Yes, We Finally Got Some

Radar estimated precipitation from the NSSL MRMS shows the entire Wasatch Front got some precipitation over the past 72 hours.  Hooray!

Source: MRMS

It looks like pretty much everywhere from Utah County north and eastern Tooele County East got at least 0.15" and most areas got at least 0.50".  Heaviest amounts were to the north along the UT-ID border.  Last night, not only was it cooler and moister, but it smelled wonderful.  A much needed cleaning.  

The airport got 0.10" on August 26 and 0.64 inches on August 27.  We'll use the former as one bookend and May 18th when the airport got 0.73" as the other.  Between those two days, the airport received only 0.35" of precipitation, the lowest on record between those dates.  

Source: xmACIS2

No doubt it was an exceptionally dry 3+ month run.  In fact, there are only 12 years out of the 152 year record with < 1.00" of rain during that period. 

Thanks goodness that streak is over, although the drought persists.

We Should Get Some Today

Our excruciating wait for "real rain" is almost over.  The isolated showers and thunderstorms that have largely missed many portions of the Salt Lake Valley or provided only some paltry precipitation amounts are now in the past.  Today we will see more widespread showers and thunderstorms.  

This morning's 1334 UTC (0734 MDT) radar imagery shows fairly widespread precipitatio over the south arm of the Great Salt Lake and Bear River Bay, as well as showers farther south in Utah County and southeast Tooele County.

This morning's sounding is "juicy" with a surface dewpoint of 56 and 1.2 inches of precipitable water, which is the depth of water you would have if you condensed out all of the water vapor in the column.  Although not exceptional, it's fairly high.  The daily record for August 26 in the sounding climatology is 1.17", although we have seen values as high as  1.66" on August 14 and 1.43" on September 3.  

Source: SPC

Models like the HRRR are producing forecasts consistent with periods of showers and thunderstorms through the day today.  The 0600 UTC run produces measurable precipitation across most of northern Utah (there are a few precipitation free areas in the West Desert), with some areas receiving more than 0.5" and peak amounts just over 1".  

The chaotic nature of convective storms is such that one can't count on the spatial detail of forecasts like that.  In fact, that run completely missed the convection that is currently over the Great Salt Lake.  Instead, we will have to see what comes at any given location as there will be variability in where these storms produce rain. Hopefully we will see wide spread beneficial rains with moderate precipitation rates and not too many storms that produce intense, slow-moving, gully washers.  

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.  

Early Fall Today, Field Campaign This Winter

I spent today scouting observing sites for a major field campaign that we will be conducting in the northern Wasatch this coming winter involving two mobile weather radars and a whole ton of other goodies.  The high at the Salt Lake City airport hit 101 and it was plenty hot in Huntsville where we were scouting, but it looked like September as there are colors on display already. 

I'm not sure how unusual this is, but in general it seems incredibly dry out there in non-irrigated areas and in many areas the foliage just seems to be giving up.  We have to hope we make it through the next few weeks without a major severe wildfire as it seems like everything is primed for explosive fire behavior if we were to get strong winds with a spark.  

Back to our scouting.  The program we are planning is called SNOWSCAPE and it will focus on winter storms across the northern Wasatch with a focus on the region from roughly Francis Peak to Ben Lomond, including the Ogden Valley.  

In the Huntsville area, we are looking for a place to operate several trailer-mounted instruments including profiling radars, laser ceilometers (which measure cloud base), and particle counters (which measure dust).  We would also launch weather balloons from the trailer during periods of "interesting" weather (no overnight operations).  We are looking for a site near or east of Huntsville, in the region between about the south branch of the south fork of the Ogden and 1300 North, with access to power and good site lines to the Snowbasin area that is open enough that we can safely launch weather balloons without worrying about entanglement in trees or power lines.  

If you think you might have a good location, would enjoy having the best weather station in the Ogden Valley this winter, and would like to entertain your friends with weather balloon launches during January and February, drop me an e-mail at jim.steenburgh at utah.edu.  Or if you know someone who might be interested, let them know and have them reach out to me.  We'd sure like to find a great site in that area and are happy to provide entertainment and potentially an educational experience for weather weenies young and old.  

