Category Archives: Snow

Everybody Gets Some, Plus Tonight’s Lake-Effect Intricacies

Finally, a great storm.  All elevations, all locations.  Some cherry picked storm totals so far based on reports to the NWS (time of measurement in parentheses):

Smithfield, Cache Valley (4 PM Sun): 12"
Ogden (5 PM Sun): 2"
West Valley City (6 AM Mon): 5.2"
Salt Lake Airport (5 AM Mon): 3.6"
Cedar Hills, Utah County (5 AM Mon): 9"
Powder Mountain (5 AM Mon): 12"
Brighton Crest (5 AM Mon): 16"
Alta-Collins (3 AM Mon): 14"
Spruces (4 AM Mon): 10"

Through 8 AM, Alta Collins is up to 18", blowing my 7-14" expected through 9 AM out of the water. 

With the KMTX radar up-and-down overnight (and currently down), getting a good handle on the action is more difficult than usual.  One thing that caught my attention is described in the tweet below, issued last night.  From 8-10, Alta-Collins recorded 6" of snow (3"/hr mean rate) and I saw some tweets of impressive accumulations near Alpine as well.  During this period, a very pronounced band extended across northern Utah County and far northwest Wasatch County, and stronger radar reflectivities also lingered over the upper Cottonwoods. 

One option when KMTX is down is to examine data from the Terminal Doppler Weather Radar (TDWR) operated near the east shore of the Great Salt Lake west of Farmington.  The primary purpose of this radar is to detect hazardous weather and wind shear over the airport.  It is blocked significantly by the surrounding topography, and provide little to know information about what is happening over the Wasatch and the broader region.  You can see, however, returns related to snow showers over portions of the Salt Lake Valley. 



Periods of snow look to continue today and tonight in the mountains and also in the valley.  The latest NAM forecast shows us transitioning into deeper northwesterly flow during the day today, with the flow transitioning to westerly overnight.


The situation for tonight is really interesting.  The latest forecasts show a pocket of remarkably cold air moving over northern Utah, with the latest NAM forcasting -22ºC over the Great Salt Lake at 1200 UTC.


In fact, the absolute minimum is an astounding -22.9ºC at 1500 UTC (8 AM).  That is a remarkably low 700-mb temperature.  It would not be a record for February (-25.9ºC is the all-time low), but we don't see too many days around here with temperatures that cold.

The Great Salt Lake is actually not that warm compared to climatology, but still, the average lake-surface temperature is almost 4ºC. 


As a result, the HRRR is fairly excited about a possible lake-effect event tonight.


Our statistical forecast system, based on the 6Z NAM, shows elevated lake-effect probabilities ovrenight tonight, peaking at 90% at 2 AM.   Note how the affected area shifts from the Cottonwoods to the northern Wasatch with the flow shift overnight. 


There are, however, three important issues to keep in mind.  The first is that wind directions beneath these upper-level troughs are tricky to forecast, so one can't count on that forecast precisely. 

The second is that we tend to fixate on lake effect, when we need to keep in mind that we could see post-frontal snow showers generated by other processes.

Finally, the third is the cold.  This is a remarkably cold airmass.  Temperatures at crest level are going to be so cold that instead of favoring dendrites, they will favor higher density crystals.  I've seen situations where this has put a damper on snow amounts in the past.  There aren't a lot of days at Alta that are this cold, but if you look at the snow-to-liquid ratios when the 650-hPa temperature is below -20ºC, there is a tendency for lower values. 


I'm thinking another 3-6" in the upper Cottonwoods through 6 PM this afternoon.  After that, I'm happy to sit in my ivory tower and watch this one play out.  Hopefully the radar will come up. 

Six Questions to Answer When Forecasting

Exciting weather is happening and on the way, so it seems fitting to organize this post around the six questions to answer when forecasting

1. What has happened?

This "winter" has thus far been like 3.5 consecutive Novembers rather than a typical November, December, January, and February sequence.  The average temperature at the Salt Lake City International Airport for 1 December - 17 February was 37.8ºF.  That's just a shade lower than the November mean of about 40ºF.  As everyone knows, we're well below average for snowfall and snowpack, especially in the lowlands.  The photo below was taken this morning looking up City Creek Canyon and indeed it looks more like a scene you might see after a November snowstorm than one would expect in mid February. 

