NOHRSC Help Page

• The NOHRSC National Snow Analyses (NSA) provide daily comprehensive snow information for the coterminous United States. The NSA are based on modeled snow pack characteristics that are updated each day using all operationally available ground, airborne, and satellite observations of snow water equivalent, snow depth, and snow cover. The NOHRSC snow model is a multi-layer, physically based snow model operated at 1 km² spatial resolution and hourly temporal resolution for the nation. Snow data used to update the model include observations from the NOHRSC's Airborne Snow Survey Program, NWS and FAA field offices, NWS Cooperative Observers, the NRCS SNOTEL and snow course networks, the California Department of Water Resources snow pillow networks, and snow cover observations from NOAA's GOES and AVHRR satellites.

• NSA product formats include daily regional maps and text summaries, and a suite of interactive map, text, and time series products. The NSA include information about snow water equivalent, snow depth, snow temperature, snow melt, snow pack sublimation, sublimation from blowing snow, snow surface energy exchanges, precipitation, and weather.

• The national snow water equivalent map is a product from the NOHRSC Snow Model (NSM) at 0600 UTC (midnight Central Standard Time).
• The change in snow water equivalent map is a product fom the NSM created at 0600 UTC (midnight CST) by computing the change of snow water equivalent from the previous 24-hour period.
• The snow depth product derived from the NSM at 0600 UTC (midnight CST).
• The hourly snowpack temperatures for the latest 24-hour period ending at 0600 UTC (midnight CST) are averaged for the national and regional snowpack temperatures.
• The national snow precipitation is an input into the NSM. This map shows the total precipitation that occurred as snowfall over the 24-hour period ending at 0600 UTC (midnight CST).
• Non-snow precipitation is an input into the NSM. This map shows the total precipitation that occurred as snowfall over the 24-hour period ending at 0600 UTC (midnight CST).
• The national snow melt is simulated by the NSM showing the total snow melt over the 24-hour period ending at 0600 UTC (midnight CST).
• The national surface sublimation and blowing snow sublimation is simulated by the NSM showng the total total sublimation or condensation from the top of the snowpack over the 24-hour period ending at 0600 UTC (midnight CST).

• A satellite snow cover product is produced for Alaska and can be seen on the interactive website by choosing the physical element "Snow Cover (Alaska)" under the Daily Satellite Obs. subheading.
• Click the Alaska Extents button to reposition the map on Alaska.
• The NOHRSC also occasionally flies airborne gamma snow surveys over Alaska, and generates maps and airborne gammma SHEF messages from those results. More information can be found on the Airborne Snow Survey page.
  

• A SHEF message follows the standard format used by NWS to distribute forecasted and point data for use in hydrologic operations. This is called the Standard Hydrometeorological Exchange Format (SHEF).
• The NOHRSC produces 2 SHEF products for the 13 River Forecast Centers across the United States daily.
• These products are snow water equivalent derived by the the NSM and snow cover by RFC.
• A SHEF message is also created by NOHRSC when a airborne snow survey is conducted. For more information about the airborne SHEF message please see key to airborne SHEF messages.

• These products are now located on the interactive website as a choice under the physical elements pull down menu.

• The automated model discussions are created daily by averaging the modeled snowdepth and snow water equivalent over a region.

• Since these images are animated with javascript and not just an animated GIF or a movie, the easiest way is probably to use the <IFRAME> tag. This creates an inline frame on a web page, into which the pop-up window that contained the animation can be placed. Something like:

  <iframe src="https://www.nohrsc.noaa.gov/nsa/js_animate.html?year=2009&month=12&day=29&type=nsm_depth&region=National" width="430" height="350" scrolling="off" frameborder="0">
  This browser does not support inline frames.
  </iframe>

  Use the URL of window containing the NSA animation in the "src" field.

• The maps use a geographic latitude-longitude "projection". The horizontal datum used is WGS 84.

• A user's guide gives the background and detailed information for the airborne snow survey program.

• The flight line map has migrated over to the interactive website.
  This page has the ability to display the flight lines with numerous overlays including states, rivers, lakes, basins, and cities.

• A key to the airbrone gamma SHEF message is located on the airborne snow survey page.

• A key to the airbrone gamma SHEF message comments is located on the Airborne Snow Survey page.