I'll be blogging more about the campaign in the future.

And Still No (Measurable) Rain

Although a few blessed locations got some measurable rain the past few days, the Salt Lake City International airport continues to be skunked and has gotten no measurable rain so far this month (through yesterday, August 16).

If my calculations are correct, this brings our streak of days without measurable rain to 43, good for the 16th longest on record.  

If we make it through tomorrow without measurable rain, it will be the driest May 19–Aug 18 period on record.  The current record is .35" in 1889.  We're at .34" currently.  

That's a 91 day period and I've picked a length that is somewhat arbitrary, but if you are wondering, the driest 91 day period on record covered the 91 days through 12 November 1952.

Weak Monsoon Surge

You know you are desperate when you get excited about the shallow cumulus that are developing over the Salt Lake Valley today,  Below is a loop showing the development of these clouds looking south from the University of Utah through about 1450 MDT.  There's even some virga! 

Those clouds are developing ahead of a weak upper-level trough that is near the Pacific Coast and a weak surface boundary that is in advance of the upper-level trough near the boarder of Idaho and Nevada/Utah.  The 2119 UTC radar image shows that area is producing stronger cells than the "cumulus patheticus" that we've had over the Salt Lake Valley so far today.  

Source: NCAR/RAL

Moisture will, however, be on the increase through Friday.  This is not a major monsoon surge, but we will see the coverage of clouds and possibility of thunderstorms and precipitation increasing. 

Let's have a look at what the Rapid Refresh Forecast System (RRFS) ensemble does over the next few days.  I'll focus on 24-hour precipitation totals ending at 0600 UTC (0000 MDT), but note that most of this precipitation is produced during the afternoon and evening when convection is strongest.

For the period ending at 0600 UTC 14 August (0000 MDT Thursday), which covers today, the RRFS gives a nothing burger to the Salt Lake Valley and most of the west desert areas of Utah.  The action is in that area around the aforementioned boundary.  Mean forecast precipitation (upper right panel) is greatest right along the ID-UT border.  Maximum forecast precipitation (lower right) is over 0.5" in some areas.   

For tomorrow, that area near the UT-ID border generally remains active, but we see a bit more action in Tooele Valley, Salt Lake Valley, and environs.  Mimium precipitation (lower left) is still zero in many areas, but the mean of all ensemble members is > 0 across most of the Salt Lake Valley.   

I would not interpret that as meaning everyone in the Salt Lake Valley will get precipitation, especially since there are only six members in this ensemble, but I would expect that we will see deeper convection tomorrow and perhaps storms that can produce rain to the valley floor.  For Salt Lake City, the NWS is going with a 30% chance of showers and thunderstorms after noon tomorrow and a 40% tomorrow night before midnight.  There's a chance!

This weak monsoon surge will keep some shower and thunderstorm chances around until Saturday.  Will we get measurable rain at the airport?  Time will tell.  

Quite an Airmass

As August airmasses go, this has been a good one.  Visibility today was really incredible.  It was crystal clear this morning on Mt. Baldy.

For those of you with the desire for turns, there's still some snow covering the Timpanogos Rock Glacier.

Sadly, our brief flirtation with cooler weather is almost over as heat returns this week.  Today's infographis from the NWS is as grating as it gets.  Blah.

Source: NWS.  Downloaded 7:03 PM MDT Sunday 10 August 2025

Perhaps It Will Never Rain Again

A weak cold front has brought a bit of cooler weather to northern Utah today (Friday).  Today's high at the Salt Lake City International Airport was a pleasant 85 and it looks like we may stay below 90 through the weekend. 

But will it ever rain?  

I'm starting to wonder.

The last measurable rain at the airport was on July 4.  That's a 35 day run.  The record is 63 days, so we have long ways to go to get to that, but the models are still advertising "nonsoon" conditions for the next 10 days.  That would get us to 45 days, which would tie us for the 14th longest streak on record.  If you are wondering, 51 puts us in the top 10.

