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

Sunniest Ski Areas?

As much as people like to argue about whether or not ski area snowfall reports are legit, but perhaps there's more to argue about in the "day's of sunshine claim."  

Snow Brains recently published a top 7 list of the sunniest ski resorts in America.  Coming in at #1 was Palisades Tahoe with "more than 300 sunny days per year."

The 300 days of sunshine claim as been around for as long as I can remember.  When I was a kid, walking uphill both ways to school in sub-zero temperatures in upstate NY, I used to read promotional brochures from the Lake Tahoe area claiming more than 400" of snow and 300 days of sunshine and dream about how incredible the skiing must be there.  I mean, it must either be snowing or sunny!  What could be better. 

Source: https://visitlaketahoe.com/ski-and-snowboard/and-the-award-for-the-best-weather-to-ski-in-lake-tahoe/ 

However, there are many things that are puzzling about that number. 

First, it is an annual number.  If you are a skier, you really want to know how often it is sunny during the ski season.  Winter is the cloudiest part of the year in the Tahoe area, whereas summer and early fall are less cloudy. Thus, the annual number is skewed by the seasonality of cloud cover.  

Second, sunny day is not defined.  Does it have to be bluebird all day?  If the sun peaks in and out it that good enough?  What if the mountain is shrouded in fog at the base and clear on top?  

For instantaneous observations, the National Weather Service defines sky coverage based on the opaque cloud coverage "octants" (divisions of eight) below.  

Source: https://www.weather.gov/bgm/forecast_terms

At what coverage does cloudy stop and sunny end? And, since cloud cover varies during the day, how does one deal with variability?  

Finally, what observations are being used?  Most ski areas do not collect sky cover observations and the closest observing stations that do are often at airports and not necessarily representative of what is happening on the mountain.  

I suspect these numbers have simply been cooked up with liberal interpretation of nearby airport observations that are not necessarily representative of on-mountain conditions.  Indeed, about a decade ago the Tahoe Daily Tribune published an article about a Tahoe area resident, David Antonucci, who runs tahoefacts.com and likes to set the record strait on Tahoe-area claims.  As described in the article Mr. Antonucci looked into the 300 days claim and suspects it is based on observations from the Tahoe Valley Airport. 

“I think where it came from is, at the Tahoe Valley airport, they used to make sky observations. So, I had some records from 21 years of observations that if you multiplied it all out it comes out to about 300 days. And I think what’s said there is there’s 300 days in which there is some sunshine. But I was also able to find probably actually a little bit better statistics. I went to a document called the Climate Atlas of the United States and it has the total number of hours of sunshine in a particular area. So, here at Lake Tahoe we have 4,446 hours of daylight each year and, of that time, at least 3,400 hours there’s sun shining, so that works out to 76 percent. Seventy-six percent of the time during the daylight hours the sun is shining, on average, is probably a better way to say it. You say ‘300 days,’ you think, ‘Oh, that was a day which is all sunny all day long,’ and it may not have been; it may have been sunny part of the day and then cloudy. I was not able to find much in the way of any data speaking to actual days of sunshine or cloudy weather, but for our region it’s probably not too far off. Reno has 251 days of clear and partly cloudy weather, Blue Canyon has 238 days of clear and partly cloudy days, so you can see it’s possible that Tahoe is higher, maybe under 300. It seems like it could be a reasonable number, but it should not be interpreted as that’s a whole day of just sunshine and no clouds.”

So, if 300 days of sunshine seems too good to be true, that's because it is.  

This isn't to say that the Tahoe-area resorts, and other Sierra resorts like Mammoth don't get a lot of sunshine compared to many other areas.  They might even be the sunniest resorts.  However, the 300 days claim is inflated. 

Visiting Old Friends and Chasing Cold Air

I've spent the past several days in upstate New York where I visited the atmospheric sciences department at SUNY Albany and attended the Northeast Regional Operational Workshop where I gave a talk on our lake-effect work.

