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.

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.  

 

March Heat and April Snow

Forget all of that crap about March coming in like a lion and out like a lamb.  None of that stuff applies this year.  March was off-the-scale and simple sayings don't do it justice.  

This is a little premature since March 31st is not in the books yet, but let's look back on what was a remarkable and unprecedented month.  

Believe it or not, it did snow some in March.  Per the Alta Snowfall History at https://www.alta.com/weather, Alta actually got 44.5" of snow from March 1st to 6th.  That seems like a lifetime ago given the heat and dryness that followed.

With one day to go, the average temperature for March at the Salt Lake City International Airport is 53.4°F, 3.3°F higher than any previous March.  A record for the month is in the bag.  

Source: https://xmacis.rcc-acis.org/

But the mean obscures the variability and some of the extremes that occurred during the month.  This March featured five days with a maximum temperature greater than or equal to 80°F.  Prior to this year, there was only one prior March day that reached 80°F (31 March 2012).  We also reached 84°F, four full degrees higher than the previous all-time March record (also 31 March 2012) and 6°F warmer than the 20th century March record. 

Every SNOTEL station with a long-term record in the Wasatch Range currently sits at < 50% of median snowpack water equivalent and every one is at their all-time low for March 30.  EVERY ONE.  Lower-to-mid elevation SNOTELs currently do not have any snow.  Although it is not impossible that they see some snow in the future, for all intents and purposes, the seasonal snowpack at lower-to-mid elevations is gone.  For these sites, bwlow is this year's first day with no snopwack compared to the prior record in parentheses.  

Ben Lomond Trail (5970 ft): March 15 (April 2)
Farmington Lower (6850 ft): March 23 (April 4)
Parrish Creek (7760 ft): March 30 (May 2)
Parleys Summit (7590 ft): March 24 (April 4)

Timpanogos Divide currently has 0.1" of snowpack water equivalent, so it may be at zero by the end of the month too and it sits at 8180 feet.  

Parish Creek might have the most impressively anomalous snowpack of these sites.  It reached no snow yesterday (March 30).  Records for this site only go back to 2000, so not as long as some sites.  Still, they hit no snow yesterday (March 30), a bit more than a month ahead of the prior record (red line, which corresponds to the 2015 water year) and more than 6 weeks ahead of median (green line).  Illustrating the fickle nature of spring, the big peak is from the 2023 water year, which saw increasing snowpack until late April with a maximum on April 25th.  

Source: https://nwcc-apps.sc.egov.usda.gov/awdb/site-plots/POR/WTEQ/UT/Parrish%20Creek.html

Talk about a tale of two water years.  

Of course, with April Fools on tap tomorrow, a change of the weather is in store.  Showers and thunderstorms will develop later today with a trough moving through overnight bringing valley rain and upper-elevation snow, both of which could be heavy at times.  Below is the GFS forecast valid 0900 UTC 1 April (0300 MDT) showing the trough over northern Utah with widespread precipitation along and ahead of it.  

The GFS puts down 1.88" of water and 18.2" of high-density snow for Alta-Collins through 5 PM on April Fools day.  For the same period, the HRRR is at 1.33" of water and 10.6" of snow while the RRFS members are mostly around 1" of water and 10" of snow although there are a couple of low and high outliers.  A reasonable middle ground is 1–2" of water and 8–16" of high-density snow for Alta-Collins, which should be high enough to see all snow. 

For Alta-Collins, the HRRR forecast below shows most of the precipitation happening Tuesday night and early Wednesday, although it is possible that something pops up Tuesday afternoon.  Note also that the wet-bulb zero level is initially above the Alta Base and then falls to just below Elberts. Perhaps Alta will see some rain at the base late today (although in a thunderstorm the snow level could drop temporarily) and this evening before changing to wet snow.  

It's good to have precipitation in the forecast again.  

Heat Wave Numbers

It is snowing today (Thursday) in Innsbruck, the first valley snow since we arrived in late February.  It's just above freezing so that the snow is sticking on cold surfaces, but sidewalks and roads are snow free.  Below is the view from my office. 

