Wednesday, May 31, 2017

We'll Always Have Paris

The media is abuzz with reports that Trump is going to withdraw from the Paris Agreement.  This isn't really a surprise since he's consistently said he would do so and every action he's taken as President is consistent with doubling down on fossil fuels.

In contrast, the Paris Agreement seeks to "[hold] the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change."

Let's ponder those numbers, although there are a few challenges to doing so.  Incredibly, preindustrial isn't defined in the Paris Agreement (a major oversight), so we need to think about it for a bit.  Scientifically, we wouldn't want to pick a single year because in any one year, natural climate variability, volcanic eruptions, and other factors might make that year anomalous.  For example, 1884, the year after the eruption of Krakatoa, would be a terrible year to chose as it was anomalously cold.  Thus, we need to pick a period, preferably at least 30 years if not longer, not characterized by anomalous warmth or cold.

However, there is another challenges.  As one goes back farther in time, instrumented records are less numerous, decreasing the reliability of global temperature estimates.

A forthcoming article in the Bulletin of the American Meteorological Society by Hawkins et al. (available here as an early online release but paywalled without subscription) concludes that 1720–1800 is perhaps the best period in terms of it predating measurable human influences on global temperatures.  They then use a variety of approaches to estimate the warming since the pre-industrial period and show that 2015 was likely the first year in which the globally averaged temperature was more than 1ºC warmer than preindustrial temperatures.  Their analysis did not include 2016, but it also exceeded the 1ºC threshold.

There are considerable ups and downs, however, in global temperatures from year-to-year.  These ups and downs are generally in the range of 0.1–0.2ºC.
Source: Hawkins et al. (2017)
Therefore, the fact that 2015 and 2016 were so warm doesn't mean we've necessarily eclipsed the 1ºC mark for good.  We might lose a little ground for a couple of years.  Nevertheless, we are probably in a period in which we are approaching a long-term globally averaged temperature that is close to 1ºC above preindustrial.

That puts us close to half way to 2ºC, with some warming still in the pipeline since the Earth is still responding to the rapid increase in greenhouse gases over the past few decades.  But why 2ºC?

The 2.0ºC limit stems from the recommendations of a 1980s World Meteorological Organization (WMO) group that considered 2ºC to be "an upper limit beyond which the risks of grave damage to ecosystems, and of non-linear responses, are expected to increase rapidly." Others have argued for a lower limit.  I don't know any scientists arguing for higher, but you can probably find a few.

The reality is that there is no magic tipping point at which global temperatures become "dangerous." Different regions, economic sectors, and ecosystems have differing sensitivities to the rate and magnitude of the temperature increase and we aren't able to understand and identify these precisely.   1.99ºC isn't good and 2.01ºC isn't bad.  Some responses to climate change are appearing already (heat waves) and will worsen further.  Others have yet to emerge.  Some are beneficial.  However, our society is built around the climate of the 20th century, not the 21st, and as the planet warms, most impacts of climate change will be problematic and not increase linearly, but nonlinearly with temperature.  Given that we are currently near a 1ºC increase, I view 1.5ºC as a "stretch goal" and 2.0ºC a realistic scenario for what we could achieve in terms of reducing greenhouse gas emissions and managing the risk posed by climate change.

Ultimately, my views on the Paris Agreement are informed by science, but also influenced by my personal values.  I'd like to see the US be a leader in efforts to tackle global warming, and I think the Paris Agreement contributes to such leadership efforts.  However, tangible and substantial steps to decarbonize energy production are also essential.  The good news is that US energy-related carbon emissions have declined in recent years due to many factors, including a migration from coal and oil to natural gas and renewables for energy production.  States like California will likely continue to pursue policies and actions that reduce carbon emissions, as will many cities.  However, the policies of the Trump Administration run counter to these efforts and managing the risk posed by climate change.  Withdrawing from the Paris Agreement would be another step in the wrong direction.

Tuesday, May 30, 2017

Flirting with Misery Tomorrow

Last weekend was simply splendid across northern Utah with mostly sunny skies, high temperatures in the 70s and 80s in the Salt Lake Valley, and a nice breeze.

However, we will take a run at 90 today at the Salt Lake City International Airport, with temperatures climbing a bit further and peaking even higher tomorrow.  The NAM forecast valid 6 PM MDT tomorrow shows a warm, southerly flow in advance of an approaching trough with 700-mb temperatures right around 12ºC.

