Saturday, March 31, 2018

Powder and Corn Season

Weather conditions are almost prime for being able to harvest corn and powder if you can work the north and south aspects.  Almost. 

On upper-elevation north aspects, the snow on north aspects is surviving it's just not very deep and there's wind damage aplenty.

Nevertheless, you can find creamy settled powder in some areas that skis surprisingly well.  Effort and perseverance can pay off.

Meanwhile, hop across the ridge to the south side and you can find corn.  The south face of Mt. Superior got a lot of attention today. 

We elected for other options, finding buttery conditions on our return to Alta.  Arguably, it needs a couple more cycles to truly corn up, but the skiing was just fine. 

Really, if the wind hadn't done damage and if we had a bit more snow in the last storm, today would have yielded pretty good conditions for a corn and powder harvest.  Although the bounty wasn't great today, the skiing was better than expected and, if we have learned anything this year, low expectations are the key to satisfying ski days. 

Friday, March 30, 2018

Your Parents Had More Powder Than You

Snowfall observations have been collected at Alta Guard for November through April since the 1945/46 season.  As noted in today's Utah Avalanche Center advisory, Alta Guard has measured 245" of snow since November, with 24.65" of water.  It does not appear that they will add to this total through the end of the month, which will result in the November to March snowfall being the second lowest on record, behind only 2014/15, when only 220.5 inches was recorded. 

Although I still consider 1976/77 to be the worst snow year on record for skiers, mainly because the early season snowfall was so poor (even worse than this year, see Deep Dive: How Unusual Is Our Snowfall and Snowpack This Season, posted 9 Feb 2018), that season is now ahead of this one from a November to March snowfall perspective, with 283.5 inches.  Nevertheless, this has been a remarkably dismal snow season and one of only 6 seasons with less than 300 inches of snow at Alta Guard from November to March.

2014/15: 220.5"
2017/18: 246"
1962/63: 265"
2011/12: 281.5"
1960/61: 291"
1976/77: 283.5"

Recent years have also been relatively poor within the period of record.  The 10-seasons from 2008/09 through 2017/18 have the lowest seasonal snowfall average with 339 inches.  In second place for a 10-year running mean is 1953/54 through 1962/63 with 359 inches.  If you want fat snow years, look to the 80s and 90s, with the peak 10-year average of 492 inches from 1988/89 through 1997/98. 

Sorry kiddies, but your parents had more powder than you.  Quite a bit more powder.  

I have been avoiding comments on the causes of recent poor snowfall years for a variety of reasons.  Perhaps the most important is that I don't think that we have done adequate research to understand the causes.  Don't label me a climate denier for saying that.  It is clear that our warming climate is decreasing the fraction of wintertime precipitation that falls as snow in the lower elevations of Utah.  It is also clear that it is affecting snowpack over Utah. 

However, the whims of the jet stream could also be playing a role, and probably a significant one.  Tree rings have been used to infer pre-historic climate over the western U.S. and illustrate that although 75 years seems like a long time for humans, it's really an inadequate sample of the climate variations that effect our region.  For example, tree rings have been used to construct streamflow for the Bear River and show much stronger (and longer) periods of drought than observed in the latter half of the 20th century. 
Source: DeRose et al. (2015).  Drought and pluvial (wet) periods illustrated by black and grey fill, respectively.  Note that this graph is smoothed to illustrate slower climate variability.
The plot above illustrates that there are slow variations in regional climate that can cause decadal (or longer) periods of wet or dry conditions.  The causes of these variations are not fully understood, but are at least in part related to variations in ocean temperatures and sea-ice coverage that I lack time to discuss here.  I suspect that recently poor snow seasons in the Wasatch partially reflects these variations.  

The long-term trends related to global warming are clear and their impacts on Wasatch snowfall and snowpack will continue to emerge during the 21st century.  However, along with these trends are slow variations in regional climate.  Understanding and predicting those variations is an important area of research and provides many thesis and dissertation topics for motivated students.  Beyond skiing, there are important implications for water resources and water resource management.  

Thursday, March 29, 2018

Instead of Winter, Two Falls and Then Spring

Sadly, the latest forecasts show scant precipitation over the next seven days.  There are a few ensemble members going for a small snowfall event early next week, but it's a low probability possibility. 

With April upon us, I feel like instead of fall, winter, and spring, this year we had two falls and then moved right into spring. 

Snow was sparse through the middle of February.  Things picked up for about a month, and now we are limping along once again. 

