Eastern Sierra - Sun Mar 21 2010
Eastern Sierra avalanche advisory |
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Today the avalanche danger is estimated to be LOW. Clear skies, lack of precipitation and above normal temperatures Recent dry weather has resulted in a relatively stable snowpack. Generally safe avalanche conditions exist. Be on the lookout for large, growing, pinwheels of snow rolling downhill, or sinking into wet glop past your boot tops. These are signs that the surface snow is getting wet enough to slide. |
Welcome to Spring 2010!
The warming trend continues one more day before the weather becomes a little unsettled and temperatures fall 5-10F. The warmest mountain temperature yesterday as reported from Mammoth Pass, 9,400 ft with a high of 56F. Main Lodge hit 52F at 3 PM. Gem Pass at 10,700 ft had a high temperature of 44 yesterday and Tioga Pass at 10,000 ft hit 51F.
North facing slopes above treeline are showing the signs of the sun and warm temperatures and a few small point release slides came off from ridges on north facing terrain today in the Rock Creek and Mammoth areas. North facing aspects from mid to high elevations remain cool and winter like except for areas in the trees. Expect sudden deceleration coming from damp powder in to areas close to trees. North facing alpine terrain is a mix of wet powder on the surface, some dry winter snow in sheltered gullies and bowls and breakable wind crusts.
Fortunately nights are staying a little cool with lows staying in the upper 20’s for at least 6 hours each night. The warming trend has been gradual and the snow on east, south and west facing aspects has had time to react and adjust to changing conditions.
With a cooling trend and increasing winds coming tonight through Tuesday, avalanche danger will continue to be Low and skiing could become interesting with stout crusts remaining hard and frozen on mid and high elevation slopes exposed to the wind. Let’s not forget this is the time of year that cornices become unstable and sensitive to release by the effects of sun and warming. Extra caution is advised on slopes below cornices and on ridgelines close to cornices.
High clouds drifted in yesterday in a southwest flowaloft between the ridge and an upper trough over the eastern Pacific. This system will bring rain and snow to northern California and Oregon today. We will see increased southwest winds blowing 50-60 mph over the ridgetops late today and tonight. A disturbance splitting off the storm north of us will bring cooler temperatures and windy conditions early in the week.
For today, high temperatures will reach the low 50’s in Mammoth, Aspendell and a few high elevation locations. Otherwise, temperatures will reach the mid to upper 40’s today. Southwest winds will pick up to 50-60 mph by the afternoon. The 8,000 to 9,500 ft elevations will see another spring day with highs in the mid to upper 50’s.
Please note that the avalanche danger rating in this advisory expires in 24 hours. This advisory is our best interpretation of snow pack conditions and NWS forecasts issued today. Backcountry travelers should be aware that elevation and geographic distinctions are approximate and that a transition zone exists between upper and lower elevations. Avalanches do not happen by accident and most human involvement is a matter of choice not chance. Most avalanche accidents are caused by slab avalanches that are triggered by the victim of member of the victim's party. Even small slides can be dangerous. Always practice route finding skills and carry avalanche rescue gear. Remember that avalanche danger ratings are only general guidelines. Distinctions between geographic areas, elevations, slope aspects and slope angles should be made.
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