Tuesday, June 17, 2014


The post-frontal pot o' gold is at the mouth of Big Cottonwood Canyon.
Rocky Mountain Power, please bury your power lines!
Quite an event.  If only we could get a storm that exceeds expectations during the winter!  Maybe this is a positive sign for next ski season.

Check out these numbers from Alta-Collins.  Looks like it was cold enough for precipitation to fall as snow beginnin at 9 or 10 am.  The automated snow-depth sensor is a big squirrelly, but if we go with 27" as the pre-storm depth and 39" as the current depth, that gives us a storm total 12" (ignore the interval stake which doesn't operate in the off season).  It might be a bit less or a bit more, but we'll call it a cool foot for a deep powder day tomorrow.

Source: MesoWest


  1. I am just curious if anyone has put together some sort of plot of the annual or seasonal distribution of significant trough events... for example, maybe based on snowfall at Alta, or on some related 500/700 mb storm parameter? It seems to me like the probability of an event like this decreases slowly through about mid-June, then suddenly drops to about zero in the following week or two, between about now and the end of the month. This idea is largely based on several cold storm events that I can recall in mid-June (I can't recall any in late June), and a fairly distinct climatological dry period in late June and early July, with precipitation after this being mostly monsoon related. I am just wondering if someone has some sort of data on the seasonal distribution of this type of event.

    1. The paper you seek is Bell and Bosart (1989, http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281989%29117%3C2142%3AAYCONH%3E2.0.CO%3B2). See their Figs. 11 and 12. They don't have a box specific to the Intermountain West, but you can see a dramatic dropoff over the southwest and adjoining Pacific from June to July. I'd expect a similar, but perhaps not quite as dramatic, transition for the Intermountain west.

    2. Thanks for the link, it is an interesting read. I was curious if any local studies had been done on this sort of thing, but maybe not. I think that Utah in particular has a significant pattern shift this time of the year, probably more dramatic than in most mid-latitude areas. My suspicion is that it is related to some lower-latitude monsoon transitions that tend to have fairly predictable timing from year to year. In particular, it seems like the development of deep easterly (monsoonal) flow across Mexico paired with a closed circulation ridge over the Four Corners region results in a fairly predictable shift in the jet stream pattern over Utah right around the end of June and beginning of July. In any case, at least Alta was able to pick up one more foot of snow before this happens.