The Alta Snowfall History shows a cumulative seasonal snowfall of only 321 inches with 8 deep-powder days (based on a minimum of 10 inches or more of snow).  The latter is about half of average.  Five of those deep powder days occurred from Feb 15 to March 17, which now stands as the closest thing to a month of winter that we saw this year. 

It's possible that we have more dumps in the future.  April can do sometimes bring the goods.  Nevertheless, even if it comes around, I feel a bit cheated by winter this year. 

There's always next season...

Tuesday, March 27, 2018

Saharan Dust Creates "Snirty" Eurasian Snow

Some remarkable photos and videos of extreme dust storms in the Mediterranean Basin and the mountains of Eurasia have gone viral on Twitter.  To begin, here's how things looked on March 22nd on Crete and March 23rd in Santorini, Greece.

In addition to bad air quality, such storms lead to dust deposition in the mountains of Eurasia, leading to "snirty" snow (a take on part snow part dirt).  The photos below are from the Caucasus Mountains near Sochi, Russia.

Although the most recent event has caught widespread attention, it is the most recent of a series of major dust storms that have impacted the region over the past few weeks. Note, for example, the dust layering in this snow pit from the mountains of Greece, indicative of a series of dust storms.
The loop below is based on daily images collected by the MODIS sensor on NASA's Terra satellite and covers the period from March 1 through March 28th.  You can see a series of dust storms originating over the Sahara with transport across the Mediterranean into southern Europe and in some cases beyond.

Favoring these frequent dust storms has been an anomalously deep upper-level trough centered over western Europe.  This has resulted in frequent cyclogenesis over the Mediterranean basin and associated strong flow over the northern Sahara.

Long range transport of this dust is evident in the MODIS images below for 25, 26, and 27 March.  Note in particular how dust is transported across the Mediterranean from multiple origins and eventually moves downstream over the Black Sea.

These events are of course lousy for skiing, which I sometimes describe as "Snirty Dancing." However, they also play an important role in mountain hydrology.  Dust is dark, and it absorbs more solar radiation than clean snow.  This leads to an earlier and faster snowmelt in areas where dust has been deposited in and on the snowpack.  Even if covered by a layer of fresh snow, as the snow melts, it percolates through the snowpack, withe the dust eventually emerging at the top of the snowpack to affect the solar radiation absorption.

Dust storms also occur frequently in the western United States and play an important role in our snow-driven hydroclimate.  For some discussion of this topic, see our previous post Dusty Snow: The Monster in the Basement.

Monday, March 26, 2018

Issues with Snow Measurement

Snow observations are very difficult to make well and even when they are done following "protocol" they still have uncertainties and ambiguities.

Let's take the latest storm as an example.  The ground prior to the storm was quite warm, and this leads to variations in accumulation depending on the characteristics of the surface.  Let's suppose, for example, that you decided to head out and measure the accumulation on the grass this morning.  Here's what you would have found this morning. 

First, the grass on most lawns is beginning to grow and is of variable height.  This in turn affects the transfer of heat from the relatively warm ground to the snow, leading to small mounds and variations in snow height and depth. 

I was able to measure anything from 2 to 4.5 inches of snow on the lawn depending on where I placed the ruler (apologies for not having my metric ruler handy!). 

This is one of the reasons why it is recommended that snowfall measurements should be made on a snowboard, which is typically a piece of wood (painted white) that is at least 16" x 16".  Ideally, snow should be measured as close as possible to the end of the storm, although one might also measure it in intervals that are no more frequent than four times per 24-hour period.  For more information, see this CoCoRAHS site

Standardizing snow measurements in that way provides uniformity, but there are still problems.  For example, it tells you little about what is happening on street and road surfaces, which is where many of the impacts of winter storms occur.  Sadly, most snowfall records provide little information on these important details of winter storms. 

I sometimes wonder if instead of trying to get one number (e.g., 4.5 inches) from each location on snowfall amount, if we should be better characterizing the distribution of snowfall across a wide range of surfaces.  Certainly providing a snowfall observation to the nearest tenth of an inch implies a level of precision and accuracy that is not representative of the snow-measurement uncertainty or local snowfall variability.  In our digital era, we might be able to do much better than a single number and perhaps consider collecting records of accumulations on several different surface types. 

Sunday, March 25, 2018

Some Snowpack Improvements and Losses Since Mid February

Mid February marked a turning point for the upper-elevation snowpack in the central Wasatch, which now sits at 70% or more of median for this date at all four SNOTEL sites (Snowbird, Brighton, Mill D North, Thaynes Canyon). 

Source: NWS
At Mill-D North and Snowbird, you can see the gap close between the median trace (purple line) and this season's trace (green line) from about mid February to the present. 

