textproduct: Medford

DISCUSSION

An upper level ridge will remain in control over the area for several more days. Temperatures will be unseasonably warm outside of the west side valleys, with strong inversions resulting in colder temperatures within those valleys.

Persistence remains the appropriate description for the duration of the forecast. While areas outside of the inland valleys will be relatively warm, dry, and with clear skies, the interior valleys will continue to experience strong inversions and stagnant air. According to the NBM, there is a 30-40 percent chance for fog in the valleys west of the Cascades tonight, and roughly 25 percent chance of temperatures at or below freezing. Typically, this pattern results in persistent fog and freezing fog within the valleys, with some areas clearing in the afternoon, and others never clearing at all, before fog reforms and spreads out within the valleys once again after sunset. With the earlier clearing in the upper Rogue Valley today, fog may be much later to reform there tonight, if at all. In some situations in the past, fog never forms and instead a very heavy frost develops instead. Despite the higher probability in the NBM, which was drastically underdone yesterday, the pattern today lends itself to much more uncertainty, mainly in fog onset times and locations. Therefore, have held of on any new fog/freezing fog advisories until confidence improves, or fog forms, whichever comes first.

An air stagnation advisory remain in effect out to Tuesday next week, along with a state issued Air Quality Advisory for Lake County, also through Tuesday.

The models continue to show the ridge breaking down and the introduction of precipitation chances and mixing air. These ridges are very well known to take a long time to break down, and this one is no exception. Despite the NBM saying the breakdown occurs Wednesday or Thursday, experience and the bulk of the longer range model suites say it could be as late as late next week, right around the end of the month. -BPN

AVIATION...16/18Z TAFs

High pressure aloft just off the PacNW coast and a thermal trough along the coast are bringing mostly moderate offshore flow across interior SW Oregon and northern California. Most areas have cleared to VFR, but persistent LIFR low clouds and fog are impacting the Umpqua Basin and Rogue Valley, including Roseburg and Grants Pass. IFR/LIFR will persist in these areas, with no or very brief clearing late afternoon or evening.

Low cloud/fog is expected to form in most West Side inland valleys again this evening and tonight, similar to the past several nights. However, some indication are that fog may be slower to develop and less widespread. Otherwise, the same general cycle of night/morning fog and daytime improvement will persist.

Model guidance indicates offshore flow easing as the thermal trough weakens today. This could lead to a southerly stratus surge up the coast or through the coastal waters later tonight.

MARINE...Updated 200 PM PST Friday, January 16, 2026.

Seas remain below Advisory level through the weekend. Northerly winds look to increase on Monday, which may build localized areas of steep seas in outer waters. Winds look to ease into Tuesday and Wednesday. -TAD

MFR WATCHES/WARNINGS/ADVISORIES

OR...Air Stagnation Advisory until 10 AM PST Tuesday for ORZ023-024- 026-029>031.

CA...None.

PACIFIC COASTAL WATERS...None.