Sastrugi

Along with graupel, sastrugi is one of my favorite weather-related words and I saw plenty of it ski touring yesterday.  

Sastrugi is defined by avalanche.org as "heavily wind eroded snow with wavy textures." Sometimes it looks rough or pockety.  In the photo below, it appears there is avalanche debris on this slope, but in reality it is all sastrugi.  

In some areas, the sastrugi was dense wind board and generally supportive of a skier. 

In others, it was actually somewhat soft and didn't ski to bad on the descent. Each turn was a mystery!

Although I like sastrugi as a word, it's not my favorite snow surface to ski.  We can blame the sastrugi in this case on the multiday easterly wind event that has been affecting the Wasatch Range and Front since Thursday.  Observations from Alta's Mt. Baldy show the winds veering (turning clockwise) from southwesterly just prior to 1200 MCT 12 March (Tuesday) to north by 0000 MDT 14 March and then locking in with easterly flow with gusts reaching over 50 mph on the 15th (Friday) when most of the damage was done. 

The large-scale setup for these winds was something that meteorologists call anticyclonic wave breaking in which a high-amplitude ridge develops in the high latitudes and leads to the formation of a closed low downstream and to the south.  Below is the GFS analysis for 1200 UTC 15 March during the period of stronger easterly flow on Mt. Baldy.  Note the ridge off the Pacific Northwest coast and the deep closed low centered along the CA-MX border, resulting in strong easterly 700-mb (crest-level) flow over the Wasatch. 

This is the same pattern that produced heavy snowfall along the Colorado Front Range. Basically, this is a complete reversal of the climatological westerlies.  They get upslope and we get downslope.  

The pattern has been very persistent and this morning enhanced easterlies ares still being observed along the east bench of the Salt Lake Valley north of Holladay, although they are weaker than at the peak.