• The flight line index gives a complete listing of the flight lines along with information such as the basin, the latitude and longitude of the center point of the flight line, and RFC.

• Gridded NOHRSC products are currently being archived at the National Snow and Ice Data Center (NSIDC). Instructions on accessing them can be found here.
• The NOHRSC also has been producing CD-ROMs annually since 1990 that contain a variety of products and data sets. They tend to capture most of the data and products that are posted during each year to the NOHRSC web site. However, due to the sheer amount of output from the National Snow Analyses, this gridded data is not included. CD-ROMs are available for $50 each from:

  Andrea Hrusovsky
  National Operational Hydrologic Remote Sensing Center
  1735 Lake Drive West
  Chanhassen, Minnesota 55317
  

  Telephone: (952)-368-2510
  Facsimile: (952)-361-6634
  Email:

There are several sites that have snowfall information besides ours.

• Your local NWS Forecast Offices has the best snowfall information. In addition to the airport weather observers and co-op sites, they accumulate all the reports from people who phone in depths into their Public Information Statements. After a big storm like last week's, they will often make a summary page.
• The National Climate Data Center is the place to go for "official" data, but it may be several days before all the data is posted. They will have a map of snowfall for the previous 3 days:
• In states west of Colorado, the Natural Resources Conservation Service operates a network of automated Snow monitoring stations (SNOTEL). They publish their work here.
• Your local TV station's website might have recent snowfall information. They usually contract with one of the big national firms that specialize in weather graphics. Different stations might subscribe to different services, so check around.

There are three main kinds of weather observers: Co-op stations send daily reports directly to the NWS -- they monitor airports, agricultural stations and such; Amateur observers who subscribe through the CoCoRaHS network (the Community Cooperative Rain, Snow & Hail network); and ordinary folks who pick up a phone and send reports to the NWS during a storm.

• CoCoRaHS has a daily map of their reports. You can zoom in on a particular state.
• The local NWS FO posts the phone-in reports on their Public Information Statement page.
• NOHRSC posts all the snow observations it receives from co-op sites, MADIS, SNOTEL, CoCoRaHS and the other observational weather data networks.

If you are lucky, there is an observer near your region of interest in one of those lists mentioned above. NOHRSC has a Observation Finder button on their front page.

Type in, for example, "SPRINGFIELD, NJ" and see nearby values for Raw Snowfall, Snow Depth and Snow Water Equivalent (SWE).
https://www.nohrsc.noaa.gov/nearest/index.html?city=Springfield,NJ&county=Union

Tim's response:

"I've got a CoCoRaHS rain gauge and snowboard in my back yard. In the winter, I go out at 7am for a measurement. I stab my yardstick straight down into the snowpack to get the Depth.

I measure the depth of any new snow fallen on the snowboard; that is the Raw Snowfall. Then I scrape off the previous day's accumulation, to start fresh for tomorrow.

The snow fallen in the rain gauge gets dumped into a pyrex bowl, to be melted and measured. This is the Raw Precip Observation, the quantity of Liquid Water contained in the previous day's snowfall.

The final measurement is the SWE, the snow water equivalent contained in the snowpack. I thrust the rain gauge straight down into the snowbank, slip a spatula under the opening and lift it to the surface. The contents are dumped into another bowl, to be microwaved and melted. The SWE is the primary statistic we model at NOHRSC.

So, the Raw Snowfall is a measurement of snow fallen since the last reading. It is a rate, rather than an amount. Many are taken daily, but some airports and NWS offices check it in six or twelve hour intervals. Snowstorms don't always fall into neat 7am-7am timeframes. We often have to split a single event into, say, midnight to 7am, sent today, and 7am-10am, reported the next day.

Check other nearby sites in the 'Observations Near' list for overall agreement. Other sources are https://www.cocorahs.org, https://gis.ncdc.noaa.gov/maps/snowfall.map?view=daily, and https://www.srh.noaa.gov/ridge2/snow.

Your local NWS Forecast Office usually issues all the station measurements, as well as one-time reports from police and Skywarn spotters that get radio'd in, along with amounts from the public posted to their NWSFO websites.

On the NOHRSC front page, follow the 'Organization' link at the top to locate the NWSFO that serves your area. Many have summary pages that post reports as they come in and final tallies after the event."