After a week of abundant rainfall along the Pacific coast, a brief lull in the action for only a few hours will cease this evening. The above image shows the first of a series of disturbances that will move over the region over the next few days. These disturbances will bring with them the possibility of additional rainfall amounts on the order of multiple inches into the Pacific Northwest.
As mentioned in Mark Heese’s article from last night, northern California has history of extreme drought over the past few years. However, this area has experienced rainfall amounts of several inches over the past week (and amounts of over a foot in the past month). The additional rainfall expected over the course of this upcoming week could have adverse effects such as flooding and mudslides, especially in valleys and other low-lying areas.
A couple of different factors will be at play contributing to the additional rainfall. First, a strengthening jet stream will set up directly over northern California and southern Oregon, setting up a path for disturbances to funnel into the region. Second, a high pressure system off the coast of the northern Baja Peninsula will steer increased warm, moist air from the Pacific Ocean into the region. The disturbances, combined with ample moisture, should result in multiple rounds of moderate to heavy rain dispersed over the Pacific Northwest this week.