Mt Hood

New storm and wind slab mainly on lee aspects may bond poorly to the existing snow surface, mainly where old crust layers where smooth. Watch for unstable slab layers and avoid steep lee slopes that may have received wind transported recent snow, especially steep NW thru E facing slopes.  

A period of moderate to briefly heavy precipitation expected overnight should build storm slab layers, especially above treeline. 

New storm and wind slab should be likely Friday, mainly above, but possibly near treeline as well. Strong winds overnight Thursday will likely have built unstable slab layers on NW-NE facing slopes, mainly below ridges.

Light and decreasing snow showers are expected through the day Friday with a cooling trend. This should allow for slowly improving avalanche conditions as storm layers begin to settle.  

On backcountry travel safety note, watch for terrain hazards (exposed rocks, trees, streams, etc.) at lower elevations and on wind scoured aspects.

...updated discussion Friday morning...

Early Friday morning observations at 6600 ft at Mt Hood Meadows, indicates a weak bond of new storm snow to the old crust, due to a thin layer of initially low wind deposited, snowfall late Thursday. New storm and wind slabs should be susceptible to human triggering Friday, especially on steeper lee terrain, near or above treeline.

Earlier discussion...

An approaching storm will move across the area Thursday night, changing the recent Snowscape significantly, from one dominated by crust layers. The last storm arrived on January 4th, depositing about 5-10 inches of snowfall, followed by warming and heavy rain on the 5th.  This likely caused the last avalanche cycle, followed by the recent stretch of high pressure.

The latest high pressure has been marked by warm temperatures and sunshine maintaining strong melt-freeze crust layers.  

The snowpack in most areas consists of strong surface melt-freeze crusts of varying thicknesses formed over stabilized rounded grain layers. Surface crusts have been recently reported to be fairly rough, which may decrease the ease of triggering new slabs. Some windward  or southerly aspects at mid and lower elevations have little if any snow cover, so terrain anchoring will help there.  

With the overall strength of the snowpack, any newly developing storm slab avalanches should be limited to new snow.