Wasatch Weather Weenies

With the 2010s coming to a close, it's time to look back at the last 10 years and highlight some of the major storylines covered by the Wasatch Weather Weenies.  We first started posting in Fall 2010, so the 2010s were our true youth.  Be warned that the 2020s will be our adolescence. The 2010/11 Ski Season Let's start on a positive note with the 2010/11 ski season which I suspect we can all agree was the best in the last 10 years in Utah.  The photo below was taken in the Avenues foothills on November 29 . Things just got better from there.  It was full on by mid December as Alta reached a 100" deep snowpack on December 20th.   How's this for coverage in upper White Pine on December 24th. And Mother Nature just kept bringing the Goldilocks storms all winter long, right up through Memorial Day weekend when we were still skiing powder. While the powder was gone, Snowbird was for the 4th of July when my son and I were skiing on Mt. Rainier....

Yesterday I forecast that there would be no "major" storms in northern Utah the rest of the year, but some might be wondering what that means after the mess today in the central Wasatch.  For that post, I was thinking of major accumulations.  Impacts, however, can be significant even with light snowfall amounts. For example, snowfall this afternoon apparently made quite a mess in the Cottonwoods, with UDOT hoisting the "Traction Law" flag and the National Weather Service noting that things look "pretty dicey" not only in Little Cottonwood but also Parley's Canyon.  4:45pm Parts of Little Cottonwood & Parley's Canyons (western portions) look pretty dicey. Avoid this area if possible. Check road signs via @UDOTTRAFFIC for chain laws. #utwx #utsnow pic.twitter.com/mfAcvk9LrD — NWS Salt Lake City (@NWSSaltLakeCity) December 28, 2019 The snowfall was produced by shallow cumulus clouds that were parked over the mountain ridges much of th...

Given that it's December 27, I don't think I'm sticking my neck out too far to say that there won't be any major storms in northern Utah until sometime next year.  The pattern is one of "deja vu all over again."  The loop below begins at 1200 UTC (6 AM MST) 25 December and extends through 0600 UTC 1 January (11 PM MST 31 December).  The pattern is one featuring upper-level troughs digging along the Pacific coast and then moving inland across the southwest.  Since graphics from the European model are now publicly available, below is the forecast of total accumulated precipitation through 0600 UTC 1 January (11 PM MST 31 December).  Utah is a state divided, with the southeastern half of the state seeing some precipitation, mainly with the trough moving through today and tonight.  Northern Utah is not completely dry, but precipitation is limited and generally near or less than 0.1 inches of water equivalent.  Source: Pivotal Weather Thus, no...

Although the Eve of Christmas Eve brought some light rain showers to the Salt Lake Valley, snowfall at Alta yesterday, overnight, and this morning has added up to a surprisingly healthy 9 inches.  If you aren't used to interpreting the "Snow Interval" column below, it's an automated measurement of snow depth on a wooden board that gets wiped from time to time.  You can see below how 2 inches accumulated through 16:00 yesterday afternoon (time increases upward), then the board was wiped, another 4" fell through 4 AM when the board was wiped again, and then another 3 inches fell through 8:00 this morning.  Source: MesoWest What will happen tonight as Santa delivers his gifts and tomorrow when Johnny and Jane want to play with their new sleds?  I'm not going to lie to you.  I don't have a good idea and I'm glad I don't have to tell Santa that.  The pattern is messy with a bunch of disorganized areas of precipitation in southwesterly flow initia...

Strong southerly winds have scoured out the valley cold pools and pollution across much of northern Utah, but not all of it. The southerlies picked up in earnest on Friday night and Saturday.  At noon on Saturday, peering into the Salt Lake Valley from above White Pine Canyon, one could see significant clearing in portions of the Salt Lake Valley, but thick smog remained over the lowlands further north.  That portion of the cold pool over the Great Salt Lake and West Desert has been incredibly stingy,  like a bad cold unwilling to go away.  Even by Sunday afternoon, despite a tempest blowing at upper elevations, the cold pool remained.  Check out the observations below from 3 PM MST (2200 UTC) Sunday.  50s across the Salt Lake Valley, but 33˚F on Hat Island, 33˚F along I-80 in the West Desert, and 34˚F in Wendover! Source: MesoWest And I would be remiss if I didn't mention Logan where yesterday's high was 25˚F!  Sadly, the pollution there ...

