Clearing Skies Bring Chilly Night, Frost Advisory for Rogue Valley Areas

Medford, Oregon- A low-pressure system that brought rain and mountain snow to parts of southern Oregon and far northern California Sunday is moving inland, setting the stage for clearing skies, colder overnight temperatures, and patchy frost in some west side valleys, forecasters said.

Satellite imagery Sunday afternoon showed the system moving onshore just south of Cape Mendocino, with lingering precipitation tapering off across southwest Oregon. The National Weather Service said the low will continue through the Sacramento Valley by Sunday evening, with drier air settling in behind it.

A Winter Weather Advisory for the Cascades north of Highway 140 was set to expire at 5 p.m. Sunday, as precipitation diminishes across the region. Forecasters said most areas will dry out overnight, though light rain or drizzle could persist along the coast north of Cape Blanco and into northern Douglas County.

Behind the departing system, surface high pressure is expected to build over southwest Oregon. That could allow breaks in cloud cover overnight and temperatures to dip into the 30s in some valleys west of the Cascades. The Weather Service issued a Frost Advisory for portions of the Rogue, Applegate and Illinois valleys — including outlying areas of Medford, Grants Pass, Eagle Point, Jacksonville, Ashland, Ruch and Cave Junction — where lows are forecast between 32 and 36 degrees.

Forecasters said low clouds or fog could reform in some of these valleys due to recent rainfall, potentially limiting frost formation. The Umpqua Basin is expected to remain warmer, with lows in the low 40s.

Farther south, a Freeze Warning was issued for the Shasta and Scott valleys and parts of the lower Klamath Valley in Siskiyou County, where temperatures are expected to fall into the upper 20s. East of the Cascades, temperatures will drop into the teens and 20s, well below the growing season threshold.

On Monday, forecasters expect partly sunny skies and continued cool conditions, with highs mostly in the 50s west of the Cascades and mid-to-upper 40s east of the mountains. Coastal areas should see highs around 60 to 65 degrees.

Another cold night is possible Monday night, depending on cloud cover, with potential for additional frost advisories. By Tuesday, temperatures should rebound to near or slightly above normal as a weak ridge builds across the region.

A weak front is forecast to reach the coast Tuesday night, bringing light rain mainly to coastal and Umpqua Basin areas before dissipating near the Cascades on Wednesday. High pressure will return midweek, followed by another system expected to arrive Friday night or Saturday.

Forecasters said the late-week front appears slightly stronger than Tuesday’s system but will again lose strength as it reaches the Cascades, bringing the highest rain chances to northwest Oregon and only isolated showers farther south and east.