Source: NWS
Source: NWS
These sites are relatively high, however, so they tell an incomplete picture of the snowpack.  At lower and mid elevations, the situation isn't nearly as rosy.  Sadly, those elevations are poorly sampled with regular observations and it is difficult to quantify how far behind they are.  In addition, the central Wasatch are doing much better than the northern or southern Wasatch.   Some of the more depressing SNOTEL observations are provided by Ben Lomond Peak to the north and Timpanogos Divide to the south, which set well below median. 

Source: NWS 
Source: NWS
The high terrain of the central Wasatch are a favored region for snowfall and snowpack climatologically, but this year, the situation is even more strongly amplified.

Saturday, March 24, 2018

Atmospheric River Aftermath

After returning from Seattle, I was finally able to sample the atmospheric river aftermath in the Wasatch backcountry today.  A polite descriptor of the conditions would be "variable."  It seemed strange, even in the upper elevations that were above the snow level, how little snow the storm produced given the amount of water it generated.  Maybe it blew to Evanston. 

Graupel was found in many areas.  In a few pockets it had collected into piles perhaps 20 cm deep. 

I don't know why, but I always enjoy digging into piles of graupel.

Exiting, we got a view down Little Cottonwood with lower clouds beginning to develop over the Salt Lake Valley. 

Periods of snow look likely for the mountains through Sunday night, although it's not looking like a major event.  The NAM is spitting out a total of about 4", although the always optimistic GFS and NAM-3km are putting out higher totals.  Anything appreciated at this point.

Wednesday, March 21, 2018

Atmospheric River Precipitation Needs Forcing Too

By now, you've probably heard that an atmospheric river is coming to Utah tonight and tomorrow.

Atmospheric rivers are corridors of strong atmospheric water vapor transport.  Such transport is dependent on both the water vapor content of the atmosphere and the strength of the flow.  Values are typically highest when the water vapor content of the atmosphere is high and the flow is strong. 

Atmospheric rivers can be associated with heavy precipitation, but strong atmospheric water vapor transport, by itself, doesn't generate precipitation.  Some forcing is needed to lift the airmass, form clouds, and generate precipitation.

In the case of an atmospheric river, one possibility is to have it cross a mountain barrier, which yields strong upslope flow and precipitation enhancement.  This happens commonly in the mountains of California during atmospheric river landfall.

Another option is to have large-scale forcing, such as the ascent typically found near cold fronts or along warm fronts.

With this in mind, the plot below shows a time-height section (time in this case increasing to the right) at a location near Salt Lake Cit airport from the 0600 UTC initialize GFS.  The color fill is the water vapor transport, and you can see how it maximizes at around 0000 UTC 23 March (6 PM MDT Thursday).  Note, however, that at this location, although there is a peak in precipitation at that time, a greater peak is found later, when the vapor fluxes are lower, but when the surface-based cold front is moving through.
Source: CW3E
This indicates the importance of forcing.  Water vapor transport can be very important, but a mechanism for generating precipitation is also needed.

That forecast above, however, is from a model (GFS) with relatively flat terrain.   If one were to go to a places like Snowbasin or Sundance, the story could be different.  At these locations, southwesterly flow is oriented strongly across the local topography and and significant generation of precipitation can occur.

Although I hesitate to use the actual totals produced by the 3-km NAM, the forecast below valid 0300 UTC 23 March (9 PM MDT Thursday) illustrates this well.  Note the heavier precipitation in the areas around Mt. Timpanogos (Sundance) and the northern Wasatch (Snowbasin), as well as over the Uintas.  These are areas where the mountains are oriented across the crest-level (10,000 ft) flow.  You can also see the heavier precipitation over northwest Utah where there is forcing along the cold front.

Sadly, ahead of the cold front, this is a very warm storm.  Our NAM derived forecast for the upper Cottonwoods shows wet bulb zero levels (typically the snow level is about 1000 feet below this) reaching as high as 10000 feet Thursday before lowering late Thursday night/early Friday morning with the frontal passage.  Much of the precipitation ahead of the front will fall in the form of rain at elevations below 8000-9000 feet.

Keep an eye on official forecasts the next couple of days.  Ultimately, the timing, intensity, and amount of precipitation will depend on both the characteristics of the atmospheric river, the mountain effects, and the cold front.  I will also add that there is the potential for strong pre-frontal souhterly winds and thunderstorms late Thursday and Thursday night.  Too much to cover in a blog post from Seattle. 

