Tuesday Storm

We need snow.  Yes, I know I'm being greedy, but despite significant snowfall in October, conditions are deteriorating, as discussed in the previous post.  

Fortunately, it looks like we will get something tomorrow as a cold front and upper-level trough move through the area.  It's not a monster storm, but it is reasonably well put together and accompanied by Pacific moisture.  

Our GFS-derived forecast for Little Cottonwood below pretty much tells the tale.  The GFS brings the cold front in at around 11 AM tomorrow morning.  It's accompanied by an abrupt wind shift from southerly to westerly, but a more gradual decrease in crest-level temperature and wet-bulb zero levels.  Precipitation occurs mainly with and following the front over approximately a 12-hour period.  GFS water equivalent from just before 11 AM Tuesday to just after 11 PM is about an inch.  Snow to-liquid ratios will be low to start (perhaps 7:1) , but increase in time, although overall this will be a higher-density snowfall than average.  

Web-bulb zero levels are high enough that this could start out with a bit of rain at the base of Alta and Snowbird, but by and large, snow levels should be about 7500 feet early Tuesday afternoon and lower to perhaps 7000 feet or so by late Tuesday.  

The SREF ensemble mean is about 0.75" of water equivalent for Alta Collins and about 8 inches of snow.  For snowfall, about 60% of the members are between 5 and 10 inches. A few are lower than that.  A few higher.  

I'll go with 6-12" for Alta-Collins through very early Wednesday morning.  A reminder that the resorts are de facto backcountry and to respect any closures for uphill skiing.  I don't know if Alta might temporarily close the resort to uphill, so monitor their web-site and social media.  Please comment if you have any information.  

I'm not one to bet the house on these sorts of things, but the extended forecasts are not encouraging.  After this storm, there could be a period of moist, northwesterly flow. It could produce a couple of inches of wet snow, but more likely rime for the central Wasatch.  The 6-10 outlooks from the Climate Prediction Center show the dice are loaded for above average temperatures and below average precipitation.  Ditto the 8-14, although we're on the fringes of the transition zone. Below are the precip outlooks. 

On the plus side, the odds above suggest that the probabilities are "leaning below" average, so this is not a lock.  Nevertheless, I am hoping we're not looking at a couple of weeks during which Mother Nature snatches defeat from the jaws of early-season snowpack victory.  Snow on high north will remain, but elsewhere we really need more snow, not warm and dry.