Tuesday, May 24, 2022

Dismal Snow Situation in the Eastern Alps

 It's looking like this past season was especially dismal for seasonal snow in the eastern Alps and I suspect by the end of summer it will have been one for the glaciers as well, if it isn't already.  

The Zugspitze on the border of Germany and Austria is my bellwether as there's a very good web cam there and it is at an elevation where there once was a glacier, but no more.  

This year looks to be a double whammy due to a "meh" snow season and the damage being done by Saharan Dust that was deposited onto the snowpack a few weeks ago.  

Below is the view looking south from the Zugspitze yesterday.  The snow cover is already spotty and covered with the Saharan Dust, which increases the absorption of solar radiation and the snowmelt.  

Source: https://www.foto-webcam.eu/

Below are images taken on the same day or prior day back to 2016 (also from https://www.foto-webcam.eu/), showing the especially poor snow coverage this year. 






Only 2020 is close, but even then, the coverage was more extensive.

Below is a view from late September of last year. 

It will be interesting to see how things look this September.  I suspect this year will be a big mass lost year at glaciers in the eastern Alps and perhaps the central and western Alps as well.  

Sunday, May 22, 2022

Build the Trails, Part II

When I first moved to Salt Lake City in the 1990s, purpose-built mountain-biking trails didn't exist near town, with the exception of the pipeline trail in Mill Creek Canyon, which I'm not sure was truly designed for mountain biking.  There was no Avenues Bonneville Shoreline Trail (BST).  I used to ride the fire road above Terrace Hills Drive and then hike a bike to the top of the Avenues Twin Peaks.  One could descend via that route or down the Bobsled or the Agony Escalator.  

In 1998 a friend and I had been looking at topo maps and decided that we should ride to Rudys Flat above  Bountiful via ridge thats west and north of City Creek Canyon.  Looked "doable" on the map.  There was to TrailForks or other app to give us a trail report. 

We left after work.  We road up the Ensign fire road past the various comms towers, which beyond the first set of towers was as bad then as it is today.  Then we started working our way out the ridge.  Initially it was a pretty good double track, then a lousy double track, then a single track, then a heard path.  The ridge is pretty lumpy and the route went straight up and straight down everything.  The vertical added up.  It started getting dark.  Finally we saw the trail down North Canyon and beelined too it.  We then descended and road home in the dark via paved roads.  I was depleted.  

I swore I'd never do it again, but a few years later I did, this time better equipped with more reasonable expectations.

I always thought it would be a great place for some properly built trails.  Although not on the ridge, the BST from above is now nearly finished to North Canyon (I've read it's not quite to North Canyon yet, but if you have a more recent update, please comment).  I rode some of it yesterday and it offers up great views as it contours in and out of the scrub oak. 

Here and there, a dense carpet of vegetation covers the ground.

The trail is very well constructed and perhaps single track and a half rather than single track.  


It's fairly easy riding once there.  The route to it from Wild Rose has a steep section that requires some pushing, but it's not a biggie.  Perhaps a lower-angle option will eventually be constructed.  

We did ascend the old-school Eagle Crest trail to the ridge above City Creek to enjoy the views of the central Wasatch.  


This is an area I always thought could offer up some great biking and hiking and it is great to see more trails being built.  Really, the potential is enormous.  

It was also a sad reminder that while other communities are moving forward with trail construction and providing more opportunities for their residents, Salt Lake City continues the pause on trail construction in the Avenues Foothills.  Let's get that process going again.   The reality is that a new trail system will be better than what we have now.  

Wednesday, May 18, 2022

Build the Trails

It's prime season for biking and hiking in the Avenues foothills.  This year it seems especially lush and the vegetation is filling in nicely around the recently constructed trails.


There could be more trails available to hike and ride, but trail construction was halted in May of last year.  This was allegedly a "pause" that would last until that fall.  Then it was extended to this summer.  In April, the city council further extended the pause until at least spring 2023.  

