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.

Ice motion in the Great Lakes

GOES-16 "Red" Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (kn0ts) in red (click to play Animated GIF)

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (knots) in red (click to play Animated GIF | MP4 also available)

GOES-16 “Red” Visible (0.64 µm) images showed ice motion in the western Great Lakes (above) and the central/eastern Great Lakes (below) on 14 February 2018. A flow of southwesterly winds at the surface was helping to move the lake ice toward the northeast. With increasing winds and a return of warmer air, the ice coverage of Lake Superior, Lake Michigan and Lake Huron had decreased slightly from their seasonal peaks a few days earlier — while the ice coverage for Lake Erie remained neared its seasonal peak. The total ice coverage for the Great Lakes as a whole was 57.9% on this day.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (knots) in red (click to play Animated GIF | MP4 also available)

Closer views of southern Lake Michigan and southern Lake Huron are shown below. In Lake Huron, small ice floes can be seen breaking away from the land fast ice.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (knots) in red (click to play Animated GIF | MP4 also available)

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly plots of surface wind barbs in cyan and wind gusts (knots) in red (click to play Animated GIF | MP4 also available)

250-meter resolution Terra and Aqua MODIS True-color Red-Green-Blue (RGB) images from the MODIS Today site (below) provided more detailed views of the ice floes in southern Lake Michigan, southern Lake Huron and western Lake Erie. The Aqua satellite overpass was about 90 minutes later than that of Terra.

Terra and Aqua MODIS True-color RGB images of southern Lake Michigan [click to enlarge]

Terra and Aqua MODIS True-color RGB images of southern Lake Michigan [click to enlarge]

Terra and Aqua MODIS True-color RGB images of southern Lake Huron [click to enlarge]

Terra and Aqua MODIS True-color RGB images of southern Lake Huron [click to enlarge]

Terra and Aqua MODIS True-color RGB images of western Lake Erie [click to enlarge]

Terra and Aqua MODIS True-color RGB images of western Lake Erie [click to enlarge]

La Nina Snows Over the Pacific Northwest Followed by Very Cold Air

The atmosphere over the eastern Pacific is thoroughly locked into a La Nina-type pattern, with the snowpack being refreshed for NW skiers and those concerned about the water supply next summer.

The snow water equivalent (the amount of water in the snowpack if melted) is in decent shape (see below), being above normal for the northern and far eastern portions of Washington State, but slipping to about 3/4 normal for the southwestern Cascades.

There was some improvement last night, when 8 inches to a foot of new snow  over the Cascades due to an upper level trough moving southward along the eastern flank of a big ridge over the northeastern Pacific (see below).


As I have noted in earlier blogs, a ridge in the eastern with cool northerly/northwesterly flow moving over the Northwest is typical of mature La Nina events. That sets up the cool temperatures, while the upper level trough moving southward provides the precipitation.

But to get lowland snow one needs to get an upper trough of just the right amplitude and position, which doesn't happen often.  Too far inland, and the cool air and precipitation are too far east.  Too far offshore, we are cold and dry.

Another, more vigorous, trough will approach on Saturday (see below), resulting in another snowy period in the mountains.


The 48h total snowfall ending 4 PM Saturday is enough to make a skier smile, with over two feet at high elevations in the Cascades and a relatively low snow level on Saturday (Snoqualmie Pass the eastern Cascade slopes will get plenty).


Another trough comes through on Sunday morning (see below), with most of the action slipping southward into Oregon, which really needs the snow.


The 48h snowfall total ending


But what really got my attempt was the very cold air predicted to move into our region early next week.  The coldest air in a very long time.  Here is the UW WRF model surface (2-m) air temperature forecasts for 4 AM Monday and Tuesday.

WOW.   East of the Cascades many locations will get below 0F, some locations will be way below.  Twenties near the water and teens elsewhere in western WA.



You might think about protecting your exposed water pipes.

Temporary transition from Himawari-8 to Himawari-9

Himawari-8 and Himawari-9

Himawari-8 and Himawari-9 “Clean” Infrared Window (10.4 µm) images [click to play Animated GIF | MP4 also available]

Himawari-9 temporarily took over for Himawari-8 beginning at 0250 UTC on 13 February 2018, as Himawari-8 underwent a 2-day scheduled maintenance. “Clean” Infrared Window (10.3 µm) images of Category 4 Cyclone Gita in the South Pacific Ocean during the satellite transition is shown above.

