Category Archives: Lake Effect

Storm Chasing Update

Prefrontal southerlies are cranking over the Salt Lake Valley, which is filled with dust as I write this just afternoon. 


We have a complicated day/night of storm chasing ahead of us.  The Doppler on Wheels is currently deployed near Daybreak where we hope that the skies are dusty enough to give us a nice picture of the cold-front penetration through the Salt Lake Valley.  We are also hoping that behind the front we will eventually get some precipitation for observing some of the interactions between the Oquirrhs and the Wasatch Range, as well as fine-scale precipitation structures in the central Wasatch. 

After this evening, we still haven't figured out what the heck we're gonna do.  The model are advertising the passage of a secondary trough during the late night hours.  At 1000 UTC (3 AM MST), the trough is pushing through the Bountiful area in the 1700 UTC initialized HRRR forecast. 


We may have some orographic snow showers and possibly some lake effect as well, but the devil is in the details.  Thus, we have some consternation about where to put the DOW.  It is a mobile platform, but we can do better science if we can operate in one area for an extended period.  We'll see what happens.  I've mentioned that this is a crapshoot enough already.

Some Truth about Lake Effect

Another day, another front, another gasp of lake effect.  Radar imagery this morning shows some lake-effect precipitation over the Salt Lake Valley and the central Wasatch.


Alta-Collins is now up to a storm total of 8 inches.  Some of that is from yesterday's and yesterday evening's non-lake-effect convection, but some of it is lake effect.  Might be some decent spring skiing up there today.

The fact we've had a couple of brief lake-effect episodes this month shouldn't be a surprise.  We are in the heart of the spring lake-effect season.  A curious aspect of lake effect produced by the Great Salt Lake is that it's not most common during the heart of the ski season, but instead during the shoulder seasons.  The primary peak in lake-effect frequency (and amount) is in November, and the secondary peak is in March and April (depending on if you are looking at amount or frequency).

Average number and amount of precipitation produced at Snowbird by Great Salt Lake events by month.  Source: Secrets of the Greatest Snow on Earth.
Fall events tend to last longer and produce more precipitation in November than March and April.  One reason for this is that the sun is much lower and the days shorter in November, which allows for stronger, more persistent land-breeze circulations at night and into the morning.  Such circulations play an important role in lake-effect initiation and maintenance during many events.  

The two seasons of lake effect produced by the Great Salt Lake is unusual compared to larger bodies of water.  For example, downstream of Lake Ontario, there is a single peak in December and January (note change in x-axis from above).  

Source: Veals and Steenburgh (2015)
This difference is closely related to lake depth.  The Great Salt Lake is a very shallow lake and warms rapidly in the spring, enabling a 2nd peak of lake effect.  In contrast, Lake Ontario is a deeper lake and exhibits a strong lag in lake temperature relative to the seasons.  As a result, lake-effect peters out as one gets into the late winter and spring.

The importance of lake-effect for skiing in Utah is massively overstated by many ski writers.  It represents only about 5% of the cool-season precipitation (on average) in the Cottonwoods.  It can, however, occasionally provide enough at the end of a storm to vastly improve the skiing.  I suspect that might be the case today.  Without the lake effect, we were clearly looking at a dust-on-crust event this morning with perhaps 4-6".  Putting 2-4" more on top of that surely will help the skiing a bit.

Lake Effect!

Desperate times call for desperate measures.  I took a look through the archives this morning and discovered that I've done only one post this entire cool season about lake effect.  Despite the phat upper-elevation snowpack, we simply haven't had much of it, despite what the marketers will tell you.

I don't want to get you too excited, but we have it this morning!  It's not much, but beggars can't be choosers.

The band showed up initially in next-generation GOES-16 imagery, which if you haven't seen it you should click over to College of DuPage for a looksee.  GOES-16 is a next generation geostationary satellite that provides unprecedented spatial and temporal resolution imagery.  The animations are amazing and the imagery is a game changer.  Below you can see the initial appearance of a narrow lake-effect cloud band at 1147 UTC (0547 MDT), which was eventually overspread by some colder, mid-level clouds by 1242 UTC (0647 MDT).

Source: GOES-16 infrared imagery at 1147 UTC (0547 MDT, top) and 1242 UTC (0647 MDT, bottom).  Source: College of DuPage
Here's a look at the band just after 1200 UTC (7 AM MDT) as I walked to the bus.  The perspective is toward the southwest, with the Great Salt Lake on the right.  Note the cumulus band at low levels and the wimpy snow showers further downstream.  It's unclear if the mid-level clouds might be providing an assist in the precipitation generation.


And of course, the radar, with image below for 1323 UTC (0723 MDT).  Not much there, but some of you in the western half of the valley are being blessed with the Greatest Snow on Earth.


Well boys and girls, that's all the excitement I can handle today.  Ski it if its white.

Kiss and Make Up with Mother Nature NOW!

Our first all elevation "winter storm" of the season is winding down.  Radar imagery from 1221–1512 UTC (0521–0812 MST) shows the last gasp of lake- and mountain enhanced showers decaying and moving downstream.