I've long considered a 700-mb temperature of 12ºC to be the lower threshold of summer misery.  Below that and afternoon temperatures in the Salt Lake Valley are tolerable.  Above it lies misery, that increases exponentially as temperatures increase further.

Climatology shows this fairly well.  700-mb temperatures average around or above 12ºC at the Salt Lake City airport from early July through mid August.  You know.  The dog days of summer.
Source: SPC
The good news is that temperatures look to drop some by Thursday as the trough moves through and ushers in some slightly cooler air.  We have reached the time of year where every trough, no matter how weak, is greatly appreciated.

Sunday, May 28, 2017

Memorial Day Reflections

In many ways, Memorial Day Weekend is one of the prettiest times of year in the Salt Lake Valley.  The mountains are still snow covered and the valley and foothills are green.  I never feel bad staying home for the holiday weekend and avoiding the traffic and the crowds elsewhere.

I got up early yesterday and climbed Mt. Wire.  It's a good early season hike for getting the legs in shape for bigger adventures and it offers a wonderful view for a meteorologist who likes to think about what happens when westerly or northwesterly flow strikes the Wasatch Front.

Mountain biking on the Ensign ridge this morning offered up a perspective on Farmington Bay, which finally has some water in it again!

If you've been up in the foothills, you've probably noticed that a lot of the scrub oak leaves are damaged.  I think this happened during the snowstorm a couple of weeks ago.  Such a shame.  I wonder if they will push out another set of leaves in the next couple of weeks.  Perhaps those in the know can comment.

Enjoying these wonderful views and the quality of life that we have in the Salt Lake Valley is only possible because of those who have paid the ultimate sacrifice.  Take some time this Memorial Day weekend to reflect on that, and given that this is a weather blog, you might check out this Reader's Digest article on Special Ops Weather Technicians.

Friday, May 26, 2017

Memorial Day Forecast

I was going to issue a Memorial Day Forecast this morning, but then I noticed none of the products on have updated since yesterday.  Good think this isn't ski season!

Thus, I'll just pass along the NWS graphic, which oddly is missing the NOAA/NWS logo.

Source: NWS
Other than some showers and thunderstorms today, and perhaps an isolated shower or thunderstorm in eastern Utah tomorrow, the weekend is looking quite pleasant.  Enjoy!

Wednesday, May 24, 2017

President's Budget a Disaster for Science and Education

Paraphrasing Mark Twain, money is for spending and budgets are for fighting over.

Most Americans would probably agree that federal spending needs to be reduced.  However, the President's Budget released yesterday takes a draconian axe to many science and education programs that are critical investments for the Nation.  The Scientific American summarizes the some of the cuts affecting science and education here.  I will discuss specifically cuts proposed to science agencies and programs that I believe will greatly slow progress in weather and climate prediction.

My science career now spans nearly 30 years and for that entire time I have received support from the National Science Foundation (NSF).  I consider NSF to be the gold standard of science funding agencies.  They support research projects initiated by scientists and are probably the most "organic" funding agency for science and engineering research.

The Trump Budget reduces NSF funding from $7.5 billion to $6.7 billion, which would fund 800 fewer research proposals.  The largest cuts would be in Social and Behavioral Sciences (10.4%), Computer Sciences (10.3%), and Geosciences (10.1%).  The research in those areas is very broad in scope and impact, but amongst the benefits are advances that ultimately improve the protection of life and property from natural hazards from winter storms to tsunamis.

In the NASA budget, five Earth-observing missions are eliminated, the Orbiting Carbon Observatory-3 (OCO-3), DSCOVR (space weather monitoring), CLARREO Pathfinder (critical for evaluating climate models and feedbacks), PACE, (ocean, cloud, and aerosol monitoring), and the Radiation Budget Instrument (measures reflected sunlight).  These missions will help improve understanding and modeling of the Earth's radiation budget.  The NASA Office of Education is also eliminated.

Perhaps the most nonsensical cut is a reduction of $5 million to delay the development of the Next Generation Global Prediction System (NGGPS) and other related weather prediction projects.

These weather prediction projects have bipartisan support in Congress because they are a good investment for national security and resiliency to high-impact weather.  The NGGPS involves the development of a new global weather prediction system designed to accelerate forecasts of critical weather in the United States.  Such a system would also greatly benefit the private sector, which relies heavily on computer models for all sorts of applications in the transportation, energy, agricultural, and other economic sectors.

In summary, the President's budget is a disaster for science and education, the Nation's intellectual capital, and technological innovation.  It is a pathway back to the dark ages, not the future.

