Measurable snow is snowfall that actually sticks to the ground where you can measure the amount of snow that has fallen.
When snow is just falling in light snowflakes and the snow doesn't stick and just melts away then that snow is not measurable.
But when a forecast says measurable snowfall or measurable snow it just means you're likely gonna get at least 1/2 inch to an inch or more of snow.
So you can expect to see snow on the ground if a forecast calls for measurable snow.