Portland National Weather Service:
SYNOPSIS: A broad Pacific trough will move over the Pacific Northwest from the Gulf of Alaska this weekend bringing a series of cold fronts to our area. The first front will move onto the coast early Saturday followed by a stronger front on Monday. Unsettled weather is expected to continue through the Thanksgiving week as the trough remains in place and cold fronts continue to move through.
PRIMARY AREAS IMPACTED: At this time, it appears Western Oregon and Southwest Washington will experience the biggest impacts.
The main impacts will be areas of heavy rain with a potential to bring flooding to the area. Of particular concern is flooding of small streams and urban areas due to clogged storm drains.
The strongest winds will be confined to coastal areas and the coast range. Most impacts will be associated with the stronger cold front on Monday.
Significant snow will be confined to areas above pass level through Monday.
The first cold front will move onto the coast Saturday morning.
The second, much stronger cold front will move inland late Monday afternoon, but rain associated with this front begins late Sunday.
Heavy Rain…Confidence is high that some areas will receive heavy rain from these fronts (especially the Monday storm) but confidence is low on location and duration of that rain.
Strong Wind…Confidence is high that the first front Saturday morning will bring strong winds with gusts near 50 mph.
A much stronger storm appears to be developing for Monday with winds during the day on Monday reaching 40 mph with gusts between 70 and 80 mph. Confidence on the wind forecast for the second storm is moderate.
UNCERTAINITIES: Model forecasts vary on the location and timing of the heaviest rain, with the central coast appearing to be the hardest hit.
Tonight and Saturday: 1-2 inches along the coast and in the coast range with up to 0.5 inches inland.
Sunday afternoon through Monday: 4-6 inches along the coast , in the coast range and in the south Washington Cascades.