Disclosure: The author currently receives research funding from the National Science Foundation, NASA, National Oceanic and Atmospheric Administration, and Office of Naval Research.

Monday, May 22, 2017

The Uinta Snowpack Is Still Quite Fat

With Memorial Day weekend approaching, I've been thinking of heading to higher country for some turns.

The Uinta snowpack remains quite fat.  The numbers from the Trial Lake Snotel, very near the Mirror Lake Highway, show an early May peak in snowpack snow water equivalent just under 50 inches, roughly double the median peak.  Despite some losses in the middle of the month, they currently sit over 30 inches, again roughly double median.

Source: CBRFC
The question is, will the Mirror Lake Highway be open?  According to an article published in the Deseret News over the weekend, UDOT is giving it a 50/50 chance.

If the road does open, you're going to find an impressive snowpack by Uinta standards.  If not too snirty, there's going to be a good corn harvest up there over the next couple of weeks.

Sunday, May 21, 2017

Review: Mountain Collective Pass

Living at the base of the Wasatch Range, I don't travel very much for skiing.  Skiing is costly, and my academic calendar means the only time I can get a full week off is either prior to Christmas when the snowpack is meager, during the holidays when everything is expensive or crowded, or during spring break, which can sometimes be quite warm.

This past season, however, I got the big crow bar out and cracked open the wallet to purchase Mountain Collective passes for my son and I.  Given my advanced age, I also bought the optional insurance, raising the price to $449 each.  After a season of skiing (with some potential we will still travel to a couple more resorts), here are my perspectives.


I have no prior experience with multi-resort passes.  I suppose I could have sprung for an Epic Pass or a M.A.X. Pass, but the mountain collective includes many iconic resorts, several of which have great snow and terrain.

For someone based in Salt Lake, there were 5 resorts last season within a 7 hour drive including Alta/Snowbird, Jackson Hole, Sun Valley, Telluride, and the Aspen/Snowmass.  We skied them all, totaling 10 days, for an average cost of $45/day.  For the 2016/17 season, we only got two days total at Alta/Snowbird, but it my understanding that in 2017/18, there will be 2 days at each resort.  In addition, Snowbasin has joined in for a total of 6 days at Salt Lake area resorts.  Plus you can add a third day at a mountain of your choice.  That makes the Mountain Collective even more attractive for a Salt Lake skier.

If you already have a pass a Mountain Collective Resort, you can get unlimited 50% off day tickets at other Mountain Collective Resorts, but keep in mind those half-price tickets can be costly given the exorbitant prices many resorts charge for a day pass.  Perhaps someone can comment if there is a discount on the Mountain Collective Pass if you have a pass at one of the resorts.

As far as the skiing goes, you can't go wrong with Alta/Snowbird and Jackson Hole and we had a great time at each.  Sun Valley doesn't typically get a lot of snow, but it did this year.  It's not a great mountain if you are looking for hard-core terrain, but a weekend of cruising its long fall lines was fun.  Telluride does have some hard-core hike-to terrain, but it was scoured to nothing by the time we went there for spring break.  As such, a day of cruising there was enough, but we skied two anyway.  We enjoyed skiing Aspen Mountain for a day while also catching the Men's and Women's Super-G.  The next day we skied Highlands and Snowmass, racking up huge vertical.  I had never skied any of the Aspen area resorts, so that was fun, but I don't consider a return to be essential.  Our general perspective is that even in a good year, it doesn't snow enough in Colorado.  The phrase, "where's the snow" was uttered frequently.

Given that I was going to Japan for work, I also got 2 free days in the Hakuba Valley.  That worked out well for our multi-day stay since we only wanted to ride lifts a couple of days and wanted to ski tour and sightsee the rest of thetime.

We haven't skied Squaw Valley or Mammoth yet, but continue to keep that as an option as summer approaches.  There's also Taos, Revelstoke, and Lake Louise, but the distance involved was too far for us this year.


The cost per day for skiing if you can get a couple of days of skiing at at least four destinations is quite reasonable, but unless you are a true dirt bag, you're going to need to pay for lodging.  There are discounts through the Mountain Collective, but the options are still costly.  Although we had a cheap option in Jackson, we stayed in Hailey for Sun Valley, Ridgeway for Telluride (1 hour each way), and Carbondale for Aspen to keep costs down.

At each resort, you have to go to their season pass office and get a new pass.  We get to the resorts early enough not to have to wait in line, but it is a pain to have to do this everywhere.   In Hakuba, I had to get my passes at the bus station, but fortunately knew that was the case before showing up at the ticket office.

