The National Weather Service Forecasts-

TODAY...SUNNY...WINDY. HIGHS 20 TO 26. NORTHEAST WIND 20 TO 30
WITH GUSTS TO 55 MPH NEAR DOWNTOWN JUNEAU AND DOUGLAS. ELSEWHERE, NORTHEAST WIND 5 TO 15 MPH.

TONIGHT...PARTLY CLOUDY. LOCALLY WINDY. LOWS 10 TO 20...EXCEPT
AROUND ZERO IN WIND SHELTERED AREAS IN THE MENDENHALL VALLEY.
NORTHEAST WIND 20 TO 30 MPH WITH GUSTS TO AROUND 50 MPH NEAR
DOWNTOWN JUNEAU AND DOUGLAS DIMINISHING LATE. ELSEWHERE...WIND
NORTHEAST 10 MPH.

MONDAY...SUNNY. HIGHS 18 TO 24. NORTHEAST WIND 10 TO 15 MPH.

MONDAY NIGHT...MOSTLY CLEAR. LOWS 10 TO 18. SOUTHEAST WIND 15 TO 20 MPH.

With the warm weather from 2 weeks ago, the rain and heavy dense snow, the lower snowpack has settled and bonded quite a bit.

There are still multiple weak layers lower in the snowpack but the heavy dense snow above them appears to be supportive at this time. Be cautious as new loads are placed on these already weak layers by new snow or even by additional wind loading.

We had several inches of new snow deposited Saturday and Monday. This has placed some additional weakness in the snowpack in places with wind deposits.

Look to see continued areas of wind loading as the snow in place is affected by winds of 10+ MPH throughout most of the next few days.

Thursday natural avalanche releases were sighted on multiple aspects due to wind loading. Be aware there are pockets of instability.

With very little snow on Mt Juneau in the urban starting zones avalanche danger is LOW at this time. Yet some of the gullies are starting to see fair snow accumulation due to crossloading from the winds.

Please remember this is not a backcountry forecast.

Please be aware that fieldwork continues to show multiple weak layers in the snowpack and natural avalanches have been sighted recently.

Backcountry danger levels could be considerably higher.

After precipitation, wind is the next most important weather variable affecting avalanche potential. It is fundamental to slab development and determines where wind-transported snow accumulates.

Wind speed:

Wind speed determines the amount and rate of wind loading. Winds between 20 and 60 mph are optimal for transporting snow, while those less than 20 mph can only transport very low-density snow ( 60 mph) often disperse snow beyond the starting zones of avalanche paths, depositing it farther down the slope. There it will stay, beyond the point where it can form dangerous wind slabs on critical slope angles. Very high winds, especially during periods with low relative humidity (such as when skies are clear) also cause snow to sublimate into the atmosphere before it can fall out and form a thick slab layer.

Average wind speeds between 20 and 60 mph transport and deposit snow of almost any density onto the upper reaches of avalanche starting zones. Average speeds between 30 and 40 mph have the greatest potential to build dangerous slabs in these areas.

Remember that new snow is not needed to form an avalanche. As long as there?s snow on the ground that the wind can transport, new slabs can form on leeward slopes.

Wind and snow accumulation rates: The combination of new snow and wind-deposited snow during a storm increases the snow accumulation rate significantly, easily doubling or even quadrupling it on leeward slopes. For example, if snow falls at a rate of 1 inch (2.5 cm) per hour for 8 hours, you?d expect 8 inches (20 cm) of accumulation on the ground. But if ridge-top winds average 30 to 40 mph from a consistent direction throughout that period, you might get snow depths of 16 to 32 inches (40 and 80 cm) on leeward slopes.

Wind direction: Wind direction indicates which slope aspects are susceptible to snow being deposited from wind loading.

Say, for example, that a storm begins with strong southwesterly winds that load leeward, northeast-facing slopes. If it is followed by northwesterly wind flow after, for example, the passage of a cold front or an upper-level trough of low pressure (in the Northern Hemisphere), southeast-facing aspects will become the leeward slopes and get the most loading.

When wind blows over a ridge top and transports snow from the windward to leeward side, it?s known as top-loading. Wind blowing parallel to a ridgeline may dump wind-deposted snow on avalanche paths. This cross-loading may be difficult to detect or monitor without observations from mid-slope and valley anemometers.

If the wind is strong enough to transport snow, the longer it blows from a steady direction, the greater the buildup of snow on favored leeward slopes.