I haven't thought about the weather in Utah in a few days.  I knew it was going to be hot, but now that I'm checking the numbers, I'm pretty blown away.  Multiple days at or above 80, including an 84(!) on   Saturday March 21. 

Let's put those numbers into historical context.  During the 20th century, the highest March temperature recorded at the Salt Lake City International Airport was 78°F, reached on 24 March 1956 and 26 March 1960.  During the 21st century, we have tied or topped that number 14 times.  This includes reaching 80°F for the first time on 31 March 2012 and reaching or exceeding 80°F five times in the current heat wave, including the mind-boggling 84°F.

Let's dig a little deeper.  For the 8-day period ending yesterday (Wednesday, March 25), the average maximum temperature was 78.3°F.  The previous March record for an 8-day period was 74.4°F set in 2017.  The 20th century record, 70.0°F, was set in 1960.  So, the average maximum temperature for this stretch is an astounding 8.3°F higher than anything observed in March during the 20th century.  

How about average temperature?  For the 8-day period ending yesterday (Wednesday, March 25), the average temperature was 64.2°F.  The previous March record was 61.6°F set in 2017.  The 20th century record, 57.8°F, was set in 1910.  Thus, for average temperature the current 8-day stretch is 6.4°F warmer than anything observed in March during the 20th century.  

I just pulled up the Alta website and noticed they are closing Wildcat and Collins Gulch early due to unseasonable warmth.

Source:Alta.com

We are deep in uncharted territory.  There is no historical analog for the current March heat wave.  Nothing is even close.    

You Were Warned

Mind boggling temperatures from the western United States currently.  Even watching from a distance here in Austria, they blow me away. 

As I write this, it is Friday morning in Austria and some of the numbers for Thursday in the US are not in yet.  Thus I'm going to use observations from Wednesday to illustrate the scale and intensity of this event before boring into what data I have access to from Thursday.  

Below are the rankings for high temperatures on Wednesday relative to prior March 18ths.  Wide spread records for the date across the southwest US but even all the way up into Montana (asterisks indicate a tie for the highest temperature of the date).  It appears every western state had at least one station that tied or set a record temperature for the date.  Washington was the "coolest" western state, but even there, Chelan tied their record high.   

Source: https://sercc.oasis.unc.edu/Map.php

Departures from average were impressively high.  Many sites were more than 20°F above average, and this is likely the 1991-2020 average so departure relative to the now old and obsolete 20th century average would be even bigger.  Some sites were at or above 25°F above average.  I couldn't find a +30, but maybe it's in there somewhere.    

Source: https://sercc.oasis.unc.edu/Map.php

Wednesday's highest temperature was 108°F at a location near North Shore, CA, which is not on the Pacific Ocean but instead the Salton Sea.  Yesterday (Thursday), Palm Springs hit 107, Thermal 108, and Indio 108.  I believe those 108s are all time monthly maximum temperature records for March and possibly all time for the entire US.  Adding to the misery a bit further east is 106 in Yuma and 105 in Phoenix.  

Records in the Palm Springs Area go back to 1922.  In 1938 they hit 100 in March for the first time.  In 1966 104.  In 1988 103. And now this year 106 (Wednesday) and 107 (Thursday).  In Thermal, records go back to 1951.  They hit 102 in 1966 and 1988 and now 107.  

Meanwhile in Salt Lake City, yesterdays 79 was a record for the date but not the month.  The monthly record is still 80, set on 31 March 2012.  Don't worry.  We'll likely set a new record on Friday and/or Saturday.  

Utah ski areas are suffering.  Eagle Point and Cherry Peak are closed.  Snowbasin's last day is Sunday.  That's a major Utah ski resort, ranked #1 in the US by some surveys and rankings, with a substantive snowmaking system, packing it in on March 22nd.  I looked at the webcam from the base of Wildcat yesterday and I simply could not believe it. It doesn't even seem possible.  

https://www.snowbasin.com/the-mountain/web-cams/

My heart goes out to the resort, which moved heaven and Earth for us this winter for our field campaign.  Despite a slow start to the season, we actually got some great data and will learn a lot, but never in my wildest dreams did I expect to see such a sparse natural snowpack in mid March.  