 
This context is important as I suspect most people are entirely unprepared for what is coming.  It will probably seem like the first storm of the year.

2. Why has it happened?

This is a good question and one that I can't answer satisfactorily.  The easy answer is that the warmth and snow drought reflects persistent high pressure and a storm track that has remained predominantly north of northern Utah.  Why that has been the case remains a subject of debate.

3. What is happening?

Wow, what a windy night.  Strong south winds at all elevations.  In the past six hours (ending at 9:20 AM MST), several sites in the northern Wasatch and Bear River Range have gusted over 70 mph and ridgelines in the central Wasatch have seen gusts as high as 71 mph.  I can find many sites in the mid elevations reporting gusts over 50 mph.  Sherwood Hills (5658 ft) near Sardine Canyon guested to 64 mph.   If there was much powder left over from yesterday's feast, I suspect it's been blown to Jackson Hole.  Peak gust at the Salt Lake Airport so far is 43 mph.

With these strong winds, we are seeing some dust.  Concentrations were especially high in the western Salt Lake Valley, which I suspect is due to emissions from the area west of Utah Lake as we have seen in recent events



4. Why is it happening?

The answer here is an approaching frontal trough that at 1500 UTC (0800 MST) was sagging southward into northern Utah.  This has created a strong pressure gradient to its south, with strong gusts at all elevations. 


5. What will happen?
6. Why will it happen?

Loaded questions!  I'll answer them together as it is easier.  As I write this, the surface front just passed Hill Air Force Base.  The HRRR shows it progressing slowly southward today, with frontal passage in the northern Salt Lake Valley around 2000 UTC (1300 MST).  Thus, expect to see a wind shift early this afternoon, if not sooner in the valley. 

Periods of snow are likely in the northern Wastach today and will develop in the central Wasatch later this afternoon.  It's a bit of an oddball situation as the latest NAM shows the frontal band over far northern Utah through 2100 UTC, but then rather than bringing it through continuously, redevelops it to the south tonight. 



Tomorrow brings the post-frontal crapshoot beneath the upper-level trough where much depends on flow direction, moisture, and instability.  The NAM forecast below isn't too bullish on snow, but the 6 Z GFS is more enthusiastic and keeps us in wrap-around moisture (not shown). 


It's worth a look at the 12-km NAM-derived forecast for Alta.  Measureable precipitation begins around 5 PM and is strongest from about 6 PM to 11 PM with the frontal forcing.  Periods of snow continue through 6 PM tomorrow in the unstable post-frontal period.  Total water equivalent is 0.6" with 10" of snow by 9 AM tomorrow and 12" by 7 PM tomorrow. 


Take a peak also at the temperatures for Mt. Baldy.  Keep in mind these are for 11,000 feet, a bit above the lift-served terrain, but this provides some idea of how cold the airmass will be.  It goes sub zero by noon tomorrow and down to -8ºF by 9 AM Tuesday.  I don't think we've seen air this cold yet this year.

To summarize, this looks to be an all elevation storm and you should be prepared for winter conditions.  We haven't had a stress test like this in some time. Thankfully, it is the President's Day Holiday, which will hopefully help with tomorrow's commute.  For Alta-Collins, I lean toward 7-14" by 9 AM tomorrow.  I have a bit more heartburn for totals after that given the variability I'm seeing in the models.  Some snow is likely, but the range of possibilities is large.  Hug a ski patroller or avalanche forecaster when you see them.  They will have a tough job the next few days. 

Finally, this is a high-impact, rapidly evolving situation.  Keep an eye on official forecasts at http://www.weather.gov/slc/. 

Powder Fever, Real Winter, Olympic Dreams

Much to talk about today.  I'll split this post into two parts, Powder Fever/Real Winter and Olympic Dreams.

Powder Fever/Real Winter


Wow, what a morning.  Yesterday's storm blew away my expectations for both snowfall amount and water equivalent.  The Utah Avalanche Center reports 12-18" of new snow in the Cottonwoods and along the Park City Ridgeline.  This morning is bluebird.  It's hard to imagine a better ski day after all the pain and suffering of the winter to date.  I suspect many dawn patrollers were out this morning and that it will be powder panic in and around the Cottonwoods this morning.   In the backcountry, the buried weak layers still give me heartburn.  Check the avy report and don't let powder fever cloud your decision making.