It's great to reacquaint with Anton Seimon (farther right below) who I haven't seen in about 20 years, but who is one of the best meteorological analysts I know.  A cyclone aficionado, he brought some Bombogenesis Double IPA with him.  Given that it was morning and we had work to do, this photo is staged.  No beer was consumed, sadly. 

I also visited the "headquarters" of the New York Mesonet, which has come together in the past few years and includes at least one station in every county.  The Mesonet has had a major impact on weather analysis and forecasting in New York and dear to my heart they have about 20 stations equipped with specialized snow-measurement instrumentation.  These are primarily on Tug Hill and in the Adirondacks, although there are a few in the Catskills and western New York.  At the headquarters, one can see live photos from every station.

I'm staying until Sunday to visit family and reminisce.  It's cold.  I did a short hike in the Adirondacks today and suspect the summit temperature was in the low 20s, with wind.  It looks like Adirondack winter.

With the cold, Gore Mountain has commenced their snowmaking operations. 

Perhaps I should stay?  The models suggest continued dryness over the next few days in Utah. 

Even Meteorologists Get Burned by the Weather

After an aborted attempt to ski Kings Peak in May (see Uinta Misadventures), my son and I decided we needed to go back this summer and make the summit.  I have lived in Utah for 23 years and incredibly haven't done Kings Peak, so we left Friday afternoon to try and bag it Saturday (yesterday). 

The hike in on Friday evening was as enjoyable as a long slog can be.  The meadows were pretty and the trail dry and fast.  We realized quickly what a folly it had been to try and ski Kings in May with patchy, unsupportable snow on AT gear.  Good golly, what a long approach for what would have been a minimal amount of turns!

Friday night I awoke at 2 AM or so and peered out at wonderfully clear skies.  Sunrise Saturday morning was beautiful. 

However, just visible in the pond reflection are some clouds that were floating about and gave me a little heartburn.  I was mainly concerned about afternoon thunderstorms.  I had anticipated a slight threat of those happening as often occurs in the Uintas, and this was also reflected in the National Weather Service Forecast for the western Uintas issued Friday afternoon. 

We left our campsite around 7:30 am, and already the partly cloud skies were starting to fill. 

Nearing the summit at 9:30 am, it was clear things were going south with showers in many areas, including looking west. 

A bit later, at the summit, it was clear that the 30% chance would "verify" and that things were falling apart sooner than anticipated, although thankfully we hadn't heard thunder or seen lightning.

As we took a summit photo, it was just starting to sprinkle. 

And, looking west, it was clear that things were going to change.

We began our descent.  When we reached the summit, we were the only ones on top and we hadn't passed anyone descending.  On the descent, the line of climbers was long.  We had fortunately brought some layers and rain gear, but others were in true Alpine style with shorts, thin T-shirts, and minimal gear if any.  A few were in sandals.  Kings Peak is a long ways from home when the weather goes south.  We were glad to have brought up some warmer clothes.

Indeed, the rain came in on the descent, and we had steady develop as we descended below Gunsight Pass. 

Fortunately, we got a break before reaching camp.  My son wanted to head all the way out so he could watch the World Cup Final this morning, so we spread stuff out to dry and I caught I quick nap.  We broke camp and began the long slog out, with rain starting again shortly thereafter. 

Really, it didn't rain all that much, but it was enough that portions of the trail turned into a quagmire.  At this point, we kept our heads down and the legs churning. 

All of this is a reminder that Meteorologists get burned by the weather too and that a 30% chance of showers doesn't mean a 0% chance of showers.  On the other hand, I the early development of showers that morning was a surprise.  I consider this a penalty for not paying proper sacrifice to the Gods of Kings Peak.   Clearly that area is cursed for me.  At least we summited and enjoyed a decent view. 

Cloud Scraping on Mt. Ogden

My knee is still talking to me on descents, and I'm sick of hiking up Snowbird, so I elected to go up to Snowbasin today, bag Mt. Ogden, and take advantage of the Needles gondola for a good portion of the descent.

It's been about 15 years since I've been on Mt. Ogden.  It's quite a peak, with a stupendous view, so I wonder what took me so long for a return visit.