We had just enough to coat the grass around campus.  Up at Alta-Collins, there is a 5" snow total with 0.27" of water equivalent, clearly on the low end of the most likely range we discussed yesterday.  Maybe they will pick up a bit more, but these are pretty paltry numbers and nothing to get excited about.

I don't know what you people have done to irritate Mother Nature, but kiss and make up now.  This has been going on for 5 years now.  FIVE LONG YEARS.  I'm not getting any younger and I don't want this year to be a sixth.

Japow Dreaming

With Dave Hanscomb, Hakuba Valley, Japan, February 1998
For much of my life I have been studying lake-effect and orographic (i.e., mountain) snowfall in some way shape or form.  This includes scientific investigations as well as personal adventures involving face shots, chin ticklers, and bottomless powder.

I was first introduced to the incredible snow climate of Japan in 1998 when I visited the Hakuba Valley during the Nagano Winter Olympics.  I was there for only four days, however, and much of my time was spent conversing with meteorologists involved in weather support for the Games.  I had time for only a brief taste of Japanese powder skiing when the Men's Super-G was cancelled, allowing for a couple of hours of storm skiing at Happo Ono resort.  

Storm skiing, Happo Ono, February 1998.  Just me and a few security guards near the top of the Men's Super-G.
This winter I will finally be traveling back to Japan and hopefully getting another taste of Japow.  I plan to travel to Nagaoka to begin a collaboration with scientists at the Snow and Ice Research Center of Japan's National Research Institute for Earth Science and Disaster Prevention to better understand orographic enhancement of lake-effect precipitation through study of storms across a wide range of geographic and topographic environments.  

I am hoping to tack on a few days of skiing in the Hakuba, Myoko, and/or Tenjin areas.  If you can share any beta on tours or guides, add a comment or send me an e-mail directly (jim.steenburgh at gmail.com).  

Lake Effect Reflections

Last night we got a bit of love from the Great Salt Lake, with the storm evolution exhibiting a number of key characteristics of lake-effect systems.  My apologies for color aliasing problems, but I couldn't correct them in the time I had available.


The action started over Tooele County and the Oquirrh Mountains and then spread eastward to the Salt Lake Valley and Wasatch range.  There are two major flavors of lake effect generated by the Great Salt Lake, banded and non-banded and you can see both in the loop above.  The band is a weak one, but affects the Oquirrhs and the western Salt Lake Valley.  The non-banded precipitation is further east.  Note the disorganized nature of the echo cells over the eastern Salt Lake Valley and the Wasatch Range.

The Oquirrhs actually receive quite a bit of lake effect, as much as upper Little Cottonwood Canyon and, because they receive less precipitation from other storms, lake-effect contributes a greater fraction of their cool-season snowfall (about 8%).

Forecasts of lake effect are notoriously tricky.  Although we've improved a lot in anticipating when lake-effect is possible, specifics on location and amount remain very challenging.  We have a paper that just came out in which we simulated 13 past events over the Great Salt Lake using a next generation, high-resolution forecast model with 1.33 km grid spacing and found the model skill to be about the equivalent of what we find for summertime thunderstorms.  In addition, the model frequently produced intense lake-effect bands during situations when only non-banded lake-effect was observed.

We still have a lot of work to do in this area!

Lake Effect Reflections

Last night we got a bit of love from the Great Salt Lake, with the storm evolution exhibiting a number of key characteristics of lake-effect systems.  My apologies for color aliasing problems, but I couldn't correct them in the time I had available.


The action started over Tooele County and the Oquirrh Mountains and then spread eastward to the Salt Lake Valley and Wasatch range.  There are two major flavors of lake effect generated by the Great Salt Lake, banded and non-banded and you can see both in the loop above.  The band is a weak one, but affects the Oquirrhs and the western Salt Lake Valley.  The non-banded precipitation is further east.  Note the disorganized nature of the echo cells over the eastern Salt Lake Valley and the Wasatch Range.

The Oquirrhs actually receive quite a bit of lake effect, as much as upper Little Cottonwood Canyon and, because they receive less precipitation from other storms, lake-effect contributes a greater fraction of their cool-season snowfall (about 8%).

Forecasts of lake effect are notoriously tricky.  Although we've improved a lot in anticipating when lake-effect is possible, specifics on location and amount remain very challenging.  We have a paper that just came out in which we simulated 13 past events over the Great Salt Lake using a next generation, high-resolution forecast model with 1.33 km grid spacing and found the model skill to be about the equivalent of what we find for summertime thunderstorms.  In addition, the model frequently produced intense lake-effect bands during situations when only non-banded lake-effect was observed.

We still have a lot of work to do in this area!

The Great Salt Lake Is Jacked

The Great Salt Lake may be near its all-time record low elevation and area, but lake-surface temperatures right now are running quite high.  Because the Great Salt Lake is so shallow, lake-surface temperatures often reflect recent temperatures at the Salt Lake City airport and so far this month the average temperature at the airport is a whopping 61.2ºF (16.2ºC).  Consistent with this observation, satellite-derived lake-surface temperatures averaged for the past 2 days are generally above 14ºC, except in shallow areas along the coast, and average 15ºC for the lake as a whole.


