Thursday, January 3, 2013

Great Mountain Microclimates Today!

This morning's observations suggests that there are some remarkable inversions in the canyons and mountain valleys of the Wasatch today.  For example, at 11 am it was 6ºF at the base of Snowbird, but 25ºF at the top of the tram.

Click to enlarge
Especially interesting are the observations near the base of Alta.  It was 26ºF and 29ºF at the two sites on the south facing aspect to the north of the resort, but only 12ºF at the site near the base of the resort (note: the plotted position of this observation is off by perhaps 300 feet - it should be further southwest in a spot that is typically shaded this time of year).

It appears that some very strong cold pools formed in the canyons overnight, and these cold pools are persisting in those areas that are still topographically shaded and haven't yet seen the sun.  The 10:45 am web cam shot of Alta shows this well.  This camera is sited to the west (left) of the two warm observations in the image above.  They are all in the sun.  Areas the canyon near the north facing slopes are in the shade or have only recently seen some sun.  The 12ºF observation is taken near the lower right corner of the image.

Perhaps someone can comment on the veracity of these observations, but I have seen situations like this previously when it is clear and very dry near the winter solstice when the sun angle is quite low.  Often you can find all sorts of cold pockets in areas where it is shaded and the air is calm.  A screaming descent of Snowbird today must be interesting.

1 comment:

  1. 5 degrees at my house in Sandy this morning... -5 down in Dimple Dell where (even more) cold air settled.