For the past few weeks, there has been a persistent trough of low pressure over the Eastern Pacific with a light southerly flow over southern BC. Weak disturbances embedded in the upper flow have given occasional showers to lower elevations while the ski resorts have continued to add to their snowpacks. Their is a big change going on in the atmosphere at this time. The upper flow is evolving into a strong westerly or zonal flow aloft.

Rainfall amounts will be quite heavy over the next couple of days especially along windward slopes of Vancouver Island and the Coast Mountains. A heavy rainfall warning has been issued for the Fraser Valley where up to 85 millimetres of rain will likely fall by Thursday morning. The mountains will be even wetter where over 100 millimetres are anticipated. With rising freezing levels, only the higher elevations will have significant snowfalls.

In the map below, you can see where the heaviest amounts are expected. Notice the subsidence or rain shadow effect over the Gulf Islands. Gusty winds are also expected over the next couple of days but nothing severe is foreseen at this time. More rain is expected at least until Friday as the storm track continues to pass through southern BC.