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Jan from Humboldt
01-30-2006, 06:29 PM
snow? or are there too many variables to do this sort of converson.

Robert Fogt
01-31-2006, 06:51 AM
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.

searunner52
02-06-2006, 02:36 AM
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)

Unregistered
05-14-2006, 05:59 PM
snow? or are there too many variables to do this sort of converson.
HOW MANY INCHES OF SNOW FOR 1 INCH OF RAIN

Robert Fogt
05-14-2006, 10:17 PM
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.

Unregistered
06-11-2006, 01:28 PM
1 inch of rain = how many inches of snow?

Robert Fogt
06-12-2006, 12:13 AM
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.

Unregistered
09-05-2006, 09:13 AM
so how would i convert 2 inches of rain per hour to mm per hour

Robert Fogt
09-05-2006, 07:26 PM
2 inch = 50.8 millimeter

2 inches/hour = 51 millimeter/hour

Anonymous guy
01-15-2007, 07:20 AM
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)

Unregistered
12-01-2007, 07:25 PM
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

Unregistered
12-02-2007, 02:10 PM
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.

cman
12-13-2007, 03:00 PM
how much rain is eqaul to 1 inch in real life

Unregistered
12-18-2007, 06:23 PM
or you could just 'catch' a couple inches of snow and let it melt then measure how much water it is

Roy Nakatsuka
12-23-2007, 02:48 PM
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:
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/conversion/newsnowfall.pdf
In fact, the NWS table was criticized in the same paper quoted earlier:
Deficiencies of NWS Table 4-9
"'The table’s 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/snowdensity/from_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:
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 -15°C (+5°F). 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 –15°C) 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!

Unregistered
07-25-2009, 07:17 AM
snow? or are there too many variables to do this sort of converson.

don't care re variables

Unregistered
02-07-2010, 12:06 PM
one inch of rain is equal to 10 inches of snow

02-18-2010, 09:30 AM
There's a huge amount of variation when trying to calculate the amount snow from the equivalent amount of rain. The U.S. Geological Survey's website,

(I'm a new user and not allowed to post links, but if you Google ""volume of snow from rain" , it should be the first link)

gives a range from 4-5 inches (the wetest, heaviest snow), to about 20 inches for dry powder. You really need to know something about the temerature and humidity in addition to the amount of rain to get an idea about snowfall amounts.

Unregistered
06-09-2010, 03:25 PM
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)

Are you sure "Old Country" doesn't mean "Google"?
That is exactly what posts all over the net say about rain-snow conversions, almost word for word.

Unregistered
02-05-2011, 01:05 AM
The ratio can vary considerabally based on temperature. Here is a link to a noaa site with a rather complete table.
The folks who run this site will not allow me to post a link to a noaa site so maybe I can modify it so it does not look like a link but a human can convert it back.
www.erh.noaa.gov/box/tables/snowfall-meltwater.html

mcl
(retired meteorologist...worked for the AF for 35+ years)

MOD NOTE: Link restored above, thanks for info. Only registered members with at least a few posts can post links. JohnS

Unregistered
05-31-2011, 08:27 AM
Convert 1 inch of rainfall to ounces of cup of water

JohnS
05-31-2011, 12:34 PM
Convert 1 inch of rainfall to ounces of cup of water

Multiply by the area in square inches of the opening at the top of the cup to get cubic inches. As 128 fl oz = 231 in³ = 1 gallon, multiply the cubic inches by 128/231 to get fluid ounces

Unregistered
09-08-2011, 03:10 PM
This storm here would produce like 1 ft. of rain that would be like 6'3" of snow! :D

Unregistered
11-09-2011, 06:16 AM
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)

My family is also from Germany and I don't remember anyone in the old country converting 1 INCH of rain to 10 INCHES of snow.

Unregistered
01-03-2012, 01:42 PM
My family is also from Germany and I don't remember anyone in the old country converting 1 INCH of rain to 10 INCHES of snow.

Maybe the Grandfather was referring to a song by George Jones that he sang about the snow always turning to rain in a country song and they got confused?

Unregistered
11-15-2012, 10:29 AM
how do you caculate if four inches of heavy wet snow are equivalent to two inches of rain estimate the water content in 8 inches of heavy wet snow.

Unregistered
03-11-2013, 08:54 AM
We are asking rain into snow not snow into water.
If we have six inches of rain in a day at 34 degrees had it been colder and the rain was snow, how much snow would we have had? That is the question here.

JohnS
03-11-2013, 09:50 AM
We are asking rain into snow not snow into water.
If we have six inches of rain in a day at 34 degrees had it been colder and the rain was snow, how much snow would we have had? That is the question here.

Lots of notes on 2nd page of this thread. Depending on temperature or how wet the snow is, an inch of rain could be anywhere from 3" - 20" of snow. The 3" for very wet, slushy snow, 20" for very light powder. It really depends on what the temperature would have slipped to. Probably 6" snow per inch of rain, if just below freezing; higher ratios require much colder weather.

Unregistered
04-07-2013, 03:42 PM
I live in central Alberta. I have shovelled snow for the past two years with the intention of piling it up against relatively newly planted shrubs. This does two things: it protects the plants from harsh winds and premature climate thaws; and it waters the plants upon melting.

I have noticed in my area that the snow is light and powdery (increasingly so) from about November to mid-January (as the average temperature lowers). The snow quality becomes heavier from January to end of April (as the average temperature increases).

This is by no means a scientific study but it is what my muscles in association with my brain tell me.