Cooler, Wetter Pattern to Settle Over Southern Oregon and Northern California

Medford, Oregon- Southern Oregon and Northern California are set to see a notable shift in weather this week, as a pair of slow-moving upper-level troughs bring cooler temperatures, increased cloud cover, and multiple rounds of rain and gusty winds to the region.

Forecasters say the first of the two troughs, now positioned offshore of Washington, is expected to move east across the area by late Saturday. A second, similar system will follow closely behind, moving in Sunday through Wednesday.

The transition to a low-pressure pattern was already evident overnight, with coastal stratus clouds developing over Coos and western Douglas counties. Those clouds are expected to lift through late morning, giving way to brief breaks of sunshine before mid- and upper-level clouds return by evening.

Afternoon temperatures will drop several degrees compared to Wednesday, and breezy southwest to west winds are forecast—strongest east of the Cascades. Isolated showers may develop late in the day and into the night, particularly over the Cascades.

By Thursday and Friday, cooler temperatures will take hold across the entire forecast area, accompanied by higher chances for rain and gusty winds. Meteorologists expect the most widespread rainfall on Friday and again Monday, with both days carrying slight chances of thunderstorms in some locations.

The main frontal system is projected to move inland Friday morning, weakening slightly as it crosses the region. Rainfall totals could reach between a half inch and 1.25 inches in Coos and western Siskiyou counties, while most areas from the coast to the Cascades may see between a quarter and half an inch. Areas east of the Cascades are likely to receive less than a quarter inch.

Saturday’s weather will be marked by lingering showers as the trough passes overhead, with additional light precipitation likely for west- and northwest-facing slopes such as the Kalmiopsis Wilderness and the Cascades. Most areas, however, will see only trace amounts—less than a tenth of an inch in many locations.

Forecasters note growing uncertainty in the forecast beginning Sunday, as models differ on the timing and extent of a stronger, wetter cold front tied to the second trough. The highest rain probabilities are currently expected in Coos, Douglas, and northern Klamath counties.

That second system is likely to keep the region unsettled Monday through early Tuesday, potentially bringing rainfall amounts similar to Friday’s. By midweek, a cool, showery air mass is forecast to linger, with high temperatures around 20 degrees lower than earlier in the week.

“Confidence is higher that our weather for the next week, and possibly the next 10 days, will be dominated by two broad, slow-moving upper-level troughs,” forecasters said, noting that cooler and wetter conditions are expected to persist well into next week.