My views align with those of Ashley Patterson's in her op/ed in yesterday's Salt Lake Tribune.  The Foothills Trail System Plan included three years of public input.  Those surprised by the construction successfully pushed the city to pause completion of the project.  Some legitimate concerns were raised and the trails community supports addressing these.  

On the other hand, we do not want to see trails construction stopped permanently or delayed significantly.  After the pause last year, consultants should have been hired to evaluate the trail construction plans, but that hasn't happened.  Instead, the can has been kicked down the road for another year.  

It is long past time for city council and Mayor Mendenhall to move this process forward.  Other communities along the Wasatch Front have built world-class multiuse trail systems.  We can too.  

For more information, see https://slctrailsalliance.org/

Tuesday, May 17, 2022

Cold Surge Coming

 There's a pretty good cold surge expected to push into northern Utah later this week.  By Friday afternoon, yesterday's high of 88˚F will be long forgotten.  

Below is the GFS forecast for 2100 UTC (3 PM MDT) Friday showing a short-wave trough moving through northern Utah with 700-mb (10,000 ft) temperatures near -8˚C.  

The GFS-derived Little Cottonwood forecast shows temperatures on Mt. Baldy dropping from 43˚F tomorrow afternoon to 13˚F Friday morning.  Your Friday morning dawn patrol will feature slide-for-life conditions in the Baldy Chutes.  

Right now, the system looks fairly dry.  The GFS produces only 0.13" of water equivalent with it on Friday at Alta.  There are a few members of NAEFS (11 out of 52) that produce more than 5" of snow at Alta Collins, but most are under 2".  


Unless a low-probability snowfall occurs, the best recreation options later this week and weekend are probably at lower elevations.

Monday, May 16, 2022

Dismal Water Numbers

Pretty good analysis of the mountain snowpack in the southwest relative to median this morning if you are into red.  If you are into a fat spring snowpack and a good runoff, not so much.  

Source: NRCS

There are a lot of SNOTEL stations that are at or near zero already in the region.  If you want to see how Mother Nature snatched defeat from the jaws of victory this water year, check out the numbers from the Kolob SNOTEL on Kanarra Mountain near Zion National Park in Southern Utah.  On January 1, the snowpack sat at 13.3 inches of water, or 180% of median for the day.  After that, flatline.  Absolutely nothing through February 21.   

Source: NRCS

Even after that dry spell, it was just a little below median, but the late winter and early spring storms didn't do the job, snowpack crested below median, and it was gone by May 6, about 2 weeks early.  

The best snowpack relative to median is in the mountains of northern Colorado.  For example, at the aptly named Never Summer SNOTEL in the Never Summer Range, the snowpack actually peaked just above median before the melt began in earnest.  The site sits right at median today, with 20.9 inches of water.  

Source: NRCS

That's actually not far behind the Snowbird SNOTEL which sits at 25.1 inches (not shown).

Another year of dismal runoff in the Colorado River Basin.

Thursday, May 12, 2022

Weather That's Good for Grass

Spring precipitation in northern Utah is often highly variable in space and time making generalizations difficult.  Below is the departure from average precipitation over the past 30 days (through 1200 UTC/0600 MDT this morning) over northern Utah and the surrounding regions.  The central Wasatch are running above average and The Salt Lake Valley near or slightly above average.  Other areas are drier, such as the Uinta Basin and West Desert south of Dugway.  


Has the past 30 days been wet or dry?  The answer to that question clearly depends on location, location, location.  

By and large, the Salt Lake Valley, however, has seen near average precipitation and weather that's "good for grass."  

For soils and plants, precipitation amount can be important, but also frequency.  If most of the precipitation we received fell in a big storm in mid April, we'd be seeing lots of brown lawns by now.  Instead, we've had fairly regular precipitation.  Over the past 30 days, the University of Utah has received almost 2.8 inches of precipitation (blue line below, scale on right).  This has been produced by several storm systems with the longest dry period about 8 days.  


