Tuesday, March 8, 2011

Lake or No Lake? You be the Judge

Count me amongst those who feel that conventional wisdom greatly overestimates the influence of the Great Salt Lake on many winter storms in northern Utah.  Although there are winter storms in which the Great Salt Lake plays a major role, last night's storm wasn't one of them, although there are some light lake-effect flurries falling around the area this morning.

An interesting period to examine possible contributions of large-scale, orographic (i.e., mountain), and lake-effect processes is from 0300-0500 UTC (0800-1000 PM MST) last night.  Wide spread precipitation is falling over much of the Wasatch Front and Back, including in areas that are not downstream of the Great Salt Lake, such as the Cache Valley and northern Wasatch Front.  There is also strong, persistent orographic precipitation enhancement over and upstream of the Wasatch Mountains, Oquirrh Mountains, and the Stansbury Mountains.  Some of this topography is located downstream of the Great Salt Lake, but some of it isn't.  Clearly synoptic and orographic processes are dominating.

Nevertheless, the loop also suggests a weak but persistent area of radar reflectivity over and along the Great Salt Lake.  MesoWest observations show temperatures over the lake were slightly (perhaps 3-4F) warmer than over the surrounding landmass.

MesoWest observations at 0400 UTC 8 March 2011.
So, perhaps during this period the lake played a minor role in the precipitation generation.  You be the judge?  What do you think about the lake influence during this period?


  1. I dont have a great experiential database from which to draw but here is what comes to mind:

    1) The 0Z sounding looks to be fully unstable WRT pseudoadiabatic motions. How often is this the case? Given this, I would think it more likely that precip would develop further upstream and downstream of the mountains.

    2) The flow was mostly along barrier and so we werent dealing with areas of downward motions and supressed precip.

    3) Alta didnt really record that much more water relative to the benches so that suggests that meso-gamma features were not dominant.

    4) The reflectivity loop makes it look as though the Lake was a factor here, but it appeared to me that the stronger reflectivities were shunted to the east of the main Lake axis.

    My cents anyhow ...

  2. How much do the mountain ranges channel the weather patterns across the lake? I've spent the last few years chasing storms around the lake. I don't the 'foggiest' idea what some of the concepts are that you are tossing around, but I'll read up. I'd like to mention this entry at http://mygreatsaltlake.com. It seems to me that the "lake" is not just the surface area of the water and below, but it is also a huge ethereal body of water that reaches high into the atmosphere, much higher than the mountains, and this too, plays a role in the developing or stopping of storms.

  3. This issue of mountain and lake influences is something we are presently examining as part of a National Science Foundation Project. Feel free to mention my post on your site. There are several other posts related to lake effect in the October and November archives. Look for "SOLPEX" which is our field-program looking at lake-efect storms.