Onshore Flow

This pattern is wet and often mild, typified by precipitation in the form of rain usually heavy. At lower elevations and snow at higher elevations. Visibility declines, especially in precipitation, as low clouds and fog form near or at the surface. If strong onshore flow is created by a deep synoptic system tracking to the north of Whistler, the rain/snow boundary can temporarily rise to 1500 meters or higher. The passage of a cold front can bring declining temperatures, somewhat drier air with improved visibilities and brisk west to northwesterly onshore flow. In strong and cooler onshore flows, heavy snowfalls of short duration can occur on the windward slopes of the coastal ranges as the rain/snow boundary descends, sometimes to near sealevel. Precipitation if heavy, in the form of rain, and in an adequately warm environment can rapidly degrade snow pack conditions. Heavy snow can fall in amounts up to 70cm overnight at all elevations. Heavy rain and/or snow will usually results after a large system approaches typically from the SW or W wind speeds in exposed coastal locations and mountain tops in excess of 65 km/h with gusts in excess of 100 km/h.