Conditions, On the Mountain

2 Experts Demystify Temperature Inversions

13 Comments 01 December 2008

“Why aren’t you guys makin’ snow?!?  Crimeny, it was freezin’ out my house in Truckee this morning!”

Yep – we at Alpine Meadows hear that quite often lately.  Morning reports from downslope towns have downright frigid morning temperatures; only to arrive at Alpine’s base to find warm air; and even warmer air near the summit.

Even though many of you reading this blog understand the meteorological components of what is known as a Temperature Inversion, it’s a new term to some.  I’ve actually tried to explain a temperature inversion to guests in the past, only to be laughed at.  “Ha!  That’s a good one!  …temperature inversion… did you make that up yourself?  Nice try through, I’ll give ya that much!”

Well, temperature inversions really exist; and it’s this pesky inversion now that’s putting Alpine’s snowmaking crew in a holding pattern.  Alpine has lots of weather experts on the mountain every day – like Dave Thatcher, our snowmaking manager.  So we asked him.  Also, California has some incredible meteorologists – like Dirk Verdoorn at KCRA.  So we emailed him.

Straight from the experts, learn about temperature inversions:

Alpine Meadows Snowmaking Manager Dave “Rasta” Thatcher:
Alpine Meadows is dedicated to snowmaking.  Our crew has been prepared and on call since October, patiently awaiting minimum conditions to make snow.

Unfortunately, Alpine Meadows has been experiencing a longer than expected temperature inversion cycle.  Temperature inversion is an increase in temperature with elevation.  Although not unusual at Alpine, this trend has frustrated the snowmaking crew.  An inversion in temperature occurs when dense cold air is trapped at lower elevations by a blanket of warmer air at higher elevations, usually at night.  This typically happens when a high pressure system stalls over the Lake Tahoe basin.  The steep valley of Alpine Meadows which is cherished for its skiing also tends to create its own climate including temperature inversions.  The fog layers we have been experiencing are proof of this inversion.  At times you may see the smoke from a neighbor’s chimney sinking instead of rising.

Along with the inversion, we have been experiencing rising humidity levels at night due to the recent dusting of snow.  High relative humidity is not conducive for the production of snow.  Under normal conditions a snow event usually blows out the inversion.  Lately, this has not happened.

We are poised and ready to go; so be patient.  It’ll happen.

KCRA Meteorologist Dirk Verdoorn:
Inversions are something that I am very familiar with living in the Central Valley.  On a typical day in California the higher you travel in elevation the cooler the temperature will get (the normal lapse rate is about 3.6 degrees Fahrenheit per 1000 feet).  During the winter when a ridge of high pressure moves over the state the wind is light and the skies are clear.  At night with the clear skies, the temperatures drop rapidly and cool air, which is heavier than warm air, pools on the valley floor.  Often this process results in the formation of fog as temperatures drop to the dew point.  This situation where the cooler air is near the surface of the ground and temperatures warm as you travel up in elevation is called an inversion.  With the cold air stuck in this bowl of a valley and no wind to mix and warm the air, the cold air sits until the sun can heat up the ground enough to break the inversion.  If fog is present then it is even harder to break up this inversion because the fog actually reflects the sun’s attempts to warm the ground, keeping the valley cool while the higher elevations are seeing sunshine and sitting a good 20+ degrees warmer than the valley.  There are times when the temperatures will stay in the 40′s with a layer of valley fog for a week or more while the surrounding hills are seeing sun and are in the 60′s.  This inversion scenario is not only present in the Central Valley but can also happen in any valley situation where the cold air doesn’t mix out or drain away.  The best way to break this inversion problem is to get some storms to move through the area, which is something, I’m sure, we would all love to have happen.

So there you have it; Temperature Inversions 101



Rachael - who has written 58 posts on Ski Alpine Meadows.
Alpine Meadows' Public Relations Guru, Rachael has been working for Alpine way longer than you'd guess based on her young age.

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13 Comments so far

  1. Chris Albion says:

    Inversions do exists….duh. But radiation cooling at night makes it very favorable for making snow. You need to make more at night than what even the strongest inversion at the 700 MB level can melt. I’m not fooled. Heavenly makes snow, they have nearly exact if not even more severe inversion temp fluctuations. Obviously your over priced season passes did not sell per your bell curve whereby you cannot afford to make snow. I bet mother nature would bless us all with white stuff if the resorts, especially Alpine (who was at one time local freindly) where more in tune with the give and take of carma. What’s worse…..I gave your corporation 400 for a Homewood pass.

    Bring down the pressure and show the community some love.

    It will work better than burning some old skis.

  2. Chris Rudolph says:

    When the fall turns in to winter, but winter doesn’t seem to get the memo, tensions run high while base depths remain low. As skiers, and we’re all in this to get the shredding done. Mother Nature is a fickle friend, and ultimately all of us are subject to the conditions that she dictates. We all commit to winter at different levels, few more so than those who not only risk their free time, but also their livelihood on the prospect of long white winters. Believe it… for the most part, ski areas employ real live skiers and want nothing more than to get snow on the ground and to spin the lifts.

    So while, there are many different schools out there in regards to snowmaking, with more variables than can possibly by listed in one blog entry, at the end of the day, it’s still snowmaking. I’m sure we can all agree that snow from heaven beats out snow from hoses every day of the week.

