Weather Education: The Effects Of A Pacific Northwest Low
The Pacific Northwest low moves on shore typically in or around the Portland and Seattle area. At location A the type of weather that can be seen is usually thunderstorms and higher elevation rain showers form during the summer. This same area will see coastal rains and heavy mountain snows in the winter.
When the system arrives at location B, the Rockies, due to topographic enhancement it can produce heavy rain/t-storms in the summer time, while during the winter this same area can see very significant snows.
The system then pushes out to location C which is the Northern Plains. In this region sometimes the system can be referred to as a low precipitation creator due to the loss of energy over the mountains, however it can draw moisture northward from the Gulf of Mexico which could create heavy rains and severe weather in the summer along with heavy snows in the winter.
Once the system reaches location D, the Ohio River valley, it has usually gained moisture from the Gulf of Mexico and can create intense t-storms during the summer months and in the winter it can create a heavy snow band if cold enough in the region.
The final spot for this low is through the Northeast where it tends to lose a lot of moisture while going over the Appalachian mountains making it a fairly dry system. However, when it moves over the lakes the winds coming out of the Northwest can lead to t-storms in the summer and lake effect snows during the winter.
This low pressure system is most common in the United States when the Pacific high is blocking from California northward to near the Oregon border. This low moves northward around the high and into the Pacific Northwest. This low pressure during the summer months can sometimes be the leftover of a Typhoon that hits Asia.
Red Orbit Meteorologist Joshua Kelly