Here are a few SNOTEL observations based on data from Wednesday, the most recent data that I have available as I write this. There is no snow at Ben Lomond Trail. Median for March 18 is 17.6".  The snowpack at Ben Lomond Peak (7690 ft) appears to be ripe (i.e., it has warmed through depth to 0ºC) and has declined 3.3 inches from its peak and sits just above it's all time low for the date.  Snowbird is not at an all-time low, but it also appears to have declined some from its peak, although that site is a little flaky so I'm not going to fully endorse that as reality (maybe someone can comment).  That said, all other SNOTEL sites in the central Wasatch have seen declines in total snowpack water equivalent in the past few days.  Not necessarily a lot, but some.  

My view of these events is that they are not the new normal, but they are the new extreme, at least for now.  We should expect natural climate variability to still give our winters and snowpacks ups and downs in the coming years, including some good or even great snow years (as we just had in 2022/23).  But, we are seeing an emerging trend to warmer conditions, meaning more frequent, more intense, and longer duration heat waves, more precipitation falling as rain instead of snow, more mid-winter snowmelt events, etc.  These trends, caused by human-caused global warming, will have the biggest impact on snowfall and snowpack in the lower elevations, as we have seen this season, but will also bring change to the upper elevations.  

The reality is that you were warned.  Some of you took it seriously.  Others have called it a hoax and even today are working to dismantle the outstanding US climate-science enterprise, such as breaking up world-class research institutes like the National Center for Atmospheric Research (NCAR).  Still others are pushing fossil fuels and delaying a transition to a lower-carbon world.  

Due to the slow response of the climate system and socio-economic change, we are already committed to more warming in the next 20-30 years (maybe longer).  Will the powers that be continue to resist change and pursue a high carbon, fossil fueled future?  Good luck with that.  

Below Median Westwide

Pretty dismal snowpack numbers westwide now.  Not a single basin has an above median snowpack as of February 4.  Missing on that plot due to the late arrival of California snowpack data is a basin in the south Sierra, but that was below median too as of February 3.   

Source: NRCS

In the Wasatch, many sites are at their lowest levels since the start of the SNOTEL record, in some cases extending back more than 40 years.  Every site is below the 25th percentile, meaning they are all in the lower quarter of prior snowpack water equivalent on this date.  

There will be no Steenburgh winter this year.  

Good Riddance to 2025

Happy New Years from the Wasatch Weather Weenies.

2025 is now in the rearview and I'm not sad to see it go.  It was a tough year for science, higher eduction, the climate system, and at least for the start of the 2025/26 ski season, snow.

Let's begin with the Murderer's Row of climate statistics for Salt Lake City.

First, 2025 was the warmest year on record (since 1875) with an averge temperature of 57.9°F.

The last 3 months of the year and the first 3 months of the 2026 water year (Oct-Dec) were also the warmest on record, with an average temperature of 48.9°F.

And of course December was the warmest on record with an average temperature of 43.7°F.

Shifting gears to the mountains and focusing on the past three month, water-year-to-date precipitation (water equivalent) is actually not all that bad.  Many stations are within 90 to 109% of median (green) and those that are lower than that are withing 90 to 89% of median.  

As shown for Snowbird, a big contributor was the early October rains.  Those were followed by a long dry stretch in late October and November.  December precipitation though hasn't been all that bad.  

The problem, however, is warmth. The early October precipitation was mostly rain.  Even at upper elevations, it didn't add up to much.  Then the precipitation we have had this month has occurred with exceptional warmth for December.  Natural snow cover below 8000 feet is currently scant due to a significant fraction of December precipitation falling as rain instead of snow.  Even above 10000 feet you can find a rain crust in the central Wasatch from the post-Christmas storm.  Snowmaking conditions have been limited.

And today snow levels will eventually get to about 8500 feet. 

So, the story of 2025 in northern Utah was warmth, warmth, warmth.  Good riddance. Let's hope 2026 is better.

Limping into December

November is in the books and except for the last day we can be glad it is in the rearview mirror.  The last day did bring a bit of snow to the Salt Lake Valley, resulting in a beautiful start to the morning today. 