Additionally, there were three well-separated wet periods around April 22-23, May 1-4, and last night.  Each of these provided a decent soaking.  Temperatures have also been near average.  If you live in the Salt Lake Valley, chances are you still don't need to run your sprinklers.  

It does appear, however, that we will see the highest temperatures of the year so far on Sunday.  I think we've hit 79 three times so far this year at the Salt Lake City Airport, twice in March and once in May.  Sundays high temperature forecast is 82.  We'll need another good soaking storm after that to extend the "good for grass" weather deep into next week.  

Tuesday, May 10, 2022

A Cool, Dusty Spring?

A lot of people have commented to me that it has seemed lie a cool spring, however, the numbers tell another story.  

At the Salt Lake City International Airport, the average temperature from April 1 to May 9 was 51.9˚F.  This is a bit cooler than we have seen since 2013, but tied for 58 out of 148 comparable periods since 1875.  

Source: NOAA Regional Climate Centers

That's not unusually warm, but it is above the median for the entire period of record.  

We have had a few upper-elevation snowfall events, but these haven't been able to counter melt losses except in the highest elevations.  Basin wide, the Jordan shows a sawtooth-like decline since late March with water equivalent increases during snowy periods interspersed with declines during intervening dry periods.  The basin-wide average now sits at 5.2 inches, or 63% of median for the date.  

Source: NRCS

Still, the episodic snowfall events have enabled some good upper-elevation skiing.  I suspect yesterday morning was a lot of fun if you got out.  

Meanwhile, we've seen several wind-blown dust events.  PM2.5 observations from the University of Utah over the past 30 days show several extended periods of slightly elevated PM2.5 (say 2.5 to 7.5 ug/m3) and then briefer but dirtier spikes to higher values associated with the passage of fronts or other boundaries.  


Has this year been exceptional from a dust perspective?  I don't know the answer to that.  Dust storms are not unusual in our region during the spring.  I've written about them since the inception of this blog (see https://wasatchweatherweenies.blogspot.com/search/label/Dust), including events much stronger than anything we have seen this year (e.g., Postfrontal Dustpocalypse and Black Tuesday Becomes White Wednesday).  

Dust storms exhibit a great deal of year-to-year variability due to meteorology and land-surface conditions.  The bed of the shrinking Great Salt Lake is an emerging dust source, but there are many sources in the Great Basin, some of which have waxed and waned over the years.  For a while, the Milford Flat Fire scar was a big producer, but that seems to not be the case anymore. Agricultural fields west of Utah Lake were big producers a few years ago, but don't seem to have been exceptionally active this year.  Some of the dust we've been seeing this year in northwesterly flow has originated over northern Nevada, so it's not all from the Great Salt Lake.  

It will take someone smarter than me to place this spring into a long-term context and perhaps try to identify key sources.  My anecdotal view is that we've seen more low-intensity dust events this year than in the past several years, but the high-intensity events haven't been as intense.  That's an anecdotal perspective, however, subject to change with additional information.  

Tuesday, May 3, 2022

Last-Night's Blow

A strong outflow boundary initiated by a precipitation system near the Utah–Nevada border produced strong winds across northern Utah last night.  Peak gusts at lowland locations included 70 mph in Dugway Proving Ground, 67 mph at the Salt Lake City International Airport,  and gusts above 60 mph at several sites near and around the Great Salt Lake.  

Outflow boundaries, also referred to as gust fronts, form from cooling within dry air beneath a thunderstorm or precipitation system.  This results in a downdraft that spreads when it hits the ground, with a sharp contrast in temperature, wind speed, and wind direction commonly found at the leading edge, which can travel in some instances more than 100 km from the initiating storm.  

Observations from the Salt Lake City International Airport show the structure of the outflow boundary as it entered the Salt Lake Valley.  Ahead fo the outflow boundary, temperatures were in the low 70s and the wind was from the south to southeast, gusting to as high as 40 mph.  With the passage of the outflow boundary, temperatures rapidly dropped about 15˚F, the wind shifted to westerly with a gusts of over 65 mph for a 5–10 minute period.  Then, the winds shifted more gradually to northwest-north and tapered off to gusts in the 20 to 35 mph range for about four hours.