The models have also been shifting to higher totals for the storm sometime late Sunday to Monday, as evinced by the downscaled NAEFS plume for Alta. 
Totals currently being spit out by the Euro and the NAM are a bit lower.  Let's see how it comes together and keep our fingers crossed. 

One thing is for sure.  It is going to feel like winter early next week.  REAL WINTER.  The current GFS is dropping 700-mb temperatures to -21ºC by 11 AM Tuesday morning.  My 20/20 rule tells me that anything above 20ºC or below -20ºC is exceptionally warm or cold, respectively, for these parts.  You wanted winter.  You're going to get it.

Olympic Dreams

For me, the Winter Olympics have kicked into high gear now that the alpine skiing events are underway.  The compressed schedule might not be what the athletes want, but as far as I'm concerned, it's great for me.  Having the two tech event runs bracketed around a speed event means skiing dominates the broadcast, which makes me happy, although NBC still managed to skip Wendy Holdener's first slalom run yesterday, which was the fastest in the field.  I bet Austrian TV is smart enough not to skip the run by the skier ranked 4th in World Cup slalom points.  The DVR has also proven it's worth as I've been recording cross-country overnight and getting up early to watch before heading into work.

The schedule for tonight and the weekend is enticing.  Super-G 7PM MST tonight, Women's 4x5 km relay 2:30 AM MST Saturday, Men's GS 6:15 PM MST Saturday, and Men's 4x10 km relay 11:15 PM Saturday.  Throw in some freestyle skiing, and there's much to look forward to.  The main weather concern for these events would be wind, which hasn't been as bad in recent days, but still has shown its ugly face at times.  Hopefully all will go off without weather having a significant impact.

A few comments on the cross country.  I had the good fortune of attending both the Men's 4x10 km and Women's 4x5 km  during the Nagano Games in 1998.  The Men's 4x10 km is the Superbowl of Nordic skiing and at the time, the Norwegian and Italian ski teams had an incredible rivalry, that is well documented in Bud Greenspan's excellent Olympic documentaries.  The Italians upset Norway on their home snow during the Lilliehammer 1994 Olympics, with Silvio Fauner nipping Bjorn Daelie, the greatest male cross-country skier of all time, at the line by 0.4 seconds. 

In Nagano, the Norwegians changed strategy, putting Bjorn Daelie in the second or third leg (I forget which).  Below, Daelie is chasing down a competitor from the Italian team.


Instead they put Thomas Alsgaard, a better sprinter, in the anchor leg and he was able to take the win for Norway at the line by 0.2 seconds.  What a race!

An equally exciting race followed in 2002 in Salt Lake, with Alsgaard once again sprinting to victory.

I think the Norwegian team this year is overwhelming, but these team sprints are often closer than expected and always worth watching. 

Which brings us to the women's 4x5 km relay.  In Nagano 20 years ago, the US team finished in 15th place, just ahead of last place Canada.  I attended the race with high mucky mucks from the US Ski Team and Salt Lake Olympic Committee, who talked at length about how to get better.  It was great to be a fly on the wall for that one. 

Fast forward to 2018 and the US women's team is one of the best in the world and Jessie Diggins has been knocking on the door for Olympic medals.   The US women have never had an Olympic cross country medal and the men haven't had one since 1976.  The 4x5 is in play, as well as the team sprint.  Let us hope that this is the year. 

Ah, the Blessed Steenburgh Effect

Sidelined with a broken bone in my hand this week, you reap the benefits.

Alta Collins has recorded 0.49" of water and 8" of snow through 7 am this morning (the 18" snow interval depth is spurious in the data below, so it's unclear if we may have ticked up or down from the 8" at 6 am).

While not a big storm it's pushing toward my arbitrary "deep powder" threshold of ten inches.  It's also pushing the upper end of predictions.

The radar imagery shows we'll add more to that total, especially in the next hour or two.


Nice to see it snowing in the lowlands as well.  Campus was covered in a thin blanket of white at sunrise this morning.


Make a few turns for me.

