The Rocky Mountains Have A Dust Problem ~ ‘especially the SW mountains of Colorado’ NPR

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Jeff Derry, director of the Colorado-based Center for Snow and Avalanche Studies, digs a snow pit at the Swamp Angel monitoring site in the San Juan Mountains.

Luke Runyon/KUNC

 

A menace lurks beneath the snow high up in the southern Rocky Mountains: Dust. Lots and lots of dust.

This dust speeds up spring water runoff, causing intense melting and streams to peak weeks earlier than usual — which wrecks havoc throughout the alpine ecosystem. Water managers and fire forecasters alike are sounding the alarm about the consequences of less water flowing in streams and reservoirs.

At first glance the dust seems innocuous. How could something so simple undermine water infrastructure, stress wildlife and lengthen the wildfire season all at once?

For most of the winter, dust stays buried under blankets of snow. Then, as the days grow longer and the sun’s rays begin to melt the top layers, it begins to show. To see the dust before this happens, you need to dig a snow pit.

In the spring, Jeff Derry can often be found waist-deep in one of these pits, somewhere in the southern Rocky Mountains. Derry, the director of the Center for Snow and Avalanche Studies in Silverton, Colo., pays close attention to the amount of dust that winds up embedded in snow.

“I’ll be curious if you’re going to be able to see the dust event we had Feb. 18 and 19,” Derry said one day in April, shoveling snow over the edge of a half-formed pit. “It is very subtle.”

Derry uses a range of instruments to pull details from the pits, each fine-tuned to measure snow qualities such as temperature, density and reflectivity. But the best way to gauge the magnitude of a dust layer is with the human eye, Derry said.

White snow melts slower than snow covered in dust because of its high albedo, or reflectivity. It reflects radiation from the sun rather than absorb it.

Courtesy of the Center For Snow and Avalanche Studies

“It’s very qualitative in a sense,” he said. “You go out, you look for it, you dig, you see what you see.”

In Derry’s current cross-sectioned snowpack, about 7 inches down, is a beige-colored band of dust.

This tiny little strip of dust has the potential to upend how water is managed in the West. Eventually, Derry says, this snow will melt and empty into the Colorado River. Its watershed provides water for some 40 million people in the southwest.

When there’s no dust on the snow, it’s brilliantly white: On a sunny day, this kind of snow can be reflective enough to cause eye damage. Without dirt or dust, the snow melts off slow and steady — like the drumbeat of a drip from a faucet. Dust cases the snow gets darker and absorb more sunlight.

“It melts the snow faster than it would have otherwise,” Derry says. “And then it melts down to the next dust layer, and so on and so forth until all the dust layers have combined at the surface of the snowpack greatly reducing the [reflectivity].”

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A thin, barely visible stripe of dust sits about 7 inches down in snowpack in Colorado’s San Juan mountains.

Luke Runyon/KUNC

 

When these dust layers combine, the sun’s radiation quickens the pace of runoff, making it all that more difficult to capture and divvy up the precious water.

This quickened runoff makes managing water harder and upsets mountain ecosystems, causing earlier green up of vegetation. And when snow melts earlier, wildfires have more opportunity to spark and take hold.

Most of the dust that’s settling in places like the San Juan mountains comes from the desert southwest, from land disturbances like farming, oil and gas drilling, cattle grazing, recreation and residential development on the southern end of the Colorado Plateau.

“It’s kind of a slow crisis, a slow disaster,” said Rich Reynolds, an emeritus researcher with the U.S. Geological Survey in Denver. “It’s not like a hurricane. It’s not like an earthquake or a volcano.”

In the past 50 years, as the Sun Belt boomed, scientists recorded a dramatic rise in the amount of dust being deposited on snow — which forces fundamental changes in how spring runoff occurs. Reynolds says reversing this trend won’t be an easy task.

“There’s no one size fits all in terms of mitigation for these kinds of source areas,” he said. “Plus, these are large, large areas.”

In a 2010 study researcher, scientists found that in heavy dust years, the Colorado River’s flow on average peaked three weeks earlier than in years without heavy dust deposition.

The same study also found that earlier melting snow reduces the amount of water that runs to the Colorado River by about 5 percent. That’s more water lost than the entire state of Nevada uses from the river in a year.

And then there’s climate change.

University of Utah hydrologist McKenzie Skiles recently co-authored a study that examined whether warmer temperatures or dust are greater threats to snowpacks.

“What we found looking at those two in this region, is that it was actually dust that controlled snowmelt timing and magnitude and sort of how fast snow ran out of the mountains, as opposed to temperature,” Skiles said. “We didn’t see any relationship to temperature at all.”

Warming temperatures are more likely to affect and diminish total snow accumulation, causing some snow to come down as rain. But when it comes to runoff, dust is the controlling factor. It’s the sun’s rays that force snow to melt, not outside air temperature.

While science is beginning to paint a clearer picture of how this phenomenon plays out, Skiles says that there’s plenty the field doesn’t know about dust.

“We still have some questions on what controls the actual dynamics of the dust events themselves,” she said. “We see dust in every year, but there’s a high variability between the amount of dust that’s deposited each year.”

Back in the San Juan mountains, Derry says he’s bracing for more dust events this spring. The mountain range has registered five dust events since October. Derry says the San Juans are ground zero for this problem. And because they’re a key part of an already overtaxed Colorado River system, he says everyone in the seven U.S. states and in Mexico that depend on the river should be concerned.

