Significant September Storm

Wednesday, September 21, 2016 at 6:48 am


A strong storm will push into the area starting later today (Wednesday) and lasting through Friday.  Temperatures will drop significantly before the storm is over with snow likely down to at least 7,000 feet by Friday.


It’s not often that I refer to a storm in September as “significant”, but there’s no other way to describe this beast.  Interestingly, if you were to look at a radar image this morning, you’d probably be like, “What storm?”  There’s a line of showers to our northwest in Idaho and Montana.  A few scattered showers in Nevada.  And then some remnant monsoon moisture in SoCal and Arizona.  Certainly nothing widespread or organized.  Don’t be fooled, those are the loose ingredients that will come together to change our weather dramatically.  The cold front and associated low pressure will drop down and strengthen in the coming days. Simultaneously, it will pull moisture from the desert southwest from the remnants of Hurricane Paine — which, by the way, is the best name for a hurricane ever!  The result will be a truly significant event for Utah.

Yesterday, we spoke about how this is a 2-part storm.  The warm, pre-frontal section from now until Thursday evening, then Thursday night we transition to the cold section with rapidly dropping snow levels.   Friday and Friday night will be the best times for snow accumulation in the mountains.  To illustrate this concept of a two part storm, check out NOAA’s grid point icon forecast for 10,000 feet in the Central Wasatch:


Thursday, the rain is all the way up to the tops of the mountains, but by Friday, the bottom falls out of the temperatures and it’s all snow!

Looking at the forecast for the Wasatch, you can see that there is plenty of moisture.  Total QPF for the Upper Cottonwoods is averaging almost 3 inches:


The tail end of the storm will bring the snowfall, with an average of about 10″ forecasted:

Overall, just an impressive storm for all of Northern Utah.  GFS total precipitation thru Saturday looks like this:


Obviously, the limiting factor for snowfall accumulations is the fact that the first 36 hours or so of this storm will be rain for virtually all elevations.  Once the snow does arrive though, it should start piling up for the high elevations.  If this were mid-winter and it were all snow, we’d be talking about the potential for FEET of snow.  But, as it is, I’d say we are more likely to be in the 6-12″ range above 8,000 feet.  I do think the highest elevations could easily top a foot.  Between 6k-8k feet, anywhere from a dusting to 6″ is possible.

It’s a tough storm to forecast because it’s complex and is very dependent on when and how much snow levels fall.  Personally, I’m hoping it’s a bit of a dud.  This amount of moisture and snowfall would likely put a premature end to high elevation mountain biking.  I’m not ready to give that up just yet.  However, can’t deny that it will be nice to see a blanket of deep white on the mountains this weekend!



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  • trailjunky

    You convinced me to put the top on the jeep, something I usually don’t do until mid October.

  • Sam Kramer

    Historically what tends to happen with Guardsman Pass after early snowfall like this? Do they plow? Never have I been so unhappy with a snow forecast…