The Dribs and Drabs Will Continue Until Morale Improves


In times like these, one learns to appreciate the smaller dumps in life.  My usual definition of a deep-powder day is a 24-hour snowfall of at least 10 inches, but we've only had one of those at Alta since December 3rd!

On the other hand, recent dribs and drabs have certainly helped the skiing some, even as we continue to lose ground to climatology for snowfall amount and snowpack water equivalent.  The 6" of quick snow Saturday afternoon and 7.5" yesterday did create some smiles.  Maybe 6" is the new deep powder day.

You'll be hearing some talk of a pattern shift probably in the coming days, and indeed there are some changes afoot.  The GFS forecast valid 5 AM MST next Tuesday, for example, has a trough over the northwest U.S. and a ridge over the east, something we haven't seen a lot of this winter.



Similarly, the ECMWF model has a trough in the west (with some differing details) as do most (but not all) GEFS ensemble members.

Penn State E-wall
However, the overall pattern is one that remains high amplitude.  Note, for example, the strong ridging over the eastern Pacific and the north Atlantic in the GFS forecast above.  Given the characteristics of this flow pattern over the eastern Pacific and western North America, I'm still not enthused about this pattern opening up the spigot from now through the President's weekend.

Instead, dribs and drabs are likely.  As shown in the NAEFS plume below for Alta, the next round of dribs and drabs looks to be late Wednesday through Thursday AM.  After that, there's a break and then a great range in the timing of possible dribs and drabs Saturday night through Monday.  As usual, there's a couple of more excited ensemble members, so my usual line of keep expectations low and hope for the best applies. 

There is one non-scientific reason for you to be optimistic.  I took a surprisingly hard fall skate skiing on Saturday and learned yesterday that I fractured a bone in my hand.  They tell me I can continue to ski with a splint, but this is likely to slow me down a bit more than usual.  Thus, there may be a partial Steenburgh Effect that increases the likelihood of a deep powder day, although perhaps not as much as when I'm out of town.  This effect, if it exists, will only last 6 weeks, so be ready.  

Deep Dive: How Unusual Is Our Snowfall and Snowpack This Season?

Skate skiing on the "Greatest Snow on Earth" at the Utah Olympic Park late yesterday
left much to be desired.
Following up on the previous post, let's take a deep dive and see how unusual this year has been so far for snowfall and snowpack.

This is perhaps an even more challenging topic than temperature.  Measurements of snowfall and snowpack are spotty and continuous records going back to before 1990, when most SNOTEL stations were installed, are difficult to find.  In addition, snowpack is strongly influenced by changes in vegetation and human activity around observing sites, not to mention factors such as wind transport.  

For snowfall, our best option is the meticulous record kept by snow rangers and avalanche professionals at Alta Guard, which is being extended and maintained today by the UDOT Avalanche Safety Office in Little Cottonwood Canyon (big hat tip to them!).  Observations were collected at the Atwater study plot above the Town of Alta Municipal Offices through 1998, after which they have been collected at a site just west of Our Lady of the Snows.  These sites are about 400 or 500 meters apart.  

Snowfall at Alta Guard for the months of November through January (blue bars below) averages 249 inches, with significant variations from year to year.  Although a linear fit to this data shows no significant trend (blue dotted line) one can see some important variations on shorter time scales.  The late 50s and early 60s featured several poor snow years, whereas the 1980s and 1990s were generally fat, with Nov-Jan snowfall consistently above average.  Since 2000, we've seen an high frequency of seasons with below average Nov-Jan snowfall.  Similar trends are seen for liquid precipitation equivalent of snowfall (orange lines). 


The bars highlighted in red highlight Nov-Jan snowfalls that are below 170 inches, which is one standard deviation below the mean.  These represent especially poor starts to the snow season.  The worst on record is 1976/77, when only 81" was observed.  This season, 2017/18, 109" fell.  Not far behind are 1960/61 (116") and 1959/60 (121").  These are very close analogs for snowfall amount.  Five other seasons since 2000 fall into the poor start category, with 2002/03 being the next worse to this season with 128".

SNOTEL observations of snowpack are easy to access and provide daily data, but they start in the 1980s.  An unfortunate reality of my business is that the atmosphere exhibits a great deal of variability and 30-40 years provides a very short sample.  It's like rolling two dice a few times and hoping you get a good probability sample.

