The National Weather Service Forecasts-

TODAY...INCREASING CLOUDS. HIGHS AROUND 31. LIGHT WINDS.

TONIGHT...CLOUDY. SNOW DEVELOPING IN THE EVENING...THEN RAIN AND SNOW LATE. SNOW ACCUMULATION UP TO 2 INCH. LOWS AROUND 29.
SOUTHEAST WIND 10 MPH.

WEDNESDAY...RAIN AND SNOW IN THE MORNING...THEN RAIN IN THE
AFTERNOON. SNOW ACCUMULATION UP TO 1 INCH...BEFORE MELTING. SNOW LEVEL 1300 FEET IN THE AFTERNOON. HIGHS AROUND 38. SOUTHEAST WIND 10 TO 15 MPH.

WEDNESDAY NIGHT...RAIN. LOWS AROUND 34. SOUTHEAST WIND 10 TO
15 MPH.

It has been clear and cool the last several days. This comes following a week of rains to summit elevations.

The lower snowpack is quite solid in place.

Saturday we received almost 4\" of new snow at upper mountain elevations.

Yesterday we were able to see that this 4\" had created slab formations in our urban starting zones. Some of these slabs failed naturally and several are still hanging.

As we go through tonight and into tomorrow the avalanche danger will rise as we start to place this cold new snow on the few slabs that are in place. Even without the presence of the slabs and weak layer, as this storm comes in accompanied by warming temps over the next few days danger levels are expected to rise.

With .67\" of precip expected for tomorrow and .79 in the forecast for Wednesday we could see some new snow buildup at upper elevations thus growing the size of the slides predicted with the increased avalanche danger.

Be cautuious over the next few days as we start to see this new snow add up. Check for bonding and weak layers.

Have a great day.

Things to consider in your forecasting and trip planning.

Air temperature not only determines the type of snow crystals that fall from the sky, but the metamorphic processes that occur within the snowpack.

You need to track:

?Daily temperature values (highs and lows) and range
?Temperature trend (increasing or decreasing) and rate and duration of change

Daily temperature values: Use daily high and low temperatures to determine freezing levels in the mountains as well as snow and rain levels during storms. Note the following.

?Crusts may form if temperatures rise above freezing during the day and drop below freezing at night; the crust can create a potential sliding layer for the next storm

?When temperatures remain above freezing for more than 24 hours, the upper snowpack becomes saturated from melt water and may cause wet snow avalanching

?When temperatures stay well below freezing for long periods of time and high and low temperatures never rise above 15?F (-10?C) day and night, weak layers may develop on the surface or near the ground in a shallow snowpack; this can create a layer that fails with the next load of new snow

Key points:

?Avalanches may occur when air temperatures rise above freezing and stay there

?Weak layers often develop when temperatures get very cold and remain that way

Temperature trend: As temperatures increase, the snowpack undergoes settlement, deforming and becoming denser.

Settlement on an incline results in creep, a slow downhill motion.

?If air temperatures increase rapidly (more than 15?F or 8?C) in less than 12 hours, the rate of creep increases, which can lead to avalanching. This is most critical when temperatures are near or above freezing because the rate of creep increases exponentially with rising temperature.

?If temperatures increase slowly over several days, settlement rates are slower. If air temperatures never rise above freezing for very long, the snowpack deforms slowly and creep rates are slower.

?As temperatures decrease, settlement and creep rates also decrease.

?Prolonged periods of cold temperatures promote the metamorphic processes that form weak layers.

?Warm days and cold nights strengthen the pack, especially overnight and during early morning hours.

?Several days of warmer temperatures followed by colder temperatures also strengthen the pack.

Key points:

?Rapid rises in temperature can destabilize a pack, while slow rises stabilize it (especially if a cooling trend follows)

?Long periods of cold temperatures build weaker snow, which isn?t a problem until the next significant snowfall