An article by Brian Maffly in today's Salt Lake Tribune discusses what a large gondola in Little Cottonwood Canyon might look like.    While in Austia last year, I rode on what I suspect would be a template for such a lift, the Eisgratbahn at Stubai Glacier.  The Eisgratbahn is a tri-cable gondola hauling 48-passenger cars 1200 vertical meters (3.8 km) with a total capacity of about 3000 people per hour.  You can read about it in this BlogTirol article .  The Eisgratbahn was built at a cost of 68 million Euro (about 75 million USD), supposedly making it the most expensive ski lift ever built (see this FallLine Skiing article ).  For comparison, the Peak-to-Peak gondola at Whistler, discussed in the Salt Lake Tribune, was "only" 51 million Canadian Dollars.  The Eisgratbahn is largely a people mover.  Most of the Stubai Glacier ski area is at altitudes above the base parking lot, pictured below.  One tends to take the Eisgratbahn u...

British statistician George Box once wrote "all models are wrong, some are useful."  When it comes to observations, I like to paraphrase that to "all observations are bad, some are useful."  This statement reflects the fact that all observations contain errors and uncertainty, but they can still be useful. PurpleAir uses low-cost laser particle counters to estimate PM2.5 concentrations.  The sensors can be purchased and operated by anyone, with data available at purpleair.com.  Many groups and individuals have installed PurpleAir sensors across the Salt Lake Valley, northern Utah, and other parts of the nation (and even world).  In the Salt Lake Valley, there is a remarkably high density of stations.  Below is a PurpleAir map of PM2.5 concentrations from 7:09 AM MST this morning.  With such a high density of stations, one can see some of the spatial variability in pollution, including the relatively low values of PM2.5 on the east bench compared to t...

After a great run of snowfall, we're in the midst of a break in the action this week.  This has led to the formation of a strong inversion over the Salt Lake Valley.  Yesterday afternoons sounding shows the inversion base at about 850 mb, or about 650 feet above the airport.  Above this level, temperatures increased about 5˚C.  Source: SPC Not surprisingly, air quality is deteriorating and is currently in the middle of the "moderate" category.  Source: Utah DAQ Above the gunk, wonderful conditions can be found in the mountains.  Yesterday's high at the base of Alta reached 32.5˚F.  Mountain temperatures will climb further today and tomorrow and the inversion will strengthen, or, if you prefer, tighten its noose.  By 5 PM Friday, free-atmosphere temperatures at 700 mb (about 10,000 ft) are expected to reach 0˚C.  However, with a trough approaching from the west, southwesterly flow is expected to increase Friday night and Saturday....

Lake-effect has brought snow to the western Salt Lake Valley and Tooele Valley and created some traffic mayhem along I-80.  I saw a report earlier this morning of a 2 hour commute from Tooele to Salt Lake. Radar imagery overnight shows the "pulsing" nature of the lake effect, which occasionally became banded.  There is a brief period of double banding as well.  Although the central Wasatch was outside the main lake-effect area, they got just enough from the edges and orographic snow showers to give Alta Collins 4 inches of what was probably pixie dust.  Below is a 1400 UTC (7 AM MST) satellite image fro GOES-17.  I've cherry picked this to highlight a time when a clear lake-effect band was apparent.  There is evidence of the cloud band extending well into Utah county at this time.  Radar imagery at the time shows lake-effect snowshowers extending from the Great Salt Lake and into the Oquirrh Mountains.  A narrow band extends further do...

