Area Forecast Discussion

DISCUSSION

Key Points:

* Shower and thunderstorm chances continue today * Thunderstorm chance (15-30%) peak through 5 PM * Drying trend begins Thursday and through most of the weekend * Warm, above normal temperatures Thursday through this weekend

Current radar has showers coming along I-5 in Siskiyou County and through the Rogue Valley. There are also showers reaching Douglas County. The upper low is starting to dig into the west coast and will bring thunderstorm chances with it. Forecast CAPEs are still on track to reach 100-150 J/kg through 5 PM, and this will be focused on the Rogue Valley (20-30%), but most areas will have at least a 15- 25% chance for the next few hours. Forecast rainfall is near 0.25"- 0.50" for more areas west of the Cascades (except the immediate coast) between 11 AM to 11 PM today.

The showers and thunderstorms will continue to track northward this afternoon. Coverage will be the greatest into this evening, but this will include mostly shower activity as thunderstorm chances decrease. Overnight snow levels will decrease to ~4,500', and through tomorrow morning another 1"-3" is possible with 4"-6" possible in higher terrain near Crater Lake and portions of the Marble mountains.

Wednesday's rainfall will be limited and scattered, and most locations will see less than 0.15" of new rainfall between 5 AM Wednesday and the rest of the day. More mixing is forecast through Wednesday, and this will bring stronger westerly winds to the surface. There is a 70-85% probability for wind gusts east of the Cascades to reach 30 mph, and this could start as early as 5 AM in northern Lake County.

By Thursday the upper low will move east out of the area and drier conditions return. Slightly above normal temperatures will be present through the long term as well. The latest runs show a slight increase in rain returning Saturday afternoon for Northern California and east side. Disagreement in the models come later Sunday, and this will be monitored. -Hermansen

AVIATION...21/18Z TAFs

A low pressure system moving inland over the area will bring showers through the TAF period, especially to northern California counties and areas west of the Cascades. Flight level generally remain at VFR or MVFR through the TAF period across the area for area terminals, with periodic changes possible as activity develops and dissipates.

Chances for thunderstorms remain in the forecast for areas along and west of the Cascades this afternoon into the early evening. Chances are highest over western Siskiyou County and into Josephine and Jackson counties. Thunderstorm chances ease tonight and snow levels drop to 4500-5000 feet into early Wednesday morning. The Cascades and Warner Mountains look to see the most consistent snowfall in this TAF period, while rain and snow showers over area valleys and basins begins to trail off.

A passing rain or snow shower can bring locally low ceilings and visibilities as well as obscure elevated terrain. Thunderstorms can also add lighting and erratic gusty winds. -TAD

MARINE...Updated 230 PM PDT Tuesday, April 21, 2026

Below advisory seas continue this afternoon as a low pressure system gradually moves inland. Increasing northwest swell follows Wednesday into Thursday, decreasing Friday into Saturday. Additionally, north winds will increase over the waters Thursday and Friday. This pattern may result in steep seas in waters south of Cape Blanco on Thursday evening into Friday. Swell eases over the weekend, but northerly winds continue into the weekend. -TAD

MFR WATCHES / WARNINGS / ADVISORIES

OR...None.

CA...None.

PACIFIC COASTAL WATERS...None.