Sunday, March 18, 2018

Warm Atmospheric River Event Possible Later This Week

Atmospheric rivers are narrow corridors of strong atmospheric moisture transport, often connected in some way to moisture exported into the midlatitudes from the tropics or the subtropics.  Although Utah sometimes sees the remnants of weakened atmospheric rivers, bonafide atmospheric river conditions in Utah happen only a few times each cool season.

However, we have a shot at one making it to the state Wednesday night and Thursday if model forecasts hold.  The average integrated water vapor transport in forecasts produced by the Global Ensemble Forecast System for 0600 UTC 22 March (0000 MDT Thursday) shows strong values extending from the Pacific Ocean northeastward into Utah.  Values exceeding 250 kg/m/s (outlined by red line) indicate atmospheric river conditions, and most of Utah is covered.

Source: NWS
Two ingredients favor atmospheric river penetration into Utah in these forecasts.  The first is that the atmospheric river is strong on the coast, with integrated water vapor transport values over 750 kg/m/s.  The second is that the flow moves up the lower Colorado River Basin, missing the southern Sierra Nevada and other high terrain features that typically generate precipitation and deplete the water vapor content of airmasses moving into the western interior.

It is still a bit early to discuss details of where, when, and how much precipitation will fall.  Not all atmospheric river events are big precipitation producers in Utah, but some are.  Much depends on the orientation of the atmospheric river, the orientation of the flow relative to major terrain features, and the efficiency of the precipitation processes embedded in the flow.  Also important is the duration of the event.  Right now, it looks like we'll see a warm, humid (by Utah standards) precipitation event developing first in southwest Utah late Wednesday and then in other parts of the state Wednesday night and Thursday.  Until then, enjoy the spring break and monitor forecasts.

Saturday, March 17, 2018

A Good Spring Break to Be Nimble

I've been surveying the forecasts for spring break and it is looking like a week where you can do just about anything if you are adaptive and pay attention to forecasts.

I think everyone is well aware that the weekend is for skiing in the Wasatch where the snow continues to pile up.  Alta-Collins got 10 inches overnight and has another 4" through 2 PM.  Between the cloud cover and the low temperatures, the snow should be holding up well on higher elevation north aspects.  Over three inches of water has fallen in the last three days, making this one of the more productive storm cycles of the period.  My advice is that you ski until you drop through the weekend.

Monday is a tougher call and one that you will need to make for yourself.  Good skiing may persist, or you might opt to head south for adventures in southern Utah.  It will be a cool day, but sunny statewide.  Tuesday looks spectacular, with upper-level ridging over the state. 

Wednesday looks to be the warmest day of the week for most of the state, but there's a threat of rain spreading into southwest Utah in the latter part of the day.  It's a bit too early to call that, so if you head south, pay attention to forecasts.

Depending on how things play out, it might be wise to be back in Salt Lake for skiing Thursday when we may see a warm storm.  Altitude will be your friend, as it almost always is so late in the season. 

Bottom line: Ski today and tomorrow.  Monday go with your instincts.  Southern Utah Tuesday, then check the forecast and adjust accordingly. 

Being nimble should allow you to maximize your hedonistic pursuits.  I, on the other hand, will be banished to a conference room in Seattle for the week.  Fortunately, there will be real, craft beer on tap each evening to dull the pain.

Friday, March 16, 2018

The Truth About Powder Skiing

"The best deep-powder skiing is not found in the lightest snow but rather in snow with enough 'body' to provide good flotation for the running ski."
- Ed LaChapelle, 1962

You can have your bottomless blower pow.  You can rave about pit deep 4%.  You can have it all.  The truth is, those deep, dry days don't provide the best powder skiing.  Give me some Cascade concrete and and put some cold smoke on top of it.  

And that's what we found on sheltered upper-elevation north aspects today. 

What we didn't find were people. We pulled into the White Pine lot at 8:15 and found only two cars in the lot.  Two!  While gearing up, I kept waiting for the yellow lights to start blinking and then the sound of incoming shells as there's no way that there can only be two cars in the lot on a powder day.  

Yet the dream was true.  

Then the day dawned clear, with a postcard view down Little Cottonwood on the climb up.  

After passing a snowshoer near the boundary for the Lone Peak Wilderness, we found no tracks.  None.  Just a hint of a skin track from a couple of souls from yesterday buried under the cold smoke to lead the way.   For hours we broke trail and did laps in perfect powder, not seeing a soul until about 2 PM.  It was like being on a hut trip in interior BC.  Nobody around.  Surfy hero snow with just the right body.  Zipping through well spaced trees as if there was no tomorrow.  Ed LaChapelle skiing. 