Himawari-9 was launched on 02 November 2016.

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.  

Cyclone Gita in the South Pacific Ocean

Himawari-8

Himawari-8 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.4 µm, bottom) images, with hourly plots of surface reports [click to play Animated GIF | MP4 also available]

Himawari-8 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.4 µm) images (above) showed Cyclone Gita as it moved toward Tonga in the South Pacific Ocean during 11 February – 12 February 2018. The tropical cyclone reached Category 4 intensity (ADT | SATCON) near the end of the animation period.

A longer animation of Himawari-8 Infrared images (below) revealed that the center of Gita moved just south of the main island of Tongatapu. Surface observations from Fua’Amotu (NFTF) ended after 0735 UTC.

Himawari-8

Himawari-8 “Clean” Infrared Window (10.4 µm) images, with hourly surface plots [click to play Animated GIF | MP4 also available]

MIMIC-TC morphed microwave imagery (below) showed that Gita underwent an eyewall replacement cycle after moving to the southwest of Tongatapu — a small eyewall was replaced by a larger eyewall, which was very apparent in DMSP SSMIS Microwave (85 GHz) images at 1533 and 1749 UTC.

MIMIC-TC morphed microwave imagery

MIMIC-TC morphed microwave imagery

Metop ASCAT scatterometer surface winds (below) showed Gita around the time that the storm center was just south of Tongatapu at 0850 UTC.

Metop ASCAT scatterometer surface winds [click to enlarge]

Metop ASCAT scatterometer surface winds [click to enlarge]

PyeongChang 2018: Cold, Wind, and Lessons for Salt Lake 2026/2030

You can always count on the Winter Olympics to serve up some good weather stories.  So far in PyeongChang, it's cold and wind.

Let's talk about the cold first.  The average temperature in PyeongChang during the Olympic Period is 22.1ºF, making its climate easily the coldest to host the Winter Olympics since Lilliehammer in 1994.  Note that the numbers below for sites other than PyeongChang are from Wikipedia and for the entire month of February.

PyeongChang 2018: -5.5ºC (22.1ºF)
Sochi 2014: 6.0ºC (42.8ºF)
Vancouver 2010: 5.5ºC (41.9ºF)
Turin 2006: 6.4ºC (43.5ºF)
Salt Lake City 2002: 3.6ºC (38.5ºF)
Nagano 1998: 0.0ºC (32.0ºF)
Lilliehammer 1994: -5.3ºC (22.5ºF)

Some of these sites have outdoor venues that are higher (and colder).  However, if you are a reporter returning to the host city each night, you are frequently experiencing a warmer climate.  There's no escape from the cold in PyeongChang.  Even in the Gangneung Coastal Cluster, near sea level, the average temperature is -0.5ºC, colder than all but Lilliehammer.

Thus, for people covering the games, even average temperatures are a big adjustment.  In addition, over the past two weeks, mean temperatures inferred from the maximum and minimum temperatures reported at Daegwallyeong in the Mountain cluster (the site used for the climatological PyeongChang discussed above temperature above) were below average except on Feb 9 and 10.
In addition, it has also been windy, resulting in low wind chills and affecting many of the outdoor competitions.  The Men's Downhill and Ladies Giant Slalom were postponed (I learned during my Olympic service that the word cancelled shall not be used under any circumstances) and watching events the past few days it was clear that wind was playing a role.

None of this is unexpected from a meteorological perspective.  The Korean Peninsula lies along the east coast of Asia, the largest continent.  During winter, dominant high pressure frequently drives cold, flow over the region.  The pre-Olympic Weather Report summarizing the climate of the region, issued in April 2017 by the Pyeongchang Organizing Committee, provides a summary of the main weather patterns that may affect the Games schedule, and explicitly states that:
Cold and dry air flow from the northwest...is the most dominant weather pattern during the Olympic and Paralympic Periods. The Siberian High brings cold and dry weather to the Korean Peninsula. When the air mass games strength, high winds and low windchill temperatures are the most influential factors in particular during the Olympic Period.
Thus, nobody should be surprised by this weather.  Climate is what you expect, and weather is what you get.

