ECMWF AIFS Forecasts Now Available

Forecasts from the ECMWF Artificial Intelligence/Integrated Forecast System (AIFS) are now available on weather.utah.edu.  Look for ECMWF AIFS in the left-hand nav bar.  An example forecast is below.  Based on the data available, most of our favored four-panel variables are available, but due to limitations in the data provided, there is no forecast of outgoing longwave radiation (used for a forecast infrared satellite image) in the upper-right panel and the precipitation is six hourly, which is a longer accumulation period than many of our products.  

As illustrated in the link at the top of this post, AIFS forecast skill at 500 mb is roughly the equivalent of the ECMWF IFS (called HRES on weather.utah.edu) through about day four. At longer lead times, it exhibits somewhat better skill.  The AIFS forecasts after 9 days are about as good as the IFS at 8.5 days, so they are basically giving you an extra half day of skill at longer lead times.  That's not enough to abandon looking at the IFS, GFS, or ensembles, but it certainly makes sense to make the AIFS an important edition to your forecast workflow.  

The AIFS forecasts are produced at ~31 km grid spacing and provided on at 0.25° grid.  The latter is similar to what we use for the GFS-0p25deg and ECMWF HRES products on weather.utah.edu.  However, the AIFS forecasts are smoother, especially for precipitation, which is a reflection of the training dataset and techniques.  

In the long run, I am interested in adding the AIFS ensemble to the Utah Snow Ensemble.  That is a 51 member ensemble run at ~31 km grid spacing and available at 0.25 deg.  We have put in for computer time and engineering support on the new University of Utah Redtail supercomputer, but a lot has to fall into place for this to happen.  It's unclear if I have enough bandwidth and compute power to make this happen otherwise, although one never knows.  

Musings on AI and Higher Education

Classes start at the University of Utah this coming Monday, August 24.  Campus is getting busier and energy levels are rising.  The start of a new school year is coming!

I was on sabbatical last academic year and although I did teach for a full semester at the University of Innsbruck, it feels like higher ed has changed dramatically since the last time I taught at the U in spring 2025.  One reason for this is the rapid advancement of AI, including weather forecasting models and generative AI assistants like ChatGPT.

My approach to teaching has been one that has brought new tech into the classroom.  The weather analysis and forecasting classes I teach today use tools and techniques that did not exist when I started as a professor and in some cases even a couple of years ago.  

As we go into the new semester, I've been thinking a lot about how to utilize AI in the classroom but also how to ensure that students are using AI tools responsibly.  The lowest-hanging fruit is bringing AI forecast modeling systems, like the ECMWF AIFS or Google WeatherNext into my lectures and weather discussions and using them alongside traditional numerical weather prediction model forecasts.

ECMWF AIFS forecast.  Source: pivotalweather.com

I'm not sure yet if I'll have time to develop my own graphics (my preference since I can tailor things for the western US and Utah) or add these systems to products like the Utah Snow Ensemble, but we will at least be using graphics from other sites.  

I am more conflicted about generative AI and related tools that may have some potential to accelerate learning but can also be used in ways that prevent students from the hard work and deep thinking needed to develop the creativity and critical thinking skills.

Students need an advanced education that includes the foundational knowledge, expertise, judgement, and vision to extract maximum benefit from AI.  There are no shortcuts to the top. A scientist needs a well trained mind just as an athlete needs a well trained body.  

As an educator, I want to ensure that AI is a powerful assistant for learning and not a training shortcut that leads to cognitive atrophy.  If I can borrow from a recent article by Mya Poe and Dylan Dryer, our students should be charting the path of scientific discovery, not machines.  

Summer Skiing Is Dead

Following up on the post from August 8th (The Death of Summer Skiing), as reported over the weekend by weathertoski, the last operating ski area in the Alps, Passo Stelvio in Italy, closed on Saturday, August 15th.  There are no summer skiing options left in the Alps.  

They suggest this may be the first time there's no (lift served) summer skiing operations in the Alps.  It's likely that applies to the Northern Hemisphere.  Mt. Gassan (Japan) appears to have closed in early July.  Timberline on Mt. Hood appears to have closed on July 19.   I believe late operating resorts in Norway are also closed.  

2026.  The year that summer skiing died. 

The Afternoon Deluge

Monsoon thunderstorms developed over the Salt Lake Valley this afternoon and brought heavy rainfall to the northeast corner of the Salt Lake Valley, especially the University of Utah. 

The event started with the development of a cell over or just downstream of the Salt Lake International Airport.  This one moved off over North Salt Lake.  Shortly therafter, two cells formed just to the south of the track of the first cell and pounded the Avenues and Avenues Foothills.  

Then things got interesting as a cell exploded west of Murray and moved northeastward to the University of Utah.  This was the beginning of a series of training storms that pounded the area around the U before things settled down.  The full sequence is below.  I'm hoping the video will upload properly as I'm working with some limitations currently.  

Storm total Radar precipitation estimates through 2200 UTC (1600 MDT), which does not quite capture the entire storm period so expect these to go up a bit show more than an inch of rain in a SW to NE oriented band from just north of Taylorsville to the foothills above the University of Utah.  

Source: https://mrms.nssl.noaa.gov/qvs/product_viewer/

Maximum accumulations of > 2" were centered on Dry Creek Canyon and Mt. Van Cott, pretty much over and just north of the burn scar above the U hospital.  

