Wasatch Weather Weenies

The weekend weather is looking splendid with a high amplitude ridge in full control. High temperatures in the valley will be in the 60s.  It will be a perfect weekeng for driving home from skiing in flip flops, drink a beer in the sun, and having a BBQ.  'Nuff said.

It's late March, there's deep powder to be had on the north half of the compass, and it is imperative you ski now.  The weekend is looking warm and ridgy, and perhaps some north aspect powder will survive, but probably not a lot.  Get out there ASAP.

It's always great to be greeted by post-frontal snowfall in the morning. I've been taking a look at the various model forecasts and I have to say that this is one of the most complicated storms I can remember.  There are a variety of frontal positions, low-center tracks, and precipitation distributions and intensities being forecast by the various models and their ensembles that make forecasting details very difficult. For simplicity, I'm going to use only the 0600 UTC NAM to illustrate some of the issues at play.  The red dot and yellow plus sign are located at the approximate location of Alta.  One can see the frontal band that is over us this morning in the early part of the loop,  Then a narrow band sets up very close to Alta, followed by more scattered precipitation. Those precipitation features are very narrow and small in scale and predicting their intensity and position with any accuracy is very difficult.  One can imagine how a slight chang...

It was abundantly clear today that I was overly pessimistic on Thursday when I assumed that the sun was going to be baking most aspects (see Dribs and Drabs Aren't Enough in Late March ).  We found plenty of good snow today on northerly aspects. Of course, spring is in full force and many areas are baked out, necessitating very un-Wasatch like approaches and departures for late March.  Although I think we have some good low-elevation snow years in the future, this folks is the snow climate of the Wasatch in the future. Now let's talk about optimism.  The models continue to key in on an active pattern for Monday and Tuesday. I'm not speculating on details yet, but I'm keeping my schedule clear for Wednesday.

Changes are afoot for early next week as a deep upper-level trough and colder air are expected to settle over the interior western U.S.  The 0600 UTC GFS, for example, parks the trough right over northern Utah on Tuesday with a very encouraging pattern for mountain snowfall. That same GFS run goes big for precipitation, producing about 2 inches of total water equivalent at Alta from roughly noon on Monday through noon on Wednesday.  Wouldn't that be nice. I'm intrigued, but am keeping my excitement in check.  Much will ultimately depend on the track, position, and intensity of the trough and this is the type of pattern that is typically characterized by considerable uncertainty in precipitation amounts.  Most members of our downscaled NAEFS are generating precipitation during the period, but amounts range from about .75 inches to as much as 3 inches of water.  That's a big range and my impression is that the uncertainty might be even greater than indica...

Readers of this blog are well aware that all snow isn't created equal.  Some storms produce better skiing than others simply because of how the snow is stacked (e.g., right-side up vs. upside down).  Once on the ground, many terrible things can happen to snow due to wind, sun, or (gasp) rain and other factors. The pattern setting up for later today through early Friday morning will probably produce a few dribs and drabs of snowfall in the central Wasatch.  The NAM generates about .3 inches of water and a bit more than 6 inches of snow for Alta Collins by Saturday morning. The GFS is more excited, but has proven to be somewhat untrustworthy for precipitation amounts, so I'm blowing it off in this discussion.  Hence, I'm sticking with a forecast of dribs and drabs.  A trace to two inches tonight and maybe 2-4" tomorrow night. If this was January, dribs and drabs aren't preferable to a larger storm, but they are a nice refresher. In late March, however, ...

This is old news for some of you out there, but I thought I would mention it in case you missed it.  Global temperatures in February were mind-bogglingly high, coming in more than 2ºF above the 20th century average thanks to global warming combined with a strong El Nino.   Source: NCEI If we look at 12-month periods ending in February, the past year was about 0.3ºF warmer than the previous year and a bit more than 0.5ºF warmer than any year prior to that.  Mother Nature sees your global warming hiatus and raising you 0.5ºF. As we've discussed previously, we're going to see some relaxation from these high temperatures once this El Nino wanes.  That will not reflect an end to global warming.  The long-term trend is up.  Count on it. 

