An Outflow Environment

An outflow environment is where a strong cold anticyclone is established over the interior of the province. This creates an easterly flow, or outflow along the coast and mainland inlets that is most strongly felt at high elevations and in the river valleys that lead to Georgia Strait and the Pacific coast. Following the passage through the region of an arctic front (which is often marked by brief shower of rain or snow), outflow conditions are dry, clear and cold in their early aspect, gradually becoming mild if they persist. A lengthy outflow condition can be associated with a reduction in visibility and air quality; normally due to air stagnation but sometimes due to the formation of fog. The initial period of an outflow environment can be marked by strong and gusty winds and cool conditions at higher elevations with the attendant risk of frostbite for unprotected individuals. Except at the very beginning, where a brief burst of heavy snow may occur, snowfall will be light or non existent in an outflow environment. In the later stages ofan outflow, temperatures may be too mild except at the highest elevations. Solar radiation will degrade the snow pack. The formation of fog late in the outflow period will significantly reduce visibilities near the surface. Air transportation may be affected. Fog in these situations does not normally extend into the alpine areas .