Source: https://mrms.nssl.noaa.gov/qvs/product_viewer/

Some transport of falling rain can occur below beam elevation, so exactly where this rain fell on very small scales is hard to say, but this does appear to have been a significant stress test for flash flooding in the burn scar area.  

As I type this, I don't have access to estimates through the end of the storm or information on the burn scar.  Hopefully it held up as that would be a significant victory.  

El Niño Is a Lock But Snow for Wasatch Less Certain

The National Weather Service Climate Prediction Center (CPC) issued their monthly El Niño/Southern Oscillation (ENSO) Diagnostic Discussion today and El Niño is looking like a lock for this winter.  They give a 90% chance of a very strong El Nino during Northern Hemisphere fall and winter.  

By most definitions, a strong El Niño is already in place over the Tropical Pacific Ocean.  Sea surface temperatures more than 1°C above average already extend westward along the equator to nearly 180° with areas more than 3°C above average near the coast of South America.  Anomalously warm sea surface temperatures also extend poleward to the west of North and South America.  

ENSO strength probabilities from CPC are near or above 90% for September-November through November to January.   The odds of a strong event decline later in the winter, although the odds of El Niño conditions persisting remain high.  

El Niño is a tropical climate phenomenon with impacts even in the mid and high latitudes as it affects jet stream and storm track patterns.  During Northern Hemisphere winter (December – February) over North America, El Niño can be associated with anomalous warmth of Alaska, western Canada, and the northwest United States and wetter conditions in the southern US and northern Mexico.  Linkages to the mid and high latitudes are weaker in summer.  

Source: https://www.climate.gov/news-features/featured-images/global-impacts-el-ni%C3%B1o-and-la-ni%C3%B1a

For the Wasatch, the relationship between El Niño and snowfall is relatively weak.  It is popular for people to look at past events for analogs, but there isn't a true analog to this event and strong events are relatively rare during the historical data period, so the sample size is small.  Additionally, El Niño is an important factor, but there are other phenomenon that can influence the weather in any given winter, including the possibility that what happened in a previous strong El Niño year more strongly reflects randomness than a real signal.  The CPC outlook (now almost a month old so maybe there will be an update) still puts northern Utah in the "equal chances" category for December to February precipitation, meaning they don't consider there to be better skill than chance for what will happen this winter in our neck of the woods. 

Source: CPC

They are, however, giving better odds for above average temperatures, although that's not all that surprising given recent trends. 

Source: CPC

My view is that the usefulness and reliability of these seasonal outlooks for anticipating what the ski season will be like is limited in the Wasatch.  In addition to the limited correlation in our part of the world, how the snow comes and how the temperatures fluctuate matter.  A warm winter can yield a good snow year at low elevations if the storm characteristics are right.  A year with above average snowfall due to big snows in November and December is very different from one with big snows in March and April.  

As such, I'm comfortable saying that I can't confidently predict how this coming season is going to play out in the Wasatch.  It's probably better to spend your time getting in shape for ski season than worrying about what the season will bring.  

Some Relief is Coming

August is off to a blistering start.  Seven out of ten days to start the month with high temperatures above 100. Six days with low temperatures 70 or above including an 81 on August 9.  The average temperature for the first 10 days of August at the Salt Lake City International Airport was 85.2°F, the second highest on record behind only 2024 (86.3°F).

Relief is coming, however, due to a subtle change in the large-scale pattern.  The upper-level ridge that has been over us the past few days is weakening and sliding eastward slowly while troughing is developing along the Pacific Coast.  The GFS forecast for 0000 UTC 14 August (1800 MDT Thursday) shows the trough along the Pacific Coast (red dashed line) with a plume of elevated integrated vapor transport streaming up the lower Colorado River Valley and into Utah (red arrow).  A weak trough is also evident at 700 mb over central Nevada and far northwest Utah.  

The net impact of these changes will be a decline in temperature, increase in relative humidity, and increasing coverage of showers and thunderstorms.  These trends begin today when we should fall short of 100 for the first time in five days, and continue through the end of the work week with each day a little cooler with increasing odds of precipitation through Thursday. 

NWS Forecast for Salt Lake City downloaded 8:35 AM MDT Thursday 11 Aug 2026

The low of 59 forecast for Thursday night and the high of 83 forecast for Friday would be the lowest temperatures we've seen since June 30th when the minimum was 54 and the maximum was 82.  

Let's hope it verifies and that we see beneficial rains for the firefighting efforts.  

The Death of Summer Skiing

Summer skiing used to be a thing in the climate system of the 20th century.  In North America, there used to be skiing on the Palmer Snowfield of Mt. Hood deep into summer.  When I lived in Seattle, we skied there on Labor Day weekend in early September calling it the "Opening Day of Ski Season" since the next winter was coming.  There also used to be skiing deep into July on the Horstman Glacier at Blackcomb in Whistler.  

In the Alps, summer skiing became a thing in the 1970s and by 1985 there were 32 operating glacier skiing resorts.  These didn't necessarily operate all summer, but they did offer warm-season skiing.  As recently as a few years ago there were resorts that operated year round or very late in the summer [Hintertux (Austria), Zermatt (Switzerland), Saas Fee (Switzerland), Passo Stelvio (Italy)] or into portions of July and/or August [Kitzsteinhorn (Austria), Mölltal (Austria), Les 2 Alpes (France), Tignes (France), Val d'Isere (France) and Cervina (Italy)].

