Wasatch Weather Weenies

It may be New Year's Eve, but its pretty scary out there, if you are in the valley. In the mountains, it was a spectacular day, with the polluted grey in town helping to keep the crowds down at the resorts.  From the bluebird skies along Alta's High Traverse, the valley stratus looked quite benign. However, it looked far more sinister during the descent down Little Cottonwood Canyon, especially as we approached the nose of stratus protruding up the canyon. However, as ominous as it looks, the development of the stratus is a good thing as it typically leads to a deepening of the pollution layer and mixing through a deeper layer.  Instead of pollution being confined to very near the valley floor, it mixes through a few hundred meters of depth and that helps keep ground-level PM2.5 concentrations lower.  It also reduces the photochemical production of PM2.5 in the afternoon. One can really see this in the PM2.5 trace from Hawthorne elementary.  ...

As Yogi Berra once said, "you can observe a lot just by watchin'" and that's especially true during inversions. Let's begin with a few key points of nomenclature and interpretation.  First, an inversion is a layer in the atmosphere in which temperature increases with height.  It is important to recognize that some poor air quality events in the Salt Lake Valley are not associated with true inversions.  Because density varies with both temperature and pressure, a dry atmosphere is stable until the temperature decreases at a rate of about 1ºC/100 meters altitude.  Periods in which the temperature decreases slowly with height can be strongly stable and associated with elevated air pollution levels.  The term "inversion" is often applied colloquially to such periods, even though that is meteorologically incorrect. Second, the inversion is not the cause of poor air quality.  An inversion simply limits vertical transport and mixing.  It is a benign atmos...

In the wake of our wonderful Christmas miracle snow storm, an ugly air pollution episode has developed along the Wasatch Front.  Views this morning from the upper Avenues showed smog and stratus over the lower Salt Lake Valley. This morning's sounding shows a deep inversion over the Salt Lake Valley.  At the time of launch, the surface temperature at the Salt Lake City airport was -7ºC (19ºF), whereas temperatures from about 800 to 700 mb were above freezing. Source: SPC Yesterday was quite warm in the mountains (I nearly melted while skinning up a sunny, windless, south aspect) and will be even warmer today. Meanwhile, the valley remains mired in pollution.  Yesterday, PM2.5 concentrations measured by the DAQ sensor at Hawthorne Elementary along 700 East peaked at 71 ug/m3, which qualifies as unhealthy.  Although PM2.5 levels have lowered some, they remain just below the unhealthy for sensitive groups threshold.  I suspect we will see another pu...

Since the epic 2010/11 season, northern Utah skiers have suffered through some down seasons.  That has all changed, however, this season, as we have a wonderfully deep and freshened snowpack entering the big holiday week. Data from the NRCS shows that every SNOTEL station in northern Utah but one (Chalk Creek in the western Uinta Mountains) presently sits at or above median snowpack. Here are a few cherry-picked sites: Snowbird: 16 inches of water equivalent (150% of official median) Cascade Mountain: 8.6 inches (139%) Farmington: 15.5 inches (141%) Ben Lomond Peak: 19.8 inches (190%) Rocky Basin Settlement, Oquirrh Mountains: 10.3 inches (147%) Mining Fork, Stansbury Mountains: 8.1 inches (176%) The plume diagram below shows the snowpack water equivalent trace at Snowbird for this year (blue line) compared to the median (magenta) and water years going back to 2011.  We are now just ahead of 2013 and well ahead of most of the rest.  The 2011 water year is e...

Words not needed. I suspect it will be better tomorrow for Boxing Day.  I'll be working, so you should get on it for me.

This morning's radar loop shows some wonderful orographic effects over northern Utah.  First, let's get oriented with a terrain map showing the areas of interest which include the Oquirrh Mountains (lower left box) northern Wasatch (top box), and central Wasatch (lower right box). With the large-scale flow out of the northwest, one can see persistent and strong radar returns over the Tooele Valley to the northwest of the Oquirrh Mountains, upstream of the northern Wasatch, especially the Bountiful Bench Area, and upstream of the central Wasatch.  Note the lack of echoes ("rain" shadowing) downstream of the Oquirrhs over the southwest Salt Lake Valley, and downstream of both the northern and central Wasatch (note: there is some blockage of the radar beam in these areas too, but there are also clear "rain" shadow effects).   Looking at a single image can sometimes help.  If you look carefully at the central Wasatch, you can see enhancement on th...

It doesn't get much better than a good snowstorm on Christmas morning.  The presents are open and we're thinking about skiing, but getting down the hill could be an adventure. Radar and HRRR forecasts suggest snow will continue in the Salt Lake Valley for most of the morning.  Enjoy!

