By Steve Benson
We've all been there. The forecast calls for an overnight dump but the storm somehow jukes, leaving clear skies, cold winds and broken hearts. If you're like me, obsessed with sliding on snow, you've been disappointed by the snow Gods too. And there's not much you can do about it. Or is there?
The National Weather Service1 does a great job of forecasting, but there are limits to their reach. They can't take the time to pin-point what a storm is going to do in each individual drainage or isolated area. But you can. Which is why I try to cut out the middle man--the weather man. That way, when that forecasted blizzard doesn't materialize, it is--as the song goes--nobody's fault but mine.
After all, orographics, a primary factor in mountain weather, "vary tremendously from one valley to the next, and one drainage to the next," says Chris Lundy, director of the Sawtooth National Forest Avalanche Center2 in Ketchum, Idaho. So if you want to predict what's going to happen on a micro-level, it requires thinking on your own, and familiarity with the local lore.
The first step is grasping the direction, historically speaking, that the fattest storms ride in from. A forecasted dump is great, but it doesn't mean much if it approaches from a poor direction. A storm can easily be tracked with radar, satellite and water-vapor imagery, which is streamed live on a variety of weather-related web sites, like Intellicast.3
"You kind of learn that with the unfavorable directions, [the NWS] tends to overestimate what we're going to get," Lundy said. "And other times they tend to underestimate what we're going to get. A lot of it just kind of lives in the mountain town lore."
Mountain snowfall, Lundy said, is largely affected by terrain, and more importantly, what type of terrain exists between the approaching storm and your home hill. The flow, or the upper level winds associated with a storm, plays a big role in winter weather pageantry.
Orographic lift refers to the lifting of air over terrain features, such as mountains. As air lifts to rise over those features, it cools and condenses, often creating precipitation. But as those mountains suck out moisture, they are essentially stealing snow from other locales in the storm's path. And that's where the dreaded term, shadowing, comes into play.
"Basically the first mountain range that might be exposed, it's gonna suck out a lot of moisture as it gets lifted," Lundy said. "And then the next range might get a little less and so on. Each range is shadowed by the ones in front of it."
One area that has terrible orographics and great shadowing--not a good combination--is Sun Valley, Idaho, my home mountain. Surrounded by a sea of mountains to the west, north and east, Sun Valley has long been known as a donut hole. Its one saving grace is storms that cruise up from the south--basically a sea of desert--can pummel the resort and surrounding mountains.
"The classic storm here comes out of the due south," Lundy said. "And as it cruises up the Wood River Valley, [Sun Valley] is at the end of the gun barrel."
This helps explain why areas like Alta, Snowbird and Solitude, located in the high reaches of the Cottonwood canyons southeast of Salt Lake City, get clobbered with an average of more than 500 inches of snow a year.
The west-facing Wasatch Range erupts dramatically off the salty desert floor, rising in some areas more than 5,000 vertical feet in less than four miles. With a swath of desert, low lying hills and the Great Salt Lake situated to the west and northwest of the Cottonwoods, storms that ride in on northwest flow bury the Wasatch in freakish and legendary dumps. (One storm cycle in Nov. 2001 dropped 108 inches in 100 hours). The Cottonwoods not only have amazing orogrpahics, they benefit tremendously from lake-enhanced snow.
But those are two extremes--dry Sun Valley and the wet Wasatch. Most resorts fall somewhere in between. Typically, Lundy said, coastal regions like the Cascades and Sierra Nevada have more predictable storms. If a storm is forecasted to hit, it's likely going to make contact since it's loaded with Pacific moisture and has little land to cross before bumping into the first major mountain ranges. But the deeper you sink east into the Continental West and the Rocky Mountains, the tougher the forecasting gets.
Take a place like Aspen, Colo., for example. With four resorts within a stones throw of each other, you'd think snowfall from resort to resort would be uniform. But that notion couldn't further from the truth.
Of course elevation plays a big role. But there's a bigger factor.
"When something is driven by orographics," such as Colorado's mountains, Lundy said, "snowfall can be as varied as the mountains they're going over. There are huge variations over short spans of distance."
While shadowed Sun Valley skirts by with a thin snowpack, other regions within Lundy's forecast area get two-to-three times as much snow, like the Galena Summit area and the Sawtooths.
So as a storm approaches, take a look at its path, its flow, and what type of terrain it has to cross before it hits your home hill. If it needs to cross numerous mountain ranges, temper your excitement a bit. If it looks like shadowing won't be an issue, and the storms path includes desert and natural funnels, get the fat boys ready.