But things have changed.  The 2020s have been rough for summer skiing and 2026 has been awful: 

• There is no longer summer skiing on the Horstman Glacier as Blackcomb pulled the plug on that a couple of years ago.
• Timberline closed July 19 due to low snowpack.
• Hintertux closed on July 26.
• Zermatt suspended summer skiing due to "persistently high temperatures, the lack of a night-time cool-down, repeated thunderstorms" on July 31.  
• Saas Fee will suspend summer skiing on 10 August.

It appears that the only ski area that could be operating this year in the Northern Hemisphere after 10 August is Passo Stelvio in Italy.  I've never skied there, but their web cam image from Friday August 7th didn't pique my interest with a near-complete loss of seasonal snow and little in sight but glacier ice and grit.

Although economics and demand can affect resort operations, in recent years the changing climate has increasingly resulted in poor snow conditions, heat waves, high-altitude rainfall, and other factors that have reduced glacial coverage, the persistence of seasonal snowfall, and summer skiing conditions.  

Although there is variability from year to year, the long-term trend is not summer skiing's friend.  

More Weather and Climate Concerns for the 2034 Games

An article published yesterday in the Salt Lake Tribune discusses eight ways proposed by professors at Utah State to improve wintertime pollution for the 2034 Olympic Winter Games.  Fraser Bullock who is leading the Utah 2034 effort is quoted as saying a few years ago that: 

"Air scared the heck out of me. It scares the heck out of me because we got so lucky last time because we had an inversion the day before [the 2002 Olympic Winter Games].  And the morning of Opening Ceremonies, in comes a storm, blows it all up [and] we had really great weather."

I was involved in weather support for the 2002 Olympic Winter Games and remember the pre-Olympic inversion well.  Prior to the Olympics, there are a lot of press from all over the world looking for stories to write.  I remember participating in a press conference in which speakers would get up, discuss something about the Olympics, and then answer press questions.  I had discuss Olympic Weather and somehow got slotted in after then Governor Mike Leavitt and the Secretary of the Department of the Interior Gale Norton.  It was one of those "what am I doing here" moments.  

Instead of talking about the Greatest Snow on Earth though, I had to answer a lot of questions about inversions and air pollution because the air quality in Salt Lake was terrible.  As an example, I was able to locate an article, written by AP reporter Rich Vosepka, in which I was quoted from the news conference:

"Inversions are created during the winter because the sun isn't high enough in the sky to chase cold air out of mountain valleys," said Jim Steenburgh, a meteorology professor at the University of Utah. "Air higher up gets warmer, and smoggy gunk stays trapped in the valley air. It takes strong wind or a storm to dispel the haze."

The title of the article was "Storm Should Clear Olympic Smog" and indeed our forecast team had predicted that to happen.  Larry Dunn from the National Weather Service was also quoted in the article as saying:

 "Yes, it's going to snow.  We're revealing the Wasatch Mountains.  We're going to break the inversion." 

So, that was the first Olympic weather miracle (there were others) and the first important Olympic forecast success.

Weather and climate affect many aspects of Olympic logistics, safety, and competition.  The concerns are many from lack of snow, too much snow, disruptions of transportation, competition delays, spectator exposure to hazardous weather, etc.  The list is very long and involves things you might not think about.  What happens when a thunderstorm pops up at a temporary outdoor venue with 30,000 spectators?  When will the moderate winds that seem benign but are a safety concern for ski jumping die down so we can start the competition?  How much snow will we need to remove from the women's downhill course tomorrow?  What is the avalanche risk outside the perimeter of Snowbasin for security teams?  

To highlight the potential Olympic weather impacts prior to the Games, John Horel of the University of Utah and Bill Alder of the National Weather Service put together a list of high impact weather events that previously occurred over northern Utah during the Olympic period.  We used to sample from it to raise weather awareness for Olympic planners and operators.  Here's a snippet of three seasons:

1996

• Feb 9. High pollution levels along Wasatch Front
• Feb 11. Record maximum temperatures in the Wasatch Mountains. Alta 57°F 

1995

• Feb 11-12. Winter storm in northern part of state. 1 backcountry skier killed in Big Cottonwood Canyon. 2-3 feet of snow ski resorts
• Feb 13-14. Major winter storm. Thunderstorms during morning commute. Winds at ski resorts to 120 mph. Hundreds of auto accidents. 1-2 feet snow at ski resorts
• Feb 19-24. Warm spell with new daily high temperature records. Park City 56°F on Feb 24. February warmest on record at Salt Lake City airport 

1994

• Feb 6-8. Major storm; 2-3 feet snow at ski resorts. Skier killed near Alta.
• Feb 10-11. Severe weather with lightning and squall line. Power out in Cache Valley. Park City schools closed. Avalanche near Solitude. 2-3 feet snow at ski resorts.
• Feb 17-19. Rain followed by snow in valleys; heavy snow in mountains. Roads flooded in Cache Valley. Slick roads in passes and Park City area. 68 mph gust in Kearns Feb 22. Snow storm during commute; over 100 accidents. Runways closed for periods of time at Salt Lake Airport. High winds and drifting snow. 10 inches snow in valley to several feet in mountains 

The internal list we had covered many more years, but as I reviewed it this week I realized that it was missing a few things that might be a concern for 2034.

