textproduct: Medford

DISCUSSION

New Year's Day looks to also make a delineation from our current dry pattern with stagnant air to a very active, wet pattern with persistent southerly flow. Conditions on Wednesday will again resemble those of the previous day, with an Air Stagnation Advisory remaining in effect for valleys east of the Coast Range.

This new pattern at the end of this week into the middle of next week will resemble our most recent active pattern from late last week. As such, Siskiyou County and the coast will receive the bulk of precipitation. Though the duration of wet weather will be unusual, amounts do not look to produce significant rises on rivers, with nothing more than the potential in Siskiyou County and the coast for nuisance street flooding or flooding of small creeks and streams.

The main update for this afternoon forecast issuance was to collaborate with the Eureka and Sacramento offices on issuing a Winter Storm Watch /PDXWSWMFR/ for the higher elevations late Friday afternoon through Sunday afternoon. In our case, this includes portions of western, central, and southern Siskiyou County above 5000 feet. Snow levels will be very high, around 7000 to 8000 feet, as light precipitation begins Wednesday night through Thursday. Thursday night through Friday, moist, upslope southerly flow into southern Siskiyou County will continue light precipitation with a modest lowering of snow levels to around 6500 feet. The high snow levels are representative of this system tracking northeastward from well offshore of southern California.

But, the first sign of at least modestly more impactful weather to follow will be increasing southerly winds in the Shasta Valley. A High Wind Watch /PDXNPWMFR/ has been issued, in effect from late Friday morning into early Saturday morning, for the Shasta Valley of central Siskiyou County. South winds of 25 to 40 mph gusting up to 60 mph are likely, with a stronger minority of ensemble members showing about a 10-20% probability of gusts as high as 85 mph. As usual, the strongest winds are expected near Weed. Peak strength is most likely to occur during Friday afternoon and evening. We will await attaining higher confidence as this event approaches, but gusty southwest winds of 35 to 50 mph east of the Cascades may necessitate issuing a Wind Advisory with similar, slightly later, start and stop timing as the stronger Shasta Valley winds..

Meantime, precipitation rates in Siskiyou County, especially farther south in the Mount Shasta area are likely to intensify Friday night into early Saturday morning, and be accompanied by lowering snow levels to around 5000 feet. Lighter precipitation is likely elsewhere in our area. It is still relatively early, with the potential for future suites of data to warrant adjusting the forecast strength and/or timing.

From Saturday through Sunday, a broader trough will track eastward from the eastern Pacific. There is also a broader range of solutions regarding the strength of this next frontal system. But, the majority of ensemble members do suggest a weaker strength compared to its predecessor, with perhaps Advisory level strength south to southwest winds...again for the Shasta Valley and portions of the east side. This system will produce lowering snow levels, most likely to around 4000 to 5000 feet.

Uncertainty rises another notch or two beyond the weekend for Monday and Tuesday with some potential for either a showery air mass, another weaker front, or even an early week break between systems. The highest probability is for a continued moist, onshore flow with mainly light or very light precipitation but also a continued lowering of snow levels to around 3000 to 4000 feet.

It warrants a quick mention that the majority of ensemble solutions do not favor the interesting, operational GFS depiction of a system of Alaskan origination on Day 9/10 late next week that would bring the lowest snow levels of the season so far.

AVIATION...30/18Z TAFs

LIFR conditions persist in the Umpqua Basin and in the lower Rogue Valley near Medford and west into the Illinois Valley. Much like yesterday, these areas aren't likely to clear fully this afternoon, though the Rogue and Illinois valleys have a higher chance. Otherwise, VFR conditions are expected across the remainder of the area with gusty east to southeast winds over the higher terrain. -9

MARINE...Updated 200 PM PST Tuesday, December 30, 2025

Northerly winds are becoming southerly through this afternoon. Overall, sub- advisory conditions are expected through early Thursday as seas remain swell dominated. Hazardous conditions are likely to return late Thursday and persist into the weekend as active weather resumes. Southerly winds increase late Thursday, possibly reaching gales south of Bandon, with steep to very steep and hazardous seas expected through the weekend. -9

MFR WATCHES/WARNINGS/ADVISORIES

OR...Air Stagnation Advisory until 4 PM PST Wednesday for ORZ023>026- 029>031.

CA...Winter Storm Watch from Friday afternoon through Sunday afternoon for CAZ080-082-083.

High Wind Watch from Friday morning through late Friday night for CAZ081.

PACIFIC COASTAL WATERS...None.