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Historic data for first Winter Storm Date

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Re: Historic data for first Winter Storm Date

Postby longri » Wed Apr 06, 2016 3:13 pm

fishmonger wrote:The data from 1980 there suggests the first snowfall dates at Donner were (if any) on these October dates - none in Sept!)

I must be blind. I don't see Donner Summit in the pulldown. Or are your using some other source?

Wandering Daisy wrote:I would just pick the time you really want to go and then keep an eye on shorter term forecasts as your trip date nears.

Of course that's the obvious common sense thing to do. But it's still fun to geek about it.



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Re: Historic data for first Winter Storm Date

Postby fishmonger » Wed Apr 06, 2016 3:35 pm

longri wrote:
fishmonger wrote:The data from 1980 there suggests the first snowfall dates at Donner were (if any) on these October dates - none in Sept!)

I must be blind. I don't see Donner Summit in the pulldown. Or are your using some other source?

Wandering Daisy wrote:I would just pick the time you really want to go and then keep an eye on shorter term forecasts as your trip date nears.

Of course that's the obvious common sense thing to do. But it's still fun to geek about it.


Donner, well, my mind just equates

Truckee #2 (834)
# California SNOTEL Site - 6509 ft

as Donner Pass. Close enough. Further north, but actually pretty low at 6500 feet. Some of the data I can see in the site WanderingDaisy posted does show snow at times that are not recorded as snow at the Truckee sensor. Got to do a few searches and graph interpretations and will update my list once I get through that site. Very detailed, and almost overkill, but it also shows how fast a 30" snowfall in October can disappear to nothing at 8000 feet - 4" of water content took less than a week to disappear after the Oct 15 2009 storm in Mammoth. Three days of 70 degree temps and it melted away

http://www.nohrsc.noaa.gov/interactive/ ... &region=us
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Re: Historic data for first Winter Storm Date

Postby longri » Wed Apr 06, 2016 6:36 pm

Well maybe Truckee is too low.

I mentioned I'd heard that Donner Summit got snow in September 2000. I found a newpaper article about it:

Los Angeles Times wrote:Snowfall in the High Sierra Sets a Record for the Date
September 03, 2000|From Associated Press

DONNER SUMMIT, Calif. — It's a winter wonderland in summer here in the High Sierra. Five inches of snow has fallen on the summit--a record for Sept. 2.

The last time snow fell here Labor Day weekend was 25 years ago. Not only is the snowfall rare, it's also unusual for it to fall as low as it has--7,200 feet.

Heavenly ski resort on Lake Tahoe's south shore reported 3 to 4 inches of snow on its upper slopes above 10,000 feet. Two inches fell on its Top of the Tram at 8,200 feet.

"Let's hope that this is a sign of things to come this winter," Heavenly spokeswoman Monica Bandows said.

Caltrans called out its snowplows Saturday to clear Interstate 80, and drivers were pulling over to the side of the road to take pictures and chuck snowballs at each other.

The snow is from a storm system that brought record rainfall to the Central Valley and low temperatures to much of Northern and Central California the last two days.

The system--which originated in the Gulf of Alaska--is typical of a storm that might move through the area in November.

"It's not normal to get this kind of snow this early, but it's not all that unusual either," said National Weather Service spokesman Terry Ryan in Reno.

"You know what they say about the Sierra: You can see snow every month of the year. This is proof of that," Ryan said.

In addition, heavy rain was reported in towns around Lake Tahoe.

http://articles.latimes.com/2000/sep/03/news/mn-14993


The Truckee data show 0.2 inches of rain for September 2nd. And a min/max temperature of 34/43. But it would be a lot of work and kind of speculative to extrapolate that to higher elevations.
.
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Re: Historic data for first Winter Storm Date

Postby fishmonger » Thu Apr 07, 2016 6:15 am

I don't think it is too difficult to extrapolate snow at higher elevations when you have reliable rain and temp data. I mostly care about 8000-12,000 feet, so doing some crude temperature loss math based on elevation and maybe add a few degrees to round this towards a conservative estimate, then search for old news items if available, photos, just to support the data.

