Sunday, March 4, 2018

Substantial Improvements in Western U.S. Snowpack and Water Resources

Some folks call it a March miracle...while others call it a La Nina winter....but in any case there has been large amount of new snow in the mountains from California's Sierra Nevada to the Oregon Cascades, which has greatly improved the snowpack situation.

First, compare the snowpack of March 4th against January 6th.   Washington is all green (near normal, 90-109%) or better, Oregon has gone from red (<50%) to orange (50-79%), as has much of northern California (click to enlarge). Northeast Washington, northern Idaho, and much of Montana are well above normal. 

Substantial parts of the Sierra Nevada have gotten 6-8 feet of new snow this week.

Reservoirs are in good shape.   Here is Washington, the Yakima River Reservoir system is hugely above normal (see plot), in fact, as full as would be normal on May 1. 
In California, the reservoirs are all at or above normal, except for the damaged Oroville reservoir that is being kept partially filled.

West Coast precipitation is not finished with us, and the next week or so should bring plenty more.  The total precipitation forecast for the next 11 days (shown below) from the NOAA/NWS GFS model indicates plenty of precipitation ahead, with 5-10 inches of liquid water in terrain from the Sierra Nevada to SE British Columbia. 

The pattern that has kept us wet has been persistent troughing over the West Coast, with high-pressure offshore. Here is an map showing the differences of 500 hPa (around 18,000 ft) heights from normal for the last week. Purple and blue over the west coast (a trough or low pressure), but red/orange (high pressure) offshore.

The trough should move westward, resulting in moist, southwesterly from CA to BC ) see forecast map for Monday, March 13 at 5 PM below).  That is why the northern half of the West Coast will be wet.

 The bottom line of all this is that water supplies from central CA to southern BC look good, and we should be in good shape for the upcoming summer.


sunsnow12 said...

Thank you for the update on California but their reservoirs have been at 100% of normal throughout the fall and winter. This recent precip is the ice (not icing) on the cake.

And here… this was a done deal months ago for Washington and you know it Cliff, you posted on it. In fact we were never remotely at risk here based on precip and reservoirs, and again, you have posted on this multiple times.

But I can guarantee you next November and December we will hear the exact same thing: Drought. Happens every year, like clockwork. Might even begin in October. The only miracle would be if we didn’t hear that.

Who believes any of this anymore. And why would anyone trust the USDA information - you have posted on the unreliability of that source (overstating drought) what, 5 times in the last 5 years? You called the drought monitor “ridiculous” (you actually put that in all caps in 2015), and backed it up.

And while we're on the subject, let’s get an update on the Cascade snowpack trend. We are up for the last ten years, aren't we? (the only reason I have that as a question and not a certainty is 2015). Let’s hear from Mark Albright; there is a source we can trust.

Here's some real time independent data: Snoqualmie Pass: Currently at a 10 year high, 143% normal (and closed as I type due to heavy snow); Stevens Pass: 145% of normal; White Pass 152% of normal. Alpental 200+" at the top and growing; Mt. Baker with a 15 foot base. All of these are packed, saturated snowpacks. And the USDA map? 96 - 105% of normal.

Please stop using it as a source. It is, as you might say, ridiculous.

Leslie Burke said...

Thank you for the update! I live in CA and love the discussion on PNW weather and how it relates to ours. Our winters are so weird and dynamic, I really appreciate the shoutout to California during the winter as it is easy to get caught up in the alarmist news headlines. Thank you for your insight and for your scientific analysis of what's going on here on the west coast!!! It is definitely appreciated by those of us down south as well!
LB, Sacramento

Ted Schuldt said...

Thank you for your great reports. I especially liked your blog on problems in addition to Climate Change.
One problem I have is that your wonderful graphics have low resolution. I could not read the wonderful map of California reservoirs.
Ted Schuldt

Eric Blair said...

As per usual, the earth cares not for the predictions of the humanoids.

Tom Butler said...

There seems to be a disconnect here:

andy hall said...

Currently in California. Seasonal water storage: In normal years, about 8-14 million acre-ft of water is stored in the wet season and used in the dry season. This compares to roughly 34 maf/yr of average net agricultural and urban water use. Human water use is highest in California’s dry summer, so crops and landscapes must be watered from stored winter and spring flows. Roughly 5-8 maf is held in surface reservoirs and 3-6 maf is held in groundwater basins.

As in many mountainous areas the true water storage is in the current snowpack. Once the snow is gone the reservoirs replenishment rate is decreased substantially.

A full reservoir in the fall with little snowpack over the winter is like filling your convertible with fuel in the fall expecting the tank to last you the entire next summer.

JWG said...

The distinct delineation between above normal snow to the north, e.g. Montana, and below normal to the south, e.g. Oregon and Washington, could be taken as suggesting a stable pattern, as opposed to a less stable pattern where the jet stream is more chaotic and hence spreads the precipitation over the north and south more evenly.

Does this make sense? and if so, would that be something typical of La Nina, or could it be an indication of less energy in the jet stream due to less thermal difference between the arctic and temperate zones.

The latter could be taken as suggestive of a climate change effect.

sunsnow12 said...

"As in many mountainous areas the true water storage is in the current snowpack. Once the snow is gone the reservoirs replenishment rate is decreased substantially."

Most measured snowpack is at or below 6k feet. And the majority of that - except in the coldest of springs - is gone by the end of June. You are correct, reservoir replenishment is decreased substantially once snowpack is gone, but can you please provide data or a graph supporting the statement "true water storage is in the current snowpack"? Because actually, true water storage is in the reservoirs, and that is what matters in July, August and September.

Here are the SPU graphs that show snowpack gone by June in their watersheds (5,414' peak height):

We just went through this in the PNW in 2015. Close to zero snowpack, but full reservoirs (winter precip was normal). And we had a summer - and actually a drier than normal summer - without any significant effects.
Here is Cliff posting on that:

I want to add here: the main issue now for water management in Washington is flooding. The concern is that we do not get warm, windy rains in the Cascades this spring. Flood control is the #1 concern of water engineers now, as the vast majority of this year's snowpack will be heading down rivers back to the ocean.

Eric Blair said...

"A full reservoir in the fall with little snowpack over the winter is like filling your convertible with fuel in the fall expecting the tank to last you the entire next summer."

So in your estimation, no one should really care about the current state of the reservoirs there, no matter what time of season it is. Good to know.

audioskeptic said...

Yikes. Looking at the snowpack over in Montana, it may be August before they get Glacier National Park open all the way!

But it's good California is getting more rain and snow. Still, it needs to get to over 100% for a few years to start to recover, yes?