Friday, July 8, 2016

A Remarkable July Cold Surge on Tap

Ask and you shall receive.  A remarkable July cold surge is on tap with a cold-frontal passage on Sunday ushering in some remarkably cold air for this time of year.  By Monday morning, 700-mb (10,000 feet) temperatures across all of northern Utah are below 2ºC and across portions of northern Utah are below 0ºC.

The GFS forecast for 700-mb temperature at 6 am Monday morning at the Salt Lake City aiprot is -0.5ºC.  The NAM is even colder at -1.4ºC.  This is rare territory for the month of July.  The sounding combined sounding record for Ogden (back in the day) and Salt Lake City shows the lowest July 700-mb temperature in the record is -1.4ºC.  For all but two days in the month, the record low is above 0ºC.

Bottom line is that on Sunday night you should throw open the windows and cool the house like you rarely can in July.  If you are going to be at upper elevations camping or backpacking, you should be prepared for cold weather and below freezing temperatures.

On Monday, the lowest maximum temperature observed in the instrumented record at Salt Lake City is 65ºF, but we will certainly be warmer than that in the afternoon.  In July, if you want to set a lowest maximum temperature record, you need a cold airmass and precipitation.  Instead, it will be dry Monday afternoon with a high in the mid 70s, which should be remarkably pleasant.  The record low minimum temperature on Monday is 48ºF.  I can't rule that out, but I think it is unlikely we'll get that cold.

If you take a look at all the minimum temperature records for the Salt Lake City airport in July, they were all set prior to 1968 except for a 48 on July 11th (which also happens to be the date on Monday), which was set in 1983, and a 54 on July 26, which was set in 1993.  It's damn hard to break a minimum temperature record at the Salt Lake City airport any time of year, but really hard in July.  I suspect this reflects several factors, including climate change, urbanization, instrumentation location, and changes in the land surface near and around the current airport observing location.  Even sniffing 50ºF would be a very impressive July minimum temperature given the current climate and characteristics of the Salt Lake City airport observing site.


  1. July snow in Idaho Wyoming!

  2. I am going to guess that we come within about a degree or two of the record low, perhaps tying it. This partly based on wind direction which may minimize urban effects on the airport site.