You get 2 days for the destination, not each resort.  For example, in Aspen, you get 2 days total at all four of their mountains (including Buttermilk), not 2 days at each mountain.  That being said, two days skiing Aspen/Snowmass was enough for me...

Bottom Line

I found the Mountain Collective to be a great option for us this year.  I think having 2 days each at Alta, Snowbird, and Snowbasin will make it even more so next year, especially with Jackson Hole within easy striking distance.  Remember that a third day can be added at one of these resorts.

The pass is especially attractive if you want to also do a road trip to California, Colorado, or Canada and ski at a couple of their resorts.

Saturday, May 20, 2017

Still Skiing

I've had an unused day of skiing at AltaBird thanks to my Mountain Collective Pass and decided I'd use it today.  With a fresh coat of the white stuff, the mountains were quite stunning this morning.

Conditions were quite good for May 20th.  Carveable up high, some refrozen spring snow down low.  Stuff softening up depending on aspect as the day went along.

Given that I hadn't ridden lifts in a month, we racked up vertical on the groomers and called it good at noon.  I like the 8 am open.  That's really nice this time of year for early risers like myself.

Unfortunately, the snow under the fresh coat looks pretty dirty.  In a couple of days, we'll be skiing snirt instead of snow.

Thursday, May 18, 2017

Record Cold Temperatures Aloft

Official temperature records are kept for the surface, but let's give some love today to the atmosphere aloft.

The cold upper-level trough that moving through our area is a record setter.  Soundings collected 0000 UTC (1800 MDT) yesterday afternoon and 1200 UTC (0600 MDT) this morning broke records for the coldest temperature observed at that date and time at 700 mb (about 10,000 ft/3,000 m) and 500 mb (about 18,000 ft/5,500 m).
700 mb
00z 18 May 2017: -9.1˚C
Prior Record: -9.0˚C

12z 18 May 2017: -9.5˚C
Prior Record: -9.2˚C

500 mb
00z 18 May: -28.7˚C
Prior Record: -27.8˚C

12z 18 May: -27.7ºC
Prior Record: -25.1˚C
Prior records are based on soundings collected at Ogden and Salt Lake City from 1948-2014, although there are gaps in which no data is available.  Thus, these upper-air records are perhaps not as impressive as a record at the surface where there is a much longer history available.  Still, it provides some illustration that this is an unusually cold airmass for mid May in northern Utah.

So, is global warming over?  Sorry, but no.  We can see that our extreme cold is regional in nature using the great Climate Reanalyzer site from the University of Maine.  The plot below is the departure of today's daily mean GFS forecast surface temperature from the 1979–2000 average.  The interior western US is a local cold spot, as is parts of interior Asia.  There is also extreme warmth in other areas, especially the northeast United States.  For the globe as a whole, the average surface temperature is 0.45˚C above the 1979–2000 average.

Source: Climate Reanalyzer
Thus, our cold weather is a nice illustration of how one region can still get unusually cold even as the planet warms.

Wednesday, May 17, 2017

Morning Ski Report

With about 6 inches of new overnight on top of a frozen coral reef base, expectations were fairly low for high quality powder skiing, but the skiing was fun this morning up at Alta.  Below, my son Erik does his best to make it look deeper than it really was ;-).

High density snow with some wind actually buried the really nasty stuff in low-angle terrain areas.

The bottom made itself more noticeable in steeper terrain.  A few people were skiing the Main Chute, which perhaps was blown in better.

With a pretty good breeze and my summer acclimatization, I was cold the entire morning, even on the descent with the puffy jacket on.  A few weeks of warm weather, including some time in Florida where temperatures reached the 90s, has made me soft.

Tuesday, May 16, 2017

Mid May Powder Prospects

OK, the cat is out of the bag.  An unusually cold airmass is on its way to Utah.  The question is, will we get some decent mid-May deep powder skiing?

Let's start with the temperatures.  The loop below shows GFS 700-mb (about 10,000 ft above sea leavel) temperature analyses and forecasts from 1200 UTC 14 May (0600 MDT Sunday) through 1200 UTC 18 May (0600 MDT Thursday).  Note how the tightly wrapped core of cold air over the Gulf of Alaska slides down along the Pacific coast and then moves inland to directly over northern Utah.

Air that cold is pretty unusual in our part of the world in mid to late May.  In fact, 700-mb temperatures below -10ºC have never been observed at the Salt Lake City airport after May 12th, although we've been close.

