Wasatch Weather Weenies

I'm not out of town, but am unable to ski today.  Hence, yesterday's storm became a clear overproducer, generating 11 inches on the Collins stake through 8 AM this morning.  If you love cold smoke, this is your snow.  Total water was only 0.56 inches, yielding a water content of about 5%.  Wear a buff or something to cover your face.  Temps are around 10ºF at 8500 feet and below zero at 11,000 feet. This storm reminds me a bit of New Year's Eve 2010, when a super cold storm produced great touring conditions. However, it was several degrees colder than today.  I remember that day well as we did over 6,000 vertical feet of climbing and I don't think I ever took my puffy jacket off.  Taking a significant break wasn't an option.  We would stop, chug some water and have a quick bite, and get moving again. This could be it for several days as the NAEFS shows little action over the next few days, then we will have to see.

Yesterday's MODOS imagery showed widespread evidence of clouds produced by trapped mountain waves over the Great Basin.  Such clouds are produced in situations when the wind speed increases rapidly with height and the atmospheric stability decreases above a crest-level stable layer.  Such conditions were very apparent in the afternoon sounding form Elko.  Note how winds increase from 10 knots at about 725 mb to 130 knots at 300 mb, the existence of a sharp inversion near 725 mb, and then a decrease in statisc stability from 700 to 500 mb.  This leads to a sequence of lee waves downstream of the mountains.  Clouds can form in the wave crests and dissipate in the wave troughs if the humidity is right, as was the case yesterday. Source: Durran and Klemp (1983); COMET Mountain waves were also evident over the Wasatch Range yesterday.  Note the wave-like undulations in the clouds in the photo below.    Really, the mountains are gen...

Early afternoon with the low-angle sun barely cresting the ridge I'm a big fan of the low-angle sun as it allows powder to persist for long periods on many aspects.  However, on a cold day like today, it gives little warmth and it allows cold pockets to persist deep into the afternoon.  Chances are you felt them as you skied around today into shady areas. Sadly, last night's northeasterly flow did some damage to the snow, at least in the mid-elevation area we were touring today.  I heard rumors of great skiing while I was out of town for Christmas, but today's skiing was so-so.  Good in places.  A bit wind affected in others.  Still, compared to last year, we shouldn't complain. The net chance of a decent refresh looks to be Sunday or Monday.  Forecasts from the SREF vary on timing and amount, with some getting things going in the morning, others later, and most of the members generating 0.2 to 0.6 inches of water at Alta Collins by New Years E...

Anyone who works in the weather business knows just how critical government weather services are for the protection of life and property. As I write this, we are now in day 5 of the government shutdown, which now looks to last into the beginning of 2019.  To illustrate the challenges ahead for public servants, here's a tweet issued by the U.S. Office of Personnel Management this morning. Feds, here are sample letters you may use as a guide when working with your creditors during this furlough. If you need legal advice please consult with your personal attorney. https://t.co/t6h6OzALsS — OPM (@USOPM) December 27, 2018 Despite the financial pressures of not knowing when they will receive their next paycheck, National Weather Service meteorologists continue to work through and provide critical forecast services.  You won't notice much of a change in their products, just some reductions in social media outreach and the like.  However, if you use other NOAA services...

I've been out of town with family for the holiday, but am returning to Salt Lake tonight.  It appears that you have all benefited from the Steenburgh effect.  A friend reports 26 inches and 1.72 inches of water since I left several days ago.  Not surprisingly, with my return tonight, the SREF is taking pity on you and giving you one last gasp for late tonight and tomorrow.  It's not looking like a big event, but it will provide a refresh.  Enjoy it as the odds of snow will go down once Mother Nature gets wind of my return.

Here are a couple of books that might make good holiday gifts for friends, family, or yourself.  In December 1968, propelled by the most powerful machine ever built, humans escaped Earth's gravity for the first time and traveled to the moon. Nobody had ever before travelled beyond low-Earth orbit. Apollo 8 is probably the riskiest endeavor ever undertaken by NASA, and this book tells the story in an exciting and compelling way.  This Christmas Eve marks the 50th anniversary of the mission orbiting the moon 10 times.  I get goosebumps just thinking about it.  A friend recommended this book to me and I liked it so much that I read it in a day while traveling.  Those who believe the government does some great things will like it.  Others may not.  It gets a nod here because it contains a major section on the importance of NOAA and National Weather Service and the need to integrate social science and improved messaging into their weather products...

It was nice to walk to the bus early this morning, enjoy the mild temperatures, and breath clean air.  For a while, south winds ahead of an approaching upper-level trough had pushed back the valley cold pool to the north valley and over the Great Salt Lake.  The transition was especially strong at the Neil Armstrong Academy where around 6 AM MST the winds increased to over 10 knots with a SSE component. Source: MesoWest  At the same time, the temperature rose dramatically, from 27ºF to 46ºF.  Source: MesoWest However, a look at the two traces above shows that the wind eventually flopped around again to NW and the temperature dropped all the way down to 34ºF. Further, the PM2.5 concentrations dropped to near zero with the temperature rise, but then crept back up to 35 ug/m3 with the shift to NW flow, although they have dropped back down to 20 ug/m3 at the moment.   Source: MesoWest The mesowest station plot for 1718 UTC (1018 MST) show...