Which brings us to Salt Lake City's likely bid for the 2026 or 2030 games.  Should those games be awarded, it would be a mistake to assume either that: (1) the weather in 2026 or 2030 will be similar to that in 2002, or (2) we will have above average temperatures because of global warming.

If you remember back to the 2002 Games, Mother Nature blew out the air pollution just prior to the start of the Olympics and for the most part during the Games, the weather was great.  In fact, Pat Bagley featured it in one of his cartoons.



However, what happens in 2026 or 2030 is going to be very dependent on the whims of the Mother Nature.  February in Salt Lake is a fickle month and a lot can happen that can affect transportation, athlete and spectator safety, logistics, and competitions.  Persistent inversions with fog and air pollution.  Downslope windstorms.  Arctic intrusions with extreme cold.  Heavy snowfall in valleys or mountains.  Strong winds in the valleys or mountains.  Lightning.

Climatologically, Salt Lake has a great climate for the Olympics, but that doesn't mean the weather will necessarily be easy on us if we host the Olympics again.

The Strange Case of the Quinault Blow Down: The Ultimate Solution

It is time to put the facts together and to explain the mystery.   Using high-resolution modeling, theory, studies in other locations, and available observations, we will attempt to solve the compelling scientific puzzle of the massive fall of old-growth and other trees on the north side of Lake Quinault during the early morning of January 27th.

Sherlock Holmes made use of a 7% solution of a certain drug to prepare for such cases.   I will make use of more appropriate drug to heighten my mental prowess, one used by many scientists in our region:   a tall Starbucks coffee.


Science is great fun, particularly for a difficult case like this.   Using limited observations and knowledge of basic physical principles, we attempt to explain natural phenomenon.     The enjoyment of an intellectual puzzle and a detective story.

And when the pieces come together, and when we gain an understanding of something that no one has understood before, the feeling is one of satisfaction and even elation.   A feeling that once experienced, becomes addictive.    A reason why many of us love being scientists.

So as Sherlock would say: "the game is on".  And I will describe my chain of logic, starting with known facts and then examining each possibility until we determine the most probable cause.

Let's review the facts

1.  A large tree fall occurred on the north side of Lake Quinault around 1:30 AM on January 27th. Many of the trees were old-growth, or at least, very large.

2.  The tree fall area was quite limited in size:  perhaps a half-mile on a side and extending from the lake toward the crest of about 2500 ft. 

3.  Several of the trees snapped off and this can only be explained by very strong winds (certainly at least 60-70 mph).

4.  The trees fell to the south and thus the winds must have been from the north.

5.  None of the limited surface observation locations in the area reported any winds even close to those needed to topple the trees.  For example, a site just across the Lake only reported light winds during the tree fall.

5.  The strong winds could NOT have been the result of microburst associated with a thunderstorm or strong convection.   Weather radar showed no such feature and the lightning detection network had no strikes in the region.

6.  An occluded front was approaching the coast at the time of big winds and tree fall.

The first question you should ask was whether the approaching weather system had strong northerly (from the north) winds associated with it.  Or even northerly winds at all.

We know that the surface winds with system did not have strong northerly winds  from the surface weather stations of the region.  But if there were northerly winds aloft, there would be the possibility of a downslope windstorm, as northerly winds accelerated down the slope north of the Lake.

Fortunately, there are sufficient observations to answer this question.  NOAA Earth Systems Research Lab (ESRL) maintains a device called a radar-wind profiler at Forks, Washington  (up the coast a bit) that is capable of determining the wind and temperatures aloft in real-time.  Here are the wind observations for 0000 UTC 27 January through 0000 UTC 29 January from the surface to 9 km above the surface.  Winds are shown by the typical wind barbs and are color coded .  The incident in question occurred at approximately 0930 UTC 27 January.  A blow up at the critical time is shown below as well.  Note that the front came in from the west and hit Forks before Lake Quinault.

The Bottom Line:  No hint of northerly flow during the period in question.  There were southeasterly winds at low levels, with increasing southerly and southwesterly winds aloft.