First, the risk of poor snow conditions due to warmth, drought, or both is greater today than it was in 2002.  Back in 2002, I was quite confident that natural or artificial snow cover at the venues was not going to be a problem.  I am still somewhat confident that with investments in snowmaking and storage we can get the job done in 2034, but I still have some concerns.  Even with snow coverage along trails, the look of the venue (a white ribbon of death is not a good look) and the quality of the snow (soft snow is generally not desirable and in some cases a safety concern) are important.  The Olympics in February have more insurance against these issues, but the Paralympics are scheduled for March 10 to 19.  I used to think Soldier Hollow was the main concern, but last season was an eyeopener for other venues.  Snowbasin closed on March 22.  

Second, the threats posted by wildfire and wildfire smoke are increasing.  This year we have already seen almost a half million acres burned this year, including almost 300,000 acres of forests and woodlands.  Eagle Point ski area was severely damaged by the Cottonwood Fire and will not open this coming winter.  All of the outdoor venues currently proposed for Utah 2034 are classified with high or very high wildfire hazard potential (orange and red below).  The potential for wildfire damage at an Olympic venue prior to the games is very real.  

Source: https://wrap.wildfirerisk.utah.gov/Map/Public/

During winter, wildfire risk is low in northern Utah, but not zero, especially at lower elevations in March after a dry winter. Of highest concern might be a grass and brush wildfire in bench and valley areas during strong southerly flow, which is typically drier and warmer, or severe downslope (i.e., canyon) winds.  

There is also the possibility of elevated PM2.5 due to transport of smoke from wildfires elsewhere.  

Third, dust storms are a possibility. I don't recall being aware of this possiblity in 2002 and they weren't in our list of high-impact weather events, but they could have been.  There certainly were dust storms in northern Utah then, but monitoring isn't as good as today and perhaps awareness was lower.  Climatologically dust storms become more frequent in March and we have seen recent events, even in the heart of winter, due to emissions from the exposed Great Salt Lake bed.  

Dust plume from the exposed Great Salt Lake Bed extending down the Salt Lake Valley January 20, 2025

The primary impacts of such events are poor air quality, degraded visibility, and deposition on snow.  

The list above is not a forecast.  It is simply a summary of some of the hazardous or problematic climate and weather phenomena that could affect the Olympic and Paralympic Games.  In 2034, much will depend on the weather prior to and during the Games.  In 2002, the weather turned out to be "perfect" or more accurately, about as good as it could be, as glorified by Pat Bagley in the Salt Lake Tribune.  

Perhaps that will be the case in 2034, but what Marshall Shepherd likes to say about hurricane preparedness applies well to Olympic weather planning.  "Hope or waiting and seeing is no longer a valid risk mitigation strategy."  

Escaping Smoke is Hard

During winter, the Salt Lake Valley often sees pollution episodes with elevated particulate matter due to the presence of low-elevation cold pools that persist due to the limited solar heating.  This enables particulate matter that forms from the emissions from automobiles, industry, home heating, and other sources build up within the cold pools, resulting in poor air quality.  This poor air quality is reflected in elevated levels of particulate matter with a diameter of 2.5 micrometers or less, or PM2.5.  Such events are known colloquially as inversions.

Because the PM2.5 is typically trapped in the cold pool, one can usually find clean air by moving to higher elevations.  The depth of the pollution varies from event to event and sometimes from hour to hour as the cold pool sloshes around in the valley.  At times, the benches may be in the clear air.  At other times, elevated PM2.5 can extend higher.  

An example, from December 15, 2025, is shown below.  Taken from about 6000 feet in the Avenues foothills, one can very clearly see the layer of pollution within the valley, but clear air at upper elevations.  

PM2.5 associated with wildfire smoke in the summer is more complicated for a number of reasons.  First, the heat and intense vertical motions associated with wildfires can inject wildfire smoke anywhere from the surface to more than 15 km.  Because the wind often varies in strength and direction with height, the transport of that wildfire smoke can also vary in direction.  As an example, note how smoke from the Grasshopper Fire in northern Oregon spread in two different directions yesterday morning. 

Source: College of DuPage

As a result, smoke can be found even at the highest elevations and PM2.5 concentrations do not necessarily decrease with height.  Sometimes they can even increase with height.  

I had planned to hike up Snowbird this morning, but thought this might not be a good idea after looking out the window and taking a look at the PM2.5 estimates from Purple Air.  Unlike in winter, elevated PM2.5 wasn't confined to the Salt Lake Valley.  One could find values > 35 ug/m3 (i.e., unhealthy for sensitive groups) even at some locations in the Snyderville Basin.  Although there are fewer upper-elevation sits, at 8:57 AM MDT the highest PM2.5 was actually near the mouth of Little Cottonwood (53-68 ug/m3), Red Pine Lodge at Canyons (83 ug/m3), and Silverfork in Big Cottonwood Canyon (61 ug/m3).   

Source: Purple Air

It's hard to say if the top of the tram would have been above the smoke. The 9 AM webcam suggested it was close, but smoke clearly enveloped the terrain to high elevations.   

Source Snowbird

I ended up going for a less strenuous walk in the Avenues foothills.  Although the PM was still elevated, my back likes having the kinks worked out. Visually inferring PM2.5 concentrations can be tricky for a number of reasons, but the view toward the Oquirrhs seemed to confirm that this morning concentrations may have been higher above the valley floor as one could see the base of the Oquirrhs (red arrow) but not the mid or upper elevations (blue arrow).  This doesn't mean the valley floor had low PM2.5 values, but just that they appeared to be lower than at mid elevations.  