Mt. Ogden from the lower Snowbasin slopes

The morning weather at Snowbasin was better than it was over the Salt Lake Valley and central Wasatch where it was raining when I left.  Nevertheless, there were some scattered showers, which made for some picturesque virga shafts.

My timing for summiting wasn't great as it was about as cloudy as it would be all day, but I have always liked being on narrow alpine ridges when there is a cool orographic cloud with the base right near the summit.  It creates a cool scene with the clearer skies upwind. 

The summit was socked in an frigid.  25ºF with winds gusting to 40 mph according to MesoWest.  I had enough layers for my torso, but could have used a thicker pair of gloves.

As soon as I began to descend off the summit, the skies began to break up a bit.  Here's a view looking southward along the Wasatch spine. 

Next weekend is the last for summer gondola rides.  They don't seem to be charging for the descent, but it's $14 for the up, not that I took advantage.

Meteorological Changes During Next Week's Eclipse

Unless you live in a cave, you know that all of North America will experience an eclipse of the sun this coming Monday (Aug 21), with the path of totality passing just to our north across central Idaho and Wyoming.

Source: NASA

Source: NASA

Salt Lake will see around 90% coverage and southern Utah around 75%.

Meteorological changes accompanying the eclipse are likely to be substantial and greatest near the path of totality in areas that are cloud free and prone to large diurnal cycles.  Studies of previous solar eclipses have documented dramatic declines in incoming solar radiation and temperature followed by recovery.  In some cases, surface-based inversions form, as one would expect under clear skies overnight.  For example, observations of the 10 May 1994 total eclipse show near-surface temperature falls of as much as 6ºC (about 11ºF) and the development of a surface-based inversion for approximately one hour.

(a) Solar irradiance (dark line) during the 10 May 1994 eclipse at Springfield, IL. I marks the beginning of the eclipse, II the beginning of the annular phase, III the end of the annular phase and IV the end of the eclipse.  Light curves estimate expected irradiance on a clear day.  (b) Ground and air temperature at several heights.  i and f mark beginning and end of eclipse-initiated surface inversion.  Source: Segal et al. (1996).

One of my former students, Jay Shafer, uncovered a study of the total eclipse of 31 August, 1932.  I am a sucker for these old studies as they required painstaking work on the part of the scientists just to collect, integrate, and analyze the data (in contrast to today where you can do it instantly on your phone).  The path of totality traced across New England where temperatures fell an average of 3ºC (6ºF, analysis below appears to be in ºF) and as much as 9ºF (5ºC).

Source: Brooks et al. (circa 1932)

Under relatively weak large-scale pressure gradients, the cooling associated with an eclipse can also affect winds.  Given that the cooling is localized, one might expect a weak area of higher pressure to develop along the eclipse path, resulting in a weak anticyclonic wind perturbation.  One might also expect a disruption of daytime upslope and upvalley winds, with possible reversal to downslope and downvalley as typically occurs near or after sunset.  This was documented recently over Switzerland during penumbral (partial) shading of an eclipse that reached totality across the UK and Russia (e.g., Eugster et al. 2017).

If you love these sorts of weather impacts, a great aspect of Monday's eclipse is that it is tracking across Jackson, WY and Stanley, ID, to locations know for large diurnal cycles.  If skies are clear, there should be a very dramatic response in temperature and thermally forced flows in those areas.  Northern Utah has a shot as well.  The Peter Sinks, for example, known for remarkably cold temperatures, might see a very dramatic drop in temperature, and canyons like Red Butte, Emigration, and Parleys, the development of a down valley exit jet.

Much will ultimately depend on weather as these effects will be most dramatic if skies are clear and relative humidity low.  Note that the Earth Systems Research Lab has been testing code that integrates eclipse effects on solar radiation into their experimental version of the High Resolution Rapid Refresh (HRRRX) model and real-time experimental HRRR ensemble.  If all goes well, experimental HRRR forecasts will include eclipse effects beginning at 0000 UTC 20 August (Saturday evening) in the HRRRX, which runs out 48 hours.  Those forecasts are available here.