I need to get out more during the week.  So few people, so much enjoyment.  Add hero snow and my favorite touring partner, and you have a perfect day.

Thursday, March 15, 2018

After the Deluge...

Storms have produced some impressive precipitation amounts (water equivalent) for March from yesterday afternoon through this morning.  Some totals through 7-8 AM or so this morning include .78" at the Salt Lake City Airport, just over an inch in Olympus Cove, 1.25" at Spruces, and 1.54" at Alta Collins.  

Sadly, much of that water fell as liquid in the lower to middle elevations.  For example, 0.68 of the 1.54" that fell at Alta Collins fell at temperatures at or above 32ºF.  During that period, snow levels were initially at almost 9000 feet and lowered to about 8000 feet.  They have since dropped to the valley floor and as of about 8 AM, it is snowing at the University of Utah.

At Alta Collins, the automated interval snow-depth sensor suggests about 10 inches of snowfall.  Initially, that snow was probably a mixture of graupel and white sludge, but densities dropped with snow levels overnight, so what is there should be right-side-up.   

Radar imagery shows that the precipitation feature currently producing snow on campus is swinging through and that we will probably see things letting up soon.  

Expect some snow and rain showers today, and maybe even some thunder.  Similarly, the mountains will see periods of snow and don't be surprised if you hear a clap of thunder there too.  It won't be as active as yesterday and thankfully it is much colder.  Hit and miss snow showers, including the band moving through presently, will produce perhaps another 3-5 inches at Alta-Collins through 5 PM.  

It will be interesting to hear how the snow holds up today now that we're into mid-March.  Sunbreaks are welcome in January, but can be caustic this time of year.  South aspects won't last long.  A real challenge for backcountry skiers as we head deeper into spring is that monsters continue to live in the basement on high-north aspects that preserve powder so well.  

Wednesday, March 14, 2018

Expect the Unexpected from This Spring Storm

It's worth a look at the combined cloud/radar and NAM cloud/precipitation forecast loop below to get an idea of the lack of organization of precipitation systems forecast to impact the weather of northern Utah over the next 2-3 days.  Note their banded or "blobular" structures.  Blobular is of course a highly scientific word (ha ha) used here to describe cellular features produced by a model that due to it's sparse grid spacing (12-km) is incapable of producing convective storms that look like those of the real world. 

The chaotic nature of those precipitation features means if you are looking for a precise forecast of when and how much it is going to rain or snow over the next couple of days, you've come to the wrong place. 

Let's start with perhaps the easy part: Today.  A combination of instability, strong flow, and vertical wind shear means we will see some showers and thunderstorms this afternoon.  The NAM forecast sounding for 2200 UTC (4 PM MDT) shows 320 Joules/kg of surface Convective Available Potential Energy (CAPE), a measure of how much energy a surface parcel of air would gain if it were lifted vertically through the atmosphere.  Locally, values may be higher.  Although such CAPE values are pretty pathetic for those looking for midwest-type severe storms, but are enough to make things interesting for Utahns.  Strong flow and vertical shear is also indicated in the wind profile. 
As such, the Storm Prediction Center has us in marginal risk of severe thunderstorms in the mid to late afternoon when "thunderstorms will offer the potential for damaging gusts and hail near severe limits." 

Source: NWS
Beyond showers and thunderstorms, expect some gusty south winds today, with the possibility of some blowing dust.  There is no longer snow cover over valleys and basins to our south and west, so dust emissions are possible if the land-surface conditions are favorable and flows are sufficiently strong.  Temperatures today will remain mild, although snow levels may drop locally during stronger showers and thunderstorms and may include large graupel or hail. 

After today, the pattern might best be described as unsettled, which is a nice way of saying there will be precipitation, but where, when, and how much is unclear.  Snow levels will fall overnight and probably be near bench level early tomorrow morning. 

The now somewhat old 0300 UTC initialized SHREF shows a mean of about 1 inch of water total at Alta-Collins by 0000 UTC (6 PM MDT) tomorrow afternoon, but the range is colossal, spanning from about 0.1 to 2 inches. 

Everything will depend on the position and intensity of precipitation features accompanying the system as it swings through. 

Stuff that falls today will likely be of the wet, high-density variety at high elevations, possibly including some big graupel or hail.  A garbage bag might be required at times, especially at mid and lower elevations, which will probably see rain that could turn temporarily frozen precipitation of a "variety of forms" during periods with higher precipitation rates.  Snow levels and densities will drop later tonight. 

