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.  

Amsterdam

We made it back to Salt Lake City today (Wednesday, July 8).  We stayed a few days in Amsterdam on the way home.  It's a little known fact that I was born in Amsterdam (Amsterdam, New York, not the big one in The Netherlands), so I always wanted to visit my hometown's namesake.  

Amsterdam (the one in The Netherlands) is a real bike-friendly and bike-oriented city.  "Parking lots" are full of them.  

Spending time in Europe makes you realize that US cities are really built for cars not humans.  

I am a fan of Dutch painters and did enjoy spending some time at the Rijkmuseum.  A lot of paintings caught my eye, but two that had a weather or climate theme are below.  The first was Dutch Ships in a Calm Sea by Willem van de Velde II because he did such a great job with the clouds.  

The second was Winter Landscape with Ice Skaters by Hendrick Avercamp because it's related to winter!  

Dutch canals still freeze over sometimes, but it has become less common in recent decades.  Such a shame.

I hope to get into blogging about Utah weather again soon.