Wasatch Weather Weenies

The snow level is a critical variable for mountain weather forecasting, but it is both difficult to define and predict.   In fact, there isn't even an agreed upon definition of snow level amongst meteorologists or the public.  One might say it is the level above which precipitation is snow and below which precipitation is rain, but its just not that simple.  Precipitation doesn't just change from snow to rain at a given altitude.  Snow takes time to melt as it falls.  Different types of snow crystals melt faster than others.  Sometimes it is snowing but not accumulating on the ground due to melt.  What do you do when there is a mixture of snow and rain or drizzle?  Where do you put the snow level?  To begin, perhaps it is easier to begin with a description of the transition zone , the layer in which snow is warming, melting, and turning to rain as it falls.   The schematic below provides a simple conceptual model of the transit...

While researching the 1976/77 drought year, I came across the article below in the Salt Lake Tribune describing the benefits of "Snow Augmentation" at Sun Valley (click to enlarge).   Published in late December 1976 when Utah resorts were not operating due to a lack of snow, it describes initial use of artificial snowmaking at Sun Valley.  Today, Sun Valley probably has one of the best snowmaking systems in the world.  At that time, during the great snow drought of 1976/77, it enabled three runs to be open for the holidays.  As described in the article, " Ribbons of artificial snow from two to three feet deep have been shot by air compressor-activated snow guns up to two-thirds of the way up the mountain. "   It goes on describe the artificial snow as " cube like crystals " with " a bit more density than nature's snow ."  I'm sure that sounds familiar to today's skiers.  The system sounded pretty cutting edge for the time, pulling 140...

I never like to bad mouth Utah skiing but I think it is accurate to say that this is a truly abysmal start to the ski season right up there with many of the worst seasonal starts on record.   But is it the worst?   Currently on this Christmas Day there is little to no natural snow at low-to-mid elevations.  For example, the base of Park City is as bad as it gets right now from a natural snow perspective, although there is a white ribbon of death thanks to artificial snowmaking.    Source: https://www.parkcitymountain.com/the-mountain/mountain-conditions/mountain-cams.aspx. Screenshot from 1:20 PM MST 25 Dec 2025. Where we have data, there are now several SNOTELs in the Wasatch Range that are at their record low snowpack water equivalent for the date.  These SNOTELs are Ben Lomond Trail, Farmington Lower, Farmington, Hardscrabble, Parley's Summit, and Payson Ranger Station.  At Ben Lomond Peak (records back to the 1978/79 winter), the 4.5...

Source: Cowboy State Daily Merry Christmas to all from the Wasatch Weather Weenies.   Apparently most of you have been naughty not nice because Santa delivered quite the lump of coal for Christmas.  Warmth and high snow levels materialized as anticipated last night.  It was a real soaker even at 9600 feet where Alta-Collins picked up only an inch of snow from 1.01" of water indicating a good deal of rainfall during the period.   My memory is hazy this morning but I can't recall a mid-winter rain event of that magnitude at that elevation this time of year.  I do recall storms that started with a bit of rain or produced some with mist and rime due to a lack of ice nucleating particles in clouds, but a full inch of water with little snow at 9600 feet in December or January I suspect is pretty unusual.  That said, I'm working off memory here and leave it to you to dig into the data to see what you find.   Meanwhile, it's 8:00 AM and 55°F at ...

A warm storm is on tap for the Night Before Christmas, one that will not make Santa or his reindeer happy.    To illustrate this, let's take a look at the forecast from the High Resolution Rapid Refresh (HRRR) for Little Cottonwood Canyon (click to enlarge).  The HRRR calls for periods of precipitation overnight (green box below) adding up to 1.5" of snow water equivalent at Alta-Collins through 7 AM Christmas morning.   That's the good news.  The bad news is that the overnight period is remarkably warm, with the wet-bulb-zero level, the altitude where the wet-bulb temperature reaches 0ºC and roughly the top of the melting layer, reaching as high as 10,700 feet (the snow line is usually several hundred feet below the wet bulb-zero level).  Our algorithms suggest this period, highlighted with green shading above, may produce rain even at the 9600 foot altitude of Alta-Collins.   Snow during other periods at Alta-Collins adds up to 8.4" by 7 AM...

Wind and warmth continue to dominate the weather here in Mordor, with the fires of Mt. Doom casting their glow over the Wasatch this morning.   The average temperature since November 1 at the Salt Lake City International Airport of 46.3°F is a remarkable 2.4°F higher than any prior November 1 – December 21 period (note: the graph below includes data from the downtown weather bureau office prior to 1928).   For the first 3 weeks of December (i.e., December 1–21) the mean temperature (43.3°F) is also the highest on record, although the gap to #2 (42.6°F in 1889) is not as large.   Frodo and Samwise Gamgee continue to their quest to destroy the One Ring and break Sauron's evil grip on the weather of Utah, but remain well short of their goal.   Hopes for the cover of precipitation increase around 0000 UTC 25 December (5 PM MST Christmas Eve) as southerly flow and an atmospheric river penetrate inland into Utah in advance of the very persistent upper-l...

