Marine Weather and Tide Forecast for Bay City, OR

SHORT TERM
Tonight through Tuesday...Current radar and satellite observations show the cold frontal boundary associated with an upper-level low off the coast of British Columbia now moving through western OR/WA bringing one final burst of stead moderate rain. Once this feature marches to our east this evening, expect a rapid transition to a cooler and showery post-frontal airmass. Snow levels likely crash to ~3000 ft tonight as a result of cold air moving in aloft - they’ve been holding around 5,000-8,000 feet so far today. Confidence continues to be high for a solid 6-10 inches of snow in the south WA/north OR Cascades above 3000-4000 feet (70-80% chance for 6 inches or more). Skiers and snowboarders rejoice! Beyond the immediate frontal passage, the period of heaviest snowfall is expected to occur late Saturday night through Sunday morning across the mountain passes. A Winter Weather Advisory for the south WA/north OR Cascades above 3000 feet remains in effect.
Further south near Santiam and Willamette passes snow amounts are expected to be lower, closer to 2-4 inches of accumulation, due to less frequent shower activity as the bulk of the energy/moisture of the upper-level low holds just to the north.
The upper-level flow will gradually gain a drier northerly component by late Sunday afternoon followed by lingering showers coming to an end Sunday evening.

From there a ridge of high pressure builds over the Pacific Northwest Sunday night through Monday characterized by rapidly building heights and the lowering of a distinct subsidence inversion aloft to 1,000-2,000ft based on NAM/GFS/ECMWF deterministic model soundings. So, with ample surface moisture, calm winds, and clearer skies anticipate areas of dense fog to develop during the overnight/early morning hours, especially in the interior valleys. The greatest amount of uncertainty early next week will be whether limited daytime heating and developing offshore flow allows for entrenched valley fog/stratus to dissipate. Given the time of year thinking it’ll be tough for portions of the central and southern Willamette Valley to completely clear out - similar to last week. Thus, adjusted high temperatures a couple degrees lower in portions of the Willamette Valley Monday/Tuesday. Also be on the lookout for the temporary redevelopment of breezy easterly winds in the western Columbia River Gorge late Monday into Tuesday which should at least help the Portland/Vancouver Metro clear out.
-Schuldt

LONG TERM
Wednesday through Saturday...Ensemble guidance is generally in good agreement with regards to how the upper-level pattern will progress for the middle to end of next week but a fair amount of uncertainty is present trying to resolve the finer details. The ridge of high pressure is expected to at least flatten to start Wednesday with a broad upper-level low in the Gulf of Alaska nudging southeastward. Almost all ensemble guidance show an attendant cold-frontal boundary then beginning to push either towards or into the Pacific Northwest as Wednesday progresses but many of the grand ensemble members are out of phase with the timing. Exploring the WPC cluster analysis reveals roughly 35% of ensemble members favor an earlier solution bringing precipitation to the region starting Wednesday morning, 50% delay it until Wednesday evening/night, and the final 15% hold it off to the west until Thursday morning. From there ensemble favor broad westerly flow aloft and additional weak weather disturbances the rest of the week although conditions likely stay within climatological norms for December.
-Schuldt

AVIATION
Mostly VFR conditions this evening in the wake of a front. Post frontal showers and light south winds are providing enough mixing to prevent radiation fog from forming.However there are a few pockets of IFR conditions with fog in places where clearing and light winds like the Central Oregon coast and small valleys in the coast range and foothills. Localized IFR and fog will expand the next few hours before clouds and showers increase late tonight through Sunday as an upper level disturbance moves over the area. Expect a mix of MVFR and VFR on Sunday.

PDX AND APPROACHES...VFR with vicinity showers this evening. South winds will provide enough mixing to limit fog from forming tonight. A mix of VFR and MVFR CIGS/VIS Sunday. ~TJ

MARINE
Gusty southwesterly winds today are causing winds to increase to Small Craft Advisory levels. Buoy 46089 and 46050 have gust to nearly 30 kt today while buoys closer to the shore in the north have been closer to 20 kt. These conditions will persist for the next several hours in the post frontal environment. As winds begin to decrease, seas will build to around 15 ft at 14 seconds.
There will be a steady building with some models suggesting seas near 17 ft at buoy 46029 by Sunday morning. Hazardous seas are expected through late Sunday.

As this front fully dissipates, high pressure builds in starting Monday afternoon. This ridge will cause winds to shift to the east-southeast. Areas near the coastal gaps and Columbia River Bar may experience locally elevated winds. Seas will slowly fall through this time period to near 6 ft at 12 seconds before building once again on Thursday with the approach of another system. -Muessle

BEACH HAZARDS
Starting late this evening into Sunday early morning seas will build behind the passing front. With these seas increasing to 13-15 feet and a long period 14 second swell, there is a high risk for Sneaker Waves on Sunday. These waves have the capacity to rush up further inland along beaches with a lot of power. They can easily dislodge logs, and sweep people off of their feet. Be sure to monitor the ocean swells, keep animals and children close, and be cautious if exploring jetties.

PQR WATCHES/WARNINGS/ADVISORIES

OR...Winter Weather Advisory until 4 PM PST Sunday for ORZ126.

WA...Winter Weather Advisory until 4 PM PST Sunday for WAZ211.

PZ...Hazardous Seas Warning from 1 AM to 4 PM PST Sunday for PZZ210- 251>253-271>273.

Small Craft Advisory until 1 AM PST Sunday for PZZ251>253- 271>273.