Add in the reliable snow data from Mammoth, which at least will tell us if there was snow in the snowiest part of the Sierra in a given month, and work through the recent years. A crude summary of this can probably be obtained in a few hours. Doesn't have to be scientifically accurate, as the Sierra is a big place and if it snows in Mammoth it doesn't always snow in Sequoia anyway, but it would be a gauge for when in the year these events happen.

And it can actually snow at all times of the year, just those snows usually don't last very long and pose much less of a risk for a hiker to get stuck in the backcountry. Snow in early September would still be a 1-2 day travel problem at the most, while October may mean the stuff stays on the ground, especially if one storm is followed by a second in close succession.

I updated my post on the first page with a lot more data collected yesterday by poking around on the NOAA snow site, mostly with data from mammoth, but also comparing to Devil's Postpile and a station at Bench Lake in Kings Canyon, which reports surprisingly complete data, but just like the others only back to 2002.

For kicks, this was July 24, 2014, and most of that was gone after the sun broke through for an hour later that morning.

Image
Below Forester Pass camp after the storm
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Re: Historic data for first Winter Storm Date

Postby longri » Thu Apr 07, 2016 4:42 pm

Those are good points. It isn't just snow, it's the amount of snow and how well it sticks, how well you can travel despite the snow and how long you're willing to be delayed if travel is difficult. That gets a little trickier to determine though. It depends not only on where you are but also on who you are.

Looking at your graph one gets the impression that a little less than one third of the time there is snow before October 15. But you've included events with as little snow as 0.1 inches. How can you know if those systems dropped enough snow up higher to be an issue?
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Re: Historic data for first Winter Storm Date

Postby oldranger » Thu Apr 07, 2016 8:58 pm

I keep it simple. No overnight parking along Tioga pass road beginning Oct. 15. I wouldn't go on an extended trip after that date. Short ones with no expectation of precip are ok. Remember skiin at mammoth on Halloween once. That means at least 2 feet of snow. Jane also experienced 9" at Roaring River on Sept. 10 or 11 once but it was gone in 3 days. I don't worry about September storms. Just willing to hunker up until things clear up and not worry about schedule.

Mike
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Re: Historic data for first Winter Storm Date

Postby fishmonger » Fri Apr 08, 2016 6:55 am

two comments - the amounts listed are Water Moisture Equivalent, and based on the numbers I saw in the fancy graphs, 0.1" of water equates to 1-2 inches of snow. The 3.5" event at the Mammoth Ranger Station actually generated 50" of snow down at Devils Postpile, over 30 at the Ranger station. Still, 2 inches of snow won't slow you down too much.

As for Oct 15 as a general guideline - absolutely. That is why my trip will end just before that date. I remember in 2001, I arrived there on October 12 and overnight parking was already prohibited, even though the weather was perfect. Did they change that date or was it a special event back in 2001? I did climb Mt. Dana that day without any clouds in the sky and nothing really happened weather wise for the next few days.

I agree that extended trips after Oct 15 without winter travel gear like snowshoes or ski are pretty foolish, even though it may take weeks or months to actually start snowing after that date.

One year not too long ago, I almost did a January JMT hike, because the Sierra was still totally dry into early January - a rare opportunity to "walk" across the range in winter. But by the time I got my ducks in a row, the big storm was approaching and the window of opportunity had closed. Sure wished I lived closer so I could be more flexible and react faster, however, these days I am forced to plan any 2+ week vacation 6 months in advance. I am already late submitting my late Sept-early Oct trip dates, but I am going to do that today. I am pretty confident that with an exit date before Oct 14, the risk of major snow forcing an abort is low enough to move ahead with those dates.
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Re: Historic data for first Winter Storm Date

Postby fishmonger » Fri Apr 08, 2016 2:48 pm

updated the graph and numbers prior to 2002 with data from Sonora Pass - not too far north, over 9000 feet up, and daily data available back to 1980.
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