Based on last night's SNOTEL observations, Snowbird sits at 6" of water (record low for December 20th at that site is 4.4"), Brighton 3.9" (record low 3.2"), Mill D North 3.7" (record low 2.0"), Thaynes Canyon 4.4" (record low 2.9").   So, technically in the central Wasatch, we're not at record low levels, but we're also not far above those records and remain below a reasonable natural snowpack for proper skiing. But is there hope of a Christmas Miracle?   Through Christmas Eve day we'll continue to see warmth and some periods of low-to-mid elevation rain and mid-to-high elevation snow at times.  There's no "big" storm, but perhaps we can get add another 0.75–1.5" of water to the high elevation snowpack in Little Cottonwood from the bits and pieces through 5 PM MST on Christmas Eve.    But what about the night before Christmas and Christmas?  Is there hope for a Christmas Miracle? Well the GFS has a menacing tro...

I'm currently in Alaska and was planning on ignoring the blog for a few days, but I felt the need to address the news released yesterday that the National Center for Atmospheric Research (NCAR) would be dismantled .    At this point we know little except that NCAR is under threat based on a social media post by the Office of Management and Budget director Russel Voight stating that the National Science Foundation will be breaking up NCAR, reviewing its activities and "vital activities such as weather research will be moved to another entity or location."  Subsequently, the National Science Foundation (NSF) announced today the intent to restructure NCAR's activities including "options to transfer stewardship of the NCAR-Wyoming Supercomputer to an appropriate operator; divest of or transfer the two NSF aircraft that NCAR manages and operates; and redefine the scope of modeling and forecasting research and operations to concentrate on needs such as seasonal weathe...

If you want to build a persistent valley cold pool in northern Utah, often referred to colloquially as "an inversion," the best way to do it is to have a strong cold surge followed by the development of an upper-level ridge. The cold surge provides the cold air at low levels while the ridge then increases the temperatures aloft.  During the winter, there's insufficient heating from the sun to warm the cold air at low levels, so one ends up with a persistent valley cold pool that is topped by a stable layer or inversion that prevents the dispersion of air pollution. This process is even more effective if there is snow on the ground.   The past two weeks, however, provided something a little different.  On December 6 we had an atmospheric river move through the area (indicated by green below...note that the meteograms for temperature and wind do not quite line up vertically).  This was followed by a period with occasional mid and high clouds, somewhat enhanced sou...

A Great Storm in Utah is something we are all waiting for but is also an essay that John Muir wrote while visiting the Salt Lake Valley in 1877.  The essay was sent to me by a former student, Matt Jeglum, who knows how much I enjoy this sort of weather and nostalgia, and contained within Muir's book Wilderness Essays . In the essay, Muir describes a storm on May 19, 1877.  The date is very close to the peak time of year for strong cold fronts in northern Utah and he was impressed. "Utah has just been blessed with one of the grandest storms I have ever beheld this side of the Sierra.  The mountains are laden with frsh snow; wild streams are swelling and booming adown the cañons, and out in the valley of the Jordan a thousand rain-pools are gleaming in the sun."  But before describing the storm, he provides some great observations of Utah snow and weather.  First, he suggests a late start to the snow season with snow piling up in the spring. "In all the upper caño...

Source: AP Photo/Luciano Bisi It's easy to become cynical about sports these days, but there are some athletes who deliver performances that are truly uplifting and inspiring.   Lindey Vonn winning the World Cup in St. Moritz on Friday is one of the most remarkable and astonishing performances I can think of in skiing if not all of sports.   Before Friday, the oldest woman to ever win a World Cup race was Federica Brignone at the age of 34.  Brignone herself is a force of nature and one of my favorite skiers as she sends it with such passion (she is currently recovering from a major knee injury and I am hoping will return for the Olympics).  Vonn is 41. 41!   Most of you know her story.  She won in every discipline on the world cup and fell just short of what was then Ingemar Stenmark's record of 86 world cup winds with 82 when she retired.  She is unquestionably the greatest speed skier of all time.   She retired in 2019....

Sigh...what a start to December. First let's have a look at the northwest storm.  Some bit water totals so far.  For the 3-day period ending at 6 AM PST/1200 UTC today (11 December), more than 10" of liquid precipitation equivalent at many sites in the Washington Cascades including 14.2" at Paradise SNOTEL (agreeing well with the expectations from the previous post) and 18.6" at the Lynn Lake SNOTEL between Paradise and Snoqualmie Pass. Source: https://www.weather.gov/wrh/hazards Crystal Mountain is reporting this morning that WA-410 is closed between Enumclaw and Greenwater, essentially cutting them off given that WA-410 is also closed over Cayuse and Chinook Passes to the south.  Most of their web cams are down but sadly, even at 6800' at the top of the Green Valley Express where a cam is working, it looks like a net loss from this storm. Source: https://www.crystalmountainresort.com/the-mountain/mountain-report-and-webcams/webcams Could be worse.  Below ...

