National Weather Force has issued a Thunderstorm Watch for the Western Oregon Cascades west through the Willamette Valley, including the Portland forecast areas.
Thunderstorms will form across the Cascade Mountains this afternoon and move within the east to west flow aloft through the rest of the watch area, including the Willamette Valley zones. Storms will be circling the same low-pressure system that moves through the area a couple of days ago. Storms will be off and on, not fully compact, so you can expect them to continue off and on this evening, and through the overnight hours, with breaks in between. Lightning, hail, and gusty winds will all be likely with it as it moves through.
A heavier and prolonged rain shield will move over on Thursday afternoon and evening for this watch area …
In addition to this, the cold air aloft will bring funnel clouds through the area.