Despite the calendar switching to May, more snow will fall in the Rockies and High Plains this weekend.

The latest in a series of late-season winter storms that have been riding into the western U.S. from the Pacific has already dumped up to 20 inches of snow in the mountains of Colorado, and there's more to come.

The weight of this heavy, wet snow downed power lines and tree branches in Holyoke and Julesburg, Colorado, and also downed branches in Alliance, Nebraska. Up to 9 inches of snow had been measured in Alliance as of early Saturday.

Three and a half inches of snow had fallen at Denver Int'l Airport northeast of the city through Saturday morning, and 2.4 inches had fallen in Cheyenne, Wyoming.

Snow will continue through Sunday in the central and southern Rockies, and through Saturday night in the High Plains of western Nebraska, Wyoming, and parts of northeast Colorado as one sluggish upper-level low slowly moves out, but is replaced by another rotating out of the Desert Southwest.

Slush or snow-covered roads have already been a problem in areas of heavier snowfall rates, particularly in the higher elevations, including the famously difficult stretch of Interstate 80 between Laramie and Cheyenne, Wyoming, which was closed by an accident early Saturday.

In the Denver metro area, the snow has been mixing with rain at times so less than an inch additional accumulation expected, mainly on grassy areas.

The heaviest additional accumulations will be either in the higher elevations from northern New Mexico into Colorado and Wyoming, or where High Plains snow is most persistent in western Nebraska and southeast Wyoming. Another 5 to 8 inches inches of wet snow may fall in the highest elevations through Sunday.

For the rest of the High Plains, only an additional inch or less is expected.

(FORECAST: Denver | Cheyenne)

Forecasting can be tricky this time of year with lower elevation snowfall accumulations because the sun angle is so high and temperatures will be near, or slightly above, freezing. Snow has a tough time accumulating during the daylight hours and it accumulates better at night in these locations.

We have seen a great example of this during this storm. Snow in some areas has been mainly confined to grassy surfaces in these areas and there has been some melting or compaction of the snow, as well.

MORE ON WEATHER.COM: Photos From Winter Storm Vexo April 2016

Snow covering a forest in Breckenridge, Colorado, makes it easy to spot a moose wandering through the area on April 15, 2016.