Storm totals from this edition of Pineapple Pow!

Ladies and gents,

Here are the latest storm totals for you all:

Mt. Rose: 11-15"
Alpine Meadows: 6-10"
Squaw Valley: 5-10"
Boreal: 11"
Heavenly: 23-25"
Homewood: 6-13"
Sugar Bowl: 8-11"
Northstar: 8-14"
Kirkwood: 13-16"
Sierra-at-Tahoe: 10-16"

Now go shred that pineapple!
Have a fun and safe weekend.

-Andy

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Choose Wisely

As new snow finally begins to fall upon the Sierra Nevada and the ranges of the Great Basin, the importance of making good decisions is at the forefront, whether you slide in or out of bounds. In short, don't be dumb. The outcomes of poor decision making will be exponentially greater in the coming 72 hours. Why?

1. Where snow currently exists, it is faceted, shallow, and weak.
2. Many aspects are devoid of snow.
3. Many shredders have been deprived of quality days thus far (road-trippers and those with good attitudes and/or high levels of creativity notwithstanding).
4. Several feet of classic Sierra cement are expected to blanket the crest over the next couple of days.

Integrating this information yields the following conclusion: Chances of disaster are high, chances of human factors driving disaster are high, and consequences are high. Oh, and the avalanche forecast will be high as well. Do something dumb and the positive reaction you will get from friends and family? Chances are it will be low.

The main problem is demonstrated here:

The coming avalanche cycle will be an interesting experiment in snowpack dynamics throughout the western cordillera as the incoming liquid equivalent represents a dramatic increase in snowpack (from 0 to something, or at least a doubling of current liquid!). This significant loading will force rapid rises in instability. The current snowpack is incredibly weak but the availability of many anchors will offset this. Sample a ride with the white dragon, however, and you will also engage in a sharp, bumpy ride; not highly conducive to minimal trauma or cracking beers post whiteroom. In ranges with few to no observations or remote data sources, use the fact that far below average snowpacks imply weak strength and high probabilities of faceting throughout. When in doubt, dig. It is only a meter to the ground...maybe...

Slopes that previously had no snow will gain some essence of coverage, meaning that they look skiable (it's almost February, right?). The gloriously smooth Sierra C will allow for high velocities to be quickly and effortlessly attained, yet the consequences of dry docking or hooking up with submerged plant or geological matter will be catastrophic.

The human factor represents the primary hazard. It is your choice to go out at all. It is your choice where you go and how you travel through that environment. It is also your choice to accept or reject, based upon observations of the situation, what your instincts tell you, what your knowledge tells you, and what your group is telling you. The heuristic trap is not fun (McCammon 2002), and once again, don't be dumb. There is no honor in succumbing to the agendas of others who do not have your best interests in mind, particularly when a bad outcome is realized (occurs). There is great honor in making an informed decision and returning to shred another day, again, and again, and again. When style matters most, returning to civilization safely and stoked is good style. To have achieved your goals safely and with minimal impact on the natural environment is the best style. The style meter plummets into the negative when people get hurt or have their experience tarnished by a lack of good decision making.

The previous statements are intended to be dire. Avoiding poor outcomes is a good strategy in life, and nobody will be bummed if you told them that you opted for something mellow rather than risk your life for something dumb. Once you let others, or your perception of how they perceive you, to make decisions for you, it's a dark, painful road that leads to a net regression of positive change and human existence. Keep praying for snow, and think about groovy arcs on steep corn slopes rather than rehab and a second job, all because you wanted to be 'rad' or get the cool photo. Consider discussing with your group (or just yourself if you are a solo ninja like I) the ideas expressed by Grant Alexander here.

Be safe, shred smart, and always pursue style.

Reference:
http://www.avalanche.org/moonstone/DecisionMaking/Heuristics/traps%20reprint.pdf

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IT'S FINALLY HERE!!!!!!!

The prodigal son returns in the form of Pineapple Pow. In what seems longer than what KT lift lines will be Friday/Saturday or on any good powder day, snow is finally returning to the Sierra. The whole length of the Sierra will receive substantial snow over the next 36-48 hours.

Let's get down to the nitty gritty right away. Mid-mountain and above (~7500 ft.) will receive a solid 2 feet. We said the some isolated areas could see upwards of 30" on Monday. Well, those areas will expand due to the cold air arriving sooner than we saw on Monday. Lake level to mid-mountain will receive about a foot of snow. Two keys for this: 1) the timing of the cold air (sometime tonight the snow level will migrate down to lake level) and 2) The first snow could fall, not stick, and melt thus slowing and delaying the accumulation process. 

So our best forecast is 5-10" near the base, 12-20" mid-mountain-ish, and 2'+ at the very top. Total melt water precipitation will be between 1-3", with some areas near the crest over 3.5" (Figures 1-2).

Figure 1: WRF predicted 72 hour precipitation. Most of the crest expected to receive 2.5"+. This model can overestimate precipitation though.

Figure 2: HPC predicted 5-day precipitation totals. Most areas in the Sierra 1-3".