Avenues Twin Peaks from University of Utah Campus 1 Dec 2025

That said, it was a bad month for skiing due to warmth and lack of snow.  At the Salt Lake City International Airport, this November was the warmest on record.  

Records in the mountains are spottier.  At Alta, the Average temperature was 37.5°F, which is the 2nd highest on record, but observations there are much spottier and I don't put much faith in that number.  The warmest November on record there (1949) has 9 missing days.  It's safe to say it was warm, but definitive statements are not possible with the historical record at mountain sites due to limited data. 

So we limp into December.  The next storm system comes on Tuesday night.  It's another system dropping in from the northwest with some similarities to Sunday's storm in that it will likely produce snow or a rain/snow mix on the valley floor with accumulations of a trace to 2" in the valley and perhaps a bit more on the benches.  Worth watching forecasts in case this changes.  

For Alta-Collins, there's pretty big spread in the models with some giving less than 2" and the biggest outliers being in the RRFS ensemble where there are two members in the 8-9" range.  

Think 3-6" and hope for more. 

After that, the forecasts range from sad to optimistic.  The Utah Snow Ensemble shows that most members of the European ensemble (ENS, yellow-orange liens below) are calling for a bit more snow later in the week and into the weekend.  The mean of the ENS is perhaps another inch of water and 10" of snow, although there are a few of ENS members going for game-changing amounts in excess of 30".

The US ensemble (GEFS) has more members who are putting out much bigger amounts over a multiday period, yielding a mean snowfall of 40" over the next 10 days.  The difference between most ENS members and most GEFS members is the storm track with the ENS members tending to be a bit stronger on the western ridge, resulting in a drier forecast (although we still get some snow), whereas the GEFS members bring more action into northern Utah.  

Bottom line is that you should be rooting for America. 

How the October 2025 Deluge Compares to the Past

More thunder and rain last night.  Observations from the Salt Lake City International Airport indicate another 0.68" in the gauge, all if it falling yesterday evening and overnight.  If my math is right, that brings the monthly total up to 4.16", topping the previous record for the month of 3.91".  Really, it wasn't even a fair fight.  It's only October 14!

With the October record easily dispatched, I thought we might aim higher.  First let's have a look at the records for each calendar month:

January 1918: 3.89" 
February 1998: 4.89" 
March 1891: 4.66" 
April 1944: 4.90"
May 1908: 5.76"
June 1998: 3.84"
July 1982: 2.57"
August 1968: 3.66"
September 1982: 7.04" (!!!)
October 2025: 4.16" and counting
November 1875: 5.81" 
December 1983 and 1889: 4.37"

And then additional months at or above 4":
March 1876: 4.00"
April 1974: 4.57"
April 1986: 4.55"
April 1984: 4.43"
April 1886: 4.43"
April 2011: 4.06"
May 2011: 5.14"
May 1977: 4.76"
May 1876: 4.30"
May 1901: 4.27"
May 2015: 4.19"
May 1898: 4.19"
September 1973: 4.07"

So, calendar months that have observed 4" of precipitation or more are February, March, April, and May in the late winter and spring and September, October, November, and December in the fall and early winter.  There have been 22 calendar months with at least 4" of precipitation, most commonly in April (6 times) and May (7 times), which aligns well with the months that on average are wettest at the airport.  The November 1875 record (5.81") is an extreme outlier for that month.  I took a quick look at the daily records though and there was nothing that was obviously bad, so I'm including it here.

Of the months with ≥ 4", 10 are before 1928 when the observing site was in downtown Salt Lake City.  Downtown is a bit wetter on average than the airport, so it's possible this contributed, but there have also been changes in observing techniques and instruments that can also affect the frequency of extreme events. 

There are also five months in the 1980s, a period that was exceptionally wet in northern Utah.  The all time monthly record of 7.04" in September 1982 is really impressive and certainly helped moistened the soils prior to the epic 1982/83 winter that ultimately led to the famous flooding during the (late) spring runoff.  