There's nothing like a spring trough passage in northern Utah.  As David Bowie said, ch-ch-ch-ch-changes. The loop below presents the 700-mb (near crest level) temperatures and winds from 2200 UTC (4 PM MDT) yesterday to 1500 UTC (9 AM MDT) this morning.  We've transitioned from warm southwesterly flow with 700 mb-temperatures near +3ºC, leading to a maximum temperature yesterday of 68ºF, to northwesterly flow with 700-mb temperatures near -6ºC. Those current 700-mb temperatures, when combined with the high precipitation rates we are currently experiencing, are sufficient to bring snow levels down to the valley floor.  We are currently seeing heavy snow comprised of large aggregates (i.e., large snowflakes formed by the sticking of snowflakes together) at the University of Utah. I took that photo about 10 minutes ago and since then the snow is piling up fast.  In addition, although the ground is warm, snowfall rates are high enough that snow is sticking o...

Snow storage for the 2014 Sochi Winter Olympics Every spring I bemoan the loss of winter snowpack.  It seems like such a waste.  If only we could start the next ski season with some of that snow. I first heard of snow storage a couple of years ago when Sochi was stockpiling snow through the summer to ensure adequate coverage during the 2014 Winter Olympics.  Then, Outside Magazine ran an article on it today (see The Future of Winter Sports Is Storing Snow ), sparking the synapses yet again. The idea is not as crazy as it sounds.  Let's suppose that you wanted to do this at Alta.  Typically closing day is in late April or early May.  That's just a bit after the time of peak snowpack, but there is typically a lot of snow left, especially on the upper mountain.  Groomers would then push the snow into large piles along Mambo and Corkscrew, which would be covered with insulated, reflective blankets.  This snow would then be used to cover the...

Chris Farley always delivered, but even if all other "tropical storms" bow before El Nino, as he suggests above, the 2015/16 "Super" El Nino continues to be a bust for the southwest United States. Let's go back to a few months ago when we knew a strong El Nino was likely for this winter.  At that time, one could find all sorts of graphics like the one below showing the "typical" wintertime pattern associated with El Nino, including the wet southwest. Source: NWS Forecasts from the Climate Prediction Center showed the dice loaded for above average precipitation in the southwest. Source CPC The fact that this El Nino was going to be strong led some people to believe that the odds of a wet southwest were high, especially since the last two strong events, 82/83 and 98/99 were fairly wet in the southwest. Let's fast forward to today.  The percent of average precipitation below covers the past 90 days (roughly since just before Christ...

Many of you have probably read that February produced the most abnormally warm temperatures in the instrumented record, and by a fairly large margin.  The cause of this extreme warmth is the combination of global warming and El Nino.  The trace below shows the global average temperature anomaly for the month of February since 1890, as analyzed by the Japan Meteorological Agency (JMA).  Note the El Nino fueled spike in 1998, toward the end of the last "uber" El Nino, and then in 2016, consistent with the current "uber" El Nino. Source: JMA Once the current "uber" El Nino wanes, global cooling is coming, at least relative to where we sit right now.  That cooling, however, will reflect short-term climate variability and will be temporary. In my post  Locally Dense Snow and Globally High Temperatures  back in November, I made made the prediction that such a drop in temperatures, as occurred following the last Uber El Nino in 1997/98, you will hear peopl...

The good news is that as of 4 AM MDT (I'm up early), we've picked up 5 inches of snow at Alta-Collins overnight, bringing the storm total to 10 inches and the total snow depth to 100 inches.  The bad news is that the storm total of 10 inches is well below expectations. My forecast issued on Sunday was probably my worst of the season (see Skinny Skiing Followed by the Storm Forecast ).  I called for .7 to 1.4 inches of water and 7 to 14 inches of snow at Alta-Collins through 6 PM MDT Monday.  Only 0.54" of water and 5" of snow were observed. One has to hand it to the NCAR ensemble.  While the NAM and GFS were going for big water, the NCAR ensemble was drier and the 0.54" that was observed fell within the range predicted. This is the future folks.  Multi-member ensembles run at cloud-permitting grid spacings (i.e., 3 km or less).  The sooner we get there, the better.