The National Weather Service has a modeling system to predict wildfire emissions and smoke transport and concentrations known as HRRR smoke. Its analysis for 1300 UTC (0700 MDT) this morning actually showed higher concentrations in upper elevation areas (e.g., Stansbury, Oquirrh, and Wasatch Ranges) compared to the intervening valleys. Although concentrations were lower than observed, it at least had the right idea. 

The HRRR smoke forecasts suggests perhaps some improvement later today and tonight.  We will see if that pans out.  Smoke forecasts are tricky.  

Note that the situation this morning with lower PM2.5 in the valley cannot be generalized to all wildfire situations.  There are times when PM2.5 concentrations from smoke can be higher at lower elevations.  Escaping wildfire smoke requires more investigation (and maybe a bit of luck).  The HRRR smoke forecast can be helpful.  I like to access them at https://sites.gsl.noaa.gov/desi. Select "HRRR-CONUS" as the dataset, an appropriate runtime (those starting at 0, 6, 12, or 18Z will extend out 48 hours whereas the other go to 18 hours but are more recent), and then "surface smoke" from the surface drop down menu at top. 

Cooler, Smoky Air

It felt almost pleasant this morning as the the low temperature was 70 or possibly 69 at the Salt Lake City Airport.  70 is actually the average low at the airport, which just goes to show how insane summer has become around here that it feels cool and refreshing when we finally have an average low.  Average in this case is based on 1991-2020, so if we went back further, we're probably still running above the 20th century average.  

Countering the coolness was the smoke, which thickened overnight.  PM2.5 concentrations at Hawthorne Elementary climbed substantially after midnight and are now above 40 ug/m3, in the unhealthy for sensitive groups category.  

Source: MesoWest

Yesterday's MODIS imagery shows several major sources of smoke in the Great Basin and Pacific Northwest including fires on the eastern slopes of the Cascades and in northeast Washington that exploded over the weekend, sadly causing serious losses of homes and structures in Spokane.  There are also fires in Oregon and southwest Idaho that are major smoke producers, as well as the Widemouth Fire in central Utah.  

Given the weak trough that came through last night, which resulted in a shift of the flow to northwesterly, the source of the smoke in the Salt Lake Valley today is not the Widemouth Fire but sources to the northwest and west.  

Sadly there's still a lot of summer 2026 to go.

Preparing for Wildfire

Fire is on the minds of many of us who live in Utah and the western United States.  Conditions favorable for explosive wildfire spread are increasing in severity and frequency.   More and more I realize that my "instincts" about wildfire risk in my region, neighborhood, and home probably do not match reality. 

I encourage everyone to take a look at an article written by Tom Cova, a Professor in the University of Utah's School of Environment, Society, and Sustainability, that was published in today's Salt Lake Tribune.   

The article emphasizes the importance of being ready to evacuate given the fact that "fast-moving fires compress every step of an evacuation."  As Eisenhower said, "Plans are nothing, planning is everything."  This is especially true during extreme wildfire spread.  

Natural Air Conditioning

Residents of the northern Wasatch Front and northern Salt Lake Valley were treated to some natural air conditioning thanks to a complex of thunderstorms that moved across the area yesterday evening.  

Source: ral.ucar.edu

Some of the thunderstorms were severe and produced wind gusts of 60 mph in Sugarhouse, 64 mph in Tremonton, and 72 mph at the I215/I80 exchange.  

There was also beneficial rain and cooling. Temperatures at the Salt Lake City International Airport dropped to 67°F, the lowest temperature observed there since July 4, and I was able to get temperatures in my house below 70°F for the first time since we returned from Austria.  

We were also treated to a beautiful double rainbow as the storm moved off to the east.  

Unfortunately, as has been forecast for a few days, the heat is expected to return in spades by the weekend, with the National Weather Service issuing an Extreme Heat Watch for SaturdayAfternoon through Sunday Evening with temperatures up to 105°F and lows in the low to mid 70s for the Salt Lake Valley and other lowland areas of northern Utah.  

The cool was brief but fun while it lasted. 

All-Time Record Tied

Yesterday (Monday) morning's minimum temperature at the Salt Lake City Airport was an incredibly warm 85°F.  Daily records though are based on the minimum and maximum temperatures over the period from midnight to midnight local standard time and last night temperatures dropped to 82°F by midnight local standard time (1 AM MDT), so that stands as the minimum temperature for the day. 

Still 82°F ties for the highest minimum temperature at the Salt Lake City International Airport.  Other days that only cooled to 82°F are 23 July 2023 and 13 July 2021.  

The top 20 highest minimum temperatures in the Salt Lake City area are below.  17 of them are in the 2000s, which likely reflects multiple factors including climate change, urban growth, and local conditions at the observing sites.

Source: https://xmacis.rcc-acis.org/

All occurred though between July 3rd and 31st.  More evidence of the misery of July.

"Hotter than Hell"

I heard a Catholic priest say in downtown Salt Lake City this weekend that the weather is "Hotter than Hell."  Who am I to argue with a man of the cloth?

That said, let's take a quick look at the data and forecast as we approach the end of July.

