The National Weather Service is monitoring an upper-level closed low off the California coastline for potential showers and thunderstorms, which could begin in Lane County and move northward along the Cascades and Interstate 5 corridor towards Portland. Until then, Portland should be partly sunny with high temps reaching 72 degrees. The weather service may also create an isolated, longer-lived thunderstorm south of the Portland area, which would produce heavy rain, lightning, small hail and strong winds. The extended forecast also includes rain chances next week and a potential for continued chilly weather.