Source: Marriott Digital Library

With those numbers in mind, a reasonable target to root for this month would be the coveted 5" barrier, which has only happened four times before.  Getting to 7" seems crazy, but not impossible.  That said, I'm going to set the over/under at 6.25" based on a quick look at the extended forecasts.  There's a lot of uncertainty in those forecasts though, so place your bets and see if you can beat the house.

There are a few other ways we might look at this exceptional run, which started on October 3 and currently goes through October 13, a stretch of 11 days.  You are probably already awaer that 4 October was the 2nd wettest day in Salt Lake (2.47").  For an 11 day stretch, this Oct 3 to 13 rates as the 30th wettest, although this count includes two exceptionally wet stretches, one in Fall 1982 and the other in Spring 1901.

Like our current stretch, each of those included one exceptionally wet day, 26 Sep 1982 (2.27") and 3 May 1901 (2.64", the wettest day on record).  This illustrates that one really wet event can set the table for a record breaking run if the pattern remains favorable for precipitation.  

Given that 1982 shows up conspicuously and the 1982/83 winter was an epic, should we get excited about this winter.  Of course you should get excited about this winter!  You are going to be skiing and a bad year in Utah is better than a good year most anywhere else (Japan excluded).  

Ah, but you probably want to know if this is a harbinger of a big winter, like fall 1982 was. The two are simply not comparable.  The 1982/83 winter was an enormous El Nino year.  We're currently looking at perhaps marginal La Nina conditions.  I look at what is happening now as not an indication of what the winter will bring.  It doesn't load the dice one way or another.  Your guess is still as good as mine.  

A Wet Start to October

Total October precipitation at the Salt Lake City International Airport through October 11 is 3.48".  This is already good for the 7th wettest October on record (tied with 2004).  

Ten wettest Octobers on record at the Salt Lake City International Airport. Source: https://xmacis.rcc-acis.org/.

The record (3.91") is only 0.43" away.  Average precipitation the rest of the month would eclipse that, so we have a pretty good shot of having the wettest October on record.

An Epic Storm

Pretty remarkable water numbers from this latest storm.  

At 7 PM MDT, the NWS reported a record calendar-day rainfall of 2.39".

The 2.39" appears to be the 2nd largest calendar-day rainfall on record, topped only by the 2.64" on 3 May 1901.  

Source: https://xmacis.rcc-acis.org/

In other news, the Collins stake sits at around 8 inches.

Source: Alta Ski Area

One Streak Ends But the Drought Continues

There's been a few drops of rain around at times the past couple of days, and late yesterday morning those drops put .01" into the rain gauge at the Salt Lake City International Airport.

That was the first day with measurable rain since the fourth of July, a 48 day streak, good for the 12th longest on record.

Source: https://xmacis.rcc-acis.org/

I wish it didn't end with such a pathetic amount of rain.  

There is one record, however, that continues, an that is the lack of rain over the past 3 months.  The period from May 24 to Aug 23 is the 2nd driest on record (.35"), behind only 1958 (.31").  If we go back to May 18, it's the driest on record. 

There will be some isolated thunderstorms today, but shower chances will be on the increase tomorrow and remain elevated early next week.  Hopefully we will get some much needed, beneficial rain showers, without too much lightning or flooding.  

It's Never Been So Warm So Early in the Year

Yesterday was a remarkable day at the Salt Lake City Airport with a minimum temperature of 56°F and a maximum temperature of 66°F.  Each of these is the warmest temperature observed so early in the calendar year, meaning they are both records for the period from 1 January through Feb 3.

The minimum temperature of 56°F blew everything prior out of the water, eclipsing the prior record by a remarkable 7 degrees.  Curiously, many of the prior highest minimum were set in January in the early 1900s.  At that time, the NWS observing site was in downtown Salt Lake City.  

Source: https://xmacis.rcc-acis.org/

But that 56°F is even more remarkable than that.  It is the highest minimum temperature observed on any day between 3 November and 17 March, tying 9 November 1927.  The 66 is not as much of a black swan, but still a very impressive maximum for early February.  And of course the warmth continues today.  