Skiing conditions are excellent in the Wasatch right now, especially for mid December.  I've probably said that a few times in the past week or two, but one shouldn't take these things for granted. Today we elected to take the bus.  Kudos to everyone packed liked sardines for an hours drive up the canyon.  It's great that UTA increased service this year, but we need even more during peak periods.  Further, trips like this are a reminder why more people don't voluntarily opt for the bus.  Sadly, real solutions, if they exist, are still years or decades away.  Thankfully, ski conditions were excellent.  No photos from our descents, so the skin track is the best I can do.  Source: Erik Steenburgh I got a pit in my stomach around 1:30 PM or so when we noticed a heli hanging over the Park City ridgeline.  Sadly, a skier was killed in an avalanche in Dutch Draw.   I thank the patrollers and responders for their efforts. ...

It's a solid start to the ski season in the Wasatch Range.  The Snowbird SNOTEL is at 11.8 inches of water equivalent, above the 10 inch threshold for the start of what I'll call solidly good early season conditions.  That's also 146% of median and 131% of average.  Ski touring conditions today were quite good for mid December, although avy conditions kept us confined to lower angle slopes. The forecast for tonight and tomorrow suggests we have another major storm coming in.  The  SHREF forecast below shows a mean of nearly an inch of water and 15 inches of snow through 0000 UTC 15 December (5 PM Saturday).  That's the good news.  The bad news is this looks like a setup for messy travel up the canyons.  Hopefully people have upgraded their tires, UTA has better trained their drivers, and desires for carpooling are higher.  Stay safe and enjoy.  I'll be working to make up for my ski time today.

An active weather period is coming over the next few days as several systems rumble through and eventually tap into moisture from a landfalling atmospheric river. The NAM time-height section shows copious low-level moisture from later today all the way through the end of the forecast period at 0000 UTC Sunday (5 PM MST Saturday).  During the period, several deeper systems rumble through, some associated with mid-level or surface fronts and associated troughs.  Timing these systems is difficult and so it's best to say that we're going to be seeing periods of mountain snow that will add up to a considerable total by the end of the NAM forecast period on Saturday afternoon.  The GFS integrated water vapor transport forecast for 1800 UTC (11 am) Thursday shows a broad atmospheric river making landfall along the Pacific coast and penetrating inland across the northern Great Basin.  We never get into full-blown atmospheric river conditions, but this is still a nice c...

Air quality has improved over the Salt Lake Valley the past two days, but is still in the moderate category in some areas. Yesterday and overnight, the valley cold pool mixed out from the top down and from south to north.  This left a shallow lens of cold air over the northern Salt Lake Valley that was filled with fog and low clouds this morning.  A look at the photo below, taken looking south from the upper Aves just before sunrise, shows fog or valley stratus over the central Salt Lake Valley, but clear skies near and over the east bench around the University of Utah.  Observations at 7 AM show relatively mild air in the upper avenues (39˚F) and at the University of Utah (35˚F) compared to sites along I-15 from the I-215 junciont northward where temperatures were 28–30˚F.  Thus, the fog evident above was coincident with a shallow cold pool over the lower portion of the northern Salt Lake Valley.  Clear air near the University of Utah was also favored by...

There's a lot to talk about this morning, so I'll go into rapid fire mode. 1. Poor Forecasts The new GFS model really handled last night's and today's event quite poorly. The 72 hour forecast valid at 1200 UTC (0500 MST) this morning called for precipitation to be confined to southern Utah, reaching no farther north than Provo.  Instead, the 1201 UTC radar imagery shows precipitation all the way into southern Idaho.  Although we can't share the Euro forecasts here, they definitely did better on location.  On the plus side, Alta-Collins has picked up 4 inches of snow, so maybe we shouldn't complain. 2. Wintery Mix Freezing rain doesn't happen a lot around here, but there was a period of it last night at the airport where light to moderate freezing rain was reported from 10:04 PM to 12:25 AM when the precipitation changed to rain.  Freezing rain is rain that freezes upon contact with the ground or solid objects.  It can occur when the airma...