Wasatch Weather Weenies

On July 1st, the low and high temperatures at the Salt Lake City International Airport were 53˚F and 88˚F, quite comfortable by northern Utah standards. In contrast, overnight minimum on this last day of July was only 73-75˚F (the official minimum won't be reported until noon) and the forecast high for this afternoon is 100˚F.   Disgusting.   I've mentioned in several previous posts that this July hasn't seemed too bad (i.e., hot) compared to recent standards, but that it has been hot by 20th century standards, and that appears where it will end up at the close of business today. With one day left in the month, the average temperature has been 80.8˚F, which ranks as the 16th warmest all time.  Source: NOAA Regional Climate Centers There are only three July's ahead of it that occurred during the 20th century, 1988 (80.9˚F), 1989 (81.1˚F), and 1960 (81.2˚F).  There's a chance we'll move up ahead of 1988 today.  I'm not sure we can catch 1989 or 1960....

It was great to go for a hike early this morning and see some showers in the area. I even got sprinkled on, which was greatly appreciated. If you are keeping score at home, we have had no measurable precipitation at the Salt Lake City airport so far in July.  Our last measurable precipitation was on June 30, so we've now gone 21 days without rain.  That's not unusual or exceptional (Salt Lake has gone 50 or more consecutive days without rain 11 times), but still I miss it. Showers and thunderstorms will be possible today across much of Utah and are also possible through and the first part of the overnight hours in northern Utah.  The HRRR forecast valid at 3 PM MDT is below.  Don't take it literally for location and intensity as convection is too chaotic for a single model run to predict precisely, but hopefully we will see some action, although I can't guarantee it at your residence.  Late tonight and tomorrow, the Salt Lake Valley may, unfortunat...

Slow and subtle changes in the large-scale circulation will cause some changes in the weather of northern Utah early this week.  The situation at 1800 MDT yesterday (0000 UTC 20 July) showed some scattered convection across Arizona, Utah, and Nevada with relatively weak radar echoes.  Precipitation was limited and the main influence of the convection was to produce some gusty winds.  One measure of the amount of water vapor in the atmosphere is precipitable water , which is the depth of water you would have if you condensed all of the water vapor out of the atmosphere.  Yesterday, values across much of Nevada and Utah were less than 15 mm and in some cases less than 10 mm (see color contours in image above).  For the Great Basin in July, this isn't much to play with unless you have a deep trough over the area, which we don't. Over the next few days, however, precipitable water values will be slowly increasing as a weak trough (emphasis on weak) approaches...

Astute observers can find evidence of falling snow in July over northern Utah, even in this heat, but you need to know where to look.  I took the photo below on Monday morning when altocumulus clouds were rolling across northern Utah.  In the center is one of these altocumulus clouds, which features a ragged cloud base with streaks extending diagonally toward the Earths' surface.  The poorly defined cloud base and streaks are produced by falling snow crystals (or snow flakes) that have grown in the cloud.  Due to the dry airmass at low levels, these snowflakes do not reach the Earth's surface, but instead sublimate or melt and evaporate before reaching the ground.  Below is another photo I took of this process that morning.  In the upper right-hand corner there's what we refer to as a mixed-phase cloud, which means the cloud consists of both liquid water and ice particles.  The liquid water particles are supercooled , meaning that they are colde...

The first 8 days of July are in the record books and as anticipated, they were hot by 20th century standards, but not too bad by early 21st century standards. The average temperature for those 8 days was 78.1˚F, which is a bit higher than the average July temperature in the 20th century (77˚F), but quite a bit lower than the average July from 2010–2018 (81.6˚F).  That period also clocks in as the 3rd coolest since 2010, behind 2010 and 2019.   Source: NOAA Regional Climate Centers So, hot for for your grandparents, but cool for your kids.  It looks, however, like we will see a trend toward misery through Saturday, although the worst of the heat may be short lived.  This morning, the GFS shows us in fairly weak west-southwesterly large-scale flow with three major large-scale flow features at 500-mb.  The first is a trough over the Gulf of Alaska.  The second is a weaker trough just off the Pacific northwest coast.  And the third is a we...

Yesterday, US Immigration and Customs Enforcement, more commonly known as ICE, announced changes to the temporary exemptions being provided for nonimmigrant students taking online courses due to the pandemic during Fall Semester 2020.  As described at  https://www.ice.gov/news/releases/sevp-modifies-temporary-exemptions-nonimmigrant-students-taking-online-courses-during , M-1 and F-1 visas will not be issued for students to enter the United States if they are enrolled at a school or program that is fully online.  Students currently in the United States on F-1 and M-1 visa who are enrolled in such a school or program must leave the country or transfer to a school with in-person instruction.  This is a cruel and xenophobic policy that also makes very little sense economically.  The United States benefits greatly from attracting the world's greatest minds, but also, these students pay tuition and spend money in the United States.  Detailed information about ...

It was an unusual Fourth of July holiday this year due to COVID-19 restrictions.  Public fireworks displays were limited, with none in Salt Lake County, but a few displays in Tooele and Utah Counties (see  https://www.deseret.com/entertainment/2020/7/3/21311412/4th-of-july-events-fireworks-parade-celebration-utah-salt-lake-stadium-of-fire ).  However, individual displays were plentiful, and one can "see" these fireworks in PM2.5 measurements collected by the Utah Division of Air Quality.  PM2.5 spikes were occurred on either the night of the 3rd or 4th or both, indicating degraded air quality.  Cache County gets the reliable patriotism award for producing spikes on both the night of July 3rd (times below local) and July 4.  Cache County PM2.5 concentrations.  Source: Utah Division of Air Quality. Utah County gets the extreme patriotism award for producing the highest PM2.5 concentrations measured by one of the DAQ's real-time sensors, with v...

July is climatologically the hottest month of the year in Salt Lake City, but so far, the first three days of July have been relatively pleasant.  One might even say that July has entered like a lamb. It's worth a look at July from a historical perspective.  July is not only the hottest month in Salt Lake, but it also features relatively little variability from year to year.  The range in average temperature from July to July is around 5˚F, with a few exceptions (e.g, 1993).  Source: NOAA Regional Climate Centers One can also clearly see that recent July's have been quite warm.  During the 20th century (1901-200), the average July temperature in Salt Lake City was 77˚F.  We have not had a July below that average since 1997 (75˚F) and since 2010 the average temperature in July has been a miserable 81.6˚F, more than 4˚F above the 20th century average.  Further, since 2010, even the coolest July, 2015 (77.4˚F) was warmer than the 20th century aver...