Marine Weather and Tide Forecast for Coos Bay, OR

AVIATION
17/00Z TAFs...A front will move into the area tonight bringing light rain, mountain obscurations and increasing MVFR and local IFR conditions. Along the coast, VFR will transition to a mix of MVFR and IFR early this evening around 01-03z, then a mix of MVFR/IFR will persist tonight through Saturday morning.
Inland, VFR conditions will persist through early this evening, then MVFR will spread inland around 05-11z and persist through Saturday morning. MVFR conditions will be widespread across much of southern Oregon along with local IFR and widespread mountain obscurations. Across northern California, expect a mix of VFR and MVFR conditions tonight through Saturday morning.

Also, there is a slight chance (15-20%) of thunderstorms late tonight through Saturday afternoon for Lake County and eastern Modoc County, including Lakeview. This risk will reach a peak during Saturday afternoon over the Warner Mountains.

Ceilings will gradually lift Saturday afternoon, transitioning to mainly VFR expect with continued showers, expect areas of MVFR to linger through the day.

PREV DISCUSSION
/Issued 253 PM PDT Fri May 16 2025/

DISCUSSION...Cloud cover is rebuilding this afternoon ahead of an approaching upper trough. The first impacts from this approaching system will be thunderstorm chances developing east of the Cascades late tonight into early Saturday morning. The best chances (10-15%) will be across Modoc and southern Lake counties, with lesser chances (5-10%) covering eastern Klamath and northern Lake counties. Any thunderstorms that develop are likely to be isolated and remain below severe thresholds. Thunderstorm chances increase to 15-20% across Lake and Modoc counties on Saturday afternoon before decreasing through Saturday evening and night.
Other areas are expected to see at least light showers at some point between Saturday morning and Sunday afternoon. Overall amounts will be unimpactful. Coos County, the Cascades, areas around and east of Lakeside, and the Warner Mountains are expected to see between 0.25 and 0.50 inches of rainfall. Occasional snow showers are possible over the Cascades early Sunday morning, but accumulation is not expected. The Umpqua Valley may see 0.10 inches of rainfall, and other areas will have rainfall measured in the hundreths. Temperatures will cool through the weekend as the trough moves over the area.

Seasonal temperatures under zonal flow aloft look to continue through the week. A couple of weak disturbances may briefly affect conditions for certain locations. On Monday, a weak front could bring some clouds to Coos and eastern Douglas counties. Brief showers are possible over these areas on Monday morning and afternoon, but amounts will be one or two hundreths at most. On Wednesday or Thursday, a weak disturbance could bring gusty winds and isolated showers to the northernmost border of the CWA
Deterministic guidance for both the ECMWF and the GFS show some upper instability passing over the area, with some variation in timing and structure. Individual ensemble members for both the GFS and ECMWF are split on showing the disturbance or not, and those that show it do so with some variation in timing and location.

Zonal flow continues on Friday, with some uncertainty for the weekend. While both models show some amount of upper level ridging, the strength and position of the ridge vary. The general expectation seems to be additional warming on Saturday and Sunday, but little overall consensus on how warm next weekend will be. NBM probabilistic guidance echos this uncertainty, with daytime highs forecast to be from seasonal temperatures to 10 degrees above on next Sunday. -TAD

MARINE
Updated 200 PM Friday, May 16, 2025
A trough will produce light showers with moderate winds and moderate swell dominated seas tonight through Sunday morning. Northwest winds will be strongest Saturday evening south of Brookings. Another seasonable system will follow on Monday with winds veering from south to northwest. Northerly winds will increase on Tuesday from the brief development of a thermal trough near shore. Meantime, building seas on Tuesday may possibly becoming high and steep with the combination of the higher wind waves and a building west-northwest swell at 13 seconds. Conditions are likely to improve slightly on Wednesday.
-DW

MFR WATCHES/WARNINGS/ADVISORIES
OR...None.

CA...None.

PACIFIC COASTAL WATERS...None.