9. Weather
Here are some of the critical elements to consider when evaluating weather patterns.
The Dew Point is "the atmospheric temperature (varying according to pressure and humidity) below which water droplets begin to condense and dew can form." (from Oxford)
As moisture-laden clouds are forced up a mountain, the colder temperature and reduced air pressure will force water out of the clouds to create rain, sleet, or hopefully snow.
The Adiabatic Lapse Rate is the change in temperature associated with the increase in elevation. The moist adiabatic lapse rate is less than the dry adiabatic lapse rate because air rising condenses out its water vapor (once saturation is attained).
The Dew Point is "the atmospheric temperature (varying according to pressure and humidity) below which water droplets begin to condense and dew can form." (from Oxford)
As moisture-laden clouds are forced up a mountain, the colder temperature and reduced air pressure will force water out of the clouds to create rain, sleet, or hopefully snow.
The Adiabatic Lapse Rate is the change in temperature associated with the increase in elevation. The moist adiabatic lapse rate is less than the dry adiabatic lapse rate because air rising condenses out its water vapor (once saturation is attained).
Here is a list of WINTER weather terms.
JumpShare GDrive
Check the weather starting the week before you head out. Be prepared to cancel or reschedule if it looks dicey. Know what you are getting into. Weather can change swiftly, so it is important to check frequently and consult multiple sources. Here are some of those sources.
https://www.sfgate.com/weather/
http://virga.sfsu.edu/
and many more...
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Added 1/25/19
I've added a graphic and link here to clarify air flow around pressure zones.
Think of the weather "kitchen." In the Northern Hemisphere, it's "High clock, low counter." Clockwise flows around the clear cold highs, and counterclockwise around the soggier lows.
The opposite happens way down south, below the equator.
------
I was staring at the picture below last year and trying to make a go/no go decision before a Dewey Point, Yosemite Park expedition in 1.5 days.
Notice how a big soggy messy LOW plays crack the whip, flinging a mass of moist warm air in red scallops while following it with the teeth of a blue chill. As weather spirals in, warmer moist messiness transitions to a cooler push of air.
What a whip! Would you go?
I've watched this pattern set up again and again.
3/1/19 (still before the trip)
A wet one. Snow, rain, where and at what elevation? The valley (elevation 3,966 feet or 1,209 metres). El Capitan, just across a lot of space from where we hope to be, stands at 7,500 ft. elevation and we will be about the same.
If we can get to Badger Pass Lodge, we can hope for snow on the way out. Accumulation? Maybe 2 feet, from what I see. Breaking trail? I always hope some hotshot snowshoers plow a path. We plan to arrive about 9 am which should give them a chance. He-he-he.
Worst case; a sleazy semi-freezy sloppy wet ice storm.
Could be epic!
3/5/19 (after the trip)
Epic it was. We started out in snow showers and a couple of LOUD thunder rumbles. The trail was in good shape, but it was a sleety wet drizzle that was hard to keep out. We arrived at Dewey Point soaked and cold.
Visibility was poor, but a rainbow in the ice crystals helped lift spirits, and the trip out, still with some precipitation, was a better experience. A few degrees cooler and the experience would have been less moist and more pleasant.
The snow drips and bombs from trees were impressive throughout the night.
http://virga.sfsu.edu/
and many more...
---------
Added 1/25/19
I've added a graphic and link here to clarify air flow around pressure zones.
Think of the weather "kitchen." In the Northern Hemisphere, it's "High clock, low counter." Clockwise flows around the clear cold highs, and counterclockwise around the soggier lows.
The opposite happens way down south, below the equator.
------
I was staring at the picture below last year and trying to make a go/no go decision before a Dewey Point, Yosemite Park expedition in 1.5 days.
Notice how a big soggy messy LOW plays crack the whip, flinging a mass of moist warm air in red scallops while following it with the teeth of a blue chill. As weather spirals in, warmer moist messiness transitions to a cooler push of air.
What a whip! Would you go?
I've watched this pattern set up again and again.
3/1/19 (still before the trip)
A wet one. Snow, rain, where and at what elevation? The valley (elevation 3,966 feet or 1,209 metres). El Capitan, just across a lot of space from where we hope to be, stands at 7,500 ft. elevation and we will be about the same.
If we can get to Badger Pass Lodge, we can hope for snow on the way out. Accumulation? Maybe 2 feet, from what I see. Breaking trail? I always hope some hotshot snowshoers plow a path. We plan to arrive about 9 am which should give them a chance. He-he-he.
Worst case; a sleazy semi-freezy sloppy wet ice storm.
Could be epic!
3/5/19 (after the trip)
Epic it was. We started out in snow showers and a couple of LOUD thunder rumbles. The trail was in good shape, but it was a sleety wet drizzle that was hard to keep out. We arrived at Dewey Point soaked and cold.
Visibility was poor, but a rainbow in the ice crystals helped lift spirits, and the trip out, still with some precipitation, was a better experience. A few degrees cooler and the experience would have been less moist and more pleasant.
The snow drips and bombs from trees were impressive throughout the night.
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