A reasonable guess for Alta-Collins would be 7-14 inches from today through 6 PM tomorrow, with more possible if they are lucky enough to get a pounding from one or more of these precipitation features.  Note that I use the scientific term "guess."  Expect the snow to come in fits and starts at times. 

Welcome to spring!

Tuesday, March 13, 2018

Intricacies of This Winters Warmth, Snowfall, and Snowpack

All generalizations are wrong, and that is especially true if one is talking about weather, snow, and snowpack.  A quick look at the numbers from this past season reveals some surprises and multifaceted reasons for the low snowpack that exists across our region.

Let us begin at the Salt Lake International Airport where there are relatively long weather records.  Total precipitation (liquid equivalent) since 1 November is 3.00 inches, well below the 1981–2010 average for the period of 5.81 inches.  However, during that period, the airport actually received 39.9 inches of snow, which is not far behind the 1981-2010 average of 45.6 inches.   Snowfall at one location, by itself, tells a pretty incomplete story.

It tells an incomplete story because the period from 1 November to 12 March is also the warmest on record, with a mean temperature of 39.9˚F.  Only three previous periods come close: 1933/34 (39.6˚F), 1977/78 (39.5˚F), and 2014/15 (39.4ºF).

Source: NOAA Regional Climate Centers
So, this winter hasn't been snowfall free in the valley.  We've had just below average snowfall punctuated by periods of warmth, and this has enabled some oddball activities, such as mountain biking in early February on the shoreline trail.

In the mountains, SNOTEL data records only go back to 1979 to around 1990 for most stations in and around Utah.  Nevertheless, if we look at the current snowpack water equivalent, many sites in Utah are at their lowest levels on record for this date.  Nearly all sites, with the exception of a few on the north slope of the Uintas and in the far northern mountains, are in the lowest 25%.
Source: NWS
Thus, in the mountains, this has been a very poor snow year.  However, the causes of that poor snowpack vary with location, aspect, and elevation.  Let us focus initially on the influence of elevation by looking at SNOTEL observations from Ben Lomond Peak (7689 ft), a relatively sheltered mid-elevation site, and Ben Lomond Trail (5972 ft), a relatively sheltered low-elevation site.  This is one of the few places where SNOTEL stations are located at two sites along a fairly direct elevation transect, enabling one to highlight how the snow climate of a given winter varies with altitude.  

At Ben Lomond Peak, 17.4" of precipitation (liquid equivalent) has fallen since October 1st.  Remarkably, 82% of that precipitation is retained in the snowpack, which has a water equivalent of 14.3".  Thus, the warmth of this winter has had at most a small impact on the snowpack at this site.  The lack of snowpack here is due primarily to the lack of precipitation.  If one were to go to even higher elevation (e.g., Snowbird snotel at 9617 ft), nearly all of the precipitation since October 1 is still retained in the snowpack.

Source: NRCS
In contrast, at Ben Lomond Trail, 17.1" of precipitation (liquid equivalent) has fallen since October 1st, but only 27% of that precipitation is retained in the snowpack, which has a water equivalent of 4.6".  That is a remarkably low number.  On average, this site would retain about 70-75% of the precipitation since October 1st in the snowpack on March 13th.  

Source: NRCS
Thus, the low snowpack at Ben Lomond Trail is due to both a lack of precipitation and warmth.  The latter reduces snowpack water equivalent by causing a greater fraction of wintertime precipitation to fall as rain instead of snow and more frequent or severe snowpack ablation events.  Ablation is the loss of snow to melt and sublimation.  

Records at Ben Lomond Trail go back to 1981, enabling one to put this season into a nearly 40-year context.  As shown by the bottom green line below, during that period of record, this is the worst snow season.  Since early February, the site recorded its lowest snowpack water equivalents on record.  The next lowest season on March 13 is 2014/15.  Note the drop in snowpack water equivalent due to warmth in early February. 

Source: NWS
An important lesson from this analysis is that the vulnerability of snowfall and snowpack to warming in Utah is strongly dependent on elevation.  The lower elevations are far more vulnerable than the upper elevations.  On the other hand, because SNOTEL stations are located in relatively sheltered and typically shady location, we don't have a good handle on how things vary at a given elevation with aspect.  South aspects are likely more vulnerable to mid-season ablation events, but how much is unclear.  That vulnerability might also vary due to factors such as dust deposition onto the snow. Perhaps those in the snow hydrology business can comment.  