The month actually started out with four days with minimum temperatures between 62 and 66 at the Salt Lake City International Airport.  And believe it or not on July 22nd, we actually had a maximum of only 87°F.  Other than thoat, it's been hot.  Since July 4th, every day but one has had a minimum temperature at or above 70°F and there have been nine days with a maximum temperature at or above 100°F, including the all-time record high of 109°F on July 12th.  

For the first 25 days of the month, the mean temperature at the Salt Lake City International Airport was 85.3°F.  This is not a record, but it is 4th all-time in the Salt Lake City area and 4.2°F higher than any equivalent period in the 20th century.  If you are wondering, the 20th century record is 81.1°F in 1985.  

The period also rates as the 4th warmest at the Bountiful Bench observing site with a mean temperature of 81.4°F, which is 3.1°F higher than any equivalent period in the 20th century.  There the 20th century record is 78.3°F in 1988.  

July is a month with less weather variability in Utah than we see in winter. On average, as shown in the mean 500-mb height analysis below, there is a mean 500-mb ridge to our east, with the axis centered over Colorado and Wyoming.  This results in the mid-latitude storm track being to our north.  Sometimes a midlatitude system can sneak in here, but it happens less frequently than in winter.  Instead, our weather is controlled more by variations in the strength and position of the ridge, which is a component of what is known as the North American Monsoon System. 

Source: https://psl.noaa.gov/cgi-bin/data/composites/printpage.pl

The forecast for the evolution of that ridge over the next several days does look hell like.  Below is the GFS forecast valid this afternoon [0000 UTC 28 January (1800 MST Tuesday)].  The 500-mb ridge (upper left panel) is centered to our east in northeast New Mexico.  Over northern Utah, the 700-mb temperatures (lower left panel), which are roughly at 10,000 feet or crest level, are around 18°C, which is quite high, but not record setting. 

That ridge though is expected to move slowly westward over the next few days and by 0000 UTC 2 August (1800 MDT Saturday) it is forecast to be parked over Utah.  The 500-mb heights are above 6000 meters, which is a value that typically draws the attention of meteorologists.  Forecast 700-mb temperature are exceptionally high and over 22°C in northern Utah.  In fact, at 6 PM on Saturday they are forecast to be 21.6°C, which would be more than 1°C higher than observed in the upper-air sounding record from the airport. 

The ridge in the ECMWF HRES is also parked over Utah, but not quite as strong.  That said, the 700-mb temperatures are also over 20°C in northern Utah and 22°C in portions of southern and central Utah. 

So, there is no rest for the wicked controlling the weather this week.  Lows at the airport will remain in the mid 70s or higher.  Maximum temperatures will be near or above 100.  If we're lucky, we'll get a thunderstorm, although the likelihood of that will be declining later in the week as the ridge moves overhead.  Temperatures will climb later in the week.  It's too soon to say if we might make a run for 105+, perhaps on Saturday, but it's in the cards. 

Hotter than Hell indeed.

Source: https://chatgpt.com/

Addendum: 3:50 PM MDT

The overnight low at the airport was an incredible 85°F.  The all-time record is 82°F.  That is a daily record, however, which means from midnight to midnight standard time, so for the 85°F to hold for an all-time record, we need to stay above that until 1 PM tonight.  

Snow Storage at SoHo

I've been wondering for some time if snow storage will come to Utah, even posting on the possibility ten years ago (see Is Snow Storage Coming to Utah).  

It finally has come, but to a place I didn't expect, the Soldier Hollow Nordic Center (SoHo).

If you walk around the center, you might spy a whale of white a bit to the southwest of their day lodge.  As you approach, you'll see an insulated mat manufactured by a company called Snow Secure covering about 60,000 cubic meters of snow.  

Last February, Soldier Hollow put eight snowguns in this area and made snow whenever they could for a few weeks.   That snow was then piled high by snowcats.  Even now, in late July, the pile is perhaps as much as 15 feet high in the center.  

SoHo is hoping that 80% of the snow they put under the mat will still be around by mid November for them to spread out on about a kilometer cross country trail, enabling them to open early and focus snowmaking efforts elsewhere to get a jump start on opening more terrain.  

Snow Secure's insulating mat does two critical things to limit snowmelt during the Utah summer.  First, it is white and highly reflective of the sun's rays.  Most of the energy to melt snow in Utah comes from the sun.  At solar noon in summer, direct sunlight onto a flat surface provides about 1000 watts of energy per square meter.  The idea is to reflect as much of that as possible, limiting the amount of solar energy input into the snow pile.  

You can actually see the importance of reflecting sun if you look carefully at the pile. It's a little bit lower where there are straps that aren't as white and higher in between.  I suspect those straps are absorbing more sunlight and the underlying snow is densifying and shallowing more rapidly underneath them.  

The folks at SoHo told us that someone climbed up the pile and left some chocolate cake on the top and that led to a dimple in the snow.  More evidence of how darker surfaces absorb more sunlight.  Lol.      

Second, the mat is insulated, limiting the transfer of heat from the outer surface of the mat into the underlying snow.  The mat also protects the snow from other weather elements, like rain and wind.  

We will see how things look in November, but after visiting yesterday, I'm optimistic they will preserve a significant fraction of snow until the start of the next ski season.  That's remarkable because SoHo is probably the most challenging ski area and outdoor Olympic venue for snow storage.  It has a low elevation (the pile is at about 5600 feet), is hot and sunny in the summer, and sees very little shading from the surrounding topography.  Additionally, they receive limited natural snowfall and have a relatively short snow-cover season.  As a result, they had to make snow for the pile rather than collecting snow from around the resort when they close for the season.  