It was a spectacular weekend in the mountains with clear skies and mild weather producing widespread smiles.  Ski touring on Saturday was pretty good, although it required effort to get to untracked powder.  The groomers at Alta today were really fantastic, at least in the morning, when the snow was grippy and you could really lay trench.  Although we need a refresh and another 2-4 feet in the backcountry would really help open up some brushy terrain, the situation is a major improvement over last season. After the Wednesday night storm, it has sadly taken only a couple of days for the pollution to return.  The current situation is quite a bit different from that earlier this week because we have an incredibly strong inversion in place right now very near the valley floor.  This morning's sounding showed a surface temperature at the airport of -2.7˚C with the temperature increasing with height to 6.4ºC at 828 mb (5800 ft). Source: SPC Compare that to the...

It's worth looking back at yesterday's radar loop because it exhibits several phenomena, some meteorological, some non-meteorological.  In particular, note in the loop below the persistent radar echoes over the Wasatch Range, then the development of a very pronounced north-south oriented band south of the Great Salt Lake, and then finally some north-northwest to south-southeast oriented bands at the end of the loop over northeast Nevada.   What is all that stuff? Let's start with the easy stuff.  The persistent echoes over the Wasatch Range and to some degree the Great Salt Lake are associated with orographic precipitation and possibly some lake-effect precipitation features.  I'll cherry pick a couple of times to highlight some characteristics of the storm during late afternoon yesterday.  The first was the tendency for some precipitation features to form over the lake (circled by a green line).  The second was the persistence of precipitat...

There's a fantastic view looking west this morning from the top of Snowbird's Hidden Peak, with a sea of stratus clouds over the Salt Lake Valley and the Great Salt Lake Basin. Source: Snowbird The scene is not unlike one might see from a hill above San Francisco in the summer as those clouds reflect what is known as a cloud-topped mixed layer, which dominate the weather along the coast of California in summer.  Below is the sounding from the Salt Lake City airport.  I have added a grey bar to denote the cloud layer.  From the surface to the top of the cloud deck, the temperature decreases rapidly with height and the atmosphere is well mixed.  Right at the top of the cloud layer is an inversion layer in which the temperature increases about 1.6ºC (about 3ºF) over a depth of about 60 m (200 ft).  That doesn't sound like much, but it is sufficient to keep a lid on the valley atmosphere.  Further aloft, a series of stable layers extend to nearly 600 mb, ...

Gordon Gecko should have been a powder skier Last night I thought of Gordon Gecko as I was bemoaning the lack of snow over the past several days.   We had a good run through last Monday.  The snowpack is much better than last year at this time.  But we need more.  Greed is good.  We certainly had some fun, creamy snow ski touring on Saturday.  But skiing it involved pinballing off a few rocks and a bony brushwhacking adventure at the exit.  I kept thinking that another 3-5 feet would be nice.  Greed is good. The skate skiing at Round Valley has been great so far this year, but on Sunday, things were starting to feel a little worn out.  I kept thinking that a few inches of high-density refresher would be nice.  Greed is good. I haven't skied at the resorts in a while and have heard a mixture of reports, but surely a major dump or two before the holidays would be nice.  Greed is good. However, there will be...

Building on the previous post ( Intricacies of This Inversion ), it is worth taking a look once again at some of the intricacies of the our current inversion as the evolution is quite interesting from a meteorological perspective. First some definitions.  An inversion is a layer in the atmosphere in which temperature increases with height.  Within a valley or basin, a cold pool is the layer of cold air beneath that inversion.  Inversions vary in strength, depth, and altitude.  The current inversion has been characterized by an elevated inversion rather than one that is very near the valley floor.  In addition, the cold pool beneath the inversion has featured high relative humidity.  This has led to a cold pool that has not only filled with pollution, but has featured haze (small water droplets that form in a high humidity environment), and clouds.  This morning those clouds largely fill the Salt Lake Valley, and the contrast between valley and mo...

As far as dismal grey goes, the past few days take first prize in the Salt Lake Valley due to frequent mid-level clouds, occasional low clouds, plenty of haze, and smog.  I was surprised to hear that we reached PM2.5 levels yesterday that were unhealthy for sensitive groups as the air was still relatively clean on Tuesday and it usually takes four days to build up to that level.  However, the PM2.5 trace from Hawthorne (below) shows it took three, although it was a spike around noon that got us to over 35 ug/m3. Source: Utah Division of Air Quality A curious aspect of the current inversion is that it has been relatively elevated.  Yesterday's morning and afternoon soundings from the Salt Lake City Airport show the inversion base is at about 825 mb, which is about 1500 feet above the valley floor.  Source: SPC Source: SPC Often, the inversion is right down near the valley floor, but in this instance, the smog is actually being mixed some.  It's ju...

If you are into microclimates and the impact of radiation on temperature, the last two days have been incredible. On Monday night, conditions were ideal for temperatures to fall and fall dramatically in lowland regions.  Tuesday night, things were different and clouds resulted in an increase in overnight temperatures overnight. To illustrate this, let's take a look at observations from the Peter Sinks, a limestone sinkhole in the Bear River Range of northern Utah known for incredibly low overnight temperatures. On Monday night, temperatures exhibited some ups and downs after sunset with some wild swings in temperature from about 1800 MST 3 Dec through about 0400 MST 4 Dec.  Those swings occurred in conjunction with gusty winds, which occasionally mixed out the cold pool that was forming in the Sinks.  However, after about 0400 MST 4 Dec, the wind died down and temperatures fell nearly continuously, reaching a minimum of about -35˚F at about 0900 MST 4 Dec when I sus...