Alta-Collins picked up about 3 inches of 10% water content snow and we now are waiting to see what the post-frontal crapshoot will do today. When it comes to post-frontal precipitation, current operational models like the NAM and GFS often have problems.  There is a good reason for this.  The clouds that populate the post-frontal environment tend to be shallow and small in horizontal scale, as illustrated by the photos below which I took this morning. With grid spacings of around 12-15 km, neither the NAM nor the GFS can directly simulate these clouds.  A meteorologist would say they are unresolved .  In addition, those models are not able to resolve the fine-scale topography we have in northern Utah, creating just a nice gradual slope from the Great Salt Lake basin to the Uinta Mountains and southeast Idaho.  Because of this poor resolution, in post-frontal situations like the one we are in today, the NAM (and GFS) often just generate steady precipita...

Hoping to get in one last hour of cross-country skiing this winter, I drove up to Soldier Hollow this morning and took advantage of the man-made ribbon of white that still covers about 10 km of trails. Conditions were surprisingly good.  The 10 K of trails that were open were well covered and meticulously groomed.  With few people out, it made for fun skiing.  Trail passes were $10, so the price was also right. By now, you are well aware of the forecast of a storm beginning tonight.  Although we may see a few mountain snow showers today, things don't really pick up until sometime between 9 PM and midnight tonight as an upper-level short-wave trough moves through.  Snow levels through midnight will reach 7000-8000 feet, before falling late tonight.  In the wake of the trough, strong northwesterly flow should yield periods of snow showers through Monday. For Alta-Collins, most of last night's NCAR ensemble members are going for 0.6 to 1.2 inches of w...

Nearly all of the snowflakes that fall on the Wasatch Mountains grow in mixed-phase clouds .  Mixed-phase clouds are comprised of both ice crystals and supercooled cloud droplets.  Supercooled cloud droplets are below freezing, but are still in the liquid phase. The beauty of mixed-phase clouds is that the relative humidity for ice is typically higher than it is for liquid water.  As a result, ice crystals grow faster than water droplets in mixed phase clouds.  This preferential growth of ice crystals is known as the Bergeron Process  after Tor Bergeron, the Swedish meteorologist who proposed it as a mechanism for precipitation formation in clouds (it is sometimes called the Wegener-Bergeron-Findeisen process since Alfred Wegener and W. Findeisen also made contributions to the theory). If you were at Alta today (Saturday), you may have seen the Bergeron process in action.  The shallow cumulus clouds that were over Alta were mixed-phase clouds.  The...

Note : Blog post has been updated to correctly identify the warmest 10 Feb – 10 Mar period on record. For the second  third year in a row, the Heat Miser (pictured above) has taken over northern Utah, bringing in a strong early thaw to the detriment of snow lovers.  From February 10 to March 10 (yesterday), the average temperature in Salt Lake City was 44ºF, making that period the 6th warmest on record.   Last year  2014 was the warmest such period on record. The warmth has ended cross-country skiing at Mountain Dell and along many (but not all) of the trails in the Park City area.  We had a decent corn cycle and a fortunate burst of powder a few days ago, but by and large ski conditions are similar to what we might expect in perhaps 3-4 weeks. A trough is advertised for early next week and if it brings the goods, I suggest you take full advantage.  

