From Dean Wilson at the Southwest Ceramic Typology Project:  Snowflake Black-on-white was defined by Colton (1941). This type as usually defined appears to represent one of several late forms of Tularosa Black-on-white, and appears to date from about A.D. 1175 to 1325.

From Oppelt (2007): 

Crushed sherd and sand, and sherd and rock, are the types of temper found in this
type. The surface is usually weU polished and has a white slip. Large jars are
predominant including seed jars and necked jars and there are occasional bowls. The main designs are bold. solid stepped elements usually opposed by broad lines.
This type has no hatching. The paint is dense dark brown to black iron-based
pigment. Snowflake is most common in the White Mountains of east-central Arizona
and is also found on the Rio Puerco of the West and sporadically north to the San
Francisco Mountains.