If I were to speculate further, here are a few expectations for what will happen in northern Utah as we move through the 21st century in a warming world:
  • Year-to-year variations in temperature and snowfall will still play an important role. In the near future, there will be some good snowfall years and some bad snowfall years, but eventually, global warming will have an increasingly caustic effect on our snow climate (it already is).  The dice are loading for warmer winters.  Low elevations are going to suffer the most.
  • As far as Utah ski resorts are concerned, Alta and Snowbird sit in the catbird seat.  They have altitude and aspect on their side.  Bad snow years at those altitudes are still driven primarily by low precipitation.  Snow that falls on their north facing slopes tends to stick around for most of the season.  They have some vulnerable areas (e.g., portions of Mineral Basin, areas around the High Traverse), but overall they have it good compared to everyone else.
  • The lower slopes of PCMR, Snowbasin, and Deer Valley are going to become increasingly dependent on man-made snow for operations, as evinced this season.  Technological upgrades will probably be needed to increase the likelihood of operations in the early and late seasons in the coming decades.  
  • Global warming will further amplify pressure for mid-winter recreation in the upper-elevation terrain around the Cottonwood Canyons.  One can see this already happening.  I have historically ski toured in other areas of the Wasatch and nearby ranges during busy weekends, but this has been very difficult this year.  There simply isn't the snow.  
Sadly, change is coming.  On the plus side, I don't think that this year is the new normal.   It represents what we can get in a warming world when natural variability favors a warm, dry period.  It does, however, provide an illustration of how vulnerability varies with location, elevation, and aspect over northern Utah.  

Monday, March 12, 2018

It Ain't over until It's Over

Don't be fooled by the balmy weather, the loss of valley snow, and the diminishing snowpack in the mountain valleys.  It is only March 12th.  There will be more powder skiing and perhaps even some tastes of winter in the valley.  Spring in the Intermountain West is typically a rollercoaster ride. 

Indeed, we're in for sum ups and downs this week.  Monday and Tuesday look mild, with the NWS forecast below showing highs Monday and Tuesday of 64˚F and 74˚F at the Salt Lake Airport. 

The weather then "gets interesting" on Wednesday in advance of a cold front that is currently forecast by the NAM to be over eastern Nevada by 3 PM MDT (2100 UTC) 14 March.  Thus, Wedensday right now looks breezy to windy with perhaps some showers around.  We may get a frontal passage Wednesday night if things hold together as presently advertised by the models.

What happens later in the week depends strongly on the structure and depth of the upper-level trough that is forecast to be located along the Pacific coast.  Most of the GEFS solutions below put us in large-scale southwesterly flow, but precipitation amounts for the mountains will be strongly dependent on small-scale details that are difficult to forecast at this stage. 

Keep an eye on forecasts this week and expect some uncertainty. 

Sunday, March 11, 2018

End of the Season for Some Nordic Tracks

Today is a sad day as both Mountain Dell and North Fork Park have closed for nordic skiing, presumably for the season.

I'd like to give a shout out today to everyone at The Utah Nordic Alliance (TUNA) and Ogden Nordic for their efforts this season.  Despite sparse snow and remarkable warmth, both tracks were open quite a bit thanks to a great deal of shoveling and careful grooming. 

Mountain Dell
North Fork Park

I grew up cross country skiing, but only this year did I start skate skiing, and it totally changed my perspective on the sport and gave me a whole new challenge in skiing.  Talk about suffering!  However, over the past couple of months, form and fitness have led to remarkable improvement.  I may be slow, but I'm not as slow as I was in December!

I also discovered that when the powder skiing is terrible, the skate skiing is often great.  Thus, skating helped me survive a less than desirable snow season. 

I'm still hoping to get out a few more times this season if the Park City area tracks can survive (tough call).  Or, if necessary, perhaps a road trip.

Friday, March 9, 2018

Sobering Kessler Peak Avalanche

Weatherwise, things are pretty ho-hum right now, so it's worth a look at the Kesspler Peak Avalanche that was triggered around noon yesterday.  Below is the video report from Trent Meisenheimer and Mark Staples of the Utah Avalanche Center.  A written accident report is available here.

Pretty sobering stuff and a strong reminder that there still are scary monsters living in the basement, as Bruce Tremper likes to say.  It is very fortunate that nobody was killed or injured on the Cardiff Fork summer road/trail, which is used frequently for exits from up-and-over tours or to access upper Cardiff Fork from Big Cottonwood.  

Wednesday, March 7, 2018

Skibbatical Plans

Innsbruck.  Host city of the 1964 and 1976 Winter Olympic Games.
The Wasatch Weather Weenies blog will be taking a road trip next winter and spring as I have received a Fulbright Award and will be serving as a Visiting Professor of Natural Sciences at the University of Innsbruck. 