The Severe Thunderstorm Warning issued by the National Weather Service for the storm caused some confusion since there only seemed to be strong winds and no thunder.  


I had a couple of friends text me asking where the storms were and why a hail threat was indicated because they saw nothing on radar. 

The National Weather Service can issue a variety of warnings, watches, advisories, and statements depending on the situation.  A severe thunderstorm warning is issued for a thunderstorm when radar, weather observations, or spotter reports indicate winds of 58 mph or greater, and/or hail of at least 1".  Lightning frequency is not a criteria.  Typically such warnings are for short periods of an hour or less.  A high-wind warning is issued when conditions are expected to produce sustained winds of at least 40 mph or gusts of 58 mph or greater.  

It could be that a decision was made to issue a severe thunderstorm warning because of the rapid onset, intensity, and origin of the winds.  A look at lightning data from yesterday shows some activity in the precipitation system that initiated the outflow boundary and winds well to the northwest of Salt Lake City.  In Utah, high wind warnings are often issued with significant lead time, as occurs for downslope windstorms or strong pre-frontal wind events, which wasn't possible last night.  These issues may have factored into the decision to issue a severe thunderstorm warning.  

Wednesday, April 27, 2022

The Great Salt Finger Lake

Given the meager snowpack that generally exists in northern Utah, it's no surprise that the Great Salt Lake is expected to drop to historically low levels this summer.  

Last year the lake dropped to its lowest measured elevation at Saltair, 4190.4 feet.  A look at the observations collected at Saltair by the UGSS since last year shows that the lake reached its maximum elevation in early May and dropped about 2.5 feet through fall.  

Source: https://waterdata.usgs.gov/ut/nwis/uv/?site_no=10010000&PARAmeter_cd=62614

The recovery during the winter and spring has thus far been pathetic.  We currently sit at about 4191 feet, nearly 2 feet below where we were last year.  The runoff situation isn't great again this spring.  About the only silver lining is that recent storms have helped the snowpack in the Bear River Basin, which is now running ahead of last year by a bit.  


However, that's not going to help a lot and I suspect we'll make a run at 4189 feet by early fall.  

I've been preparing some material on the future of the Great Salt Lake for the 2nd edition of my book Secrets of the Greatest Snow on Earth.  I'll be including a bathymetric map of the lake based on work by Dave Tarboton at Utah State to illustrate what will happen as the lake shrinks.  The deepest portion of the lake lies along a northwest to southeast axis.  As the lake shrinks, it will become increasingly confined to a narrow channel along this axis.  Basically, the Great Salt Lake becomes the Great Salt Finger Lake.  


At about 4170 feet, the lake becomes two salt ponds.  That may sound crazy, but the lake is currently down about 20 feet from its most recent high stand in the late 80s.  Another 20 feet and we are there. 

The Modis image below was taken on September 27, 2021when the lake was near its minimum and historical low elevation.  It corresponds quite well with the 4191 foot contour above with a small arm of water wrapping around the north and east side of Fremont Island and a sliver of water along the Jordan River as it flows through what was formerly Farmington Bay to the east of Antelope Island.  


The implications of the withering Great Salt Lake are more dust, less lake-effect snow, and the demise of one of the most important bird habitats and ecosystems in western North America.  

Tuesday, April 26, 2022

The Weather Whiplash of the 2021/22 Season

I hope you enjoyed the Gift from the Gods last weekend.  What a long strange trip this season has been.  It was the best of times.  It was the worst of times.  Weather whiplash for sure.

I'll summarize with the Snowbird SNOTEL measured snow water equivalent (SWE) of the snowpack.  At this elevation, the season got off to a good start with SWE increase of 4.7" from October 8 to October 27.  

Then the spigot turned off and we only added 1.3" from October 27 to December 9.  The snow faceted on the north half of the compass, forming a persistent weak layer that would haunt us for a significant part of the winter and in many areas melted out on the south side.  

