Tahoe Daily Snow

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By Bryan Allegretto, Forecaster Posted 6 years ago March 26, 2018

Thank You March...

Summary

Sunny and cold today with highs in the 30's on the mountains and light winds. We warm into the 40's on Tuesday and 50's for Wednesday and Thursday. By Friday we may hit 60 at lake level. Next weekend we may start to cool down a few degrees as the high pressure ridge shifts away. The weekend of the 2nd we may continue to cool. Still watching the 5th-11th to see if we could see some more storms.

Short Term Forecast

The snow showers did fire up yesterday afternoon, especially down along the crest, but only scattered showers with no more than a dusting of snow.  I got on Sugar Bowl and can say that the powdery snow off trail was definitely closer to a foot than the 5 inches reported.  It was a beautiful day of skiing.

sb

So we will stick with the final storm totals from yesterday of 1.5-4 feet for the storm on the upper mountains.  Here are the March and season totals...

reports

Here are the summary stats including a comparison for total water pulled of today's 8 Station Northern Sierra Index.

stats

For this storm with the warm half and high snow levels I mentioned a few days ago I was adjusting the forecast on the resort pages based on where the mountains measure.  On the summary table I use here on the blog all the mountains are wrapped into 4 regions and all at 8k.  That doesn't work on warm storms only cold ones.  So on the individual resort pages with this storm I was using the 7k forecast for resorts that measure below 8k and and the 8k forecast for resorts that measure above 8k.  Mt. Rose I was using 9k,

I added in the measuring elevation on the reports chart up top for the resorts that measure above 8k so you could see how that correlates to their higher snowfall reports.  For the keep me honest report for this storm we are comparing the original forecast from 6 days out for the total storm forecast.  I put in the 7k forecast for the lower elevation measuring resorts like I was doing on the individual resort forecasts this week.  It seemed to work out pretty well on a storm like this with 7000-7500' accumulating snow level.  I'll remember that for next season.

kmh

Mountain Reports vs Actual Experience:

During the cold storms earlier in the month there were no complaints about the snow reports from the resorts as everyone was drowning in the snow.  Whenever we have a warm storm we do get a few grumbles, but on here I always do my best to talk through the snow levels and explain the rain at the bases and big increases in snowfall as you go higher.  For this storm we had 0-3 inches at lake level, up to a foot at 6500', up to 1.5' at 7000', up to 2' at 7500', up to 3' at 8k, and up to 4' at 8500'. 

So you can see how you can go up a foot just 500' higher as you go up in these warm AR events due to temps and snow ratios.  So it's important to pay attention to the forecast for snow levels and know the elevations on the mountain you ride.  For next season I will add in the measuring elevation for each ski resort on the reports table.  

Some people came up this week expecting to see 15 feet of snow towering over their head from the snow this month, but there is a big difference between snowfall and snow depth.  The NWS reporting guidelines require measuring in a wind protected area and taking several measurements around your measuring area to get an average.  They allow measuring up to 4 times a day, once every 6 hours and then you can clear the measuring each time.  Then you add up your measurements for the 24 hour total.  If the storm ends you can go out and take a final measurement and then clear the board. 

Most of the ski resorts are using this technique of measuring off the snow board in a wind protected area, but only 2 times a day and clearing the board and adding the two together.  What this does is it gets the snowfall amounts recorded before any settling or compacting of the snow.  Each ski resort measures at different elevations which can affect the numbers, on top of the fact they are in different areas getting different amounts.  Their method is the correct method and they could actually be measuring 4 times a day which would increase their totals.

However, when you get to the mountain you are not skiing or seeing the the total amounts reported most of the time.  That is due to many factors.  One is wind because the mountain is not wind protected like the measuring area so the wind can blow off the snow in spots and deposit more in others. 

The main difference is settling and compacting.  As more snow falls on top of snow already on the ground the weight compacts the snow below it.  As the snow sits it also shifts and settles.  When the sun comes out and temps rise that accelerates this process as the top layer gets heavier and some snow is melting.  If the snow falls on top of bare ground that was warm before the storm there is also melting from below.

With the storms we had earlier in the month the snow was very dry a powdery with lots of air in it.  So the process was accelerated as that snow had a lot of settling to do and was weighed down much faster, especially when it warmed up last week before the latest storm.  So the several feet compacts down to a couple feet.  This is not counting the areas touched and skied on which is obviously flattened.  Then with a warm storm with heavy wet snow and rain obviously there is a ton of compacting and melting in the rain.  

This is why when you arrive  you see a few feet of snow where several feet fell.  But instead of being able to jump in up to chest like when it was falling, you can walk on top of it now that all those feet of snow have settled and compacted down described as the snow depth, snow base, or snow pack. 

I'm not saying no resort using marketing inches, but I wanted to explain the way snowfall is measured and reported versus what you may experience, and how the elevation measured at can make a big difference in the reported totals.

Back to the Forecast:

 Sunny through the weekend with highs in the 30's today but warming into the 50's by Wednesday through the weekend.  We could hit 60 at lake level by Friday.  We may cool a little over the weekend as the ridge near the coast shifts towards the Aleutian Islands and trough drops into the West.

Extended Forecast

Next week it still looks like we will see a trough in the West and maybe an active storm track returning to the Pacific NW.  That should drop storms down into the Rockies through the week. 

The pattern looks to become more active off the Pacific into the Pacific NW the 5th - 11th.  The question is how far South will the storms track.  The European model keeps the storm track to our North, while the GFS drops it further South over us.  So we will watch closely.

With the trough trying to push South into the West through the period we should at least see some cooler air keeping us from seeing really warm Spring temperatures.

trough

Stay tuned...BA

About Our Forecaster

Bryan Allegretto

Forecaster

Bryan Allegretto has been writing insightful posts about snow storms for over the last 15 years and is known as Tahoe's go-to snow forecaster. BA grew up in south Jersey, surfing, snowboarding, and chasing down the storms creating the epic conditions for both.

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