The National Weather Service Forecasts-

TODAY...SUNNY. PATCHY FOG IN THE MORNING. HIGHS AROUND 43. NORTH WIND 10 TO 15 MPH.

TONIGHT...MOSTLY CLEAR. LOWS 21 TO 27. NORTH WIND 10 TO 20 MPH.

SATURDAY...SUNNY. HIGHS AROUND 44. NORTHEAST WIND 10 MPH.

SATURDAY NIGHT...MOSTLY CLEAR. LOWS 18 TO 24. NORTHEAST WIND
10 MPH.

We had a 2 plus week period of dry cold temperatures with winds much of the time from 40-80 mph.

Much of the deeper upper mountain snowpack is quite solid in place.

We have received 8-9 inches of snow since the 12th. Temperatures have warmed by 8 degrees during that time. Today we will see the warmest temperatures since February 1st. This places serious additional stress on the snowpack.

We have had light to moderate winds. Some windloading is present but quite minimal.

Spatial variability remains high. The old snow surface has multiple structures currently and the new snow bonding will vary from location to location.

Look to see snow cleaning itself off of rocks and trees as well as surface sluffing in steep open areas.

We expect to see some small to moderate mid-day to late afternoon avalanche activity. The possibility exists for these avalanches to slide at deeper layers than we have been concerned with in the last few weeks.

In long steep open areas this could entrain quite a bit of mass.

Small slabs may also be present in isolated locations. Some slab activity was sighted yesterday primarily on N-NW Faces.

Danger levels are Considerable today do to new snows from the previous few days and diurnal fluctuation with afternoon temps going well above freezing once again in some of our mountain starting zones. This will be the warmest day in 7 weeks.

This melt freeze process we have seen the last few days and nights begins to build strength in the snowpack. But it is important to recognize the snowpack becomes weak during the above freezing, or warmest, part of the day.

Use extreme caution as we get to the later, warmer part of today.

Perhaps it is a good day to avoid places such as the Flume and Perseverance Trail.

ENJOY A BEAUTIFUL DAY!

Sun Crusts:

A frozen sun crust sometimes forms a hard bed surface for future avalanches to run upon. However, a sun crust typically has a fairly rough texture when compared to the more slippery rain crust, and snow deposited on the crust tends to bond better than you would imagine. However, a sun crust forms a strong mechanical discontinuity in the snowpack, which tends to concentrate any shear deformation within the snowpack to the layers just above and below the sun crust. But probably more important, crusts tend to concentrate temperature gradients above and below them and they can grow a thin and almost invisible layer of weak faceted snow. This probably accounts for most of the avalanches that occur on sun crusts, especially in non-maritime climates. Also, surface hoar that grows on top of a sun crust can be a very nasty weak layer.

Sun crusts, of course, form only on sunny slopes and not at all on the shady ones. So we find them mostly on southeast, south, southwest and west facing slopes at mid latitudes in the Northern Hemisphere (and conversely forms more uniformly on all aspects in tropical and arctic latitudes). Instabilities associated with sun crusts usually stabilize fairly quickly after a storm, depending on temperature, except if faceted snow has grown around the sun crust or surface hoar has grown on top of the crust, it can produce much more persistent avalanche activity.

Hot Tip:
When new snow falls on a sun crust, it's important to check out whether the sun crust is wet or frozen when the snow starts. If it's wet, the new snow will stick to it and you most likely won't have any immediate avalanche problem, but if the crust is frozen, then the new snow does not tend to bond very well.