Friday, February 6, 2015

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One, Two... Dump

Deep tropical moisture from east of Hawaii will finally make its way into the Sierra this afternoon and hang around through Monday morning.  Two wet and unfortunately for all of us skiers, warm systems will impact the region this weekend.  The first is currently knocking on the door with moderate to heavy rain currently overtaking the Central Valley. The second system is scheduled to move in on Sunday and persist through Monday morning.

-Two very moist systems will clobber the Sierra this weekend thanks to an Atmospheric River
-Due to the tropical nature of the moisture, snow levels will be high (7400-8200 feet) before dropping to lake level Sunday night
-Sierra Cement will pile up above 8200 feet with 4+ feet possible on the highest peaks

Precipitable water from the 06Z GFS model showing an Atmospheric River stretching from east of Hawaii into the Norther California.

The first system will dump two to three inches of precipitation over the Tahoe Basin by tomorrow afternoon.  The crest and points northward will likely see more with some some locations getting as much as six inches of precip.  The storm will begin to wind down tomorrow morning but moisture will continue to stream into the region throughout the day providing additional precip accumulation of an inch or two. Before another colder system moves in Sunday and drops another two to three inches of precip over the area.  The Weather Prediction Center (formerly the Hydrometeorological  Prediction Center) has as much as 11 to 13 inches of precipitation along the crest through Monday afternoon...

Forecasted total precipitation amounts through Monday at 4 pm PST

We haven't had this much precipitation in the Sierra in a three day period in over two years!

Unfortunately for us skiers, the majority of this precipitation will fall as rain from 7800 feet down, at least until Sunday night when snow levels drop to lake level. The majority of ski areas will see significant degradation of their snow pack from lower mid-mountain down.

Where snow does fall it will be very heavy with snow to liquid ratios of 6-8 to 1.  That means classic Sierra Cement and even some "dippin-dots" (technically known as graupel) at times due to the very deep moisture in the atmosphere.

The precipitation amounts will drastically drop off east of the crest with the first storm. Leaving higher elevations of the Carson Range with 7 to 14 inches of snow through Saturday. The second storm is much more favorable for spillover as the atmosphere will be more unstable and could see some areas of the Carson Range with 2 feet of the snow.

Bottom line stay up high and enjoy the Sierra Cement.  Places like Kirkwood, Heavenly and Mt. Rose look to do extremely well this weekend due their higher altitude.

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