CoCoRaHS - Community Collaborative Rain, Hail & Snow Network

An observer writes: "We haven't had snow for a while, and although there is still some in clumps in shady areas, or in windblown drifts (none more than an inch deep), mostly the ground is snow free. How do I report this? "

Great Question! Here's our answer: As snow melts, when more than half of the ground is bare you report a "T" for Trace.

An observer in Oklahoma writes: "I have some confusion on snow measurement despite reading through the procedure. I tried to enter a snow amount of 1/4 inch or 0.25 but it wouldn't accept it. What am I doing wrong?"

Good question! Here's our answer: New snowfall depth is measured to the "tenth" of an inch, not "hundredth" as rainfall is. So the system would not take 0.25", but it will take 0.3". So when reporting snowfall depth remember only one decimal place.

If you are using a regular ruler here is a review of the conversions to the nearest tenth-inch increments: 1/16 = 0.1, 1/8 = 0.1, 3/16 = 0.2, 1/4 = 0.3, 5/16 = 0.3, 3/8 = 0.4, 7/16 = 0.4, 1/2 = 0.5, 9/16 = 0.6, 5/8 = 0.6, 11/16 = 0.7, 3/4 = 0.8, 13/16 = 0.8, 7/8 = 0.9, 15/16 = 0.9

We do have snow rulers marked off in tenths available from WeatherYourWay.com if you are interested in purchasing one.

An observer from North Carolina writes: "If you physically observe snow during the 24-hr period preceding your observation, but it all melts once it hits the ground (or melts overnight), what's the best way to report in CoCoRaHS that the snow actually occurred and that it may have contributed some to total water in the gage?"

A quick reminder when measuring new snow! Do not measure the depth in the gauge.

When you measure "new snow", it is best to do so on a flat surface on the ground (such as a snowboard -- 14"x14" piece of white plywood) that has been cleared since the last snow fall. You only measure the depth of the new snow that has fallen. By all means do NOT measure depth of new snow by measuring the "depth" of what has fallen in your gauge.

Freezing Rain . . . watch your step!

Freezing rain is rain that falls in liquid form but freezes on contact with the ground and objects above the ground. Do NOT report freezing rain as "Snow". If you have an inch of freezing rain accumulate, you melt and measure the moisture that has accumulated inside your gauge and you report that as your daily precipitation amount. You report ZERO for your new snow amount (assuming it all fell as rain, and no sleet or snow accumulated). You DO report the total depth of freezing rain that has accumulated on the ground and enter that in the "Total Snow on Ground" column. Again, make a note in your comments section of your report so that we know its freezing rain.

A very useful measure of freezing rain is the "radial thickness" of ice on wires, branches, etc. If you can, measure the ice thickness on a wire or branch and report in your "Comments" the average radius of the ice (not the diameter).

Please remember, your safety and well-being is our #1 concern. If the path to your gauge looks like an ice rink or conditions are such that you risk injury in order to get to your gauge, leave it until conditions have improved. We would rather have a two-day or three-day accumulation (use the Multi-Day Accumulation report) than have you slipping and getting injured.

Effective December 15, 2008 the default value for daily snowfall will be changed from 0.0" (i.e. assumes no snow) to NA (i.e. no assumption).

The reason for this change is that some observers who measure precipitation but who don't measure snow have been leaving the 0.0" snow amount. This fills our snowfall maps with incorrect information.

If you receive snowfall in the past 24 hours, please enter that amount in the "Depth of New Snow" category by replacing the NA with the appropriate value in inches and tenths. If you do not receive any snow, be sure to enter 0.0 in this field. If you enter 0.00" for your daily precipitation amount, it will automically put in a zero for snowfall.

It's the end of October and snow has already fallen in some of our observers backyards. As we move into the month of November many more of you will experience snow as well.

Snow is very important for our environmnent as well as our daily activities. Your reports of "New Snow", "Total Snow on Ground" and "Snow Water Equivalent (SWE)" provide valuable information.

This is a good time of year to review the information on our website on how to measure snow. Click here: http://www.cocorahs.org/Content.aspx?page=snow

As you think about the approach of winter, keep in mind that water left in the inner cylinder of our gauge will freeze and crack the gauge if left outside in prolonged subfreezing weather. It is best to bring the funnel and inner tube inside and catch the winter precipitation in the large outer cylinder.

Finally, many of you have asked where to find good rulers that read in tenths of an inch. We now have a source. Snow rulers were recently designed and manufactured specifically for distribution and use by CoCoRaHS volunteers.

Here is a link to where these new snow rulers can be ordered:
http://www.weatheryourway.com/cocorahs/store.html

Many thanks for your autumn snow measurements!!

Snow is very important for our environmnent as well as our daily activities. Your reports of "New Snow" and "Total Snow on Ground" provide valuable information.

"Total Snow on Ground" is the average depth of snow and ice (including the glaze from freezing rain) that remains on the ground at the time of your daily observation. Measure and report to the nearest whole or half inch, unless you feel you can measure it more precisely. If the depth of snow/ice varies around your yard, then take the average of several measurements.

Our computer automatically inserts NA (not available) for your total snow report. Just move your cursor to that position and type in your report.

1. If snow falls but entirely melts on contact with the ground and never whitens the ground or grass, then report T for "New Snow" and 0.0 for your "Total Snow Depth"

2. If snow falls, accumulates, but then melts prior to the your daily observation, report the greatest depth of new snow that had accumulated during the day prior to melting and settling. But if all the snow has melted, still report 0.0 for the "Total Snow Depth"

3. If you can, measure the water content of the new snow and report that as your daily precipitation amount "Rain and Melted Snow"

4. If you add warm water to help melt the snow in your gauge, remember to measure that amount before you pour it in. Be sure to remember to subtract out that amount of warm water added to get the daily precipitation amount.

If you have questions about measuring snow, please ask!!

December 2007

SNOW MATTERS

CoCoRaHS observations of snowfall, snow depth and water content are very important. There are surprisingly few sources for official local measurements of snowfall. Your measurements really help.

Measuring winter snow and ice can be difficult. If you are not as agile and steady on your feet as you once were, this is a good time of year to take a break from CoCoRaHS and let the younger folks do the observing.

Whether or not we take observations, we can still enjoy the complexities and beauty of snow with the help of NOAA's National Hydrologic Remote Sensing Center (Chanhassen, Minnesota) and the National Snow and Ice Data Center (Boulder, Colorado).

Take a look at these websites when you are in the mood for snow:
http://www.nohrsc.nws.gov/
http://nsidc.org/

November 2007

CARING FOR YOUR GAUGE IN WINTER

Winter can be hard on us and our rain gauges. Here are some tips for making it easier.

    * Avoid letting water freeze in the inside measurement tube of your gauge. Remove the funnel and inner cylinder if subfreezing temperatures are expected.
    * Your outer cylinder may freeze and stick in the mounting bracket. Apply a lubricant to reduce friction and avoid freeze-up.
    * Consider an alternative mount for your gauge when snow and ice are present. Try a small platform on or just above the ground that holds the gauge straight and keep it from blowing over in strong winds.
    * Remember, gauges do not readily catch wind-blown snow. Protected locations nearer the ground are better for winter measurement than open-windswept elevated locations.

Measuring snow can be challenging. It melts, it settles, it changes density and it blows around. Sometimes it sticks to the rim of the gauge, and sometimes it barely lands in the gauge. We measure the water content of snow, the accumulation of fresh snow, and the total depth of snow on the ground. Sometimes we take core samples of fresh snow or total snow on the ground so that we can better estimate the water content.

If you have a high speed internet connection, please watch the snow measurement training video.