Extending back into the weekend, this has been a disastrous period for the low-elevation snowpack between the rain, clouds, and temperature.  It is remarkable how long snow can persist in shady areas this time of year if its cold and cloud or even clear with maximum temperatures in the low 40s.  However, low-and mid clouds with such warmth strongly modify the snow energy balance by providing long-wave radiation input to the snowpack.  Such radiation is typically an equal-opportunity offender, meaning it affects the snow on all aspects.  Like that, poof, the snow behind my house was gone.  

Similarly, this period has been a catastrophe at Mountain Dell.  Such a shame for the Nordic skiers. 

Source: https://utahnordic.org/mtndell/

Wind and warmth look to continue into tomorrow.  There is a front coming in during the day tomorrow, but temperatures will remain above seasonal norms even after the frontal passage.  This is no way to run winter.

Snow in Southtown

If you've ever seen the Rankin-Bass holiday classic "A Year Without A Santa Claus" you know that there is a long negotiation between Mrs. Claus, Snow Miser, Heat Miser, and Mother Nature to bring snow for just one day to Southtown.  If you have seen it, then maybe like me you were thinking of it yesterday when it was snowing along the Gulf Coast.  And if you haven't seen it, you should check it out as it is a must for the meteorologically inclined.

In any event, the snow totals from the Gulf Coast are impressive, with many CoCoRAHS observers from Louisiana to the Florida Panhandle coming in at more than 8.3 inches (red shade below).

Source: CoCoRAHS

The highest amounts reported by state were 13.3" in Grand Cotaeu (LA), 10.5" in Waveland (MS), 9" in Summerdale (AL), and 9.4" in Pennsacola (FL).  

I'm not versed in southeast meteorology, but it appears that this was truly a historic event.  For example, the Pensacola News Journal was reporting that official snowfall at the NWS site there had broken Florida's all-time snowfall record with 5" of snow (I'm not sure if this was the final total or not). 

Many weather records are based on daily (or 24-hour) totals and storms can sometimes cross over days.  Thus, I decided to pull up the largest 2-day total snowfalls for the Pensacola Area and indeed 3" is the prior record.  The one disadvantage of this approach is that a single one day storm can be listed twice (e.g., the 2.3 and 2.1 inch totals), but a quick subjective analysis suggests 9 unique events that produced an inch or more of snow in the Pensacola Area since 1880.   

Source: xmACIS2

Given the cold airmass combined with snow cover, minimum temperatures overnight set or were near all-time records.  Lafayette, LA dropped to 4F, an all-time record with observations back to 1893.  Mobile, AL hit 6F, their third lowest on record.  Incredibly, Mobile's all time record is -1 set on 13 Feb 1899.  

This event is a catastrophe for the unhoused and those in buildings that are poorly equipped for these extremes or lose power. The 2021 cold-air outbreak in Texas resulted in 246 deaths, a disaster was compounded by widespread power outages.  I am seeing reports of up some power outages this morning, which taken on huge significance in that region.  I am hoping that they remain localized and short lived.  

About Yesterday's Snow Bomb

Impressive snow totals and snowfall rates occurred yesterday in Little Cottonwood Canyon.  The big winner was Alta.  As readers of this blog are well aware, the Alta Ski Patrol maintains a great snow-study plot in the upper elevations of Collins Gulch.  The hourly measurements from this site are a treasure trove to meteorologists like me who are starved for observations from higher-altitude locations.  The "snow interval" data below is collected by an ultrasonic snow-depth sensor that is mounted on a pole above a white snowboard that is wiped every 12-hours.  It recorded 20" of snow over and 11 hour period prior to being wiped just after 1600 MST.  

Really, the 20" mark was attained in only 9 hours, from 0400 to 1300 MST, yielding a mean snowfall rate of more than 2 inches and hour for that period, with a peak snowfall rate of 5 inches from 0600 to 0700 MST.  Due to roundoff of the measurement, there is a little uncertainty in that estimate, but it's safe to say it was snowing very hard at that time.  A bit more snow fell 1300 MST, but its rate of accumulation was roughly balanced by new-snow settlement, so the final tally remained 20 inches.  