The storm track returned in December and Mother Nature added 15.7" of SWE to the snowpack through January 7.  That was a pretty good run and the only period outside of October that the snow accumulation rate that exceeded climatological expectations [i.e., the slope of the median (green) line] for more than a few days.  

We then lived on that snow until early March.  From January 7 to March 5, Mother Nature only added a scant 2.1" to the snowpack.  I have heard rumors it was the least snowy February on record at Alta.  I haven't seen the numbers for Alta Guard yet, but before this year, the minimum there was 34" and the resort reported 26" based on their snowfall history page, so chances are we set that dubious record.  

From March 5 through today, we've seen a series of storms interspersed with ablation (snow loss) events.  The SWE trace (black line) during this period shows ups and downs.  In the net, the SWE increased about 10.2" during this period, a rate that was still less than median for the period.  However, if my calculations are correct, the Snowbird lost 2.4" of SWE during those ablation events.  Without those losses, the accumulation for the period would have been 12.6", very close to the median SWE increase for the period of 13.1".  

I see that period from March 5 to April 25 as perhaps an example of the future Wasatch spring snow climate, with the snowpack ripening earlier, significant losses occurring on south aspects, and the frequency and severity of ablation events on north aspects increasing.  

My grade for the season is an incomplete.  I'd like to give it a C+, but due to a foot injury, I haven't done much skiing other than groomers since early February and had to sit out the storm cycle this weekend.  Thus I lack the ability to properly asses the season and encourage you to input your grade and justification in the comments below.  

Thursday, April 21, 2022

Gift from the Gods

The next three days are going to be exciting and interesting for weather and snow lovers as a major spring storm moves through the region.  

Today a surface cold front slowly sags into and intensifies over the Great Basin.  The GFS forecast valid 0000 UTC (6 PM MDT) this afternoon shows the front extending across central Nevada and northern Utah very near the Salt Lake City.  For much of the day, we will see strong southwesterly pre-frontal flow, possibly with dust (I assume you haven't had enough of that).  

The northern Wasatch Front will probably see a shift to westerly or northwesterly flow late in the day, but it's unclear if that will happen in the Salt Lake Valley.  Right now I'd say the odds favor that not happening, but I can't rule it out, especially for the northern part of the valley.  It will, however, be a dry front this afternoon, so the main impact will be on winds and temperatures.  

The models differ on the exact movement and position of the front overnight, although they keep it over northern Utah.  The GFS forecast valid 1200 UTC (0600 MDT) Friday morning has a disorganized surface front over northern Utah with the precipitation band to its northwest is filling in nicely.  The flow at upper levels and for the central Wasatch remains strong and out of the southwest. 

On Friday, the GFS does two things.  First, it develops widespread showers ahead of the frontal precipitation band by 1800 UTC (1200 MDT).  At that time, the frontal band is moving into northwest Utah and its leading edge is over the West Desert.  Note the accompanying surface wind shift in the lower right-hand panel below.    

That afternoon, the frontal band moves in and the flow shifts to northwesterly, with widespread precipitation over most of northern Utah by 0000 UTC (1800 MDT) Friday.  

Friday night is the post-frontal crap shoot with mountain induced precipitation over and upstream of the Wasatch Range and a chance of a little lake-effect involvement. 

By and large, Saturday looks like a gift from the gods.  Our GFS derived forecast for upper Little Cottonwood shows a total of 1.35" of water and 18" of snow for Alta-Collins through 9 AM Saturday, with some additional precipitation during the day.  

The ECMWF model is just a bit below that.  By 23/18Z (1200 MDT) Saturday the SREF has 3 low members under five inches to give one heartburn, but 18 out of 26 members generate 10 inches of snow or more.  

Make some turns for me. 

Tuesday, April 19, 2022

A Quick Update

It's been a while since I did a post, but I've been busy working on the 2nd Edition of Secrets of the Greatest Snow on Earth.  It's coming along nicely and I'm hoping to get it to my publisher by the end of May.  

