Northwest Daily Snow

What is SWE?

Summary

-All NW ski areas are closed for the season -- no uphill travel, no avalanche control. Respect ski area closures. -NW Avalanche Center: As of March 24th, NWAC has suspended backcountry avalanche forecasting until further notice. Check the website for details. (www.nwac.us). - “Stay at home ” order in effect – no backcountry, no AT skiing, no looking around, no snowshoeing, no x-country skiing, etc. Besides social distancing protocols, the main issue is; if there is a problem (like a rescue or assistance), valuable medical and SAR resources cannot be easily reallocated. They are needed for the Covid-19 fight. Please respect our medical and emergency workers – they are giving their all for you – as they always do. Thanks! Please stay healthy and follow official health guidelines.

Short Term Forecast

Weather:

Expect 3-6” of Cascade snow with a snow level of 4,000 feet on Sunday, as a weak system brushes us. There will be more snowfall (5-10”) with a lower snow level (2,000ft) on Monday and Tuesday. By Wednesday and Thursday expect a break, then additional snow in the Cascades for Friday. As the days get longer, there will be hints of spring in the lowlands, but not so much in the Cascades.

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Importance of SWE

I have done dozens of field SWE snow survey measurements via helicopter in the Cascades, flying to remote areas. You may recall, I worked as a meteorologist in flood control and water management for the US Army Corps of Engineers for years. That job was after I did 25 years of on-air TV weather for KING-TV (and others) in Seattle, WA and Monterey, CA. The fieldwork was so fun, being out in the mountains buzzing around in the helicopter to unbelievable sites. Always interesting to see and measure the layers of snow using an aluminum tube shoved into the snow to sample and weigh (for water content) a core of the snowpack. You see the different layers of the entire season in the core. Looking at the bigger picture you’d  see how snow drifted in spots and scoured in other areas. Some snow is dense and icy, some fluffy. You try and find an “average” spot to go back to every time for consistency.  I am in the red jacket.

SWE is snow water equivalent. A field snow specialist or a permanent field station called a SnoTel measures SWE measures the SWE in the snow. SWE is the amount of water (inches) in the depth of the snowpack at a particular place. The percent SWE is a good proxy to estimate the overall snowpack depth, density and water content.

 

For skiers, SWE gives us an objective idea of how the snowpack and snowfall season has unfolded and what is the current depth. The map above shows the current SWE in % of normal. You’ll notice WA and North ID are at or slightly above normal, which was the ENSO neutral forecast for the NW last fall – so this NW forecast verified in the end. But it was a slow start. Oregon is lower, but not a concern.  Typically the snowpack starts to melt in early April at lower elevations working it’s way up into the higher elevations.

Water managers can tell how much snowmelt runoff to expected in the spring by using SWE. And in the spring, while the melt is in progress, how much snow to melt is left in the mountains. It’s like a bank account, saved for summer water supply.

Typically snow falls at a 1-10 ratio – 1” of liquid precipitation equals 10” of snow (10%) but can vary.  Snow sitting for a few days or week degrades and settles to 20%-25%. After a few weeks will be 25-35%.  In spring as it warms the density shoots to 35-45%. By the time it gets to in the 40% range and above the snow starts to melt. I have never seen snowpack density over 50% and not be melting (except ice which is 95%). Remember 50% SWE is 1” liquid equal 2” of snow – that is wet snow! When groomers groom wet snow, they call it “squeegee the snowpack “

The graph below shows the Steven Pass Snotel well above normal but not in record range. Note: the slow start (black line), then a big steep climb (abundant snowfall) from late Dec to early March. Ave is green line.

Extended Forecast

I did TV on-air weather in Seattle for 20 years and Monterey, CA for 5 years. Also, I was on the "Bill Nye the Science Guy" show (episode on Wind) see below - you probably saw me in your science class.

One of the perks of doing TV is you get invited to do some really fun stuff...

This one is tough to beat: flying with the Blue Angels! The pilot even let me fly the jet through a barrel roll at 350 mph over the Big Sur coast. That's me in the back seat.

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