Observations from Mt. Baldy show that the first 6 inches fell as the flow switched from WSW to WNW and the temperature dropped about 4F from 0400 to 0600 MST.  That indicates a frontal passage, but even during this period, there wasn't a strongly organized frontal band, although there were scattered showers and clear evidence of orographic modulation of the precipitation, meaning related to flow interaction with the topography.  Radar imagery at 0425 MST (1125 UTC) when snow was picking up at Alta showed strong modulation of radar echoes by the Oquirrhs and the Wasatch with echoes strongest over and/or windward of those features and strong precipitation shadowing in their lees, including over the western Salt Lake Valley.  So, this was very much an orographic storm right from the beginning. 

During the period of heaviest snowfall from 0600 to 0700 MST, the flow on Mt. Baldy was WNW and radar coverage became more extensive.  Still, echoes were strongest over and windward of the Oquirrhs and Wasatch Range, including the northern and central Wasatch and weakest over the western Salt Lae Valley.  

Finally, by 0848 MST (1548 UTC), the influence of the Oquirrhs and central Wasatch remain apparent, but there is also an elongated band of higher reflectivity extending from the Great Salt Lake to the central Wasatch.  

We have done computer model simulations of similar storm periods in the past in which we were unable to reproduce such a precipitation pattern unless we included both the lake and the topography.  Below is an example from one northwesterly flow storm in which we ran with the best representation of the lake and terrain possible (CTL), removed the lake and the topography (FLAT-NL), removed only the topography (FLAT), included the lake and the Wasatch (WAS), included the lake and the downstream terrain but no upstream terrain (DT), and removed the lake (NL).  There's a lot to digest there, but if there's no topography, the event only produces some light downstream snowshowers.  If there is no lake, only light precipitation occurs over the higher terrain including the Oquirrhs and central Wasatch.  However, when you run with them both (CTL), you get a solid storm.  Thus, both lake- and terrain-driven processes contribute. 

Source: Alcott and Steenburgh (2013)

I suspect this may have been the case for this later stage of the storm yesterday, although that's just a hypothesis at this point.  Overall though, I see yesterdays storm as one that was strongly driven by flow interaction with topography, with perhaps some lake influences thrown in later in the event.  

A few more thoughts

Yesterday's storm was impressive for snowfall rate as measured by depth, but less of an outlier from a water-equivalent perspective.  The 20" of snow that fell had a water content around 5%.  During the period when 5" fell, only 0.15" of water equivalent was observed.  That would be around 3% (although that estimate may be a little low due to gauge undercatch of snowfall).  Peak 1-h water equivalent rates were around 0.17".  That's not bad, but it's also not exceptional.  If you are wondering, the highest 1-h water equivalent was 0.17".  That's not bad, but it's also not exceptional.  The record hourly water equivalent snowfall rate at Alta-Collins is 0.54", which occurred from 0300 to 0400 MST 5 Jan 2008 in southwesterly flow accompanying a "warm and juicy" atmospheric river event just ahead of an approaching trough.  

I share these observations to highlight to different ways that one might measure and evaluate extreme snow rates.  One is based on snowfall amount.  The other is based on water equivalent amount.  Yesterday's snowfall extreme occurred due to the high snow-to-liquid ratios (i.e., low water content).  From a water perspective, it all that impressive.  Storms that produce high water equivalent rates are often warmer, with lower snow-to-liquid ratios, yielding lower snowfall amount rates.  For these storms, my eyebrows pick up when we start approaching 0.3" per hour.  

Thus, much depends on the metric that you use, although none of these scientific semantics take away from what I hear was an outstanding day of skiing. 

Yes, 2024 Was Warm

Final numbers will become available in a few days, but it is likely that 2024 will be the warmest year on record globally.  I'm not sure if the difference from 2023 will be statistically significant, but that doesn't really change the story of long-term warming.  

With an average temperature of 57.4F, it was also the warmest year on record in the Salt Lake City area based on observations collected by the National Weather Service, and by a pretty wide margin.

Source: https://xmacis.rcc-acis.org/

If fact, it beat the previous record holder, 2012, by 0.8F.  Given the inevitable grousing about the representativeness of the airport site, I'll also add that this was also the warmest year on record at the Bountiful Bench site, which has continuous records back to 1975.

That site observed an average temperature of 55.0F, topping the previous record holder, 2012, by 0.6F.  

