The Curious Case of Sunrise Snow

Recently, a cursory perusal over five years of Meteorological Phenomena Identification Near the Ground (mPING)precipitation-type data over the months spanning November through March revealed an increase in the proportion of snow observations around local sunrise. The higher rate of snow observations lasts 3-4 h and then decreases. Dubious of this, ASOS observations over the same period are examined and show a similar characteristic. Finally, we examine RAP 1 h precipitation type forecasts and also see the same signal. This paper examines these characteristics in some detail and further refines their observational characteristics, while examining possible explanations.