Sierra Snowpack and Stream Flow Data / Maps

Questions and reports related to Sierra Nevada current and forecast conditions, as well as general precautions and safety information. Trail conditions, fire/smoke reports, mosquito reports, weather and snow conditions, stream crossing information, and more.
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Re: Sierra Snowpack and Stream Flow Data / Maps

Post by oldranger » Sun Apr 14, 2019 5:25 pm

paul wrote:
Mon Feb 18, 2019 5:02 pm
If you are looking for a quick, overall view for the whole range, rather than local detail, the easiest thing from the state is here:
This is updated roughly every working day - no weekends or holidays - and gives a quick visual. The default display is the biggest year, the lowest year, and the current year. At the top you can select from a list of years to include in the graph.
I added 2010-2011 to the graph and this year is remarkably similar. Depending on spring and early summer conditions should be similar this summer. If so then expect snow at 11,000 feet thru july in
central and N. sierra.


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Re: Sierra Snowpack and Stream Flow Data / Maps

Post by rightstar76 » Mon May 06, 2019 4:06 pm

Here's another one:

USDA Forest Service Sierra Snow Depth:

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Re: Comparing conditions to past years

Post by tomba » Tue Jun 11, 2019 9:21 pm

To compare snow coverage to past seasons we can use MODIS compare view. Example: ... 6876822385

This is A-B comparison. B (right) is today, A (left) is 2011-06-21 (another high snow year). Drag the split image slider left and right to compare. Snow coverage is similar on those dates. Click "A" and "B" in the upper-left tabs, and click the up/down year/month/day arrows in lower left to change the A or B date (or drag the slider at the bottom, or use the left-right arrows between the date slider and the date). Scroll down the panel on the left side and click Aqua or Terra tiles to show/hide the approx. 10:00 or 14:00 views for the selected day to pick the clearer image.

We did a trip to that region early July 2011: viewtopic.php?f=34&t=6282&p=45172#p45172.
-- Found trash? Please pack it out. Thank you.

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Re: Sierra Snowpack and Stream Flow Data / Maps

Post by wildhiker » Tue Jun 11, 2019 10:38 pm

I've looked at the modis satellite views a lot, but never knew about the comparison mode. That's amazing! Thanks for sharing. And we should all thank our dedicated civil servants who make these great tools available to everyone for free!

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Re: Sierra Snowpack and Stream Flow Data / Maps

Post by cantare » Thu Jun 27, 2019 10:55 am

I've looked at various snowpack report and visualization links and found they are limited by low-resolution images and difficulty with orientation and interpretation--either in matching photos to desired locations or in deciphering sensor placement and the real-world meaning of tabular technical data ("snow water content", eg.)

This CalTopo resource (arbitrarily centered on a Sierra Nevada overview) combines the latest weekly high-resolution Sentinel image with meaningful road/trail/stream/lake overlays: ... 0.42&a=mba

If you click the dropdown menu at upper right, the MapBuilder Topo layer under "Additional Layers" has a 0-100% opacity slider that fades a detailed and comprehensive topo map in and out, so you can easily zoom to an area and check current snow coverage at precise points of interest. (I've set it to an intermediate value to start so both layers are visible.)

The MapBuilder Overlay (checkbox) shows basic orienting info (major routes, lakes, streams) at 100% opacity even when you're viewing the satellite image exclusively. You can also fall back to daily low-res MODIS images via the "Base Layer" dropdown if the weekly image is stale, and also check the progress & rate of melting over the past days/months/weeks. I do note that the weekly high-res layer may become subscription-only, but it is freely available as of this post.

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Re: Sierra Snowpack and Stream Flow Data / Maps

Post by Dwwd » Sat Jul 06, 2019 6:33 pm

Check out the comparison discussion of Caltopo high resolution snow/ice images versus the data original site at Sentinel Hub.(free)

I particularly like to compare the current snow year, April 1 amounts, to any historical data from above discussion links with similar (4 closest) April 1 amounts from this Ca Water site. ... _1_SWC.pdf. I do not focus on snow depth. Only snow weight. Weight zero on calendar historical date => no snow at sensor elevation/location, provided the sensor is working. White pixel in low res image of lake = ice. Blackpixel = water. Between April 1 and start of summer trips, the spring melt rates (heat waves/colder than normal May + June) does modify the snow out/ice out times to some degree. Hence the need to look at historical data for the four closest similar snow years. Then with the Sentinel data you can follow the high resolution images up to a few days before your trip for final verification.

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