Source: SPC
We'd have a shot at getting a -10ºC in the record books except soundings are only taken twice a day, at 1200 UTC (0600 MDT) and 0000 UTC (1800 MDT) and it appears right now that the coldest air at 700-mb will be here between the sounding times.  Right now, the forecast for 1200 UTC are -9.6ºC for the NAM and -9.0ºC in the GFS, so we'll have to hope things come in a bit quicker or colder to set a new mark.

Next, let's talk about precipitation.  Today we'll see some scattered showers and thunderstorms, which may produce snow in the highest elevations (emphasis on highest).  Things pick up overnight with the approach and passage of the cold front, which is expected to be pushing into the Salt Lake Valley around 0900 UTC (0300 MDT) tonight.  

Precipitation will be in the form of rain initially in the valleys, but if current forecasts hold, snow levels will fall to bench level and probably even the valley floor prior to sunrise.  That will be at the tail end of the frontal band, so most of the precipitation will fall as rain, but don't be surprised if you see snow on colder surfaces tomorrow morning.  The weather story graphic below from the National Weather Service summarizes the situation quite well.  

Source: NWS
After that, we may see some additional periods of rain or snow showers through early Thursday.  Right now, none of that seems very organized, so I'll call it "scattered", but it's worth paying attention to forecasts, especially if perhaps the lake can get involved Wednesday night.   

For the mountains above 8000 feet, the models are putting out numbers that are tantalizingly close for good powder skiing conditions.  At Alta, the NAM pumps out about 2 inches in scattered storms through midnight, and then another 5 inches overnight, with about 7 inches through 9 AM tomorrow.  The typically more bullish GFS is laying down quite a bit more with the frontal passage, with a total of 13" through 9 AM tomorrow.  NCAR ensemble plumes total about 1 to 2.25", although that includes dribs and drabs from last night that in some members that were probably overly done.  

I'll go for perhaps an inch or so in scattered showers through early tonight and then 5-10 inches through 9 AM tomorrow at Alta-Collins.  Good deep-powder conditions will require something at or above the top end of that distribution and getting turns in the morning tomorrow as  I think we'll see mostly scattered snow showers tomorrow during the day and some potential for things to get manky. There's a possibility of additional snow late Thursday and Thursday night, but it's really a crap shoot at that long lead time and the odds of a major dump are low (but non zero).  

Unfortunately, we're not receiving data from Alta-Collins at the moment.  If that continues, some guesswork might be needed in the morning concerning totals at upper elevations.  

Monday, May 15, 2017

How about a Second Season?

May 16, 2015.  A reminder that late-spring storms are part of the Wasatch climatology.
We've said it many times this spring, it ain't over until its over.  It was only a few days ago that I was bemoaning the return of colder weather to California as I was thinking of a Sierra corn harvest trip.  Well, if I'm lucky, things might just work out just fine, but in an unanticipated way.  Forecasts from the day of that post showed a deep, closed, upper-level flow digging through northern California on its way to the southern Sierra.  Not a great scenario for either Sierra corn or, for that matter, Wasatch powder.

However, forecasts change and that trough is now expected to amplify later and moves into the western U.S. as an open wave accompanied by a strong cold front that is expected to push through northern Utah late Tuesday night and early Wednesday morning.

Ooooh, the lower right hand panel of that GFS forecast is a beauty!

The forecast, however, is no slam dunk because this is a case where the trough is amplifying and closing off over the western US, as evident a bit later in the forecast cycle.  

That closing off process tends to be somewhat chaotic, and that in turn leads to uncertainty regarding the position of low, accompanying precipitation bands, and the characteristics of the flow impinging on the Wasatch Range.

Thus, we'll take a look at the downscaled forecasts from the short-range ensemble forecast system.  Some members produce some precipitation this evening, tonight, and tomorrow in advance of the trough.  Others are dry for that period.   Perhaps we'll see some scattered mountain rain and snow showers with a clap or two of thunder.  That would be nice, but the potential for real snow is really Tuesday night and early Wednesday with the frontal passage.  Temperatures during that period will also be dropping like a rock.  Most members are enthused about the frontal passage and produce anywhere from about 0.6 to a bit more than an inch of water.
Much will depend on how much falls with and following the frontal passage.  We need a pretty good dump to bury the coral reef that will exist underneath the new snow as the spring snowpack refreezes, although falling temperatures and a right-side up snowfall certainly helps.  No guarantees, but I'm keeping an eye on this.