Also of interest, this year we also had a 34 day streak that ended on June 22nd.  That streak began on May 19.  On May 18, we had a soaker, with 0.73" of rain.  Since then we've had 0.34", good for the 4th lowest on record out of 152 years for the period from May 19 to August 8.

If we were to make it through August 17 without measurable rain, it would be the 2nd-driest May 19 to Aug 17 on record.

And if we were to eek out one more day, and go precipitation free until August 18, it would be the driest May 19 to Aug 18 on record.  

It would sure be nice to see a rainy day.

A Brief But Intense Lake-Dust Event

Late yesterday afternoon, strong winds associated with outflows from storms to the north brought a brief but intense lake-dust event to the Salt Lake Valley.  Satellite imagery showed this dust moving southward through the Salt Lake and Utah Valleys.

Source: CIRA.  Loop also available at https://col.st/80KK0. 

Take a close look at that look, especially the last few frames, and you can also see an area of dust moving off of the Farmington Bay playa and over the south arm of the Great Salt Lake.  There's also evidence of dust from other sources to the west moving through the Skull, Tooele, and Rush Valleys.

Winds at the University of Utah began to pick up at around 1835 MDT when increased to more than 9 mph with gusts to 12 mph.  The peak gust of 20 mph occurred at 1852.  This roughly bracketed a spike in PM2.5 concentrations to just over 8 ug/m3 from 1845-1850 UTC. 

Source: Mesowest

Although the PM2.5 concentrations were not very high, that measurement focuses on smaller particles less than 2.5 microns, whereas wind-blown dust from the lake often contains larger particles and is better measured by instruments that focus on particles up to 10 microns (called PM10).   

Events yesterdays are typical of most July-August dust storms.  They tend to be intense but shortlived and generated by precipitation falling into sub-cloud dry layers, which leads to evaporative cooling.  The evaporatively cooled air spreads outward from the precipitation region, often resulting in strong winds.  The leading edge of this outflow is sometimes referred to as an outflow boundary or gust front.  Often you can see several, which can merge and interact, as evident in yesterday's satellite loop. 

If the lake was full, dust would have been more limited.  Some of us might have only felt a cool and refreshing north wind.  Wouldn't that have been wonderful. 

The Curious Case of July 2025

Many people I have spoken to in recent days as commented that this July wasn't that bad temperature wise.  My impression is somewhat similar, but curiously, the numbers tell a more complex story. 

With an average temperature of 82.9F at the Salt Lake City International Airport, July 2025 rates as the 12th warmest on record.  With records going back 152 years, that puts it solidly in the top 10% for July warmth.  Additionally, there is no July prior to July 2003 that was hotter.  This July was hotter than any July in the late 19th or entire 20th century. 

So why didn't it seem so bad?  A few hypotheses.  For one, it was the coolest July in five years and July 2021, 2022, and 2023 are the three hottest on record, so this July was cooler compared to the recent past.  

Second, although the average temperature is high, we did not see high temperature extremes.  There were no record highs set and we only hit 100 3 times.  On those days the high was 100.  

So this July was characterized by relatively sustained warmth without extremes.  Highs ranged between 89 and 100, and the 89 occurred on only one day (July 4).  Low temperatures on 19 days were 70 or higher, but we did get into the 60s on 12 days.  

Finally, a lack of any strong monsoon circulation or surges means humidities have generally been low.  

The lack of moisture is reflected by the lack of rain.  Measurable precipitation at the airport was recorded on only two days (July 2 and 4), totaling 0.18 inches.  July is a dry month here, averaging 0.49", but 0.18 puts us just inside the upper quarter of driest Julys.

June was also dry and the total precipitation at the airport in both months totaled 0.34", which is the 13th lowest on record.  June-July 1994 is the driest on record with 0.06".

The monsoon is notoriously difficult to predict and there's always the chance that the airport gets nailed by an isolated thunderstorm, but for the most part, the models suggest a continuation of the weather monotony the first week of August and the outlook from the Climate Prediction Center for the 2nd week promises more of the same.  

Source: NOAA/CPC

You get what you get and you don't throw a fit.