A resort that has snow after they close for the season could potentially use that snow for storage rather than making it.  This would make storing snow less energy and water intensive.  Additionally, saving snow from the prior season would allow a resort to open in the late fall or early winter even if the weather is not favorable for snowmaking.  

A look at Snow Secure's web site shows a remarkably large number of resorts in North America and Europe are now storing snow.  I suspect we will see this list expanding in the future. 

Thunderstorm Safety

In the wake of recent tragedies, it's worth a bit of review of flood and lightning safety.  In the case of floods, here's some data from the National Weather Service and their partners:

• More deaths occur due to flooding than any other thunderstorm hazard.
• Over half of all flood-related drownings occur when a vehicle is driven into flood waters.
• The next highest percentage of flood-related deaths is due to walking into or near flood waters.

Source: National Weather Service

A full run-down of National Weather Service flood products, including outlooks, watches, advisories, and warnings is available at https://www.weather.gov/safety/flood-products.  In Utah, the National Weather Service also provides flash flood potential ratings for southern Utah and covering 12 recreation areas at https://www.weather.gov/slc/flashflood.  

As evident in near the Cottonwood Fire and Beaver, fire scars can be especially problematic for flash flooding and debris flows.  

National Weather Service lightning safety tips and resources are available at https://www.weather.gov/safety/lightning.  Lightning kills about 20 people a year nationwide, most commonly in summer, but deaths have occurred in all seasons (and in fact lightning is a threat for skiers in Utah which has a relatively high rate of thundersnow).  If you can hear thunder and are outdoors, you should move indoors or into a hard-topped car if you can.  If you are car camping and are in a tent of soft-sided trailer, move into a vehicle.  If you are at an outdoor sporting event, move indoors or into your car.  

Source: https://www.weather.gov/media/owlie/backcountry_lightning.pdf

In the backcountry, more than 30 minutes from an enclosed modern building or vehicle, lightning safety is about minimizing risk.  The most important thing is to monitor forecasts and time your visit to high-risk areas such as mountain peaks, ridgelines, and open water areas accordingly.  Think of it as being the equivalent of selecting the proper terrain for a given avalanche hazard.  Next is to move to safer terrain, as quickly as safely possible, if you hear thunder or believe the thunderstorm hazard is increasing.  This will not eliminate risk, but strikes are more random in lower elevation areas.  Avoid high trees, open areas, and if you can find a dry, lower elevation area, move there.  Pick tent sites to minimize risk too, but be careful when looking at ravines and other gullies if there is a possibility of flash flood.  

Below is more detailed information from a brochure put together by the National Weather Service and NOLS.  Note that getting into the lightning position is a last resort.  If you can move to a safer location focus on that.  For example, if I was on a ridge, I would move down in elevation as fast as I safely could rather than stay there in the lightning position.  

Source: https://www.weather.gov/media/owlie/backcountry_lightning.pdf

Many of the "FACETS" heuristic traps in avalanche accidents also apply to lightning safety.  

F=Familiarity.  Something that feels familiar feels safer, but just because you've survived lightning storms at high elevations in the past doesn't mean you will today.  

A=Acceptance.  You want to fit in or impress your friends by climbing a line or bagging a peak, which might increase your tendency to push it as weather hazard increases.   

C=Commitment.  You don't want to turn around from the summit when you have invested time and effort and are more likely to to push it as weather hazard increases.

E=Expert Halo.  There's a tendency to defer decisionmaking to others with more experience.  Don't assume your friend with years of mountaineering experience is going to make the right weather-related decisions.

T=Tracks/Scarcity.  This one might be more seasonal, but since there is lightning risk in winter, don't ignore it because you want to get first tracks of the top of Mt. Superior. 

S=Social Facilitation.  This one is actually very valid to lightning safety.  It is much harder to move to a building or car, turn around from high elevations, or get off the lake when noone else is doing it.  However, just because nobody else is doing it doesn't mean you shouldn't be doing something to reduce risk.  

All of that said, I've been there.  In fact, the event that I often think of as pushing me into meteorology happened when I was a teenager backpacking with my Dad and we had to run very rapidly from and Adirondack peak to a lower-elevation pass as a thunderstorm moved in.  I've been pelted by hail and graupel during thunderstorms in the Uintas, keeping to the lowest terrain without flood potential possible.  And I've spent time in the lightning position on backpack trips.  On Saturday, we hiked in the morning because of the increasing thunderstorm hazard during the day, yet were just getting to our car when the thunder started at 11:30.  

Use the tips above to adventure at the safest times and to know what to do to minimize risk when you are caught out.  

A Tragic Friday and Saturday

Sadly there were six weather-related fatalities in Utah on Friday and Saturday.  A man was killed after being stuck by lighnting on the American Fork Twin Peaks at around 12:20 PM.  

We hiked up Snowbird that morning, reaching the summit around 11 AM.  There were a few sprinkles around at that time.  When we reached our vehicle at around 11:30 we heard the first rumble of thunder.  The strongest radar reflectivity in the Snowbird/American Fork Twins area was observed at 12:02 PM.  It was a fairly small scale cell.  

Source: https://weather.ral.ucar.edu/

Three lightning strikes were observed on the Alpine ridge yesterday (orange dots below).  One was just south of the American Fork Twin.  

