Monday, February 23, 2015

Mountain snow at record lows? Any relief in sight?

Many across the Inland Northwest may be wondering if our mountain snow pack is at near record levels and if there is any relief in sight.  We'll answer those questions in this blog.

First, let's look at precipitation in the mountains.  Given the lack of snow pack in the mountains, the assumption might be we haven't had much moisture.  As the image below shows, this is clearly not the case.  All of the Pacific Northwest mountains have received their normal precipitation since the start of what we call the Water Year (October 1st).

So, how does our snow pack look - not good!

Clearly, a good portion of what has fallen in the mountains has been in the form of rain.  This is especially true across the central and southern Washington Cascades, and Oregon.  Much of this rain fell early in the season (October and November) before a snow pack had been established.  There have been more mountain-rain events during the winter as well. 

So, now let's answer the question, is this a record for low snow pack?  Let's break it down by region, starting with Northeast Washington and North Idaho.  Each dot is a SNOTEL site showing where we are at this year compared to normal.  

More simply put...

red = awful snow pack
orange = not good
yellow = a little low on snow
green = doing well

As you can see, the snow pack is not good, and downright awful in spots.  Now, to see if this is a record we need to look at individual sites.  Let's look at Mount Spokane (Quartz Peak) and Lookout Pass.

Blue Line = highest recorded snow pack
Green Line = where we should be
Black Line = this season's trace (2014-2015)
Red Line = lowest recorded snow pack

So looking at the black line (this year's trace), both sites are close to a record low, but not quite there.  It's important to note that SNOTEL data started in the late 1970s and early 1980s.  Thus, the traces for "lowest" and "highest" snow pack ever only go back about 35 years at most.

How about Southeast Washington, it looks very bad.  See for yourself...

Let's look in the Blue Mountains at Touchet...

Also well below normal, just above the record low value.

And finally, the Cascades, how do they look?  The West Slopes are in bad shape.  Mission Ridge area also in bad shape.  Further north however, the mountains surrounding the Methow Valley are doing much better.

Let's see the traces from Stevens and Harts Pass

Stevens Pass isn't looking good, but is above record low value.  Harts Pass in the North Cascades is actually running right where they should be for this time of year.

So, while the snow pack is low this year, most areas are not at record levels.  You may be asking yourself "what's the problem?" since the mountains have received their normal precipitation, just in the form of rain instead of snow.  The mountain snow pack acts like summer precipitation in the western US.  By that we mean, in the West, we don't get a lot of rain in the summer.  But the mountain snow pack acts like rain in the mountains, and keeps our rivers running through the dry summer/fall months.  With a low snow pack, it will likely melt earlier than normal.  This will likely result in low stream flows in the late summer and fall months.  Whether this has an impact (e.g. irrigation, fish, etc) remains to be seen.

The Northwest snow pack typically peaks around April 1st, so we still have about a month to at least ease the bleeding.  Looking ahead, are changes in store?  Yes, but not in a big way.  Here's the GFS precipitation forecast for Thursday night and Friday.

GFS 24-hour Precipitation forecast ending Friday morning

The light green shading represents 0.01" to 0.10" of liquid, which isn't much.  The low pressure system (red L near Portland) is actually moving from north-to-south, meaning that most of the precipitation will stay west of our area.  For the mountains, all of this will fall in the form of snow.  In the lower elevations, the precipitation could be in the form of rain or snow.  But as is typical with spring weather here, snow that falls during the afternoon/evening hours probably won't accumulate.

Looking farther into the future, we get another chance of some light precipitation early next week.  Here's the same GFS forecast for next Monday and Monday night.

GFS forecast of 24 hour precipitation ending Tuesday morning, March 3rd

Again, not a strong storm by any means.  Other models (Canadian, ECMWF) are even less excited about this system.  So there's nothing coming in the next week that will bring much mountain snow.

How about farther into the future?  The 6-10 day outlook isn't encouraging.  Here's the expected temperature pattern:

Just about the entire lower-48 states will be below normal next week.  So that's encouraging.  But here's the precipitation outlook:

The dry weather continues for the western US.  That doesn't mean we won't see any more snow.  The GFS does show some other potential for snow into March.  But suffice to say, the weather pattern doesn't look cold and wet.

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