Wasatch Weather Weenies

I've been delinquent on posting about the recent monsoon rains, have now provided measurable precipitation to nearly all locations in the state.  Gauge observations of precipitation over the 72-hour period ending at about 8 AM this morning show nearly everyone has gotten something, with a few stations reporting over 1.5 inches.   Source: NWS In some areas, this has led to flash flooding, especially in southern Utah where such flooding is common during the North American Monsoon.  It is a strange combination of beneficial and hazardous weather since precipitation is sorely needed to help vegetation and lessen drought impacts, but can damage property or put lives at risk.  Concerning the drought, the latest Drought Monitor shows portions of southern and eastern Utah have gone from exceptional to extreme drought.  Statewide, 70% of the state was in exceptional drought last week.  Currently that's down to 52%.  Progress! Source: https://droughtmo...

Tragedy struck yesterday in a major dust-storm induced crash in Millard County in which at least seven people have been killed and 20 vehicles were involved.  Video below provided by Emma Hahne and tweeted by Fox13 shows the visibility impairment in the area. Video from I-15 this afternoon, near where a 20+ vehicle pileup happened in Millard County, shows how hard it was to see during the dust storm that passed through the area. UHP believes this is what ultimately caused the crash with at least 6 dead. https://t.co/G6cy1lHhUR pic.twitter.com/npSAzH4Y2n — FOX 13 News Utah (@fox13) July 26, 2021 Some of the worst vehicle accidents in US history have occurred due to localized visibility restrictions along US interstates.  Perhaps not surprisingly, one of the easier summaries to access is provided by the personal injury attorneys Martin, Harding, & Mazzotti ( https://www.1800law1010.com/the-worst-traffic-accidents-in-u-s-history/ ).  It provides a list of what they call...

In the prior post, we examined the causes of the recent drought in southwest North America.  Here we take a look at the Great Salt Lake, a terminal lake with no outlet that fluctuates in elevation and area depending on the water balance of the Great Salt Lake Basin. New reports in recent days have highlighted that the elevation of the Great Salt Lake is near its historic low.  Measuring the elevation of the Great Salt Lake turns out to be a tricky thing.  Wind pushes water around and since the 1960s the lake has been divided by an earthen railroad causeway, so the north and south arms sometimes have slightly different elevations.   A news release issued by the USGS on July 16, 2021 indicates that the daily average lake elevation just prior to that news release was 2.4 inches above its historic low and that they expect water levels to continue to decline.  The historical trace from the USGS web site is below and shows current levels near the previous 1963 m...

Utah and southwestern North America are currently in a deep drought.  Although this year represents the greatest coverage of extreme and exceptional drought in Utah, the reality is that southwestern North America have been in the grips of an extended drought period, sometimes referred to as a megadrought, since about 2000.  As described in a paper in Science by Williams et al. (2020) , the evidence for this megadrought is apparent in several climate indicators including reduced snowpack, reduced runoff and lake levels, declining ground water availability, drought stress, wildfire activity, etc.   Weather and climate records for southwestern North America only extend back to the late 1800s.  However, it is possible to reconstruct past climate using other indicators, such as tree rings.  This typically requires the identification of a suitable tree in a representative region, coring of the tree, and measurement and dating of the tree rings.  Statistical ...

Yesterday morning I opened the door at 6 AM for a walk and was blown away by a hot blast.  It seemed ridiculously warm.   Indeed, the remarkably high 82˚F minimum temperature mentioned in yesterday's blog post held up for the calendar day held up as the minimum for the day, setting a new all-time record for the highest minimum temperature.   Below are the 63 highest minimum temperatures observed in Salt Lake City (basically, every day with a minimum of 77˚F or higher).  You will likely noticed something not all that surprising.  A supermajority (about 78%) have occurred in the 21st century.   Additionally, yesterday was the hottest day on record in Salt Lake City, with an average temperature [i.e., (Tmax+Tmin)/2] of 93˚F thanks to a maximum temperature of 104˚F.  This was a full 1.5˚F warmer than the previous record of 91.5˚F set on 15 July 2007.  There are 19 days on record with an average temperature of 90˚F or higher, and all b...

A shift in the wind overnight has given us a temporary reprieve from the smoke in the Salt Lake Valley, but brought in some clouds that kept it remarkably warm overnight.  Many of the features in yesterday (Monday) morning's sounding at the Salt Lake City airport were typical of July with an inversion at the surface (which burns off rapidly with morning heating) and then what is known as an "inverted V" profile up to about 500 mb.  The inverted V is characteristic of something known as the residual layer , a remnant of the previous days boundary layer in which thermals generated by surface heating mix the atmosphere.  The flow was light at low levels and northwesterly aloft, the latter bringing in smoke from upstream sources.   Source: SPC This morning there are two key changes.  First, the flow has increased and shifted to southerly at low levels and shifted to southwesterly aloft.  This is why we are getting a temporary reprieve from the smoke. ...

We returned to Hades from our Northwest vacation late yesterday.  Sadly, we awoke this morning to an apocalyptic scene thanks to heat and smoke from fires in Oregon and California.  Below is the view from my morning ride on the BST in the Avenues foothills.   Although we suffered through the Seattle heat wave and it was beginning to get uncomfortable on our last day of hiking in the central Oregon Cascades, for the most part, we had enjoyable weather for our time in Southeast Alaska and on the Oregon coast.  Below are a few photos in case you miss clear skies and sub-80˚F temperatures. Let's take a peak at the meteorological insanity of the past few weeks.  June was blistering hot across the Great Basin and adjoining region.  The map below was produced by Brett  Brettschneider (@climatologist49 on Twitter)  and shows the temperature ranking for counties in the contiguous US during that fateful month.  Every county in Nevada, all but 2 in...

I noticed it hit 100 today in Salt Lake City, with a forecast of 101 for tomorrow.  Good luck with that.  We are still enjoying the maritime climate of Ketchikan, Alaska.  I've done most of the hikes around here before, but don't mind doing them again.   If you've never hiked here before, let me give an introduction.  The first thing to remember is that the forests are impenetrable .  If the devil's club and other prickly bushes don't get you, the mud and muskeg will.  Stay on the trail?  Essential, except in a few places above treeline.   The old-school trails here are similar to the one below, with wooden treadways.  I can't even fathom how long it must have taken to put these in.   More recently, they've shifted to using gravel, which I suspect lasts longer and isn't slippery when wet, although I always liked the wooden planks and the thrill when they don't break with each foot stomp. Although I love airy summits, ...