textproduct: Medford

KEY MESSAGES

-Slightly cooler weather continues this weekend (and into Mon) with isolated to scattered showers from the Cascades eastward. -Isolated pm/eve thunderstorms are also possible, but primarily across NorCal (Mt Shasta region eastward). -Showers chances are lower west of Cascades, but can't rule one out here or there Sun/Mon, especially higher terrain. -Activity shifts eastward Tue/Wed with warming trend Wed- Fri. -Next increased chance of showers is next Saturday.

DISCUSSION

Satellite imagery this afternoon is very revealing of the upper air pattern across the Northwest United States. A thin veil of high thin cirrus is dropping southward across southern Oregon at this time and is the leading edge of an upper trough digging into WA/OR. Meanwhile, cumulus developing across NorCal are indicative of increased mid-level moisture and instability associated with another upper trough moving onshore just south of San Francisco.

As these two areas come together this afternoon/evening, we expect showers and isolated thunderstorms to develop, mainly from the horn of Trinity County (that juts northward into southern Siskiyou County) eastward across the Mt. Shasta region (near and south of Medicine Lake) and into Modoc County. Moisture available in these areas isn't that impressive, generally PWs of around 0.50 of an inch or so. Neither is instability, for that matter (~250 J/KG). But, due to the persistent alignment of the upper flow (W->E), activity could redevelop over the same areas well into the evening. The highest probability of this occurring is to the south in Shasta/northern Lassen counties. Even so, some of the stronger cells that develop could bring brief downpours (in addition to cloud to ground lightning, gusty winds and even pea- size hail) around Mt. Shasta City, Dunsmuir, McCloud, Day, Lookout and Adin. While a shower or two can't really be ruled out farther north, that's where most of the activity will be through tonight and even perhaps into Sunday morning.

With the trough axis overhead on Sunday, showers/isolated t-storms continue in NorCal. There is a little better chance of showers extending into southern Oregon, but these will be mostly focused near elevated heat sources (mountains/higher terrain), where the best instability is located. Valley PoPs will be generally 10% or less. Overall, temps the next 2 days will be near to slightly below normal -- with the lowest maxTs compared to normal in areas where the most cloud cover/precip is -- in eastern Siskiyou/Modoc counties. Snow levels this weekend could drop to around 5000 feet, but any snow accumulations will be minimal and confined to the higher mountains around Mt. Shasta and also the Warners. Activity Sunday should wane after sunset with the loss of instability.

By Monday, with a kicker trough swinging southward just offshore, the main trough axis will push east of the Cascades. There could still be pm/eve showers over the East Side then, but most areas will be dry with seasonable temperatures. Onshore flow could lead to the development of stratus along the coast both Monday and Tuesday mornings, especially north of Cape Blanco. Depending on the depth of the moist layer, this may impact portions of the Umpqua Basin as well.

A strong upper ridge is forecast to develop and move into the area mid-late next week and this will bring a period of dry and warmer weather with high temperatures (areas inland from the coast) generally 10-15F above normal for late April and early May. Coastal areas could continue to experience intrusions of late- night/morning marine stratus.

Latest 12z long range deterministic guidance is hinting at the potential for a trough to approach the coast by next weekend with the possibility of showers and thunderstorms. But, ensemble guidance is split on this with a majority (60%) of members maintaining a dry pattern. -Spilde

AVIATION...25/18Z TAFs

VFR conditions prevail across the region with the exception of some scattered MVFR ceilings in the Brookings area and some low end VFR ceilings across the Modoc Plateau and around the Medicine Lake area in southeastern Siskiyou County. Overall, VFR conditions will prevail through the TAF period for most locations with some breezy west to northwest winds developing this afternoon. Showers and isolated thunderstorms are expected to develop just south of the OR/CA border this afternoon as well, mainly from the Mt Shasta region and areas eastward. Shower activity looks to continue into the overnight hours, but once they clear, areas of MVFR ceilings will likely linger across far northeastern CA into Sunday morning.

Along the coast, marine stratus will return to the coastal waters and along the coast/coastal valleys. Expect MVFR/IFR ceilings to return around 06-08z and persist into Sunday morning. /BR-y

MARINE...Updated 1215 PM PDT Friday, April 24, 2026

High pressure offshore and a low pressure trough along the coast will maintain gusty north winds today. Advisory level winds are expected this afternoon south of Cape Blanco, resulting in continued steep seas due to wind waves combined with a low background northwest swell. North winds will persist through the week, but the pattern weakens some Sunday into Monday, resulting in less steep seas and improved conditions through early Tuesday.

Northerly winds increase again late Tuesday, especially south of Cape Blanco, and persist through much of the week. Steep seas could return around mid-week due to increasing wind waves and another 4-6 ft northwest swell moving into the waters. High end advisory level winds are possible late in the week, with areas of gales south of Gold Beach also possible. /BR-y

MFR WATCHES/WARNINGS/ADVISORIES

OR...None.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT Sunday for PZZ356-376.