There is one prediction that is probably relatively easy.  Attendance on the first day of classes at the University of Utah, which is also Monday, is likely to be light!

Uinta Misadventures

As many of you already know, the Uinta Mountains are often another world weather wise compared to the Wasatch Front.

Indeed that was the case today as our hike turned into a quagmire thanks to thunderstorms that fired up near the Uinta crest.

I knew there was a chance we'd get caught out, so our plan for the day was to hike the Highline Trail to either Rocky Sea Pass or Naturalist Basin, hopefully being down in the trees if anything sparked.    Ideally, we would have had a crack of dawn start, but it's hard to get the teenager out of bed, so we hit the trail mid morning.

After a quick approach, we approachedNaturalist Basin, but heard a few rumbles to the east.  Not a good sign.

Eventually it was clear the time had come to turn around, so we headed back down.  That's when things really fell apart.  First heavy rain turned the trail into a quagmire.

And then the pea size hail started.  Although not large, the some of the larger stones stung pretty good.

The hail began to cover the ground.  Unfortunately, my camera battery was dead today, and my cell phone crapped out after the photo below, so that I couldn't take any photos after the trail was buried deeply in the stuff.

It was really hard to believe it when we got to Park City and there was barely a cloud in the sky!  Goes-16 imagery for 2032 UTC shows the contrast well.

Record Heat Prospects and Mountain Hail Encounters

With 29 days in the bag for the month, the average temperature at Salt Lake City for this June is 77.3ºF, just 0.2ºF behind 2015 for the hottest of all-time.

Source: NOAA Regional Climate Centers

I've run some quick numbers using the last night's minimum temperature (74ºF) and the forecast maximum for the day (91ºF).  Those will bump this June up about .15ºF, which will put us very close to 2015 (and within the roundoff uncertainty of the monthly mean data I have access to, which is rounded off to the nearest tenth of a degree).  Much will depend on today's maximum and whether or not we get some dramatic cooling from precipitation to lower the minimum.  In either event, 2015 and 2016 will stand as back-to-back Junes of unusual warmth compared to past Junes in the historical record.

Meanwhile, here in the Northeast, yesterday was an "excursion" day at our conference, allowing us to get out into the Adirondack Mountains and climb Giant Mountain.  The day started out optimistically with partly cloudy skies.

The hike up Giant is short, about 2 3/4 miles, but involves about 3000 vertical feet of ascent up an extremely rugged Adirondack trail.

On the summit, we were treated to a nice view of the high peaks.

However, as we summited, we heard a low rumble of thunder and after a couple of minutes on top, it was clear we had to descend and descend fast.

After getting a few hundred vertical feet off the ridge, the skies opened up, initially with rain, but eventually with a deluge of pea-sized hail.

Here's a handful.

Steep Adirondack trails are nasty enough when dry, but even tricker when wet and covered with ball bearings of ice.  We also encountered quite a bit of "hail fog," a shallow fog mainly in the canopy layer due to cooling from melting ice.

Due to the retreat, our group photo was taken about half way down, after things dried out and the camera partially defogged.

Just another day of adventure with the Steenburgh group.

Top 10 Ski Area Microclimates

A microclimate refers to the unique meteorological conditions that occur at a given location or area.  Mountainous regions tend to produce a plethora of microclimates due to the strong influence that complex terrain has on meteorology.  Below are my top-10 U.S. ski-area microclimates, plus some honorable mentions, based on remarkable aspects of the snowfall characteristics compared to the surrounding area or region.

10. Wolf Creek Pass, CO

Colorado is not especially snowy, but Wolf Creek Pass is the exception to the rule.  At an altitude of 10,640 feet, the long-term observing site at Wolf Creek Pass has an average annual snowfall of 435 inches, highest in the state.  In addition, Wolf Creek Pass is well situated to be pounded in warm storms with southwesterly flow, resulting in snow with a higher average water content than found elsewhere in Colorado [10.3% (Judson and Doesken 2000)].

