High Sierra Topix

I have noticed that the overwhelming advice of early season creek crossing is to do it in the "conventional" early morning or late evening.
My own experience, at least in late May on Falls Creek(Jack Main Canyon-Northern Yosemite) is directly the opposite.
I have been travelling this area in late May for 18 years and Falls creek is absolutley at it's highest just after dawn 'till about 1 pm from above Hetchhetchy to the cataracts at the intersection of the PCT/ Tilden Canyon trail.
The lowest is in early afternoon beginning 1PM to 7 PM.
We are talking a matter of feet here.
This is counter-intuitive, I know.
I also have read that many other PCT thru hikers rate this particular creek as one of the most dangerous to ford..
Indeed, I have risked my life there for almost two decades. Twice I was nearly killed (No Joke). I am wondering if this phenomenon could be the culprit. Has anyone else an exp-laination for the reverse "tide" in this area? The best I can conclude is that by geography ,the afternoon melt is greater than in the area above the fords due to the orientation of Jack Main canyon to the sun at this time of year.
I would like to hear any opinions on what causes the "reverse" tide there in Jack Main canyon. It would prove invaluable to early season travellers and I intend to post my findings to other boards as well as let others on the trail know if I can figure out the answer. I have not travelled the area much in late June.. just late May. So perhaps this phenomena only occurs at that time.. but it is interesting.
A good place to witness this happening is only a dayhike away from Hetchhetchy itself, at Lake Vernon upon the Falls Creek trail bridge. From May 20th to May 31, regardless of snowpack, the water level is lethally high at dawn and crossable in early afternoon. Directly opposed to everything I have read about other fords in the Sierra. And possibly the cause of confusion/risk for many early sesason travellers.
One thing I can add: Having been there in early season(2004) in Paradise Meadow(Jack Main Canyon), and having no snow on the ground(there but several feet left in New Grace Meadow), a warm rain fell and FILLED the canyon floor with melt water in a period of hours. This could be a case of odd geography or perhaps a common happening among Sierra canyons at this time.
Anyone have any experience with this or any ideas what is going on?
What we find might save someones life. Thanks, Hetchy

Every stream is going to be different, and I have always found that rule to be a little misleading. Yeah, snow melts most in the afternoon--but that doesn't always mean that the creeks are highest then...it's all a question of how long it takes that snowmelt to work its way down into the watershed.

I seem to remember camping at Merced Lake thirty-five years ago, and camping near the water--only to wake up in the morning with the water darn near lapping at the sleeping bag.

As with any rule in the woods, your mileage may vary!

Quite right. Variable due to a number of factors:

http://www.yosemite.org/naturenotes/StreamFlow.htm

g.

GD the link does not work.

Hmmmm. Worked for me, but who can understand the vagaries of the metaverse? Go to Nature Notes at www.yosemite.org/naturenotes. Go to Article Archives, then look for:

Sierra Nature Notes, Volume 4, June 2004

When is the best time to cross a mountain stream?
Understanding daily variations in streamflow
Jessica Lundquist, Soon-to-be PhD
Hydroclimatology Group, Scripps Institution of Oceanography

Maybe a little too much information, but interesting.

Hope that works!

g.

Eeeeek!

They're changing the web site as we speak. Sorry about that, didn't know. We may have just lost Nature Notes -- no one told me, of course. I see if I can find out what's happening.

g.

Update: Just talked to my buddies at Yosemite Association. They're migrating the whole site. The redesign will include Nature Notes, but it may take longer -- maybe a week +. Oh well.

Thanks for the 411.