But we have another observing asset as well:  the Langley Hill radar near Hoquiam.  This radar is a Doppler radar and provides wind information aloft.  Specifically, it provides the radial wind component--the speed of precipitation (and the air it is in) towards or away from the radar.

Here is the Langley Hill radial velocities from the lowest scanning angle at 0927 UTC.  Green and blue indicate flow towards the radar, yellow/red/orange the opposite.  Not easy to read without experience.   But to my practiced eye, the radar suggests southeasterly winds of up to around 30 knots at low levels, turning to southerly and then southwesterly aloft.    Consistent with the profiler.  No northerlies

So if the air coming in off the Pacific was from the southeast east or south, where did the powerful northerlies come from?  Perhaps the comments pushing a secret government project,  aliens, or a meteorite strike were on to something.

Or perhaps not.  There is no evidence of any space object reaching the earth in this region (I checked).  And there IS a possible meteorological explanation:  a rotor circulation associated with a strong mountain lee wave.

But first some atmospheric rotor 101.  If fairly strong winds are approaching a mountain crest, they can undergo wavelike undulations in the lee of the barrier.  A situation in which air surges down the mountain and then suddenly rises up, followed by potentially more down and up motions.  If the wave has sufficient amplitude, a rotor can form underneath the wave, with flow moving in the opposite direction from the flow approaching the mountains.  You see why this is interesting...here is a way to get northerly flow when the general flow is southerly.


Mountain lee waves can increase in amplitude as the winds approaching the mountain strengthen.  But they can also amplify if there is a stable layer near the mountain crest, or if there is what is called a critical level above the crest level.  A stable layer is one where air temperature does not cool rapidly with height, and a critical level occurs when the wind component perpendicular to the mountain reverses direction.  These features help trap and amplify the low-level wave energy, producing stronger waves and stronger rotors.

But it is even better than this.  A large rotor can in turn break down into highly intense subrotors that can have strong winds associated with them.  Two colleagues of mine, James Doyle of the Navy Research Lab of Monterey and Dale Durran, a fellow faculty member at the UW, did a very nice paper showing the results of an ultra high-resolution simulation of these critters.  Here is a vertical cross section across the lee slopes mountain that shows the rotor and subrotors (indicated by the red colors).
And there have several observational studies of rotors, including the T-REX (the Terrain-Induced Rotor Experiment) project and intense studies near the Hong Kong Airport.

Could these conditions have occurred during the early morning hours of January 27th?  I think the answer could be yes.

As the offshore front approached, the wind approaching the crest to the south of the lake increased (see topographic map, which indicates the key terrain features and the direction of the flow).


During the period in question, cooler air near the surface (in  the southeasterly flow) was surmounted by warmer air above.   This results in increasing stability above crest level.  And with southeasterlies at the surface and southwesterlies developing aloft, this led to the development of a critical level, where the flow reversed.   So all the factors supporting a strong mountain lee wave and potentially a rotor were in place.

But do any observations suggest such a development? 

The development of a strong wave would result in substantial sinking along the lee slopes of the terrain feature.  Sinking causes warming and pressure falls.  We happen to have a weather observation just to the north of the terrain slopes (located on the south side of Lake Quinault, see map).    Wow...there was a sharp pressure fall around 1:30 AM, just as the big blowdown occurred (see below).  Suggestive.


But we have a tool that Sherlock would be envious of:  high resolution numerical simulations.  Considering the small scale of the blow down, I suspect we would need to run our model (called WRF) with uber-fine resolution (grid spacing of around 100 meters).   The best the National Weather Service models do is around 4-km.  Our UW WRF is 1.3 km.    But for this case, UW graduate student Robert Conrick took WRF down to 444 meters and fellow student Nick Weber has produced some nice graphics.   

So let us see whether we can simulate this event...or at least determine whether we are on the right track.  I am going to show you a series of vertical cross sections, oriented SSE-NNW, that pass over the blowdown site.  Each cross section will have potential temperature (solid lines), wind vectors  in the cross section, wind speed (color shading) and vertical motion (blue for descent and red for ascent).

