[pct-l] Snow Level Planning Tools

[Dan C. aka Thumper]

So after a great deal of discussion today I thought I’d write a little 
about two snow level information resources.

The first is United States Department of Agriculture, Natural Resources 
Conservation Service, Water Climate Center.  This is the agency that 
operates and manages the Snow Telemetry (SNOTEL) and Snow Course Data 
and Products.  Most individuals who follow this list-serv have heard of 
the SNOTEL reference.  The following link will open a page that will 
then have links to clickable maps of Northern California, Oregon and 
Washington;

 
http://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2_046173

 From there select the state you are interested in and then the 
particular site.  For purposes of demonstration I’ll select Washington 
and then Harts Pass. Once on the Harts Pass page there will be a list of 
reports.  Let’s select the second report,  “7-Day In-Depth Report - 
Hourly data for standard SNOTEL sensors”  Once the page opens unclick 
the check-box titled “Fit Table To Screen” to view all the data.  I do 
not recommend using this page for historical data unless you want hourly 
information.

Next let’s get daily historical data.  From the Harts Pass page select 
the first report, “7-Day Summary Report - Midnight data for standard 
SNOTEL sensors”.  Again, unclick the “Fit Table to Screen” box.   What 
is presented is the last 7 days data.  Now in the header area is a 
drop-down titled “Time Period”.  Set as desired and the historical data 
will present itself.  Note that a Water Year is the same as the Federal 
fiscal year, 1 October through 30 September.

There are 2 methods of outputting the data, first is to copy and special 
paste into a spreadsheet and the second is to use the “Output” drop-down 
in the header to output into a CSV format which you then need to copy 
and paste.  Personally I like the first copy and paste method better as 
it is quicker.

So that’s SNOTEL in a nut shell.  There are many reports and many years 
of data available.  A few comments;  There are no SNOTEL sites in NORCAL 
that would be of any value to a PCT hiker;  SNOTEL sites are a set of 
specific measurement tools and as such do not necessarily reflect the 
surrounding areas.  The position in the topography and exposure to sun 
are just two major variables that contribute to accuracy, or lack 
thereof;  SNOTEL sites are not necessarily in close proximity to the PCT 
so data may be deceptive as it relates to trail conditions; Finally, 
there are some SNOTEL sites referenced via the postholer.com maps, 
Location Type Snow Sensor, but not all that are relatively close to the 
trail are listed (Harts Pass) and other that are listed are no longer 
active (Miners Ridge).  Additionally on the postholer.com does list many 
of The California Data Exchange Center (CDEC) sites  along the PCT.

So that’s a great segue into the second snow level information resource. 
It is the US Department of Commerce, National Oceanic and Atmospheric 
Administration (NOAA).  NOAA operates and maintains a series of 
satellites that report all kinds of useful data.  This link is for Snow 
and Ice offered products: 
http://www.ospo.noaa.gov/Products/land/snow.html .  Like anything else 
in this life there are very technical things happening in the 
background.  Our friend at postholer.com has made a very hard thing 
pretty easy.  Subscribing to the NOAA data postholer.com and their 
on-line trail maps has many of google maps.  The overlays, or as they 
call them, “Map Skins” contain subject areas including Weather, Snow 
Analysis, Fire, Miscellaneous and Wilderness areas.  The Snow Analysis 
features are discussed in a postholer.com journal entry found at 
http://www.postholer.com/forum/viewtopic.php?f=2&t=1956

The snow data is updated by NOAA each day at 0400EST and postholer.com 
accesses the data through web-services which makes it somewhat 
transparent to the user.  To access the trail maps go to the following; 
http://www.postholer.com/ and then in the header click on “GMaps” and 
then select your map. Once the map opens you will note the trail line 
laid on the typical Google maps we all use on a daily basis.  You can 
select the map type using the drop-down and select My Topo, Map, 
Satellite or Terrain.  Note on the right area of the map header is a 
drop-down titled “Map Skins”.  This has the list of available map 
overlays.  It’s that simple.

So let’s make it a little harder and also show a real-life illustration. 
First off, historical overlays are available, and yes through the 
postholer.com website but you will need to understand how to construct 
the URL.

