific volume.

                      1 inch rain :6 inches of snow, would be a good although rough guide for snow

                      alternating factors would be wet snow to dry snow, which would vary the compaction, with wet snow being more like a 1:4-5 and dry snow being more 1:6-7

                      i think 1:10 is something that is just being thrown around and not based on anything factural, seems like a rather too nicely rounded value to be true. got proof? let me know

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                      • #12
                        Re: Convert 1 inch of rain to ? inches of

                        It really does depend---5 inches of very wet snow (almost to the point of sleet) is about an inch of liquid water, whereas "dry" snow, especially powder, which precipitates at colder temperatures can sometimes be 16 or even 20 inches of snow per inch of liquid water. Generally 8 to 12 inches of snow per inch of water is a pretty good conversion.

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                        • #13
                          Re: Convert 1 inch of rain to ? inches of

                          how much rain is eqaul to 1 inch in real life

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                          • #14
                            Re: Convert 1 inch of rain to ? inches of

                            or you could just 'catch' a couple inches of snow and let it melt then measure how much water it is

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                            • #15
                              Re: Convert 1 inch of rain to ? inches of

                              Originally posted by Unregistered
                              or you could just 'catch' a couple inches of snow and let it melt then measure how much water it is
                              That is definitely a simple and sensible way to make a measurement. Just need to be sure the container has a flat bottom so the depth measurements are valid.
                              _________________________________

                              As for the well-known "10-to-1 rule" for the snow/water ratio, here is an explanation of its historical origin:
                              ". . . the 10-to-1 rule appears to originate from the results of a nineteenth-century Canadian study. Potter (1965, p. 1) quotes from this study: 'A long series of experiments conducted by General Sir H. Lefroy, formerly Director of the Toronto Observatory, led to the conclusion that this relation [10 to 1] is true on the average. It is not affirmed that it holds true in every case, as snow varies in density. . . .' The 10-to-1 rule has persisted, however, despite the almost immediate warnings concerning its accuracy."

                              from "Improving Snowfall Forecasting by Diagnosing Snow Density"
                              http://sanders.math.uwm.edu/snowratio/roebber.pdf
                              The U.S. National Weather Service (NWS) uses a conversion table for estimation, with snow/water ratios increasing from 10:1 to 100:1 as surface temperature decreases:
                              Code:
                                      Surface  | Snow/water
                                  Temperature  | Ratio
                               ----------------+------------
                                     28-34 F  |   10:1
                                     20-27 F  |   15:1
                                     15-19 F  |   20:1
                                     10-14 F  |   30:1
                                      0-9  F  |   40:1
                                -20 to  -1 F  |   50:1
                                -40 to -21 F  |  100:1
                              
                                "New Snowfall to Estimated Meltwater Conversion Table"
                                http://www.ncdc.noaa.gov/oa/climate/...ewsnowfall.pdf
                              In fact, the NWS table was criticized in the same paper quoted earlier:
                              Deficiencies of NWS Table 4-9
                              "'The tables temperature dependence of density is not based on actual measurements but rather on general impressions in the eastern Tennessee and western North Carolina areas. Hence, the reality of the apparent temperature dependence is uncertain.' As was shown in the previous section, this temperature dependence is, in fact, inadequate."
                              For a really detailed study, see the following very informative report (127 pages) at the Meteorology Education & Training website of the University Corporation for Atmospheric Research:
                              "From mm to cm... Study of snow/liquid water ratios in Quebec"
                              http://www.meted.ucar.edu/norlat/sno...m_mm_to_cm.pdf
                              Here's what the author says about the ten-to-one rule:
                              "Ten-to-one rule (10:1) Despite the fact that this rule constitutes the operational tool most frequently used by meteorologists, there is not much more to be said about it. Several climatological studies clearly demonstrated its inaccuracy in about 50% of all cases."
                              The report proposes a classification of snow into six main categories, with corresponding mean snow/water ratios as follows:
                              Code:
                                4:1 - very heavy snow
                                7:1 - heavy snow
                               10:1 - average snow
                               15:1 - light snow
                               20:1 - very light snow
                               25:1 - ultra light snow
                              One interesting and important piece of information in the report is that snow is least dense (i.e., "fluffiest") at temperatures around -15C (+5F). For this reason, the NWS table also gets criticized by the study:
                              "In practice, as well as in theory, it has been clearly shown that there is an optimal range of temperatures (around 15C) where lower densities are observed. At lower temperatures (e.g., 20 or 25 C), a return to higher density crystals occurs. This peak does not appear in Table 21 [the NWS table]. As a result, this kind of conversion table will tend to overestimate snow/water ratios at low temperatures, and therefore to overestimate snow accumulations."
                              The next time your local snow forecast turns out to be way off the mark, you may at least understand better why that happened!

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