At 0400 UTC (8PM), you can see wave-like undulations in the temperature, modest downslope on the terrain and some weak northerlies over the blowdown area at low levels.

As 1240 AM (0840 UTC), the flow had strengthened greatly aloft and a rotor was obvious in the lower atmosphere over the valley.
 The rotor strengthens over the northern side of the Quinault Valley at 0850 UTC
And at 0915 UTC (1:15 AM 27 January), all hell breaks loose with huge amplification of the wave pattern, with stronger northerlies at low level, just as they did in reality.
The amplification at this resolution (444 m) was much greater than for the coarser grids (e.g., 1.3 km or 4 km), and I suspect amplification would be far greater if we ran the simulation at 100 m or less.

But we have seen enough, I believe.  The strong winds were not from UFOs, an angry Sasquatch, a microburst from convection, or some errant meteor.

An approaching front produced just the right conditions to produce a high amplitude mountain wave on the upstream ridge, which resulted in a strong rotor that produced powerful reverse flow (northerlies).   As in the research work cited above, a very energetic subrotor was probably produced, and that resulted in a localized area of intense winds as it rotated down to the ground.

Perhaps we will try going down to higher resolution, but I have substantial confidence that the puzzle is solved.  If I were Sherlock Holmes, I would take out my violin.   But my reward, other than the satisfaction of completing a large puzzle, will be to catch up on the Olympics...or to watch one of my favorite TV shows---Air Disasters--but don't tell anyone.

_______________________________


Announcement:  A very interesting free lecture open to the public

The history of cloud seeding to enhance precipitation, and prospects for the future.  Professor Bart Geerts, University of Wyoming


February 15th, Kane Hall, University of Washington Campus, 7:30 PM
For information and to register go here:

La Nina-Like Cool Period with Some Limited Lowland Snow

(Sherlock Holmes and the Olympic tree fall will return on Sunday---and the answer may be in hand!)

Relatively cool air is now over the Northwest and should in place over the weekend.  And a few folks over the lowlands might seem some flakes before the weekend is over.

With high pressure offshore, northerly winds have developed in the lower atmosphere, as seen in the time-height plot above Sea-Tac airport (below, red is temperature, heights in pressure--850 is about 5000 ft, time increasing to the left).  Over the last 24 h, temperature at 850 hPa (again about 5000 ft) has dropped from 3C to -4C.


The cool air will continue to spread southward today and, as shown in the plot below, will reach the Oregon border by 7 AM (1500 UTC) tomorrow morning.  Note that there is a large pressure change (gradient) in northern CA associated with the leading edge of the cool air.  This makes sense, since cooler air is more dense than warm air, thus a gradient in temperature produces a pressure gradient.


Expect frosty temperatures on Saturday AM with cold air aloft and clearing skies (which allows good radiational cooling to space).

On Sunday morning an upper level trough will approach our region, bringing clouds and some precipitation.  I would be talking about the potential for lowland snow, except the trough is going too far offshore and south of western Washington....not quite the right set up for Puget Sound.


The 24-h precipitation total ending 4 PM Sunday shows plenty of precipitation along the coast, but little over Puget Sound (due to rain shadowing from the Olympics and Mountains of Vancouver Island under NW flow).


The forecast snow total for the same period is disappointing.  Not much on the coast because it is too warm there and nothing over Puget Sound.  Only over far NW Washington and southern BC, will there be sufficiently low temps and enough moisture to get a dusting.  And not much good for the mountains.


During the past few days and this weekend, we have had an area of high pressure offshore, with lower pressure inland, similar to the typical La Nina pattern.  But only similar... strong La Nina's have the high pressure farther offshore.  Here is the typical 500 hPa (upper level) height anomalies (difference from normal heights) for La Nina years, with red indicating above normal heights (pressures), and blue/purple the opposite.

Compare that pattern with the forecast pattern for 4 AM Sunday (below).  Similar, but the features are displaced eastward.  And it looks like La Nina's days are numbered....the latest model forecasts show a transition to neutral (or La Nada) conditions by summer.


In any case, there should be lots of sun on Saturday.

(Again, the third and final blog on the Olympic Mountain mystery tree fall will be released on Sunday....)

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.