Marine Weather and Tide Forecast for Scappoose, OR

SHORT TERM
Now through Monday Night...A stalled boundary remains draped across central OR as it slowly progresses southeast. A weak atmospheric river continues to bring moisture into the region while a shortwave trough moves overhead from the west. This is supporting continued light rain over much of NW OR and SW WA, with the exception of the Astoria and Pacific county areas which remain relatively dry. Shower activity is slowly building northwest toward Astoria and Pacific county as the shortwave trough approaches. Snow levels over the SW WA Cascades have dropped below 4500 feet but remain around 5000-6000 feet across the NW OR Cascades. Snow levels are expected to steadily drop this evening and overnight to between 3000-4000 feet as the shortwave advances east and colder air aloft moves in. Shower activity is expected to increase as the disturbance passes overhead, tapering off through the latter half of Monday.

Additional precipitation is expected to vary across the area.
The Willamette Valley and central OR coast and Coast range can expect around 0.10-0.25 inches through Monday, higher amounts for the north OR Coast and Coast Range around 0.25-0.40 inches.
There is a low ~15% chance for thunderstorms along the coast this afternoon and evening as colder air moves in and the atmosphere becomes unstable. The Cascade foothills should expect another 0.25-0.50 inches with higher amounts at greater elevations, though precipitation is expected to transition to mainly snow above 4000 feet. This will bring snow accumulations to pass level but amounts are expected to remain below advisory criteria. Government Camp has a 75% chance of seeing at least one inch and a 25% chance of seeing 3 inches or more. Santiam and Willamette passes to the south have a better chance of seeing 3 inches at 60-70% but only a 10-15% chance of 6 inches or more. -19

LONG TERM
Tuesday through Saturday...There is strong consensus that dry weather will return to the region from Tuesday through much of Thursday as weak ridging builds aloft. An area of low pressure favored to track into northern California Tuesday into Wednesday may bring light precipitation to the central Oregon Cascades and foothills in Lane and Linn Counties, but chances are only 15-25%. Cluster analysis shows the ridge breaking down toward the end of the week and into the weekend. This would favor a return to a cooler, wetter, and more active pattern Thursday night into next weekend as upper-level troughing is reestablished over the Pacific Northwest. The details and timing of this pattern change remain relatively lower confidence, but rain and mountain snow chances look to increase dramatically late in the workweek. -19/36

AVIATION
Westerly flow aloft as an upper trough moves across the region tonight. The main front has shifted east of the Cascades, but expect another round of rain showers with a mix of VFR and MVFR conditions through at least 14z Monday. By 17-18z Monday, probabilities increase for VFR as conditions are expected gradually improve.

KPDX AND APPROACHES.. MVFR conditions are likely (40-50% chance)
to continue through at least 14z Monday. By 20z Monday afternoon, there is an 80-90% chance for VFR. Scattered rain showers continue tonight into Monday morning. Generally light southeast winds around 4-6 kt expected. /DH

MARINE
Current buoy observations show seas of 7 to 9 ft at 11 to 14 seconds with winds below 15 kt. While conditions remain rather benign thanks to a slow moving cold front over the central and southern Oregon, will finally move out of the region late tonight/early Monday morning. As this system exits the region, a fresh westerly swell will result in seas building towards 9 to 11 ft at 12 to 14 seconds. Therefore, will maintain the current Small Craft Advisories that start this evening and persist through early Tuesday morning. Given that the background conditions will be around 10 ft, and that ebb currents at the mouth of the Columbia River are around 1-4 kt at peak tide, this could result in conditions near the bar towards Small Craft thresholds.
Therefore, will also maintain the Small Craft Advisory from 1 AM Monday through 1 AM Tuesday for the Columbia River Bar.

High pressure returns to the region by the middle of the week, and will bring a brief period of relatively benign marine conditions.
Looking towards the latter part of this week, long-range guidance continues to show a broad, trough dives southward out of the Gulf of Alaska. This system looks to bring elevated seas back into the forecast, with seas building towards the low to mid teens.
However, exact timing and details remain rather broad thus keeping overall confidence low at this time. /42

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.
WA...None.
PZ...Small Craft Advisory from 1 AM Monday to 1 AM PST Tuesday for PZZ210.

Small Craft Advisory until 4 AM PST Tuesday for PZZ251>253- 271>273.