Due to the great moisture connection (aka atmospheric river), the snow will be very wet, which will be great for filling in the many gaps and bare areas across the Sierra. Precipitable water values will exceed 1" and even approaching 1.5", which is very high (Figure 3). These values are a classic Pineapple Pow signature.

Figure 3: Large quantities of water in the atmosphere getting transported our way. Pineapple Pow!

The ridging is giving way to zonal flow and an extremely positively tilted trough (think a forward slash (/)) over the West Coast. This tilt promotes and maximizes the moisture connection in the Pacific that we currently have (Figures 4-5).

Figure 4-5: Transition from ridging to zonal flow to positively tilted trough in 24 hours. Looking at mid-level heights, winds, temperature.

Also as I mentioned above, cold air is moving in a little faster than was forecasted a couple of days ago. So a quicker change to snow, higher snow to water ratios, and more snow at lower elevations will be the result of the colder air. The longer range model (GFS), is still holding the cold air off a little longer than some of the shorter range models (WRF, NAM).

Figures 6-7: 9-1000 ft. temperature, height, and winds. Temperatures drop this afternoon through tomorrow night. Transition from rain to snow will occur at lake level overnight.

A narrative of the event should unfold like this: 1) Rain starts today (already has) and continues through the afternoon. 2) Snow levels slowly fall through the late afternoon and evening. 3) Snow levels will fall to lake/base level overnight sometime between 10pm - 4am. 4) Heaviest snow/rain will occur late this afternoon and last through tomorrow morning. 5) Finally, snow will linger through tomorrow evening/night.

So go out and enjoy the powder over the next few days. And remember to practice that sick voice or perfect the out sick email today.

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And We're Back But, Don't Call it a Comeback!

It is with great pleasure to reintroduce Powdiction back to the wild. We stepped away because we knew this winter wouldn't be good (WE KID!...but seriously...haha). Anyways we decided to say, 'hey day jobs and school, the world needs Powdiction and so do we'. So as Randy Quaid said while helping save the world in Independence Day, I'm (we're) baaaaacccckkkkk! (And no we weren't abducted and probed by aliens).



Well well, we finally have some snow in the forecast. Some light rain/snow is falling in the northern Sierra now due to a very nice moisture connection with the Pacific (Figure 1). This moisture is helping to destabilize the area, which is a fancy way of saying, helping to kill the ridge of death.

Fig 1: Amount of water in the atmosphere. And there's a lot for winter, Pineapple Pow! Valid Tuesday.

Some other factors are helping to squash this ridge. An approaching Pacific trough is helping, and the ridge built so far north and wide that it is actually a party to its own demise. This is how. The ridge is thinning over the west coast of US and the overall blocking pattern is allowing and helping bring very cold air from the arctic south (POLAR VORTEX WHAT UP?!)(Figures 2-3).



Mid-level temperatures. Very cold air coming south form the arctic with some of the air pushing SW.

 

Figs 2-3: Mid-level spin/instability in the atmosphere. Vortex cores moving south from Arctic with core approaching west coast.

Well this cold air is pushing south-southwest, which is helping to break down the ridge from the east. The current moisture and approaching upper level trough in the eastern Pacific are breaking down the ridge from the west and the ridge kind of splits with a small component going over NW Canada and the rest of it pushing south (Rossby Wave Break in da house?!). This is happening now and over the next two days (Figure 4-5).

Figs 4-5: Trough off the PNW coast with very cold air coming from the Arctic. This flattens the ridge and brings much needed precipitation to the Sierra.

Due to the strong moisture connection (atmospheric river) and the ridge softening the blow of the cold air and the effects of falling heights with the approaching trough, this event will start Wednesday and continue into Friday night. Rain/snow will begin to fall Wednesday afternoon/evening with the snow level near the top of the crest. The snow line will slowly fall to base/lake level by Thursday afternoon (Figures 6-7).

Figs 6-7: Fig 6 shows rain/snow starting Wednesday afternoon/evening. Fig 7 shows one of the heaviest 6-hour rain/snow periods during the event, Thursday morning/afternoon.

So to summarize (and for those who just scroll to the bold/italics text), rain/snow begins Wednesday afternoon with snow levels around 8500-9000 feet. It takes about 24 hours for it fall to and below lake level by Thursday afternoon. So about half, if not more of the precipitation will fall as rain below 7000 feet. However, the timing of the snow level drop is still tentative and the amount of snow below mid mountain elevation (7500-8000) is very tenuous.

The heaviest rain/snow will be Thursday morning through Thursday night. Total precipitation for the mountains will range from 1-3" for the event (Figure 8). Snow totals will range from 1-2' with high peaks and snow loading areas possibly seeing upwards of 30". Rain to snow ratios will be lower in that Pineapple Pow range of 6-12 to 1.

Fig 8: Total amount of liquid precipitation forecasted to fall over the next 5 days.

The snow will be some fine Sierra Sticky Icky or Pineapple Pow if you prefer, with a good atmospheric river connection. So it will help cover the rocks and pretty bare slopes around Tahoe and the Sierra. Also, remember as LL said, DON'T CALL IT A COMEBACK!

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