Source: lightningmaps.org

Given uncertainties in strike geolocation, that may have been the one.  

On the prior day in southern Utah, a family of five were killed in a flash flood at a campground near Bicknell.  

These are sad reminders of the hazards of monsoon convection.  Let's hope we see beneficial rains in the coming days, but it's likely that flash-flood and lightning hazards will remain a concern.  

Update on the Great Salt Lake

Mid July is here and it's worth a look at the Great Salt Lake.  Satellite imagery from July 11, when northern Utah was cloud free, showed considerable lake bed exposed in the Bear River and Farmington Bays.  

Source: https://worldview.earthdata.nasa.gov/

Elevation data shows that both the north and south arms had early and broad peaks in April and began to decline in earnest around mid May.  The north arm currently sits at an elevation fo 4190.5 feet and the south arm at 4190.9 feet.  Each of these above their respective record minimums in 2002, which were a bit below 4189 feet.  It's unlikely we will get down that low this year, but getting below 4190 seems to be in play.  

Source: https://greatsaltlake.utah.gov/current-conditions

Next winter will be critical for whether or not we end up flirting with a record minimum again.  There are good reasons to root for a good snow year besides skiing. 

A New All-Time High

The Salt Lake City International Airport reached 109°F today (Sunday, July 12), setting a new all-time record for the site.  

If you are wondering, 20.4°C was observed at 700-mb in the 0000 UTC (1800 MDT) sounding, which is also the highest observed in the sounding records (the old record was 20.2°C).  

It really was a dry heat.  At the time of the 109°F, the dew point was 26°F, resulting in a dewpoint depression of a remarkable 83°F and a relative humidity of 6%.

Stay hydrated my friends.

A Beastly Ridge

Forecasts for the next several days show the development of a strong ridge of upper-level high pressure over the north-central United States.  The GFS forecast valid 0000 UTC 14 July (1800 MDT Monday) shows 500-mb heights above the dreaded 6000-m level centered over Minnesota with anomalously high heights across most of the continental United States.  

Source: pivotalweather.com

This is a recipe for extreme heat to affect a good chunk of the continental United States, beginning in portions of the interior western US today and this weekend.  Currently, extreme heat warnings are in place for an area spanning from Utah to North Dakota and I suspect we will see warnings spreading farther east across the northern tier of the continental United States as the ridge fully develops. 

For northern Utah over the next few days I'll invoke my 20/20 rule here for recognizing temperature extremes.  The 20/20 rule says that anything above 20C at 700-mb (10,000 feet) is exceptionally warm, whereas anything below -20C is exceptionally cold.  In the Salt Lake City upper-air sounding record, 700-mb temperatures of +20C have been observed three times (soundings are only taken typically at most twice a day, so this is a somewhat unsampled record) on 13 July 2002, 14 July 2002, and 16 June 2021.  The high temperatures at the Salt Lake City International Airport on those days were 107F, 101F, and 97F, so the correlation between that level and the surface on any given day isn't perfect, but the 107F on 13 July 2002 is tied with four other days for the all-time record at the airport, the 14 July 2002 observation was preceded by a 107 on 13 July 2002, and the 16 June 2021 observation was preceded by a 107 on 107 on 15 June 2021.  So, all three times we reached +20C at 700 mb we tied the all-time high at the airport at some point during that heat wave. 

Yesterday afternoon we were only 14.4C at 700mb at the airport, so not in exceptional territory yet.  But let's look at the next few days.  I'll focus on GFS forecasts valid 1800 MDT, roughly the hottest part of the day.

1800 MDT Friday 10 July: 18C
1800 MDT Saturday 11 July: 20C
1800 MDT Sunday 12 July: 21C
1800 MDT Monday 13 July: 19C
1800 MDT Tuesday 14 July: 14 C

So the GFS is really pushing it into rare territory this weekend, especially on Sunday, before a cooling through Tuesday.  The ECMWF deterministic is also at 20–21C for Sunday afternoon. 

Whether or not Sunday can tie or break the all-time record at the airport will depend on factors such as cloud cover and local winds (those can make a difference of a few degrees in the maximum temperature, but the National Weather Service recognizes the potential for all-time records on Sunday, with guidance (forecasts from computer models and statistical approaches) putting the odds of meeting or exceeding the all-time high of 107 at the Salt Lake City airport at 30%.  

Their summary is below.  

This is all a reminder that July is a four-letter word.  

weather.utah.edu

The servers we use to produce graphics for weather.utah.edu and to allow access to the web site are really having a devil of a time right now.  The 700-mb temperatures for the GFS and ECMWF above were pulled by eye from pivotal weather as even I can't access that information on our system at the moment.  I apologize for all of the problems with the web site.  

 

Dusty Convection Outflow

I wish I could say I'm glad to be back in Utah, but the aridity and dust leave much to be desired.

Yesterday at around 2000 MDT strong outflow wind from convection north of Salt Lake City picked up dust and briefly caused a spike in PM25 in some areas of the Salt Lake Valley.  Below is a photo of the dust looking south from the upper Avenues at 2007 MDT.

Observations from the University of Utah show a spike in PM2.5 to almost 40 ug/m3 at 2020 MDT.  

Source: MesoWest

There's a good chance that the exposed bed of the desiccating Great Salt Lake was a contributor to some if not most of the dust in this event.