Precipitation for the year at the airport was 14.78" which was just a skiff below normal (15.52").  Snowfall for the year was 26.2" which was about half of average (51.9").  I have not had a chance to carefully break that down to see if that was due to dry cool months or a greater fraction of cool-month precipitation falling as rain, but a quick look at the graphs suggests the latter dominated.  

As an anecdote, we have now made it roughly through my 2024/25 "snow blowing season", that period during which I normally blow out my south-facing driveway after storms since the sun is too low to melt it out in a short period of time.  I haven't run the snow blower once.  It's sitting in the garage collecting dust.  Nothing that has fallen on our driveway or sidewalk has survived for more than a few hours.  

Colorado and (gasp!) Texas Running Away With It

 Looking for snow?  Forget the Collins glacier.  Go to Alta or maybe Texas.  

Over the last four days, Colorado, New Mexico, far western Oklahoma, and the upper northwest corner of Teas were absolutely pounded.  This includes the high planes.  Texline, TX recorded 24" of snow.  Boise City, OK, not Idaho, recorded 26".  

The big winner was a site 12.9 miles ENE of Fort Garland with 53.3".  The NWS does not provide specific locations for privacy reasons, but that looks to be a site in the low pass through the Sangre de Cristo between the San Luis Valley and the I-25 Corridor.  Some big numbers as well in the high plains of Colorado and the mountains of New Mexico.  A look at Angel Fire (40") this morning.

https://www.angelfireresort.com/weather/

I've always wanted to ski there just for the name.  One of the best in the business. 

The fattest snowpacks in the Utahrado region are now in the San Juans and Sangre De Cristo Mountains. The big winner (blueish dot) is Beartown at 11,600 feet which is sitting at 7.7 inches.  This is the equivalent of their median snowpack on December 20th, so they are running about 6 weeks ahead of median. 

Source: NRCS

Hayden Pass in the Sangre De Cristos now sits at 5.8 inches, the equivalent of their median on December 28 and way above anything on record, although observations at this site start only in 2008.  

There are, however, other sites at record levels for this date in the Sangre de Cristos, Pikes Peak, and Buffalo Peaks.  These are historically dry areas, so an extreme event like this is really exceptional. 

It's a weak La Nina year and this has guided seasonal forecasts.  Here's one for Nov-Jan from the Climate Prediction Center that now looks on track to bust for at least parts of southern Colorado and northern New Mexico.  

This one event has produced about 2/3 of the average Nov-Jan precipitation showing how an extreme weather event can strongly contribute to seasonal precipitation and snowfall.  This is a characteristic of the cool-season snow climate of some regions of the western United States that is often overlooked when seasonal forecasts are being issued.  It introduces an element of randomness to the year-to-year variability in western precipitation that can limit the reliability of seasonal forecasts based on long-term means and similar analyses.  There is a good paper by Lute and Abatzoglou (2014) showing that 20-38% of the annual snowfall water equivalent and about 2/3 of the year-to-year variability in that metric can be attributed to the top ten decile (10% largest) snowfall events in portions of the western United States.  Basically, a handful of big events, sometimes just one or two, make or break the season.

Congratulations to the early season snowfall winners.  

Crazy Heat in Phoenix

The wheels have come off in Phoenix or maybe better put burned off.  They have now set or tied daily records on what appears to be 8 consecutive days, set an all-time record of 117 for September and set an all-time record of 113 for October.  The murderer's row of daily records is:

Sep 24: 108
Sep 25: 113
Sep 26: 110
Sep 27: 113
Sep 28: 117
Sep 29: 113
Sep 30: 108
Oct 1: 113

The eight-day mean average high temperature of 111.8F obliterates the previous eight-day mean average high temperature record after September 1 of 108.6, which was set in the seven day period ending on 11 Sep 1979.  

The graph below shows the 8-day average mean temperature for 24 Sep - 10 Oct each year since records began in the Phoenix area, and illustrates just how anomalous the 8-day period has been.  

Min temperatures during this period have also set a record for the 8-day period.

Forecast highs for the airport are in the high 100s to 110 for the next several days.  What a stretch of fall misery.