Another option is snow course observations, which are collected manually near the end of the month, using coring tubes, by the Natural Resources Conservation Service.

Observations at the end of January or early February were collected at a snow course site north of Parley's summit at an elevation of 7500 ft from 1952-2002.  Starting in 1979, a SNOTEL site was operated at a nearby, slightly higher location (7584 ft).  Data from these two sites is presented below.  One sees considerable variability, but curiously, there are ten seasons with lower snowpack water equivalent than the 6.8" observed this season on 1 February.  February 1977 is the big loser with only 2.8".  Also apparent is a paucity of "fat" late January/early February snowpacks since the late 1990s, consistent with the Alta snowfall record above.


Another option is the Mill D South snow course in Big Cottonwood Canyon (7400 ft).  Observations in late January and early February have been collected here since 1956, although a house built near the site in the early 2000s may influence measurements.

Here we also see considerable year-to-year variability in snowpack water equivalent.  Curiously, last season featured the highest value in the record, followed by this season's pathetic situation.  This season's late Jan/early February value of 5.3" is eclipsed only by 1977 (2.3") and 1981 (4.9").  Years only slightly better include 1961 (5.4"), 19060 (5.5"), 1963 (5.6"), 1992 (6.6"), 2003 (6.3"), 2007 (6.6"), and 2014 (6.8").


Finally, we have Brighton, where we can amalgamate observations from three sites, Silver Lake (with observations back to the 1930s!), Brighton Cabin (1961-present), and the Brighton SNOTEL (since 1986).  Again, significant variability from year to year.  Late January/Early February 1977 is still the big loser, with only 2.6" or 4.2" of water depending on measuring site.  Aforementioned years in the early 60s also look poor.  The Brighton SNOTEL (grey line) is prone to having lower values than the other sites, and this is quite apparent in low snow years.


Obviously, the picture one gets from this analysis is clear for some conclusions and muddy for others.  This reflects a number of factors, including the difficulty of snowfall and snowpack measurements, changes in site characteristics or sampling procedures, and the fact that snowfall and snowpack evolution feature tremendous spatial variability.

However, it is clear that if you are looking to crown the champion of crappy early (Nov-Jan) ski seasons, 1976/77 is the clear winner.  It is also clear that the 1980s and 1990s were very healthy for early season snow, and that the late 1950s and early 1960s, as well the first part of the 21st century, featured a high frequency of relatively poor early season snow and snowpack years.

Sorry kiddos, but your parents, shredding in the 80s and 90s, had it better than you.

Now for some words of caution.  Observations are often treated as "truth", but all observations have their errors and uncertainties.  I haven't dug deeply into these issues in this blog post.  Second, there is a difference between a trend and trend attribution.  Explaining why we have periods of poor or good early season snowfall is challenging.  Teasing out the influence of long-term global warming from climate variations in recent years is also challenging, as is possible contributions of dust-on-snow and other climate factors.  I am not tackling those issues here.  Finally, this analysis focuses on stations above 7000 ft.

In a future post, we may do an even deeper dive by examining what is happening at the end of the snow accumulation season.

Curious Comparisons with Previous Snow Drought Years

After several days of cloudy weather, the 6 or so inches of recently new snow combined with bluebird skies this morning will probably make for one of the nicer ski days in about a week and a half.  I wish I was skiing, but I'm not, so I thought I'd dig into the archives for some curious comparisons of this year with previous snow drought year.

I will focus on SNOTEL observations from Snowbird, because they are convenient, although they only go back to the 1990 water year (the water year begins on 1 October and is denoted by the calendar year in which it ends) and changes in the site characteristics, exposure to wind transport, and other factors means that this isn't a perfect comparison.  Nevertheless, we shall plow forward.

At this site, we currently have 12.1 inches of snowpack water equivalent.  There are actually three other water years at or below the unlucky 13-inch mark on this date: 1992 (12.4"), 1994 (12.0"), and 2007 (11.2"). 



Of those water years, 1992 (mustard colored line) took a dramatically different path to sub-13" infamy.  It featured significant storminess in late October and November, reaching 10.4" of water equivalent on 3 December, which represents a robust early season snowpack.  Then the spigot turned off.  December and January were also only 1.4ºF warmer than the 20th century average in the northern mountains, so unlike this year, snowpack losses at lower elevations and on southern aspects were probably more limited compared to this year (although this is admittedly speculative). 