9. Gore Mountain, NY

Not all microclimates are good for skiing.  The problem at Gore is that it is too far east to get much lake effect and a bit to far northwest to receive as much nor'easter snow as the mountains of New England.  C'est la vie.

Source: Northeast Regional Climate Center

8. Mt. Bohemia, MI

Mt. Bohemia might be the most geographically isolated ski area in the contiguous United States.  It's on the Keweenaw Peninsula, about as far north as you can get on the UP of Michigan and nearly surrounded by Lake Superior.

Source: Google Maps

You want lake effect?  Mt. Bohemia is the place.  The resort claims an average snowfall of 273 inches and, although it's difficult to confirm this given a paucity of long-range observing sites in the area, it's clearly the snowiest ski area in the midwest.  And it's bloody cold too.  Deep powder, certain frostbite, what are you waiting for?

7. Jay Peak, VT

In 2008, Trevor Alcott and I wrote a paper for the Bulletin of the American Meteorological Society entitled Secrets of the Greatest Snow on Earth (I ultimately used the article as a springboard for my book of the same title).  When in review, one of the anonymous reviewers took great offense that we did not include Jay Peak in the analysis.  Fair enough.  Jay does especially well in northwesterly flow thanks to the orientation of the mountains of northern Vermont and a lack of substantial upstream terrain.  There are other northern Vermont ski areas benefit from these characteristics, but perhaps not to the extent of Jay Peak.  Plus the Jay Peak powder cult has threatened me enough that I no longer question the power of the Jay Peak cloud.

6. Alyeska, AK

Alyeska rises above the Turnagain Arm just east of Anchorage and has a base elevation of only 250 feet.  Due to the formidable nature of the Chugach Mountains and the maritime nature of the region, it probably has the largest snowfall gradient with altitude of any major resort in the United States, which results from both the increase in precipitation with altitude and the increase in the fraction of precipitation that falls as snow.  Resort statistics suggest a 208" mean snowfall at the base and a 512" mean snowfall at mid mountain (~1400 feet).  That staggering increase is characteristic of coastal Alaska, but where else do you find a major ski area cutting through it?

5. Snow Ridge, NY

In my view, Snow Ridge has the best quality natural snowfall in the northeast United States.  The area reports a very believable average snowfall of 230 inches, most of which is lake effect generated by Lake Ontario.  Even my snow-snobby students enjoyed a powder day there when we were working on the Tug Hill Plateau a couple of years ago.

4. Mammoth Mountain, CA

Mammoth Mountain gets an absolutely sick amount of snow for the eastern Sierra.  If you want to know why, look at the map below.  Note how big and broad the Sierra are to the north of Mammoth, and how big and broad the Sierra are to the south of Mammoth.  Then look at how the San Joaquin River cuts a path right to Mammoth Mountain's doorstep.  As a result, Sierra storms dump less load before hitting Mammoth, and Mammoth gets an unusual amount of snow for it's extreme eastern location.

Source: Google Maps

Meteorologists call the depletion of atmospheric water vapor by precipitation airmass transformation.  An interesting aspect of atmospheric water vapor is a very small fraction of it contains hydrogen isotopes that are relatively heavy (they have one proton and one neutron instead of just a proton).  Water vapor molecules that contain this heavier hydrogen isotope, known as deuterium, tend to condense more readily and rain out as an airmass pushes inland.  As a result, the snowpack in the eastern Sierra tends to be somewhat depleted of deuterium, except at one place.  Mammoth.

The map below is an oldie but a goodie and shows an analysis of deuterium in the Sierra snowpack.  Note the nose of higher values at Mammoth, illustrating that airmasses impinging on Mammoth Mountain have experienced less transformation and water vapor depletion that those that have traverse broader, higher topography to the north and south.

Ratio of deuterium to hydrogen (D/H) in Sierra snow expressed as a per mil
 departure from that found in standard ocean water (Friedman and Smith 1970).