Perhaps the most revered, yet cursed, forecast is the winter storm warning. Illuminating and exciting, a winter storm warning can turn moody and dark. These advisories from the Weather Service occur frequently throughout the season in most of the mountain West. While typically celebrated--no news spreads faster in a gossipy ski town--they're also over-hyped. Not necessarily by the Weather Service, but by our snow sliding brethren. As a result, they seem to me to be a curse, and are taken with a thick grain of salt. I do not trust them anymore. I should have learned my lesson as a kid, when a gigantic Nor’Easter was pegged to wallop New England with record snow. Following a dramatic winter storm warning, school was cancelled before a single flake fell from the sky. And in the end, a single flake never did fall. The ground remained brown. While I didn’t have to go to school, I also didn’t have mountains of snow to play in. But I did not learn.
Am I a pessimist, or a realist? It doesn't really matter. All I know is a winter storm warning is not to be trusted. The Weather Service is responsible for warning, and therefore protecting, the general public from potentially life-threatening weather events. That means that occasionally a storm system may draw more attention than it warrants simply because it has the capability to become severe. Obviously, most winter storm warnings are necessary and deliver as advertised. But many are issued 12 hours before a storm's arrival, which gives it plenty of time to slip away. They can also be fairly broad-brushed and often include a large forecast area. I've seen just as many winter storm warnings leave a meager inch as unadvertised storms blossom from seemingly nowhere and drop a phantom foot.
When you see these warnings, calm down, regroup, and take a closer look. I’ll often turn to the Weather Service’s daily forecast discussion page, which is basically meteorologists communicating with each other about what's going on with the local weather. When storms approach, the discussion can be very enlightening to the weather novice, which is basically all of us non-meteorologists. While they can be technical and often over my head, they can also shed light on key factors in a given storm. Specifically, the discussions can highlight areas meteorologists think may be favored by more intense precipitation, and which ones may receive the shadow effect, or simply less snow. Or, they may even hint at a weakening system and a potential downgrade from a winter storm warning to a mere winter weather advisory, which is not a good thing. When that happens, the party ends before it even starts. Leave your hopes and dreams at the bar.
Still, while short-term forecasts will help you get a better understanding of how storms materialize, long-range forecasts shouldn't be overlooked.
Giant, stubborn high pressures can turn a powder haven into more of a beach environment with sunny skies, warm temperatures and bikini tops. But there's a silver lining (besides the female fashion): for high pressures to budge, it usually requires a whopper of a low-pressure system. After Sun Valley winced through a brutal six-week high pressure last February and March, the mountain was deluged with nearly five feet of powder in one week. Similarly, that 108-inch storm that buried Alta in late Nov. 2001, was preceded by one of the driest and warmest Novembers on record. Local lodges held meetings urging employees to spend Thanksgiving elsewhere, as there was no snow, guests, nor paychecks--and an ever-decreasing food supply. More so, local managers began whispering that when the high finally moved out, a mega storm cycle would likely follow. Turns out they were right. The Climate Prediction Center4 is a gem, offering a host of long-range forecasts.
"For people living in mountain towns, often just knowing those things they can one-up the weather forecasters who take such a broad brushed forecast," Lundy said.
1 There are a host of good weather-related web sites out there. But the most reliable is the National Weather Service, which has offices scattered all over the Intermountain West. NWS.gov is a good starting point, and you can easily navigate to your local region. NWS also offers great streaming satellite and radar imagery pages.
2 Local Avalanche Centers are treasures. Not only do they offer comprehensive daily advisories on snowpack and mountain weather, they are phenomenal educational resources. Reading the advisories on a daily basis will open you up to whole new winter world and keep you on par with the constant changes occurring in the mountains. Local avalanche centers are dotted throughout the West. Find yours here: Avalanche.org for the U.S., and Avalanche.ca for Canada.
3 Intellicast.com is full of helpful weather-related products, especially their national and local radar and satellite imagery.
4 The Climate Prediction Center, which is a part of the National Weather Service and NOAA (National Oceanic and Atmospheric Association), releases daily long-term precipitation and temperature trends ranging from 6-10 days, 8-14 days, 1 month, and 3 months. These are great when looking at the big picture, such as stubborn high pressures, or large troughs of low pressure. These are trends, not short-term forecasts. They're best used for trying to determine what the trends will be in the coming weeks and months--and at the start of a road trip, which direction to turn the steering wheel.