The 2007 water year also featured more early season snow than this year and it tracked near or just below median through mid December, when the spigot turned off.  Temperatures in December and January were 0.3ºC cooler than the 20th century average, so despite this being a poor snow year to date, the healthier holiday snowpack and cooler temperatures would have yielded better skiing overall than this year. 

So, if you are looking for an analog since 1990, 1994 is it.  That season tracked very close to this one, and featured intermittent storms separated by dry periods (note the sawtooth like pattern for both season).  It also was 2.9ºF warmer than the 20th century average temperature in December and January.  The National Centers for Environmental Information hasn't published the temperature numbers for January yet (they usually come around the 10th of the month), but one difference is that this year is probably going to be quite a bit warmer than that. 

A curious thing about the 1994 water year is that on January 5–6, Alta set the state record for 24-hour snowfall with 55.5" of snow.  Although the graph above is for Snowbird, this event is clearly evident in the trace.  The water content of that snow, based on measurements at Alta, was 3.2", for a water content of 5.8%.  In addition, that year featured a major storm cycle from Feb 8-12 when the snowpack water equivalent increased from 12.5 to 19 inches.  Several day's later, an avalanche fatality occurred on Peak 10420 near Brighton, with the run now named Lane's Leap after the victim.  I mention this as a reminder that even if we do get a game-changing storm cycle in the next few weeks, we are still probably going to be dealing with persistent, tricky avalanche conditions in the backcountry. 

As we look forward to the future, the NAEFS forecast plume shows nothing significant happening through the weekend from a precip perspective.  Maybe a few snow showers.  After that, perhaps a trough will flirt with us, although spread right now ranges from practically nothing to about an inch of water. 

Really, only 5 runs produce more than 0.6" of water and a foot of snow.  Thus, such a dump might not be impossible, but it is a low probability outcome.  As I've said many times this season, keep expectations low and hope for the best.  

Brady or Belichick, Weather or Climate?

A few days ago, Bill Barnwell of ESPN asked the question, "Who contributed more to the Pats' dynasty, Tom Brady or Bill Belichick?"

That's a great question to ask for barroom conversation because it is impossible to answer unambiguously and thus invites vigorous argument and debate.  One can play games like how many Super Bowls would the Pats have one without Brady or without Belichick.  It could be that the answer in both cases would be zero and that Brady and Belichick together add up to greater than the sum of their contributions.  Such an interaction is called synergistic.

Although it is not a perfect analogy, I thought of similar issues related to trying to tease whether or not weather or climate contributed more to a particular weather event or season.  For example, many people have been asking me if this season's snow drought is caused by climate change, a question that I loathe to answer because it is so difficult to disentangle weather and climate given our warming world. 

In reality, weather and climate are highly coupled and quite synergistic.  Extreme events are often weather events (e.g., heat waves), but those events may be more frequent, prolonged, and/or severe due to climate change.  If I invoke the Brady or Belichick analogy, Brady throws the 4th quarter comeback touchdown pass (weather), but Belichick creates the system that makes such a play more common (climate).  Perhaps under a normal coach, Brady has 20 4th quarter comebacks, but under Belichick he has 42. 

Which brings us to this winter.  The lack of precipitation this winter is clearly related to a very anomalous upper-level flow pattern.   In addition, it has also been unusually warm.  At the Salt Lake City International Airport, the mean temperature for this December and January was the 5th highest on record. 

Source: NOAA Regional Climate Centers
So, if we wanted to simply take sides in a barroom argument based on this evidence, one could argue that yes, it's been dry and warm, but there have been droughts in the past and this years warmth is not unprecedented.  The 76/77 winter was worse, and there have been years in the past equally warm, so this could just be weather or natural climate variability.  One could also simply say this is due to persistent ridging, and thus is consistent with such variability.  On the other side would be someone who argues that global warming is affecting the jet stream and shifting global temperatures to make the likelihood of such warm weather more likely.  Hence, what we are seeing this year is a reflection of global warming.  