The role of libraries is changing in the digital age, but their importance isn't.  Librarians stand as protectors of history and conduits to knowledge.  Here at the University of Utah, the Marriott Library is a key cog in the machine of education and innovation.  I use the resources provided by the Marriott Library at least daily if not hourly for teaching and research. Readers of this blog may be interested in the Marriott Library's  Utah Ski Archives , which were created to preserve the history of skiing in Utah and the Intermountain West.  Amongst the treasures in the archives is this historical video of skiing Alta in 1946, which has been posted up on YouTube. Click on the link and find many more. Materials and reports produced by avalanche research at Alta are also available at the Marriott Library, including a subset that you can access digitally here .  For example, there's Barry Nielsen's 1966 report on forecasting snowfall rates at A...

No time for a post today as I'll be giving the Global Change and Sustainability Center seminar this afternoon at 4 PM in 210 ASB.  Those of you on campus should stop in for the pre-seminar refreshments and, hopefully, hang around for part of the talk.  Details below.

Yesterday and last night provided a much needed return of weather to northern Utah.  Wind, thunder, falling snow levels, and a decent pasting of high-elevation snow made for an exciting day.  If I'm adding up the totals right, Alta-Collins came in with nearly 1.4" of water and 11 inches of snow.  I suspect the high-elevation skiing should be decent today. Although we may see a few hit-or-miss snow showers through Wednesday, the work week ahead looks mainly dry, which means we're back to looking far into the future for the next storm.  As such, now is a good time to discuss the experimental downscaled products from the North American Ensemble Forecast System (NAEFS) that we provide on weather.utah.edu . Ensemble forecast systems are now de rigueur for medium-range forecasting and are quickly reaching that status for short-range forecasting.  They are run by several major forecast centers.  The NAEFS is comprised of ensemble forecasts produced by the U.S...

After many days (seemingly weeks) of little storm action, we are going to get some tomorrow and tomorrow evening.  Details are difficult to project, but it's more action than we've seen in some time, so that has me excited, even if I'm uncertain how it will all play out. The NAM forecast for 2100 UTC (2 PM MST) tomorrow shows some of the key features of the event.  The first is precipitation associated with moist, southwesterly flow ahead of the approaching cold front and occuring in the forecast below over the Wasatch and Uinta Ranges.  The second is precipitation associated with the cold front, which at 2 PM tomorrow, is forecast to be pushing into western Utah. The NAM precipitation forecast graph below shows the two part system with a burst of precipitation in th southwesterly flow from about 5 AM tomorrow to 1 PM in the afternoon in the moist southwesterly flow, then a lull in the precipitation, and then a burst with the front late tomorrow and tomorrow evenin...

No-Change Forecast Not much change in the forecast from yesterday to today.  The models are still calling for a front to move through northern Utah on Sunday.  Most of the NAEFS ensemble members, for example,  are calling for a significant event, although I think the totals might be a bit overdone (e.g., Alta below). After that, most (but not all) of the NAEFS ensemble members are keeping us mainly dry with only a few snow showers here or there through the middle of next week.  The European has a similar solution.  After that I'm not speculating. Arctic Sea-Ice Record As most of you know, globally average surface temperatures have really jumped through the roof over the past several months due to the combination of long-term global warming with a strong El Nino event.  Much of the focus has been on the tropical Pacific and projections of impacts on the western U.S., but this has also been a remarkably warm winter in the Arctic.  This warmt...

When suffering through a dry spell, it's easy to read too much into the extended range forecasts, but we will take a peak today, keeping in mind that we are still 3-4 days from seeing a possible storm moving in late Sunday. In the short term through Saturday, the warm-weather corn harvest will continue, with just a few clouds at times (like this morning).  For you weekend warriors, Saturday will be characterized by warm southerly flow with 700-mb (10,000 ft) free atmosphere temperatures reaching nearly 2ºC by afternoon. Given that we've had virtually no snow now for some time, treat Saturday like an April day and work the aspects. Right now, Sunday looks to be a transition day with a possible frontal passage late in the day.  The 0600 UTC GFS put the front just downstream of the central Wasatch by 0000 UTC 7 March (5 PM MST Sunday). It's a bit too soon to have confidence in the exact timing of the front, but it does look like we will finally see some precipita...