First Snow?

For a couple of days now the models have been suggesting that the coldest trough of the season so far will push into the Pacific Northwest during the middle of next week.  Below is the GFS forecast valid 0000 UTC 13 September (6 PM MDT Thursday) with the 500-mb low center over central Colordo and northwest Utah in the cold air behind the accompanying cold front.  

Precipitation chances for northern Utah vary depending on the model run.  We've been working on a new ensemble for snowfall forecasting over Utah based on the European Ensemble Prediction System (EPS) and the American Global Ensemble Forecast System.  It will have 82 members, downscaling to 800-m grid spacing, and a new snow-to-liquid algorithm based on machine learning with observations from 14 western U.S. snow study stations.  The run from 0000 UTC shows that the EPS control is producing a bit under an inch of snow at the highest elevations in the central Wasatch, a mean of up to 0.4", and a max of 5.7 inches for the 24-h period ending 0000 UTC 13 September.  

So, chances are probably more likely than not that we won't get much, but it's something worth keeping an eye on and a welcome change from summer weather.