Friday, May 12, 2017

Climate Change and Skiing in the United States

Projections of how climate change will impact snow and skiing are of great interest to readers of this blog.  There are, however, a number of major challenges to making these projections.  Our climate models have large grid spacings, which means they do not explicitly simulate the effects of nearly all mountain barriers on precipitation, humidity, temperature, etc.  Without reasonable mountains, they don't explicitly simulate the mountain snowpack, or the effects of elevation and aspect on that snowpack.  Therefore, projecting how snow will change in the future typically requires some modeling gymnastics to account for local effects in mountainous regions.

A recent paper by Wobus et al. in Global Environmental Change uses a variety of approaches to project future climate change impacts on snow, skiing, and snowmobiling in the contiguous United States.  The paper is unique in that it doesn't focus on a particular ski area or region, but instead provides a nationwide perspective on climate change and skiing.

They use the Utah Energy Balance Model (UEB), developed at Utah State to simulate the water and energy balance of seasonal snowpacks, to simulate natural snow at each ski area or winter-recreation location (247 in total).  They drive the UEB with projections from five climate modeling systems (selected to provide a reasonable sample of climate change scenarios generated by the full spectrum of climate models), which are adjusted using a variety of approaches to account for the regional and local climatic effects on temperature, precipitation, and moisture conditions at each ski area and winter-recreation location.  They present changes in season lengths for cross-country skiing and snowmobiling sites, which one could think of as relevant for backcountry skiing, as well as alpine skiing resorts, which also attempt to account for snowmaking.  They do this for two scenarios, RCP4.5, which represents a scenario in which greenhouse gas emissions are strongly reduced in the coming decades, and RCP8.5, with continued high greenhouse gas emissions growth.   Season length is defined as the difference between the first and last dates with at least 10 cm (4 in) of snow-water equivalent at the base of each ski area.  Exactly how snowmaking is incorporated into all of this is a bit unclear.  I'll comment on this later.
Let's first have a look at the results.  For brevity, I'll focus solely on changes in downhill ski-season length.  These are averages from the climate model projections and attempt to account for snowmaking.  Not surprisingly, there is a decline in ski season length at most ski areas that increases through the 21st century and is largest for the continued high greenhouse gas emissions growth scenario (RCP8.5).  In general, declines in season length are largest in the Northeast and midwest, and smallest in high-elevation regions of the interior west.  There are a few ski areas, mainly that show increases in season length through 2050 under both scenarios and under the RCP4.5 scenario through 2090.

Source: Wobus et al. (2017)
These regional results are generally in line with my expectations.  Vulnerability of snow and skiing to climate change is greatest in the northeast and warmer regions and elevations of the west.  The greatest resiliency is at colder, high-altitude locations Colorado, Utah, and Wyoming.   This means, for example, that Utah's ski industry has more resiliency than Washington's, but also that Alta and Brighton have more resiliency Sundance.

For those of you who want to know what they found for your ski area, the authors include this information in a supplemental file with the paper online.  For kicks, I decided to check out what they found for Utah and got a bit of a chuckle.  Amongst the ski areas were "Park City Ski Area" and "Park City West Ski Area."  Apparently they are using a database that is quite old for ski area information.  But who can blame them for confusion on what to call Park Wolf Canyon City Mountain Resort?  In addition, Alta was not included.  No worries.  God has ensured that great skiing will continue there even in a warming climate.

I would caution, however, in using these numbers quantitatively.  It is my view that this study is most useful in providing qualitative guidance for how ski regions might fare under climate change.  Predictions for specific ski areas should be used cautiously for several reasons.  First, validation of their technique for season length during past years (2004-2010) shows some ability to predict season length geographically, but the scatter for individual stations is fairly large.
Source: Wobus et al. (2017)
Second, they provide only an average, and there are variations in season length amongst the various climate model projections and uncertainties in both the rate of change of temperature and precipitation that must be considered and ultimately mean a range of possible outcomes must be considered.  There is strong consensus amongst scientists and models that temperature will increase in the coming decades, but no real consensus concerning precipitation.  For example, some locations may be able to offset declines in season length due to increasing temperature if precipitation and snowfall increases, but season length will suffer even further if snowfall decreases.

Even with the various warts and caveats that any study of this type has inevitably, the long-term big picture is one of concern for snow lovers.  I see a future in which the differences between the haves and have nots grows.  The decline of snow will be faster in regions and locations that already have marginal conditions and slower in those areas that generally have good conditions.

Wednesday, May 10, 2017

California Dreaming

With the semester over, I've been doing some California dreaming and debating whether or not to drive over to the Sierra for a few days of blue skies, California sun, and corn harvesting.