I have good news and bad news on the forecast front.  The bad news is we just had a frontal passage in the Salt Lake Valley and it has come loaded with dust.  

The moisture lags the surface front by a good ways and is pretty scant at that.  We'll see a few valley showers and mountain snow showers later this afternoon or evening, but the latter won't add up to much. 

The good news, however, is that the system coming in late Thursday night/early Friday morning and affecting us through Saturday looks more potent.  Below is the downscaled NAEFS plume showing some healthy totals with a mean of between 20 and 30 inches.  

Don't bet the house yet.  The GFS is a bit more subdued (and it tends to be wet), with just over an inch of water and about 16 inches of snow.  Regardless, keep your fingers cross for another April dumpage, just in time for the weekend.

Wednesday, April 13, 2022

Bits and Pieces

It's been a pretty good April storm cycle so far.  Totals at Alta Collins per automated measurements:

4 PM Monday 11 April - 4 AM Tuesday 12 April: 11 inches
4 AM Tuesday 12 April - 4 PM Tuesday 12 April: 2 inches
4 PM Tuesday 12 April - 4 AM Wednesday 13 April: 6 inches

I suspect the skiing was pretty good yesterday and will be excellent this morning where untracked.  The northern Wasatch also got hit pretty well.  Snowbasin is reporting 15 inches in the last 48 hours and has announced they will reopen for skiing Friday through Sunday.  It's never over until it's over.  

I'd like to summarize the forecast through Friday afternoon as "dribs and drabs" but that seems unfairly discouraging for April, so I'll say "bits and pieces" instead.  Currently radar shows snowshowers moving into the northern Wasatch from the west.  


This general pattern will continue this morning, with the northern Wasatch likely to receive the most snowfall and the central Wasatch intermittently getting into the action. For example, the GFS shows westerly flow at 700 mb (10,000 ft or crest level) across northern Utah at 1800 UTC (1200 MDT) today with the heaviest precipitation in the northern Wasatch (color fill).  


Through Friday afternoon, a series of weak systems will move through northern Utah with the large-scale crest-level flow fluctuating between westnorthwest and southwesterly.  Expect periods of mountain snow through Friday with occasional breaks and snowfall heaviest at upper elevations in the northern Wasatch.  Temperatures will also be increasing, so getting on it quickly will be important as it is April and the sun has no mercy for fresh dendrites.  

The GFS-derived accumulated precipitation and snowfall graphs below for Alta-Collins shows the situation well with a pulse of snow this morning and early afternoon, then a break, then a couple more small pulses before a few inches Thursday night into Friday morning.  There's another brief period of snow Saturday evening.  


The timing and strength of these periods of snow can't be forecast precisely.  I guess the operative word for this pattern is unsettled, with conditions becoming more mild as temperatures rise (note the the warming trend on Mt. Baldy in the upper right panel).  

Enjoy it while it lasts.

Tuesday, April 12, 2022

Graupel is Good

 The storm delivered as forecast (I love to say that!) in most areas including 11 inches through 8 AM at Alta-Collins.  

Here at the University of Utah, the ground was sprinkled this morning with some beautiful graupel particles.  Below is an example of a pea sized, conical-shaped graupel particle outside the Student Life Center. 


Graupel forms as tiny supercooled cloud droplets collide and freeze on an ice particle.  Typically it has a higher fall speed than snowflakes (3 meters per second compared to 0.5 to 1 meter per seconds) and requires a fairly strong updraft to form.  Radar imagery overnight suggests that the convective cell moving over the University of Utah at 12:40 UTC (6:40 AM, see below) may have produced it, although there were one or two other cells that moved through the area earlier.  

We are now solidly into the unstable, postfrontal flow, although as shown in the time-height section below, the flow direction below and at crest level is predominantly westerly to west-northwesterly and perhaps not quite optimal for Little Cottonwood.  

