Friday, January 4, 2013

Mother of All Cold Pools

The Peter Sinks are limestone sink holes located in the Bear River Range east of Logan.  There's not much too them.  They are just shallow depressions at high (~8000 ft) elevation.

Photo: John Horel
They are famous for their incredibly low minimum temperatures and strong cold pools.  The lowest temperature ever recorded in Utah (and second lowest ever recorded in the contiguous US), -69.3F, was measured in the Peter Sinks on 1 Feb 1985.

Last night, it got down to -31ºF in Peter Sinks.  Yeah, that's not that cold compared to the all time record, but it is 46ºF colder than the minimum temperature observed on the rim of the sink less than a mile and 300 vertical feet away!

Minimum temperatures since midnight MST 4 December 2012
 Check out the difference in the temperature trace at the two stations.  Temperatures remain relatively steady overnight on the rim, fluctuating between about 15 and 25ºF, whereas on the floor of the sink, they drop like a rock shortly after sunrise and hover near -30ºF most of the night.  Note the change in scale between the two graphs.  

Indeed, it pays to know where to pitch your tent on a clear calm night in the Bear River Range.  


  1. I am curious about a couple of things right now: Is most of the Great Salt Lake frozen over? It looks like it on the visible satellite image, but didn't know how cold the saltier portion has to get in order to freeze.

    Also, how does the presence of snow cover correlate with fog formation during these types of inversions? I am thinking they are negatively correlated, at least in the current case as the snow cover seems to be preventing fog development in most areas. Either the extremely cold temps in general, or very cold snow surface at night seems to cause deposition processes to take over.

    1. Jim/David, First of all thank you for publishing this blog. There is a group of brine shrimp fishermen on the GSL that regularly check into "WWW." Our fishery is extremely weather dependent, and WWW has proven to provide us with valuable info.

      The short answer is no, the GSL is not frozen over. There is thin sheet ice surrounding many of the freshwater inflows into GSL. Obviously, these ice sheets form during calm and cold periods as the freshwater inflow (less dense) stratifies over the more dense saltwater. These ice sheets tend to drift around following the prevailing winds and lake currents. In the main body of the lake we are currently experiencing ice near the South Marina and the in Promontroy Point/Fremont Island area.

      Thanks again for the great work.

  2. I just took a look at the 250-m modis images from the past couple of days and I think there is a thin layer of low clouds over the lake. I don't think it is frozen over. Farmington "bay" is snow or ice covered, but I'm not sure there was much water in it.

    I don't know the answer to your question, but I would suspect that snow is "good" for fog development, all else being equal.

    1. I do think that it is good for fog in more moist situations, especially so if the dew point gets above 0C. Although starting to think now that in the cold, dry inversions we often get, the very cold snowy surfaces (particularly below -15C) may be preventing fog development by basically turning everything into ice. I would take some fog right now over this bitter cold, dry weather!

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