“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