What an opportunity.  Innsbruck sits in the heart of the Tyrol within where the Wipptal (Wipp Valley) meets the Inn Valley.  

Looking southward at Innsbruck and the Wipptal under "Foehn" conditions (warm southerly flow).  The Brenner Pass
to Italy is shrouded in cloud.
The University of Innsbruck has one of the strongest atmospheric sciences programs in Europe and its Institute of Atmospheric and Cryospheric Sciences is known worldwide.  When I think of Universities with a ideal settings for mountain meteorology and snow science, the University of Innsbruck immediately comes to mind. 

I will be developing and teaching a four-credit graduate level class tentatively called Cool-Season Precipitation: Fundamentals and Applications.  Although I will be able to draw on some material form my courses at the University of Utah, this is largely a new course for me, so I anticipate it won't be all fun and games.  I also hope to strengthen existing research partnerships and forge new collaborations with faculty and graduate students at the Institute.

We are planning to be in Innsbruck for 4-5 months, beginning in January of February, so there will be some skiing, sightseeing, mountain dining, and adult beverages.  I have skied in Austria once previously, but suggestions appreciated, especially for ski touring. 

As far as this blog is concerned, I suspect we'll do some reporting on European skiing and weather.  On the plus side for you, if the Steenburgh Effect is as robust as we all suspect, next year might not be so good in Austria, but it could be a banner year in Utah.  

Tuesday, March 6, 2018

Spring Fever Kicks in Today

Good for me, bad for you, the Steenburgh Effect is back.  Sponsors: Please send me a new hat!
Although temperatures will only be in the 40s in the valley, I think today is the type of day that should cause an outbreak of Spring Fever.  We've had a warm winter, but no matter what you do in January, the days are short and the sun angle low.  We're now into March and the days are noticeably longer and the sun is beginning to feel like a microwave.  Today dawns with clear skies and will be full of bright sun.  Spring fever is here. 

Ski conditions in the Wasatch on Sunday and Monday were outstanding.  My hand has healed up enough that I was finally able to get out and do some touring.  Note the froth at the mouth in the photo above (really just sunblock, but who knows, maybe I was drooling).  It was good to sample some of the Greatest Snow on Earth finally. 

Unfortunately for you, that means the Steenburgh Effect is back.  Best if you drop everything and ski today. 

Saturday, March 3, 2018

This Lazarus Storm Will Rise from the Dead

I know what you're thinking.  This was the storm that wasn't.  But don't let down your guard or give up hope.   Despite our skunking yesterday and last night, snow is still coming.

The analysis loop below shows what happened.  The surface-based front made it to Salt Lake City yesterday around 3 PM and the accompanying surface trough has lingered just to our south.  The precipitation, however, was less cooperative, providing a bit of snow for the northern Wasatch (1-3" according to the Utah Avalanche Center), but never really making it down to the central Wasatch or the Salt Lake Valley for reasons discussed in yesterday's post. 

Currently, the surface trough appears to be draped across the southern Salt Lake Valley, but is a bit amorphous.  Note the north winds near and around the airport and the south winds near and around Point of the Mountains. 

The Salt Lake Valley will likely see a return of southerly flow today as the surface trough shifts a bit northward.  More important, as the upper-level trough finally decides to swing eastward, the precip band gets its act together once again and like Lazarus rises from the dead.  Note in the NAM forecast below how the precipitation fills in and the upper-level 700-mb trough intensifies over Nevada.  As these features move eastward, we finally get some tonight and tomorrow, along with some post-frontal action late tomorrow and tomorrow night. 

That NAM run puts down 0.75" of water and 13" of snow at Alta-Collins by 9 AM tomorrow and 0.94" of water and 16" of snow by 11 PM tomorrow night.  For what it's worth, the SREF puts out 0.35 to 1.18 inches of water for the period.  The Euro 0.6". 

I know what you're thinking.  You're not going to get suckered into this again.  Fair enough.  The past 24 hours haven't been pleasant for my profession.  But I think you should be ready.  Unlike Friday and Friday night, when there was great uncertainty in the position of the front and frontal precipitation, we can be confident that the front and trough are going to come through tonight and tomorrow, so the issue here is just how productive those features will be.   In this case the odds favor a powder day tomorrow.  I'll go for 7-14" at Alta by 9 AM tomorrow morning.  And, while we're at it, some overnight snow for the valley's too.  As always, monitor official forecasts and expect a cluster tomorrow at the bottom of the canyons.