Thursday, November 21, 2019

Changes Are Coming

Precipitation analyses for the 30-day period ending yesterday at 1200 UTC (0500 MDT) show that northern Utah has clearly gotten the shaft.  Totals are highest across the far northwest, dropping down through Wyoming and Colorado.  To our south, this week's storm has even given them something. 

Source: NWS
Things may, however, be changing for Thanksgiving week as there is a shift in the large-scale pattern expected to begin later this weekend into early next week.  GEFS forecasts valid 0000 UTC 26 November (1700 MDT Monday) predominantly favor a trough  over the west.  

As do most (but not all) forecasts valid 1200 UTC 27 November (0500 MDT Wednesday). 

Source: Penn State E-Wall
Thus, at a minimum, cooler, possibly much cooler temperatures are likely to prevail next week.  It is also likely that we will see some mountain and possibly some valley snow. 

When one here's the phrase "pattern change" there is a tendency to get excited when we've been persistently warm and dry this time of year.  I like to keep calm and carry on.  After deducting totals for today, the NAEFS ensemble forecasts through 0000 UTC 28 November (1700 MDT Wednesday) generate a mean of about 30 inches of snow at Alta Monday, Tuesday, and Wednesday, but this number is jacked up by several Canadian Members that produce huge, unrealistic totals.  The GEFS mean (red line) suggest around 18 inches, but the GEFS range is also between about 8 and 30 inches for the period.

Thus, change is coming, but exactly how much falls before the Thanksgiving holiday depends on  the structure and track of the weather systems as they enter and move across the western U.S.  There is also the potential for snow during the Thanksgiving holiday, although I'm not inclined to speculate at such long lead times about amounts as there are a wide range of possibilities. 


  1. Last year there always seemed to be one Canadian member predicting apocalyptic amounts of snow for each storm (I remember seeing 10 feet pretty regularly). Glad to see it's continuing to sway the mean this season.

  2. I love that plucky Canadian model. Keep doin' your thing, guy.