High Sierra Topix

One of the problems with books/articles/discussions of field weather forecasting in the summer is that most of it assumes a frontal system model common in the Midwest and east coast. The southwest including the Sierra is dominated by the North American Monsoon in the summer – quite different from a frontal system.

The North American monsoon usually forms over the four corners region in July. Since it is a high pressure system it produces a clockwise rotation often moving into the Sierra roughly from the south. It usually picks up moisture from the Gulf of California and northern Mexico and sometimes the Gulf of Mexico. If it reaches the Sierra, as it rises in the midday it cools and produces precip.

As has been mentioned, the key is watching the clouds. My daily forecast method is fairly crude. If there is significant buildup mid to late morning, I plan for likely storms. Otherwise I expect it will likely be dry (doesn’t always work?).
For a short range forecast prior to a trip, I look at the weather maps for afternoon monsoon activity over the four corners (usually there in July). If it reaches into or across Nevada, it often gets into the Sierra. If not, it will likely be mostly dry for the next few days.

When disaster strikes: My worst trips weather-wise have been associated with hurricanes in Mexico and western Gulf of Mexico. Sometimes the remnants of a tropical hurricane move north and are captured by the monsoon and dragged into the Sierra – very bad. Watch for news of these storms when they move north.

Years ago I thought I could use my altimeter to monitor for impending storms. It doesn’t work in the southwest. Monsoons do not produce pressure shifts prior to storms the way that frontal systems do. A digression – I was once looking at reviews for a high quality altimeter and saw a review with one star. The guy was using it in the Sierra and thought it was defective because it didn’t show a pressure drop prior to thunderstorms. His thinking was defective, not the altimeter.

On the other hand I am interested in photography. Blue skies usually produce boring images (almost as boring as grey skies). The best landscape photos usually are produced around building and clearing storms. A mild monsoon is often the best.

On the other hand I am interested in photography. Blue skies usually produce boring images (almost as boring as grey skies). The best landscape photos usually are produced around building and clearing storms. A mild monsoon is often the best.

Something I preach to my photography class students and at my art shows to my investors!
A cloudless sky is a naked sky, clouds add character, drama, intrigue, and tell the story of that particular art piece, to me no clouds = a blank canvass!

Here is David Brower's rule about skies in photography:
"Everyone knows it is there, so don't bother to show it unless it is doing something interesting - then show a lot of it!"

-Phil

This is helpful, thanks Maverick. We got caught in a couple nasty storms last year in the Sierra, and I've been meaning to look more into cloud types to help make decisions.

A couple of thoughts: Lenticulars over the crest are a sign of the jet stream shifting which often means a storm front coming in. Not always, of course, but often enough that it's worth paying attention to (in addition to being the coolest cloud formation around). Incidentally, there was a confirmed tornado at about 11,000 feet near Mt. Tyndall some years ago.

If cumulus start forming before 10AM, there's a pretty good chance you'll get thundershowers and, of course, lightning. If you hear thunder, get down from wherever you are and don't go up and over passes. It's rare, but there's cases of lightning striking a mile or two horizontal from cloud build up -- clear sky above you. From looking at tree strikes, there's really no absolutely safe place but I notice more strikes along ridges and along benches just where the slope drops off again.

I was just re-reading the medical report on the Scout/Sandy Meadow lightning incident many years ago and it notes that burns were on people's backs and buttocks, indicating they were not in a more protective lightning crouch (crouched with only feet on ground surface, knees folding and arms wrapped around knees).