I don't find either of these arguments very compelling because weather and climate are so intrinsically coupled, much like Brady and Belichick.  This is also why I HATE being asked how climate change affects a weather event.  As a scientist, I am interested seeing in depth analysis of historical observations and numerical simulations to investigate this problem, which is known as extreme event attribution (see the climate.gov article Extreme Event Attribution: The Climate Versus Weather Blame Game for more information).  Such studies assess how the likelihood of an event has changed in a warmer world.  The approach is not without its warts.  A lack of historical data and limitations of models sometimes create some issues, but provides insights that are not possible if two climate scientists simply sit in a bar and take sides.  For example, we might not be able to say that this winter was caused by global warming, but instead how much more likely (or potentially less likely) this winter was given global warming.  

"Potentially less likely" might seem unlikely (did I just say that?), but much depends on the question you ask.  A warm winter like we have had is almost certainly more likely today than it was 100 years ago.  The dice are loaded as I like to say.  On the other hand, it could be that the lack of precipitation is less likely.  That might sound crazy, but most climate models run for the last IPCC assessment report increase the average wintertime precipitation over northern Utah.   Thus, what is meant by drought is important.  The answers one might get might depend on if one is examining precipitation amount or snowpack water equivalent.  They also depend on how far in the future that you look as the response sometimes requires more warming to become detectable.  

None of this is to suggest that the climate is not changing and that the ski industry will be just fine at the end of the 21st century.  Change is happening.  Weather variability will give us some good snow years in the future, and Utah's colder, higher altitude climate gives us more resiliency than other regions, but during the coming decades, we are going to see the emergence of a dramatically different snow climate.  

A Primer on Sea-Effect Snows of Japan

Utah may have the Greatest Snow on Earth, but Japan has the Greatest Snow Climate on Earth.  Nowhere in the world does it snow with such intensity, at such low latitudes, at such low elevations, with such prolific mountain snowfalls.

The driver of all this snowfall is the so-called Asian Winter Monsoon, which is characterized by a cold, northwesterly flow from Asia over the Sea of Japan.  This produces copious sea-effect snowfall that inundates northwest Honshu and Western Hokkaido Islands. 

Source: Secrets of the Greatest Snow on Earth
The snowfall accumulation is relatively punctuated, but incredibly intense.  Compare, for example, the average monthly snowfall at Kutchan, a Japanese Meteorological Agency observing site near the base of Hokkaido's Niseko resorts to that at Alta.  Alta features a broad peak from December through March (the minimum in February largely reflects the smaller number of days), whereas Kutchan features a pronounced maximum, exceeding 140 inches, in January.



The Japanese Meteorological Agency observing site at Sakayu Onsen, in the Hakkoda Mountains south of Aomori averages 181 inches of snow in the month of January and 695 inches a year and may be the snowiest regular observing site in the world.  This is why I say that there is no surer bet for deep powder skiing anywhere in the world than in the mountains near the western coasts of northern Honshu and Hokkaido Islands in January.

The Sea-Effect machine is currently raging in Japan and the satellite imagery is marvelous.  One can see the two primary modes of sea-effect snowbands in the modis imagery from yesterday.  The first are longitudinal mode bands (or "L-mode"), which are oriented roughly parallel to the low-level wind.  The second are transversal mode bands (or "T-mode"), which are oriented roughly perpendicular (or across) the low-level wind.  Upstream coastal geometry and coastal geometry often affect the initiation of the L-mode bands.   It is curious that both types can be observed simultaneously over the Sea of Japan for reasons that perhaps we will discuss sometime in the future.

As I often like to say when it comes to sea- and lake-effect precipitation, "there are a lot of critters in the woods."  L-mode and T-mode bands aren't the only sea-effect features observed during the winter monsoon.  There can be areas of larger-scale convergence, such as the Japan Sea Convergence Zone that affects Honshu and convergence zones that form downstream of the Sikhote-Alin Mountains of eastern Russia that affect Hokkaido.