“We’re located at the headwaters of four major watersheds,” Derry says. “And our mountain systems are undergoing change at a fundamental level.”

Change that could make the West an increasingly dry — and dusty — place.

This story is part of a project covering the Colorado River, produced by KUNC and supported through a Walton Family Foundation grant.

San Juan Mts. 24 hr. SWE ~ 4/8/18 @ 12:00

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Under typical  (what is typical anymore?) spring SWE (snow/water/equalivant) this 1.7″ of H20 would translate to 17″ of snow @ 10% density (or whatever, you do the math).  This rain event was nice but it subtracted from the already thin snow pack depth by shrinking/melting our Snow Bank that represents a slower run-off through gradual melting. 

rōbert

 

Why weather forecasters still struggle to get the big storms right ~ The Washington Post

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The Jan. 4 “bomb cyclone,” a particularly strong nor’easter. (CIRA)

 

It was March 2017, and a winter storm named Stella promised to deliver as much as a foot and a half of snow to New York City and parts of New Jersey. Officials pushed out blizzard warnings, suggesting the city was under imminent snowy siege.

But only seven inches fell. Gov. Chris Christie blasted forecasters. “I don’t know how much we should be paying these weather guys,” he said. “I’ve had my fill of the National Weather Service after seven and a half years.”

For anyone following the weather, forecasts for big storms are sometimes still roller-coaster rides — with sudden shifts in track or intensity. As a meteorologist who forecasts for a large urban market, I can attest to the frustration. Why can’t we get it right every time, given this era of 24/7 weather data, dozens of satellites and sophisticated computer models? The answer lies in the quirks between the most popular forecasting models.

Battle of the models

Computer forecast models have become the mainstay of weather prediction across North America and many other parts of the world. Run on fast supercomputers, these sophisticated mathematical models of the atmosphere have gotten better over the past couple of decades.

Human forecast skill has improved by approximately one day per decade. In other words, today’s four-day forecast is as accurate as a three-day forecast was a decade ago.

Forecasters in the United States routinely examine several models, but the two most discussed are the American and the European. When the models disagree on the track of a big storm, forecasters must often choose which they believe is most correct. This decision can make or break a critical forecast.

Most meteorologists agree that the European model is the most skillful. This was cemented in March 1993, when it correctly forecast the track and intensity of a historical nor’easter. Called the “Storm of the Century,” the storm dropped a blanket of heavy snow from the Gulf Coast to the northern tip of Maine.

The storm was a milestone for what is termed medium-range forecasting, or forecasts made three to seven days out. The European model nailed the prediction five days in advance. That meant officials could declare states of emergency before the first flakes ever flew.

CONTINUE

San Juan Mountains Weather Forecast ~ Friday, April 6, 2018 @ 11:20

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The Pineapple Express (strong atmospheric river of very moist subtropical air) is hammering the central California coast this morning and will move inland today favoring the northern and central Colorado mountains through Sunday.

This large storm will begin in earnest late afternoon and continue through tonight with a  lull Saturday morning then will kick in again Saturday night into Sunday bringing very wet sleet/snow/some rain to alpine terrain and rain below in the valleys. Very warm spring temperatures accompony this storm and until a cold front joins the equation late Saturday evening/early Sunday morning the impressive moisture plume will produce mostly rain and sleet except above 12,000′.

The San Juans unfortunately will generally receive less snow because the storm track of these two large disturbances are just north of us although we might get 8-12″ of snow if the firehose express tracks a bit south. This is a very impressive warm/wet storm for this time of year… check out more information about the Pineapple Express.

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Visible Water Vapor – GOES West 12 hr Loop

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GFS – US – 500mb – Loop

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A winter roundup and a look into the spring. Joe Ramey ~ Mountain Weather Masters

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Joe Ramey out for a ski.. a former NWS meteorologist/forecaster and now happily retired but waiting for a weather gig with MWM.
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Welcome to spring! Grand Valley trees are producing buds and flowers, and our tulips have emerged.
It has been an unusual winter. La Nina winters typically have a snowy January and that certainly didn’t happen this last winter. One pattern I have noticed is the second La Nina in a row is often dry and drier than the first La Nina. The last two “second La Nina in a row” were 2011-12 and 1999-00. Both of those seasons were dry overall but with a snowy January. Attached is a spreadsheet showing the winter’s and March’s Colorado precipitation and their comparison to average. It shows that the typical La Nina pattern of a wetter north and drier south did occur. This last winter it seems the storm track was shifted further north. You have to go up into Wyoming’s Wind River Range to find above normal snowpack.
This pattern has continued into March with the south really falling far behind normal. In the first attached image you can see the last 90 days have been warm and dry for the Great Basin, Southwest, and central-southern plains.
The outlook for April and the Apr-May-Jun season shows the La Nina pattern persisting, see attached second image. The storm track remains across the northern tier of states while the SW and south remain warm and dry. A dry spring is typical during La Nina seasons. Fire season has already started in SE Colorado and we are in heightened fire danger as we head into the warm season.
There is some reason for hope. A low snowpack is correlated to an earlier start to the monsoon season. Fingers crossed.
The outlook for next cold season currently shows an equal chance of El Nino and ENSO Neutral. El Ninos typically favor SW Colorado (and AZ-NM) with precipitation, while ENSO Neutral years are wild cards with no favored storm track.
Enjoy the spring!
Joe
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