Timeline: Rain, snow, thunderstorms around Oregon this week

PORTLAND, Ore. (KOIN) -- Oregon's expecting it all as a major fall front moves through the Pacific Northwest later this week.

Rain, snow, and thunderstorms are all possible from the coast to the Cascades of Oregon and southwest Washington. A dip in the jet stream is the cause for the active weather and blast of fall-like conditions. Portland could see the coolest overnight lows since May come Thursday night into Friday morning.

Fall rain timeline around Portland

The increasing clouds seen over the Willamette Valley will eventually give way to more persistent and heavy rain showers Wednesday morning.

Rain showers are expected to ramp up along the Willamette Valley late Tuesday night into Wednesday morning. Heavy downpours are expected for Wednesday morning. Rain showers will last much of the day Wednesday. A few dry moments are expected later in the evening Wednesday to early Thursday morning.

Rain showers will ramp back up again Thursday morning and last much of the day. It's during the mid-morning hours both Wednesday and Thursday that could potentially see thunderstorm activity.

Oregon's thunderstorm potential

Thunderstorms are possible as this latest round of unsettled weather moves through the region Wednesday and Thursday. Afternoon highs Wednesday will warm into the low to mid 60s. That's where the chance for mid-morning thunderstorms is greatest. Temperatures Thursday will struggle to warm higher than the upper 50s, but thunderstorms are still possible.

Not everyone in western Oregon and southwest Washington is expecting to see lightning or hear thunder Wednesday and Thursday. Forecast models are predicting greater-than-normal potential energy around the metro area during the mid-morning hours on Wednesday and Thursday that could aid in the development of thunderstorms. The best chance to see a potential thunderstorm or two is before noon on Wednesday and Thursday. However, the lightning potential remains greater east of the Cascades on Thursday afternoon. Cooler evening temperatures and slowly clearing skies on Thursday will decrease that potential rapidly.

Mountain snow returns to the Oregon Cascades

The first big snow event of the season is expected this week with snow accumulation nearing a foot in some locations. The central Oregon Cascades will likely see the most snow Wednesday and Thursday. Snow elevation levels are expected to fall to nearly 5,000 feet this week. Temperatures will remain cold enough that snow will likely stick around above 6,000 feet for a few days.

A few wet flakes are likely over high mountain passes late Wednesday night into Thursday. Some snow accumulation is possible around the mountain passes but is more likely in the central regions of the state.

Mt. Hood won't see as much snow as the central Cascades, but nearly eight inches of snow is possible around Oregon's highest peak. Places like Timberline Lodge and Mt. Hood Meadows will likely see accumulative snow by the end of the week.

The cooler and wetter weather pattern expected this week will keep temperatures near average this weekend along the Willamette Valley. Some drying is anticipated by the end of the week and continues through the start of the weekend.

Stay with the KOIN 6 Weather Team as more active fall-like weather returns to the region in the weeks to come.