    So let’s focus our energy on whatever it takes to get that natural snow; do the dance, burn the skis, just make it happen. In the meantime, we can all learn something from AC Slater:

    “Don’t Hate, Recreate”

    Chris Rudolph
    Stevens Pass WA

  3. JB says:

    Where does it end?? What about next year when it doesn’t snow until Christmas??All weather forecasts point to continued high pressure for at least the next 7-10 days and then only a slight pattern shift with moderate showers. I want to make turns just as much as the next guy; I also did last Thanksgiving and I’m sure there were many more skiers around years before myself who have cursed a dry Turkey Day.
    The answer is not more snowmaking. Last year one local resort pumped their water storage ponds dry trying to meet the public’s insatiable need to slide. Yes, they had lifts spinning before Thanksgiving, but at what cost to the environment and their consumers. Snowmaking is expensive and will never put a mountain at capacity. I’m no accountant, but you’d think the more a corporation puts into snow guns and 1200 horsepower compressors – the more costs they have to hand down to skiers and snowboarders to make payroll. Especially in today’s economy.
    I say tune-up the bike for some trail time without the summer crowds. I’m happy to wait for the real stuff than fight for turns on a ribbon of death that raises costs for everyone involved.
    - JB

  4. Tahoe ski bum says:

    In retrospect to the Dec. 1 blog, these statements truly reinforce who and what type of person is typing here…ie. a) wet snowless ground evaporates due to radiational cooling, which creates “humidity”. We have seen high overnight humidity (70 to 85%) for the past month. b)”700mb” where’d you get this?..if you have watched local weather forecasts find pressures averaging 30.10 to 30.40 “inches of mercury”..high pressure forces cold air down into valleys and Truckee..Martis valley..the warmer SW night winds we have had for the last month flow over the top of the suppressed cold air and create an “inversion” where we record temps 10 degrees higher at 8000ft than at 6000ft. With conditions like these in place, we only make “water” and waste energy and water in the process…Heavenly was able to make snow above the inversion because of their altitude and their gondola to access these (2) runs above 8000ft…check out the “facts” dude…NO ONE is making snow…Boreal can’t make snow above their first lift tower at the base, they must push it with a cat to make their 100 yard “poststamp”… dude see the reality and stop playing the blame game we see so much of in politics..we want to ski and board too..and thank “UR” colder conditions have arrived, for the moment….a veteran snowmaker

  5. Gapper says:

    as a biochemical engineer i would recommend using Snomax Snow Inducer, a protein raising the freezing temperature of snow allowing to cover the mountain with white bliss. Check is out alpine, it won’t open cartoon land but i’ll settle for roundhouse at this point. I blame al gore and global warming

  6. ashley says:

    we want snowwwwwwwwwwwww!!

  7. Bill says:

    It is stupid to think that they are not making snow becuase they don’t want to spend the money. They make snow any chance they can, even if it is going to melt during the day. If you don’t beleive it, drive up there and see for yourself. Be sure to bring a thermometer and a wet/dry bulb humidity tester too. Anyways its not the man made stuff that we really want to ski.

  8. Holes says:

    I have been reading the weather discussions on NOAA for the past few days-especially, hoping that snow will come soon and save all of our jobs up here. Not too much to report besides inversion information and a possible change in the cycle by next weekend. I’m sure Alpine, as well as the rest of the mtns up here, would love to make snow to get ready for the holidays. Who the hell wants to ski/ride 1 or 2 crammed slopes of man-made snow when a little patience will bring some real skiing. Those who do should get their passes to Northstar. The pre-season is a wash this year, we just need to pray for snow by Christmas to bring the customers.

  9. Skoty says:

    Get out and do some snow dances, howl at the moon, but let’s skip burning skis (don’t need the extra emissions). Oh and have faith in Rasta and his crew. Those are some of the hardest working and least appreciated (see Dec 1, duh) people you will ever meet. If you enjoyed the opening of the last few years, thank Snow Making. If I see any of those black jackets near a tap, you’ve got a frosty cold golden amber beverage coming your way. Thank you for all the hard work and on call status.

  10. JReece says:

    Well, if the locals are getting itchy, Mammoth does have top-to-bottom skiing right now with about 6-8 lifts going overall. As of last Thursday the snowpack had yet to turn into armor plate. I also consider the 3.5 hour drive down scenic recreation. However, they *are* charging full-fare.

  11. glenshire friend of rasta says:

    Just to let the haters know rasta and his boys are on it.Everybody knows all about snowmaking until its your turn to come out here at 12 at night!Inversion is a thing that even rasta cant fix it is part of the game i think that the boys at alpine and homewood are doing a hell of a job with what they have. They want snow just and bad as you so they can get on with there life of removing snow from the parking lot and building some jumps for your kid to hit so you should thank god there are boys out there willing to work all night in ugly conditions so you can ride! Come ski there great mountain and so some respect for the boys of night .

  12. LW Scott says:

    I skied Alpine full time from 1974 through 2005 logging over 2200 days, also having named CB chute for the memory of Craig Badami. Knees have taken there toll.

    Inversion is real. For those new and waiting, take advantage of mountain biking, motor cycle riding, and our other activies Tahoe has to offer to stay or get into shape or you will go nuts while waiting.

    Prior to snow making, Alpine use to haul snow daily from Blackwood Canyon, and haul it up the hill, then reload it onto snow cats and bring it up the hill to keep the mountain’s runs open.

    Once temps happen, you can bet they will make the best. I use to ski under the guns to get small powder shots.

    It’s usually marginal till Janurary 15th anyway, unless we are lucky. That’s a fact!

  13. Tahoe ski bum says:

    Thanks Skoty, that means alot to us…real good to know managament has our backs…question?..if we do get 4 or 5 feet by next tues. how long would prep take with all depts. to open the Summit chair, or has a contingency plan been discussed for a quick opening for this chair…Skoty..if there’s 4 foot of powder..everyone will want up the Summit chair!!!! Here’s to dreaming about powder turns….

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