3. Alta/Snowbird, UT

It's a bit self-serving to put Alta/Snowbird at #3 on this list, but I've yet to find an area in the contiguous United States with a better combination of quality and quantity than the upper Cottonwoods, and Little Cottonwood gets the nod here because it is a bit snowier than Big Cottonwood.

Source: Secrets of the Greatest Snow on Earth

All sorts of crazy ideas exist concerning why it snows so much in the upper Cottonwoods, but the most obvious is almost always overlooked.  The terrain around the Cottonwoods forms an island of high terrain that is exposed to flow from nearly every direction.  Alta and Snowbird are well known for snow in northwesterly flow, but they almost always get something even when the flow is from other directions.

Source: Secrets of the Greatest Snow on Earth

This tremendous diversity of storms leads to the large annual snowfall totals and contrasts with other high areas of the Wasatch (e.g., Mt. Timpangos), which lie along linear ridges and have a narrower storm spectrum (e.g., predominantly southwesterly flow).

2. Mt. Baker, WA

Snowiest ski area in the world.  World record 1,140 inches recorded in the 1998/99 season.  Admittedly, Mt. Baker ski area isn't even the snowiest location in the region it sits in due to its low altitude, but an average snowfall of nearly 650 inches puts it at #2 on this list.

1. Snoqualmie Pass, WA

I'm guessing you didn't see it coming, but Snoqualmie Pass has a truly unique and remarkable microclimate.

The problem in the Cascades isn't moisture, it's temperature.  West of Snoqualmie Pass and along much of the western slopes of the Cascades, skiing isn't viable at 3000 feet elevation, the base elevation of the ski areas in Snoqualmie Pass.  If you drive to Snoqualmie Pass from Seattle, the snow line is often above 3000 feet, but turn the corner and enter the pass and you find a huge snowpack.

There's one main reason for this: cold easterly flow.  For much of the winter, the Cascades separate relatively mild marine air to the west from colder continental air to the east.  This cold air frequently pushes into Snoqualmie Pass, resulting in locally lower snow levels than found to the west.

The climate in Snoqualmie Pass is very similar to that in Stampede Pass, which is just to the south and has had an official weather station for many years.  If you look at a wind rose for Stampede Pass in January, you see a predominance of easterly flow.

Source: Steenburgh et al. (1997)

And this has a significant impact on temperature.  If you compare the mean temperature at Stampede Pass to Paradise ranger station on Mt. Rainier, it's actually colder from December to February, despite the lower elevation.  This is because Stampede Pass (and Snoqualmie) are frequently under the influence of cold, easterly flow, whereas Paradise is west of the Cascade crest and cutoff from the cold easterlies.

Source: Steenburgh et al. (1997)

If you could plug the low-elevation corridors that issue from eastern Washington to Stampede and Snoqualmie Pass, the snow climate would change dramatically, a much greater fraction of wintertime precipitation would fall as rain instead of snow, and one of the busiest ski areas in the United States would probably cease to exist or be barely viable.

Although the cold easterly flow is a remarkable refrigerator, it's not going to be able to hold off the inevitable as the planet warms in the coming years.  The snow climate of Snoqualmie Pass is one of the most vulnerable to global warming because of its low elevation and frequent snowfalls at temperatures near (and above) 0ºC.

Honorable Mentions:

Grand Targhee, WY (prolific snowfall on the windward side of the Tetons)
Crystal Mountain, WA (Mt. Rainier cloud and precipitation shadow)
Stevens Pass, WA (cold easterly flow)
Mission Ridge, WA (strongly shadowed)
Mt. Shasta Ski Park, Mt. Bachelor, Mt. Hood ski areas (large volcano influences)
Keystone, CO (strongly shadowed)
Steamboat, CO (large, low-density, seasonal snowfall for Colorado)
Whiteface, NY (really cold, but hey, at least it doesn't snow very much too)
Snowshoe, WV (snowy spot for mid-Atlantic region)

Add your $0.02 by commenting.  I've focussed on ski areas here for brevity, but feel free to think broadly (i.e., backcountry) and globally.