Please answer a question about the following article about Seattle:

Seattle typically receives some snowfall on an annual basis but heavy snow is rare. Average annual snowfall, as measured at Sea-Tac Airport, is 6.8 inches (17.3 cm). Single calendar-day snowfall of six inches or greater has occurred on only 15 days since 1948, and only once since February 17, 1990, when 6.8 in (17.3 cm) of snow officially fell at Sea-Tac airport on January 18, 2012. This moderate snow event was officially the 12th snowiest calendar day at the airport since 1948 and snowiest since November 1985. Much of the city of Seattle proper received somewhat lesser snowfall accumulations. Locations to the south of Seattle received more, with Olympia and Chehalis receiving 14 to 18 in (36 to 46 cm). Another moderate snow event occurred from December 12–25, 2008, when over one foot (30 cm) of snow fell and stuck on much of the roads over those two weeks, when temperatures remained below 32 °F (0 °C), causing widespread difficulties in a city not equipped for clearing snow. The largest documented snowstorm occurred from January 5–9, 1880, with snow drifting to 6 feet (1.8 m) in places at the end of the snow event. From January 31 to February 2, 1916, another heavy snow event occurred with 29 in (74 cm) of snow on the ground by the time the event was over. With official records dating to 1948, the largest single-day snowfall is 20.0 in (51 cm) on January 13, 1950. Seasonal snowfall has ranged from zero in 1991–92 to 67.5 in (171 cm) in 1968–69, with trace amounts having occurred as recently as 2009–10. The month of January 1950 was particularly severe, bringing 57.2 in (145 cm) of snow, the most of any month along with the aforementioned record cold.

What type of snowfall is not often seen in Seattle?
heavy snow