It forecasts mixed rain and snow developing at lower elevations over most of the coast tonight, before switching to snow in most locations overnight.
Total snowfall is expected to range from just a few centimetres near the coast, up to 20 cm at higher elevations and inland, it said in a storm watch bulletin issued Saturday morning.
The snow is forecast to change to rain late Sunday as warm Pacific air invades the region.
There is also a risk of freezing rain over the eastern Fraser Valley Sunday night before the transition takes effect.
The snow and freezing rain are expected to give way to heavy rain of more than 50 mm through Sunday night and Monday.
The weather service says to prepare for quickly changing and deteriorating travel conditions as highways, roads, walkways and parking lots become more difficult to navigate due to accumulating snow.
It recommends postponing non-essential travel until conditions improve.