The snowpack there is, of course, outrageous.  Having achieved remarkable depths by April, the Sierra snowpack now shows clear signs of ripening and melt in mid elevations of the southern and northern Sierra.  I suspect things have corned up nicely, with only timing the key for good turns.  

However, there is a fly in the ointment for the future.  Medium-range forecasts show a transition beginning on Friday and upper-level troughing persisting along the Pacific coast for about 5-7 days thereafter.  

Perhaps this weekend things will still corn up during the afternoon, but next week the pattern is one that will eventually produce highly variable conditions with everything from coral reef to cream on crust.  Later in the period, perhaps they will even see a decent dump.

So, next week might be tough going for California sun and Sierra corn.  

Tuesday, May 9, 2017

Lessons in Lightning Safety from Yesterday

Yesterday afternoon, a series of convective storms formed over or near the central Wasatch and moved northwestward toward Bountiful and portions of the Salt Lake Valley.

The first of these storms was near Parley's Canyon at 2059 UTC (1459 MDT) and organized in a line. It looked like a close call for the University of Utah to receive rain, as well as thunder and lightning.

Over the next 13 minutes, the storm shifted northward and became more cellular in structure.  By that time, it was northeast of campus and we had missed out on any significant precipitation.

However, it is important to realize that threats from lightning can often extend many miles from the rain shaft and indeed, that was the case yesterday.  I was taking the occasional glance at the wonderful lightning products at and noticed a strike not only on Little Black Mountain close to the storm, but also in the mouth of City Creek Canyon, not far from downtown.

That strike illustrates that lightning can strike outside of the rain shaft, sometimes 10 miles (or in some instances more) from the storm.

Now there is some possibility that there is an inaccuracy in the data, but lightning studies have shown that strikes up to 10 miles from the rain shaft in the absence of rain happen.  If you can hear thunder, even if it isn't raining at your location, you should move indoors.  If you are at a sporting event, move into your car.  In the United States from 2006 to 2016, there were 31 lightning fatalities during sports-related activities, with the most at soccer events, followed by golf.  Many more are injured.

Source: Jensenius (2017)
Note that picnic shelters, dugouts, and porches are not considered lightning safe.  Move to a substantial building or a hard-topped automobile if you are at an outdoors sporting event, rock concert, whatever.

For outdoors oriented people like myself, it's best if you can rearrange your schedule to recreate when lightning is not a concern.  We did this yesterday as we waited until late evening to hike in the Avenues foothills.  There are times, however, when you can't wait or find shelter.  I've had some miserable and scary experiences hiking and backpacking during thunderstorms.  In fact, I became a meteorologist in part because of a miserable storm night my dad and I had in the Adirondacks when I was a teenager.  In these instances, the goal is to reduce the threat.  This involves:

  • Moving from a tent to a car if possible
  • Avoiding open areas, ridge lines, and mountain tops.  
  • Moving to lower elevation (Note: Avoid washes and other areas if flash-flooding is a concern)
  • Staying away from tall, isolated trees and objects.  Find lower tree stands if possible.
  • Spreading out if you are in a group
  • Avoiding open water
  • Avoiding laying on the ground.  Minimize contact with the ground. 
Now I'm no "angel" when it comes to lightning safety.  I've sat too long on my porch or have tried to squeeze in a workout when I shouldn't on several occasions.  Being human is hard.  Nevertheless, it's a good idea though to practice good lightning safety practices and minimize risk as much as possible.

Monday, May 8, 2017

Snowpack Numbers from California

It's no news to readers of this blog that California has had a winter for the ages.  As of May 5th, automated snowpack sensors showed the snowpack in the northern Sierra/Trinity region at 189% of average, central Sierra at 193% of average, and southern Sierra at 168% of average.

Those numbers are impressive, but here are the peak snow depths from manual snow course measurements taken in late April and early May from each region:

  • Northern Sierra/Trinity: Lower Lasen Peak, 8250 ft, 266" snow depth, 131.5" water content
  • Central Sierra: Bond Pass, 9300 ft, 192" snow depth, 101.0" water content
  • Southern Sierra: Piute Pass, 11,300 ft, 166.5" snow depth, 85.0 inch water content

For comparison, the Alta-Collins snow depth sensor and Snowbird SNOTEL measured 125" snow depth and 58.3" of water equivalent yesterday.

Stay thirsty my friends...

