Wasatch Weather Weenies

This afternoon we've had a remarkable mixout of the inversion in the upper Avenues and around the University of Utah.  Check it out and the lens of dirty air remaining along the valley floor.  University of Utah just to the left in the photo below. Things remain gunked in over the many other portions of the valley, including the area near downtown. The cleansing agent in this case was a weak surge of easterly flow that pushed into the Avenues and the University area at about 1400 (2 PM) MST, which pushed by the valley cold pool and scoured out the pollution.  The trace below shows the onset and then persistence of this easterly flow at our mountain meteorology lab near the mouth of Red Butte Canyon over the past three hours. Source: MesoWest At the same time, the air pollution in the heart of the Salt Lake Valley is still getting worse and PM2.5 is at the highest levels of the event. Source: Utah Division of Air Quality The trough brushing by to o...

Air quality in the Salt Lake Valley is now what I consider to be the worst of the event thus far with the  24-hour average PM2.5 sitting at 49.1 ug/m3 compared to a National Ambient Air Quality Standard (NAAQS) of 35 ug/m3.  Hourly average values last night were not the highest of the event, but close to those seen on the 27th and 28th and certainly more sustained. Source: Utah Division of Air Quality Box Elder, Cache, Uintah, and Weber Counties also have 24-hour average PM2.5 above the NAAQS.  Utah County is just below it, but was above it yesterday.  Nastiness all around. Watching the evolution of this event from the Avenues reminds me that having data from only one site in all of Salt Lake and Davis Counties is unacceptable.   For comparison, the Puget Sound Air Pollution Control Agency provides hourly real-time data from 15 sites .  We should at minimum have coverage on the benches where people often assume the air is cleaner.  Although ...

Photo during heavy snow from the Bushnell/University of Utah North Redfield SnowCam. I know everyone in Utah is missing snow.  I can't help much, but click here and you'll see 30 cm/12 inches in 6 hours from our el cheapo snow cam on the Tug Hill Plateau earlier this month.  Refresh and repeat until you feel better.

Yesterday's weak trough did drop temperatures above the inversion and does appear to have reduced PM2.5 concentrations somewhat, but hardly to levels we would like. Yesterday morning, the 5 AM sounding from the Salt Lake City Airport showed a very strong inversion with temperatures increasing from about –8ºC at the surface to about +4ºC at 775 mb (approximately 2250 m/7500 feet). Source: University of Wyoming With the passage of the weak trough yesterday, temperatures aloft cooled quite a bit.  This morning, the 5 AM sounding showed a surface temperature of about –7ºC with temperatures increasing only to about -3ºC at 830 mb.  Source: University of Wyoming Although the cooling aloft weakened the inversion, it didn't break it.  It has merely helped ventilate the valley a bit and both hourly and 24-hour average PM2.5 levels are lower today than yesterday.  That's good news, but only in a relative sense.  We are still fluctuating around levels that are...

The weak upper-level trough and cold front pushing through northern Utah today has stirred the pollution a bit, but has thusfar provided little relief.  I went for a hike this afternoon in the avenues foothills and the pollution is deeper today than it was yesterday.  The photos below show the deepening and thickening of the smog over the 3 days since Christmas. Here are a couple of additional views, the 2nd photo taken from my place in the Avenues at 4:30 PM for comparison with those in previous posts, although skies were overcast at that time making it look even bleaker. 24-hour average PM2.5 peaked this afternoon at 42.8 ug/m3, the highest of the event thusfar.  Hourly PM2.5 did drop in the past couple of hours, in contrast to the previous couple of days when it became elevated around noon and stayed that way all afternoon and evening.  Perhaps we are seeing a bit of mixing related to the upper-level trough and cold frontal passage, or the cloud co...

I was going to wait and do this post tomorrow, but weather never sleeps and it seemed like a good idea to do it now. Today was the first day I got up to the mountains during the current inversion.  The weather was as nice as you can get in December with blue bird skies, warm temperatures, and barely a whiff of wind.   I never tire of the view of Mt. Superior Balmy.  Temperatures as high as 43ºF were recorded at the top of the Collins chair today, but I suspect this was a bit higher than the free-air temperature as the winds were light and this often leads to overheating of the sensor when it is sunny.  In addition, the ski conditions at Alta were fun too.  The groomers are grippy and carvable.  Fast is fun.  Then came the dreaded descent into the Salt Lake Valley.   And for comparison with the photos in the previous post , here's today's 4:30 PM shot from the Avenues.   As discussed in that post, the buildu...

The build up of pollution in the Salt Lake Valley the past two days has been quite remarkable.  Below are photos taken at about 4:30 PM on December 24 (Day 0), 25 (Day 1), and 26 (Day 2) showing how we went from pristine skies to serious smog over a period of about 48 hours.  PM2.5 data from the Utah Division of Air Quality showed that the 24-hour average PM2.5 for yesterday was 25 ug/m3.  It currently sits at 27.6 ug/m3.  Recall that the National Ambient Air Quality Standard (NAAQS) is 35 ug/m3.  The rise from 0 to 27.6 ug/m3 occurred in about 48 hours during a holiday period, which is both remarkable and disturbing.   Source: Utah Division of Air Quality An interesting aspect of the PM2.5 evolution is the dropoff in hourly concentrations during the overnight hours.  At 6 AM this morning, hourly concentrations had dropped to 14.8 ug/m3, but I would expect them to rebound later today.   This case further illustrates my vie...