What happens to these sea-effect snowstorms as they approach and interact with the coast and topography of Japan depends on a number of factors.  There are events that sometimes produce heavier snowfall in the coastal lowlands, for example, rather than in the mountains, which is more common.  In a classic study on ice crystals and sea-effect snowfall at Hokkaido University, Magono et al. (1966) referred to storms with heavier lowland snowfall as "Satoyuki" type and heavier mountain snowfall as "Yamayuki" type.  Their conceptual model for Satoyuki-type storms is below, and features a strong inversion layer near mountain top that likely prevents the flow from surmounting the barrier.
Source; Magono et al. (1966)
With support from the National Science Foundation, we have been working with researchers at the Snow and Ice Research Center in Nagaoka, which is part of Japan's National Research Institute for Earth Science and Disaster Resilience, as well as scientists at the University of Hokkaido, to better understand the processes affecting the distribution and intensity of snowfall along the Japanese coast and inland mountains.

We have one paper currently in review that examines the transformation of T-mode bands as they interact with the Shakotan Peninsula of Hokkaido Island, generating a region of more persistent and intense precipitation over the Ishikari Plain, which includes the city of Sapporo.

Source: Campbell et al. (in review)
We have also been using the Japanese radar network and space-borne cloud radars to examine sea-effect storms over the Sea of Japan and their interaction with Honshu, focusing on the area around Nagaoka.

I have had to good fortune to travel to Japan twice, the first for the 1998 Olympic Winter Games and the second to meet with scientists in Nagaoka.  I consider both trips to be career and personal highlights.  It is worth going over for more than just skiing.  Seeing how the Japanese deal with such prolific snowfall is quite interesting.  In Nagaoka, for example, much of the snow falls at temperatures at or just above 0ºC.  Warm water is sprayed on the roads to melt the snow, which then flows through the cities water system.  


Here's an example of another warm-water-based snow removal system at the Snow and Ice Research Center.


Then of course there is the skiing.  Japan is often described as deep, not steep, and indeed you can find plenty of low-angle powder skiing there.  However, there is also some incredible terrain for backcountry skiing.  A challenge is finding an opening with good weather and stable snow.  We were fortunate to get some on last year's trip.  Below one of my graduate students, Peter Veals, gets the goods in the backcountry of the Hida Mountains.


With big relief and a relatively poor start to the snow season that year, the exit of that tour involved a walk through bamboo forests, fueled by cold pot stickers.


What could be better?  

The More Things Change, The More They Stay The Same

"Pattern change" is currently on my list of banned words and phrases for good reason as it was being thrown around repeatedly for weeks despite the fact that nobody really knows what it means. 

As I've been watching the large-scale pattern for the last several weeks, there has certainly been variability.  Ridges and troughs have formed and dissipated.  There have been some major cyclogenesis events.  However, one thing has remained constant.  The large-scale pattern has been very high amplitude, meaning a wavy jet, especially from the Pacific Ocean to Europe. 

That situation looks to continue for the foreseeable future.  Below is the 10-day GFS forecast for the northern hemisphere dynamic tropopause.  The dynamic tropopause separates the troposphere, or the lower atmosphere in which we all live and reside, from the stratosphere and basically sits at jet-stream level.  Note in particular the high-amplitude, wavy nature of the pattern, with strong ridges and anticyclones (high-pressure systems) forming in several areas including over the Behring Sea and North Atlantic.  Basically, the large-scale flow is highly disrupted. 


This is essentially what we have seen now for weeks.  High amplitude patterns like this can be good for snow if you are in the right place (check out the Alps), but we haven't.  The tendency in Utah has been for us to be under the influence of high-amplitude ridging or just to the south of the storm track. 

So, the more things change, the more they stay the same.  We get the occasional storm, but a real storm cycle is hard to come by.  Unless the storm track shifts southward more than currently predicted, that looks to be the case over the next seven days.  Our best bet for snow, as indicated by the NAEFS forecast plume below is Thursday and maybe Thursday night, with maybe a bit here or there thereafter. 

The NAEFS plume above may even be a bit optimistic for Thursday and Thursday night as the water equivalents advertised by the NAM, GFS, and Euro fall in the low end.  Most members of our downscaled SREF are generating only .1 to .5 inches of water equivalent.  The optimistic Canadian model (CMCE members in the plot above) appears to be an outlier. 

As usual, keep expectations low and hope for the best.  A small storm will be appreciated, but recognize that I have yet to see the whites of the eyes of a real pattern change.  However, my crystal ball only sees out about 7 to 10 days.  Let's hope February is better.