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.