Nevertheless, periods of snow will predominate today and, given the April sun, we will probably see some strong snow showers this afternoon, possibly with thunder and lightning.  Expect to seem some graupel or pea-sized hail as well.  My best guess is 3-6" more for Alta Collins, although the hit-and-miss nature of what we will see later means there's a wide range of possibilities.  A direct hit by a strong cell would really add up, for example.  

Monday, April 11, 2022

The Gathering Storm

It's hard not to look at the satellite loop below and not get excited.  There's a deep cyclone making landfall on the Pacific Northwest coast with the concomitant cold front pushing across eastern Oregon.  

Source: College of DuPage

As I type this, it's pretty easy to find the front.  It just blasted through Rome in southeastern Oregon, resulting in a wind shift from southwesterly to northwesterly and a 10˚F drop in temperature in an hour. 

Source: MesoWest

The pattern being forecast by the HRRR model for today is, however, not straightforward, due to the effects of terrain on the storm system.  The forecast for 1800 UTC (1200 MDT) is pretty consistent with the observation and shows a cold front (blue line) extending across northwest Nevada into southwest Idaho, with Rome being in the post-frontal environment.  


However, as the cold front moves eastward across northern Nevada, a sharp windshift known as the Great Basin Convergence Zone develops ahead of it (dashed yellow line).  The forecast for 2100 UTC (1500 MDT) shows this feature is forecast to form just south of Salt Lake City and may result in a wind shift in our area before the arrival of the cold front.  At this time, precipitation occurs both ahead of the front (prefrontal) and behind it (frontal).  


This pattern persists through 0000 UTC, with prefrontal showers becoming more widespread in the central Wasatch and environs.  Again, the flow ahead of the front has shifted to northwesterly in the vicinity of the Great Basin Convergence Zone.  


By 0300 UTC, the front has reformed along the Great Basin Convergence Zone.  This is an example of discrete frontal propagation with the front jumping ahead of its earlier position.  Frontal precipitation now covers the central Wasatch and most of the Salt Lake Valley.  


All of that might be an example of TL;DL, but it shows some of the complexities of how cold fronts move through the Great Basin.  We will see if it verifies.

The GFS is jacked about precipitation in and around the Wasatch Range this evening, generating more than 0.5" of snow-water equivalent in the central Wasatch and western Uintas in the 3-hour period ending at 0300 UTC (2100 MDT).  Although there may be a little rain this afternoon in Park City, snow levels will come crashing down later today and this evening, so much of this precipitation will fall as snow.  


Our GFS-derived forecast product below shows the burst of snow with the complex frontal system beginning just before 6 PM MDT with 1 inch of water equivalent and 13" of snow forecast through 4 AM Tuesday.  Snow showers add an additional 0.5" of water and 10" of low density snow during the day on Tuesday, bringing the total to 1.5" of water and 23" of snow through 6 PM tomorrow afternoon.  


For an ensemble perspective, the SREF members generate 0.65 to 1.5" of water and 9 to 24" of snow through 0000 UTC 13 April (6 PM MDT Tuesday), so the GFS may be an upper-bound forecast.   Note that most of the spread develops after the frontal passage, which is not unusual as the post-frontal environment is often more difficult to forecast.  


I expect 12-20" at Alta Collins through 6 PM tomorrow.  Ski conditions tomorrow morning will depend a lot on how things bond to and bury the frozen coral reef that currently covers the Wasatch Range.  Low end amounts will probably yield quite a bit of bottom feeding.  High-end amounts should result in pretty good conditions that will get better as we add more snow.  Keep in mind that we are in low-tide conditions in many sun exposed areas.  There will be hidden hazards.  

Also, our snow algorithm is going for very low density snow tomorrow (5% per the GFS).  I'm not sure if that will verify.  It's April, and the sun, even through clouds, is pretty caustic.  Additionally, we could see convective storms with riming and possibly graupel, which is higher density.  This is why I've cut the upper-end snowfall amount to 20" rather than about 24 as suggested by the GFS and SREF.  You won't complain if that ends up being low.