Look closely at the following 2 urls:

http:// www.postholer.com/gmap/gmap.php?trail_id=1&depth=1

http://www.postholer.com/gmap/gmap.php?trail_id=1&depth=20151201

trail_id=1 is the PCT (2 is the CDT, 3 is the AT, 4 is the JMT and so 
on.  Remember the link http://www.postholer.com/google-maps, well you 
can decode the trail_id from there)

&depth=1 is the Snow Depth for the current date

&depth=20151201 is the Snow Depth for December 1, 2015 in YYYYMMDD 
format (this is historical information)

So basically you can put in any date back to mid-October 2005.

SNOTEL historical data is tabular where map overlays are visual.  There 
are no animations for the overlays but maybe I can offer a quasi 
animation.  A quasi animation could be setup as follow.  Lets say you 
wanted to look at the weekly snow depth since 20151130, a Monday.  You 
would then paste in the first date into your browser, enter, and then 
modify  the date , enter and so on.  When done you can use your back and 
forward buttons to sort of scroll through the date range and get an idea 
of the snow levels.  Each URL would look like this;

www.postholer.com/gmap/gmap.php?trail_id=1&depth=20151130

www.postholer.com/gmap/gmap.php?trail_id=1&depth=20151207

www.postholer.com/gmap/gmap.php?trail_id=1&depth=20151214

www.postholer.com/gmap/gmap.php?trail_id=1&depth=20151221

www.postholer.com/gmap/gmap.php?trail_id=1&depth=20151228

www.postholer.com/gmap/gmap.php?trail_id=1&depth=20160104

www.postholer.com/gmap/gmap.php?trail_id=1&depth=20160111

Okay now let’s do the same thing but zoom in on a particular area of the 
map.  I selected where the PCT crosses Hwy 2 near Stevens Pass as the 
map center and a zoom level of 8. The map is now viewable between Rainer 
and Harts Pass.  Using the same dates as above the URLs now look like 
this;

 
http://www.postholer.com/gmap/gmap.php?trail_id=1&lat=47.74750&lon=-121.08750&zoom=8&depth=20051012

 
www.postholer.com/gmap/gmap.php?trail_id=1&lat=47.74750&lon=-121.08750&zoom=8&depth=20151130

 
www.postholer.com/gmap/gmap.php?trail_id=1&lat=47.74750&lon=-121.08750&zoom=8&depth=20151207

 
www.postholer.com/gmap/gmap.php?trail_id=1&lat=47.74750&lon=-121.08750&zoom=8&depth=20151214

 
www.postholer.com/gmap/gmap.php?trail_id=1&lat=47.74750&lon=-121.08750&zoom=8&depth=20151221

 
www.postholer.com/gmap/gmap.php?trail_id=1&lat=47.74750&lon=-121.08750&zoom=8&depth=20151228

Note the insertion of “&lat=47.74750&lon=-121.08750&zoom=8” which is the 
Lat Long of the selected map center and the desired zoom level.

I only have 3 more points and then I’m done with this for a while. 
Remember the link: 
http://www.postholer.com/forum/viewtopic.php?f=2&t=1956 .  Near the 
bottom of the page is a list of the Snow Page reports available to the 
Postholer.com maps.  Look at the Snow Depth URL and you will see 
“&depth=1”  Well we know the =1 is the current date and =YYYYMMDD is 
some historical date.  The “&depth” is the report identifier.  So if you 
wanted the SWE report change “&depth” to “&SWE”. Or the 24 Hour Snow 
Melt would be “&meltday”, and so on.  The point is you can get 
historical overlays back into 2005.

Next, if you’re a journalist on the postholer site these overlay, “Map 
Skins” are available on your personal maps including last SPOT Location 
which auto-zooms the map to a zoom level 10.

Finally, and as a test, I promised a real life example.  I began a hike 
on June 25, 2010 SOBO from Manning Park.  We arrived at Harts Pass on 
the 30th. Using the SNOTEL historical data look at the reported snow 
depth for that date range.  The use the following url to compare 
information;

 
http://www.postholer.com/gmap/gmap.php?trail_id=1&lat=48.7217&lon=-120.669&zoom=10&depth=20100625

What’s your conclusion?

Thumper