Saturday, May 6, 2017

DCAPE, Microbursts, Pollen, and Wind Damage

This morning's sounding showed classic conditions for strong microburst winds with an "inverted V" profile created by the temperature (red) and dewpoint (green) traces above the shallow surface-based nocturnal inversion.

Source: SPC
Microbursts are are sudden strong winds caused by downdrafts induced by precipitation and may be "wet" or "dry", with the latter occurring when the precipitation evaporates before reaching the ground.
Source: Wikipedia
One measure of the potential for strong downdrafts and microburst winds is what is known as the downward convective available potential energy or DCAPE.  DCAPE is maximum energy available for a negatively buoyant parcel of air cooled by evaporation assuming no mixing with the environment.  Values above 1000 Joules/kg are considered high and significant.  This morning, the DCAPE at Salt Lake City international airport was 1223 Joules/kg.

Not surprisingly, we've had some strong winds in northern Utah.  This morning, I observed a modest microburst drive an impressive "pollen front" into the Avenues (sorry, no pictures, but I did sneeze). Subsequently, several valley locations have reported microburst wind gusts in excess of 60 mph including the Kennecott Tailings Pile (61), Lake Point (63), Vernon Hill/Tooele Valley (65), Syracuse (66), and Pleasant Grove (68).

The biggest gust so far was recorded on Fremont Island in the Great Salt Lake, with a gust of 91 mph.  The NWS just tweeted that there is wind damage on nearby Antelope Island.

Friday, May 5, 2017

Is This the Beginning of the End?

As we discussed a few weeks ago, the ski season is never over until it's over.  That being said, we are probably very close to the "beginning of the end."

By beginning of the end, I mean the onset of the rapid decline in snowpack on upper-elevation northerly aspects.

The low-elevation snowpack already suffered a premature death in March with the beginning of the end produced by the unseasonably furnace-like temperatures we experienced in the middle of the month.

The snowpack at mid-elevation and relatively sun exposed upper-elevation areas has, however, been able to stave off the beginning of the end for a remarkably long period of time.  For example, peak SWE at the Mill-D North SNOTEL was reached in early March.  Since then, there have been two melt periods, each followed by an accumulation period.  The most recent peak in SWE, achieved on May 1, was just a bit below the early March peak.

At Snowbird, which benefits from both elevation and north aspect, we now sit at the peak SWE.  That's not unusual.  On average, peak SWE at this site is achieved in late April.

The net loss of water in the snowpack has yet to begin there, but I suspect the snowpack is close to ripe and that we will see a downward trend starting today or tomorrow.  Although I won't rule out more snow in the next couple of weeks, I suspect that we are now at peak SWE for this site.

One other quick note.  The Utah Avalanche Center is no longer issuing forecasts, but noted yesterday on instagram concerns about avalanches over the next few days.

The overnight minimum temperature at Alta-Collins (9600 ft) was only 41ºF last night.  If there was a freeze of the snowpack, it was extremely thin and shallow.  Temperatures today at that elevation should reach well into the 60s.

Unfortunately, we have had late-season fatalities in the Wasatch Range under similar conditions.  In late April 2001, two climbers were killed by a likely glide avalanche in Stairs Gulch.  That April had been snowy, and was followed by a rapid warming.  The night of the accident was especially warm, with minimum temperatures in the 40s.  Bruce Tremper's accident report is worth a read if you are considering touring today or this weekend and is available here.

Wednesday, May 3, 2017

Looking Good for Commencement

The University-wide commencement ceremonies for the University of Utah are tomorrow (Thursday) night, with most college ceremonies on Friday.  Although the ceremonies are indoors, we do our best here at the University of Utah Weather Control Center to arrange for nice weather for your photographs and outdoor activities.  We have conjured up an ideal pattern for tomorrow night, with an upper-level ridge in full control.

Friday looks nice as well, with a south breeze in the afternoon.  Other than perhaps having to hold your mortarboard as you walk around campus later in the day, things look just fine.

Tomorrow night's commencement address will be given by Conrad Anker.   Conrad is a U alum and mountaineer, most recently featured in the film Meru, which won the US Audience Documentary Award at the 2015 Sundance Film Festival.

Decision making by the U administration has come into question recently, but they made a good choice in selecting Conrad.  Quoting the University of Utah press release,
"The reality of the school’s close proximity to nature allowed Anker to enjoy the outdoors while taking classes. He worked for the school’s campus recreation program and found his business courses to be especially useful and even started a company while in school. He eventually sold the startup, KÜHL, for $10,000, which he used to go climbing."
That's a story I suspect many of you can relate to.