The Weather Channel has gotten into the habit of naming winter storms and is calling this one Winter Storm Europa . I give them credit for coming up with catchy names, but I think they should call this one Santa's Storm as the big guy is delivering one that should make for great skiing. Snow conditions in the Wasatch yesterday were best described as "tired."  We have a decent early season base, but desperately need a freshening up.  From late yesterday through 7 AM this morning, Alta-Collins picked up 4" of snow with .34" of water.  I don't have an up-to-date new snow total for Snowbasin Middle Bowl, but their water is up to 0.5" and that all fell as snow.  It's not a lot, but it's creamy and should help greatly improve ski conditions.  Plus, it's just the start. Between now and Christmas, a strong upper-level trough will swing through the southwest States.  By 0900 UTC (2 AM MST) Christmas Morning, when Santa will be delivering present...

Today, December 23, is Festivus, a holiday invented and made famous by the Seinfeld sitcom that includes feats of strength and an airing of grievances. Feats of strength for this year's Festivus celebration involved backcountry skiing.  The vertical feet climbed for the Festivus celbration was modest, but the quality of the skin tracks meant an exceptional amount of effort was exerted per vertical foot.  Nevertheless, there were grins and settled powder to be found. Kyle Van Peursem  near the summit of Mt. Raymond Professor Powder in Raymond Glade Now on to the airing of grievances.  Wasangelas is a remarkably busy place and there are hoards of tourers out and about these days.  Stop the brutal skin tracks! There's no need for frequent kick turns in terrain like this Steep skin tracks are not bad ass.  They are stupid, inefficient, and wear out fast.  Kick turns?  Avoid them when you can and spread them out as much as is safely...

It is a little known fact that several of Santa's elves recently completed their weather forecasting degrees at the University of Utah and are now putting that knowledge to work optimizing routing for Santa on Christmas Eve. The challenges faced by these elfin forecasters are immense.  Anyone who has been on a long trans-Atlantic or trans-Pacific flight knows the value of a strong tailwind and the delays posed by strong headwinds.  Santa needs to take advantage of the former and avoid the latter as much as possible.  Turbulence?  If you think it is bad on an airplane, imagine traveling at high speed on an oddly shaped sleigh loaded with gifts, many of which are fragile.  Visibility?  The addition of Rudolf has reduced, but not eliminated, weather delays due to clouds, fog, and snow. For short-range forecasting in the mountain west of the United States, the elves naturally favor the NCAR ensemble and many of the specialized products we produce on weather...

This year, my son and I decided to do something different to celebrate his high-school graduation.  We bought a couple of Mountain Collective passes in order to ski some resorts that we either don't visit enough or need to get to before I'm too old. Although there was good powder to be had in the Wasatch this weekend, my back was worked up and I needed some lower intensity groomers.  Yes, I know it is heretical to skip out on powder, but I do what my back tells me.  Thus, we went up to Sun Valley for some high-speed cruising.   I have visited Sun Valley in the summer, but this was my first time skiing at the resort.  While they lack serious advanced terrain, the resort has good cruising, especially from the Warm Springs base area where there is a non-stop fall-line exceeding 3000 vertical feet and the Challenger high-speed quad to ensure you can take full advantage.   On Sunday, the weather was perfect.  Not only was it bluebird, but th...

With additional low-density snow overnight, the total snow depth at Collins pushed to 63", just above my 60" threshold for good early season conditions. Indeed, the upper-elevation snowpack looks better at this point of the season than we have seen for a few years.  Snow water equivalent at the Mill-D North SNOTEL (green line for this season) now sits just above average for the date and higher than any water year since 2011 (that was a huge year and I left it off the graph). Snowbird looks pretty good too and also sits above average, but does lag 2013.  The water total from the last storm looks a bit high at that site, perhaps due to wind transport, but I think it's safe to say that things are looking good heading into the holiday season. I expect the conditions today will be very very good.  Alta-Collins got 9 inches with the frontal passage and another 6 inches of cold smoke last night.  The snow is stacked perfectly for flotation and face shots. ...

A few numbers from today's storm.  As of 3 PM, Alta Collins has a 24-hour water equivalent total of 2.18" and a snow total of 19 inches.  After a break this morning, they got plastered with the frontal passage in the afternoon, picking up a very quick 8 inches of snow. I opted to ski tour today.  The scene from the parking lot at Solitude where we started our tour was positively Cascadian.  It was raining to just below this level.  The lot was very slush and the snow concrete. Ski conditions above 9000 feet were actually fun where the wind wasn't roaring.  On the Park City Ridgeline, we found a tempest.  I took this photo during a "lull" just prior to the frontal passage. Although I wasn't in the valley to observe the frontal passage, a friend sent me the photo below.  I'm sure you all enjoyed it.  In the mountains, the visuals weren't as dramatic, but there was thunder and eventually heavy snowfall of 2-3 inches an hour. ...