High Sierra Topix

https://www.fs.fed.us/r5/webmaps/SierraSnowDepth

I just found this Forest Service site which gives snow levels all over the Sierra. I wonder how they derive this data, and how accurate it is. Does anyone know of other snow level maps, data, or descriptions? I am looking for accurate accounts of the snow levels for the area from the JMT east to the Main Divide.

Thanks for any help and advice on this question. Harlen.

A lot of extrapolation in that. The best data is from the state Dept. of Water Resources. Takes some time to get used to navigating the site to find the level of detail you want, but they basically have al the information that exists, and any other source you look at is working from their dataset.
This is the main page: http://cdec.water.ca.gov/snow/current/snow/
Under the heading on the left, "SNOW COURSE INFORMATION", you have the manual survey data. Under the heading on the right, "SNOW SENSOR INFORMATION", you have the data from the remote sensors scattered throughout the range.
What you need to do is become familiar with the stations, both manual and remote sensing, that are within or close to the area you want to visit. If you go to "Latest Real-time snow water content data" in the right column, you'll get a list of remote sensing stations grouped by river drainage, with water content numbers . Click on the number and you see a list of readings - usually hourly. Click on the station ID instead of the number and you get info on that station. Near the top of the page with the station info you'll see "Map of surrounding area", with the word "Map" a link. click that and you see the map, with stations shown on it, and from that you can figure out which stations you want to look at. The map shows all stations, not just the remote sensors, so it takes some work to sort out which have remote sensors and which are manual survey only ( some are both). But eventually you'll know which ones to look at for the areas you want. This gets you the most detail that is available anywhere.

Fantastic Paul!

This is exactly what I was after. Thanks for pointing me to it. Since you are already expert, can you tell me what the Bear River and Mono River crossings look like to you? The former map showed bare ground around the Mono river at the JMT crossing? I don't want to risk getting swept with Bearzy. I suppose I would be able to ski upvalley to the east to find a snow-bridge. Thanks again Paul, Ian.

Anyone know if current NASA Airborne Snow Observatory data is posted anywhere? The main web site only seems to have stuff up through 2017. Is the map at https://www.nohrsc.noaa.gov/interactive/html/map.html partly based on that data?

I also love this page on the Snow Survey https://cdec.water.ca.gov/cgi-progs/sno ... no/COURSES

https://www.postholer.com/snow/Pacific-Crest-Trail/1
just saw this don’t know if it helps