Is it based on radar analysis. Is it ground observations. Or a combination of both. I understand that snowfall is typically based on a 10:1 ratio. And can change based on the dendritic growth zone.

Is snowfall measured differently than its liquid counterpart (rain).

Thanks.

airmorse: "Is it based on radar analysis. Is it ground observations. Or a combination of both. I understand that snowfall is typically based on a 10:1 ratio. And can change based on the dendritic growth zone.

Is snowfall measured differently than its liquid counterpart (rain).

Thanks."

Good question. Quite deep (no pun intended) and can be confusing.

Not radar ( rain can be) -- ground observations.

The snow/liquid ratio is based on temperature at 850mb (about a mile up) temperature.-- ie where the snow crystals form. At around 32F to 27F it's right near 10:1. 27-22F is about 13-15:1 -- 22-17F is about 16:19:1 and below 16F-14F is 20:1 and so on.
The most efficient temp for best accumulating snow at 850mb (deep topic that I will go all in on here-- based on formation of the crystal itself) is about 18-19F at the 850 mb level.

Now to measuring snowfall. Most people do it wrong but it's mainly because they don't have the time to do it like it's supposed to be done. Part of my job is measuring snow. During a snow event, we measure off 2-3 snow boards (white 16" by 24" plastic) every hour- and clear a section each hour and add up totals. We use 2-3 boards for wind issues/drifting etc. Every hour - 24 hours a day if so. Most people measure once the snow event is done or at noon/6pm/midnight/6am -- but that allows for settling or even melting. At 00Z/06Z/12z and 18Z we also give snow depth -you will see this in meter codes as the "4" group, but not all major airports measure snow because they don't have a good place to do it.
Pic is of today's event here in DSM.
We also melt down the snow that has fallen into a 8" diameter steel tube and find the snow/liquid ratio. The automated junk (ASOS) does OK when the temp is near 32F but really struggles when the snow gets more like powder when the ratio is higher. It's an automated heater that melts the snow and converts to liquid but snow is "lost" in the process. Sadly- the "official" melted water used is the auto junk because only 10% of climate sites have human observers-- thats why you will see crazy ratios like 40-50:1 ina cold event
Soo- in todays event-- 5.6" is event total. ASOS liquid total .25" but manually .36".
I hope this helps.

If your really bored-- this really does a good job explaining --
https://www.weather.gov/gsp/snow

Great job explaining. This is what I was looking for. Thx. And congrats on the snow at DSM.

Thanks WW, I was wondering this the other day and just noticed this post for some reason.