A truly spectacular airmass pushed into the Salt Lake Valley and gave us a remarkably clear Christmas Eve.  As the sun was setting and Santa approached, one could breath easy for their long winter's nap.  4:30 PM MST Christmas Eve, 2013 However, it didn't take long for a veil of smog to begin to develop.  On Christmas, air quality was still good, but one could begin to see the effects of all the yule log burning on the visibility over the valley (I'm not sure if wood pollution is the problem, but "yule log burning" seemed to fit well there).  Note in particular the smoggy tint in the right-hand side of the image below.   4:30 PM MST Christmas The view from the Avenues Foothills also showed a veil of Christmas smog hanging over the valley on an otherwise unbelievably spectacular day. A thin veil of Christmas smog over the Salt Lake Valley The latest observations from the Division of Air Quality shows that the hourly PM2.5 concentrations peaked l...

For new readers, a link to the now classic post, " The Untold Story of How Santa Claus Really Comes to Town ." For fair weather skiers and resort owners and operators, a big ridge and mild weather for Christmas Day and at least a couple of days thereafter, with forecast 700-mb (near 10,000 ft) temperatures climbing to positive numbers by Thursday evening (i.e., just above 0ºC).   For powder skiers and water managers, hope that this pattern changes and we get more snow in 2014.   Merry Christmas and Happy Holidays to everyone.  

Great turns in 10% yesterday at Alta As some of you know, my favorite days to resort ski are not bluebird powder days but storm days during which it starts snowing high-density, heavily rimed snow in the late morning.  Yesterday was such a day as heavily rimed, high density snow began to pick up in intensity around mid morning.  From 9 am to 4 pm, the Alta Collins stake recorded four inches of snow with a water content of about 9%.  That's perfect for smooth, creamy turns and also good for base, so we were happy to accept it. Contrary to conventional wisdom, water does not necessarily freeze when the temperature is at or below 32ºF/0ºF.  Typically to convert from liquid to ice, it needs something to help it arrange it's molecules in the proper configuration to form ice.  That something is known as an ice nucleus.  Water that is below freezing but still in a liquid state is supercooled .  Wintertime storm clouds in Utah and many other regions ar...

On Friday I received four new snow measurement tubes from SnowMetrics, which was a nice early Christmas present thanks to generous support provided by many individuals to our  Mountain Meteorology Fund . We've been getting by with just a couple of these, but have needed more for some time.  In particular, I will be putting the new measurement tubes to good use in upstate NY in January when I will be visiting some of the local schools.  They will allow us to let the kiddies go out and make some of their own snow and snow density measurements, which is far better than just having them stand around and watch one of us do it.  In the long run, it will allow us to expand our snow sampling efforts during field programs. SnowMetrics makes all sorts of great tools for snow and avalanche geeks and hobbyists.  If you order today, they claim they will have them in the mail tomorrow morning.  I'm not sure that guarantees a delivery by Christmas, but your specia...

We have a couple of weak storm systems passing through northern Utah today that will bring some light snow to the mountains where it is sorely needed and ensuring a white Christmas for the Salt Lake Valley.  Drive and ski carefully.  There are plenty of slick spots on the road and booby traps in the mountains.  I haven't ventured into the Wasatch backcountry since returning from New York, but the list of backcountry avalanches is really long, with numerous close calls , including by people sporting air bags.  Let's be careful out there. Over the past couple of days I've been having the first good look at some of the data we collected on the Tug Hill Plateau and thought I would do a comparison of the weather and snowpack evolution there over the past two weeks with that at Alta Ski Area in Utah.  To do this, I'm going to use data from ultrasonic snow depth sensors at the two sites.  These are extremely useful instruments and they tell us a lot about how mu...

Yesterday was a great day for the Utah team in New York and Wasatch snow lovers. In New York, the University of Utah snow study team was finally able to enjoy some of the fruits of their labor.  The final numbers are in and, from 7-18 December, we recorded 252 cm of lake-effect snow at our North Redfield observing site.  That's 99 inches, which falls just short of the coveted 100 inch barrier, but we would have easily been over that if we had included some of the non-lake-effect snow that also fell during the period.  Very impressive. With freshies to be had, the team hit Snow Ridge ski area, which is on the east side of the plateau and offers up 450 vertical feet of the tugs finest.   Apparently they had a pretty good day, although they would not share with me any photos of their "secret stashes."  Maybe they are pulling my leg, but having skied Snow Ridge when I was in high school many years ago, it would not surprise me if they found some pretty good powd...

Many of my regular blog readers who have a great interest in Wasatch weather are probably wondering if I have gone off the deep end given all the posts I have been doing from northern New York.  What can I say.  We're having a great time.  Yeah, there's some good weather in northern Utah right now, but my mind is still locked on the incredible storms we observed over the past couple of weeks on the Tug.  So, let's have a comparison or, dare I say, a cage match.  This will also introduce new upstate NY readers to the remarkable snow climate of the Wasatch Mountains. Topography The Wasatch Mountains extend roughly north-south through northern Utah with the highest and broadest portion of the range rising up to 7000 vertical feet above the Salt Lake Valley to the southeast of the Great Salt Lake.  This high portion of the Wasatch Mountains, which contains many world-famous ski resorts such as Alta, Snowbird, Solitude, Brighton, Canyons, Park City, an Deer ...