It's very difficult to place these lake-surface temperatures in a long-term context.  The satellite record is fairly short, and most of the long-term observations are from Saltair a single location on the south coast.  Nevertheless, if we look at the lake-surface temperatures from Saltair for 1972–1988, we find that 15ºC is near or above the upper margins of the range for November 1 (data is bimonthly).
Source: Steenburgh et al. (2000)
So we can probably safely conclude that the Great Salt Lake is quite warm for this time of year.

Will that mean a big lake-effect storm?  It really depends on whether or not the atmosphere decides to cooperate.

Does Size Matter for Lake Effect?

It's a question I am asked repeatedly.  Does size matter for the Great Salt Lake effect?

The Great Salt Lake is a terminal lake, meaning that it has no outlet.  The only way for water to escape is by evaporation.  As a result, its size varies during the year, from year to year, and from decade to decade depending on the amount of freshwater inflow.

Landsat satellite images of the Great Salt Lake in August 1985 and September 2010.  Source: USGS Landsat Missions Gallery, "Great Salt Lake 1985–2010," US Department of Interior/USGS.
In the historical record, the Great Salt Lake at its historic high covered 2300 square miles, whereas at its historic low, it covered only 937 square miles.

Source: http://learn.genetics.utah.edu/content/gsl/physical_char/
We are currently near a historic low (see Is the Great Salt Lake Approaching a Record Low Stand?), so should we expect less lake effect this winter?

All else being equal the answer to that question might be yes.  If we could, for example, have an exact repeat of the weather of any given winter, but change the the size of the lake, I suspect we would see an increase in lake effect with increasing lake size.  This increase would probably be small, but it would be there nonetheless.  

However, the most important factor controlling the lake effect in any given winter is the meteorology.  If you get lots of cold troughs you get more frequent lake effect than in a winter dominated by warmer westerly or southwesterly flow storms.   

For example, the top graph below shows the number of lake-effect events per cool season.  There are large variations from year to year with as few as 3 in 2005 and as many as 20 in 2010.  These variations are produced not by changes in lake size, but meteorology.  This is shown in the bottom figure which shows the relationship between the number of events (bars), lake area (solid line with dots), number of trough days (solid line), and the number of days in which the lake-air temperature difference exceeded a minimum threshold for lake effect (dashed).   These are expressed as standardized anomalies.  Without getting into details, a large positive number indicates a greater than normal frequency and a large negative number indicates a smaller than normal frequency.  There is a stronger correlation between the frequency of lake effect and the number of trough days and days that meet the minimum temperature difference threshold than the lake area.  2008 and 2010 both produced a large number of lake effect events despite the fact that the lake was very low.  They were active lake-effect years because the meteorology was favorable for lake effect.  

Source: Alcott et al. (2012)
You'll note that I put frequency in italics above and there is a good reason for this.  Lake-effect events can be pretty short lived and wimpy, or they can be very large.  The graph below shows the amount of snow-water equivalent (SWE) produced during lake-effect periods at Snowbird during the 1998–2009 cool seasons.  Half of those periods produced less than 6 mm of water equivalent, which equates to about 3 inches of snow.  

Source: Yeager et al. (2013)
If we're talking lake-effect periods that really lay it down, we need to look at events that produce more than about 20 mm of SWE, which equates to about 10 inches of snow or more.  These events are pretty rare and average only about one event per year.  They are so rare and episodic that it is impossible to draw any meaningful relationships that we can use to anticipate whether or not we're going to get a big lake-effect event in any given winter.  The largest lake-effect event at Snowbird occurred during the 2001 Hundred Inch Storm when the lake was a bit below average size.

Of course, this analysis is based on historical variations of the lake with an emphasis on the lake effect in any given winter.  If the lake continues to shrink, we could go below a critical threshold where there is a dramatic drop off in lake effect even if the meteorology is favorable.  Further, if the lake remains very low for say a decade or two, that might have a small effect on the total snowfall during that entire period.  It is worth noting, however, that lake-effect periods contribute only about 5% of the total snowfall in the Cottonwoods, so it will be difficult to detect.  The shrinking of the Great Salt Lake is certainly a concern for many reasons, but in the long run, the direct impacts of global warming will have a greater impact on snowfall and snowpack in the Wasatch Range than a shrinking Great Salt Lake.  

Webinar on Lake Effect


The American Meteorological Society Committee on Mountain Meteorology hosts a webinar series exploring various topics in mountain weather research and forecasting.  Yesterday I had the opportunity to give a webinar on the influence of mountains on lake effect, which was followed by a discussion of operational issues by Paul Sisson of the National Weather Service Forecast office in Burlington Vermont.

I considered embedding the video here, but it's much better viewed in full format, which you can access by clicking here.

Access to the complete seminar series, which includes a number of topics that may be of interest to readers of this blog, is also available by clicking here.