Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board Another weather question

At the risk of making experienced Whitney hikers roll their eyes at another weather question....

Four of us will be attempting Whitney next week, staying two nights at Trail Camp. I've heard alot about snow lately. How cold can we expect it to be at night/morning and at the peak. We are having our final shake down meeting tonight and I want to make sure everyone brings enough layers without over packing.

Advice is appreciated.
ChrisQ

This time of year gets dicey when trying to predict the weather and temps at Whitney. Your best bet would be to bring everything you would need to stay warm and dry considering temps as low as the teens at night and 30-40 on your hike. It could also be above freezing at night and 40-70 during the day. Check the extended forecast prior to leaving for any last minute changes in what you bring. Light base layer, medium second layer, warm vest, waterproof shell, light wool cap and light gloves are my typical choice this time of year unless severely cold weather is predicted then all I do is change my shell, cap and glove choices. The key is to stay dry and be ready for wind.

CrhisQ, having been up Whitney a number of times, I would say I am a very experienced hiker, but I am confused about trying to predict the weather up there too.

Last weekend Weather.com predicted 0% precipitation, but there was a snow storm. The NOAA weather site also predicted 0%. Neither website saw these storms coming.
I have a permit to go back next week and weather.com is predicting 20% precip while the NOAA is predicting 0%. Now is this weather prediction predicting weather for the town of Lone Pine or the High Sierra? Is 20% precip at the higher altitude anything to worry about? Does this 20% mean that the air is so unstable it would open the door for 100% precip over the mountains?

It costs me roughly $140.00-plus to drive to Lone Pine plus gas/motel and then to have wrong weather info and only be able to hike to Lone Pine Lake or a lower level is the pits, not to mention potentially dangerous. Can you weather experts out there explain if 20% precipitation means in the valley or on the mountains?

This is a common inquiry, almost completely unanswerable! I heard the lows in the mountains were in the low 20's, on Mammoth or Bishop radio, last weekend. Good to stay tuned if you don't have Internet access.

I often leave for other ranges, and check weather.com for the local forecasts. They can be helpful.

You must realize, even with state of the art technology, they can't tell beforehand when a 15 degree temperature drop happens, when it's supposed to be hot! And when is any report always 100% correct when it comes to such a simple thing as rain, say?

Just be prepared, and go! Most summer weekends, I just take off with alternatives in mind. I'd say my success rate is about 80% or more. But then, when I detect a major problem, it isn't hard to cancel!

I was up there laborday weekend sunday morning 3-5A.M. was 15 degree F. Better be prepare two layer glove & clothes

There was a long debate earlier about the in/accuracy of weather forecasts, so I won't repeat it. As a climber on a big mountain like Whitney, you are basing you comfort and possibly safety on how prepared you are for various weather conditions in the mountains. My view is that you should bring the gear necessary to climb comfortably and safely if the weather forecast turns out to be wrong (as it so frequently is on Whitney).

As to your question about what does 20% probability mean - it is a very clever way that forecasters can hedge their forecasts while giving the appearance of accuracy. If I say there is a 20% chance of rain or snow, I am covered no matter what happens because rain snow means I was correct in my 20% prediction while sun means that I was correct in my no rain/snow prediction. As a climber, you must bring gear to be ok whether the 20% rain/snow happens or not.

The probability is temporal as well as spatial.

"The probability of precipitation has the following features:
The likelihood of occurrence of precipitation is stated as a percentage...
The probability is for a specified time period...
The probability forecast is for any given point in the forecast area...

"Here are two examples giving the same result:
(1) If the forecaster was 80% certain that rain would develop but only expected to cover 50% of the forecast area, then the forecast would read "a 40% chance of rain" for any given location.
(2) If the forecaster expected a widespread area of precipitation with 100% coverage to approach, but he/she was only 40% certain that it would reach the forecast area, this would, as well, result in a "40% chance of rain" at any given location in the forecast area."

http://www.utexas.edu/depts/grg/kimmel/nwsforecasts.html

Forget the weather report--it has nothing to do with what really happens up there. Plan for lots of layers. The wind is often more of a factor than the temperature. When you are climbing and exerting, 30 degrees can feel like 75. The nights are COLD! There is heavy wind at Trail Camp. Even 3 weeks ago, when it was quite warm during the day, the minute the sun dropped behind the mountains, the wind kicked up fast. By midnight, there were 50knot winds that sounded like a freight train going through our tent. You can often see storms coming, which form in the mid-afternoon.