I've mentioned in prior posts that the storm track will be just to our north over the next several days.  Indeed, the Pacific Northwest is in for a deluge as they are raked by a series of storm systems.  Below is the Utah Snow Ensemble forecast for the 10-day period ending 0000 UTC 18 December.  Ensemble mean (upper right) liquid precipitation equivalents above 9" for most of the Cascades from Mt. Hood to Canada.   It's worth a look at the plume for Paradise Ranger Station on Mt. Rainier, one of the wetter locations in the Cascades.  The ENS mean is > 20" over the 10 day period with the GEFS mean > 15".  There is tight clustering over the first 5 days of the forecast with most ensemble members between about 12.5 and 17.5".  We see a lot of spread in the ensemble forecasts sometimes, but this is pretty tight clustering for a major events.   The ensemble grid point for Paradise is at 4942 ft, which is a bit lower than the actual rang...

The overnight Utah Snow Ensemble forecast for Alta-Collins may be the crazies I've ever seen.  Most of the European Ensemble (ENS) members are producing little to no precipitation over the next 10 days including during during the period from 10-11 December (more on those dates in a minute).  The wettest ENS member puts out about 0.8" of water and 11" of snow.   Some members of the American Ensemble (GEFS) have very different ideas.  There are 31 GEFS members and 10 of them put out more than 1.5" of water just through 00Z 12 December.  Several more put out between 1 and 1.5" of water.  There are some that track with the ENS (hard to see but they are there), but many GEFS members are much wetter. What gives? I don't plot or attempt to look at forecast plots like our four panel synoptic diagnostic for all 82 members of the Utah Snow Ensemble.  Nobody has time for that.  So I'm going to start here with the ECMWF HRES forecast that serves as the E...

Twenty-four hour totals at the Alta-Collins automated observing site added up to 1.79" of water and 15" of snow, yielding a mean water content of 12%.  Snowbasin-Boardwalk came in with 1.26"/8"/16%.  As evidence of the wet, windy, and rimey nature of the storm, I couldn't verify our 70 mph forecast for Mt. Baldy because the sensor rimed and is no longer spinning.  The Utah Avalanche Center report this morning says that "at 11,000 feet the wind is absolutely ripping, with sustained speeds at 50–60 mph with gusts pushing into the upper 70s."  That's good enough for me.   The Alta-Collins snowstake photo this morning is one of the most comical I've ever seen.  Dense snow apparently carved by wind?  Perhaps with the flow wrapping around the Alta sign?  Who knows.  Come up with your own explanation.   Snowfall at lower elevations is certainly lower and probably a soggy mess between 6000 and 7000 feet (or higher), but that's just a g...

In the previous post ( Windy Storm on Tap ) we discussed an approaching storm system that would come in today (Friday), but really pick up Friday night as strong flow and an inland penetrating atmospheric river move into northern Utah.  That forecast is still on track.  Overnight last night and today we are seeing the dribs and drabs at the leading edge of the storm system, as expected.  Overnight through 8 AM this morning Alta-Collins picked up about .16" of water and 2" of snow and Snowbasin-Boardwalk came in with 0.24" of water and 3" of snow.   But the big story is not today but tonight when the precipitation efficiency looks to increase as an upper-level trough moves through and high integrated vapor transport (IVT) noses into northern Utah.  The GFS forecast valid 0600 UTC 6 Dec (11 PM MDT Friday) shows heavy precipitation over the mountains of northern Utah (or better put what the GFS thinks is the mountains of northern Utah) as the trough (dashed li...

Batten down the hatches because we have storm that might have everything but the kitchen sink in it for the Wasatch Range. Right now Thursday looks dry, but the leading edge of the storm looks to move in on Friday with some mountain snow, mainly in the northern Wasatch, but probably tickling the central Wasatch some too. Then Friday night things really start to get rolling.  The GFS forecast valid 0300 UTC 6 Dec (8 PM MST Friday) call for very strong flow (red ovals) to move over a low-amplitude ridge that is centered west of SoCal.  This leads to the inland penetration of an atmospheric river, as indicated by the filament of high integrated water vapor transport (IVT) that extends from southern Oregon to northern Utah (red arrow).   This general pattern persists until Sunday morning, although flow, IVT, and precipitation intensity weaken late Saturday (if forecasts hold).   The Utah Snow Ensemble forecast below focuses on the 24-hour period ending 0000 UTC...