Marine Weather and Tide Forecast for Scappoose, OR

SYNOPSIS
Widespread precipitation returns to the area today as a Pacific frontal system moves inland and low-level flow turns back onshore. Expect rain below 3000 ft with accumulating snow above 3000 ft this weekend. High pressure will bring a return to dry weather and low-level offshore flow Monday through Tuesday before chances for rain increase late Wednesday onward.

SHORT TERM
Now through Sunday Night...The persistent weather pattern the area has been stuck under over the past week will finally come to an end today as a Pacific frontal system moves inland, bringing widespread rain and Cascade snow. Low-level flow will eventually turn back onshore today, bringing an end to easterly winds in the Columbia River Gorge. Stagnant air concerns for inland valleys away from the Gorge will also come to an end due to increased mixing and precipitation. The increased mixing has already helped fog lift over the southern Willamette Valley with observed surface visibilities now up to 5-9 miles as of 2:45am Saturday. With the improving visibilities, have decided to cancel the Dense Fog Advisory.
With the increasing low level mixing and precipitation, have also cancelled the Air Stagnation Advisory that was in effect for inland valleys away from the Gorge. In response, expect air quality to gradually improve today.

How much precipitation will this weekend weather system bring? Confidence is very high for rain amounts over 0.5 inches from 4am Sat-4am Sun as NBM probabilities are now around 95%, except 80% in Eugene-Springfield, Cottage Grove, Creswell and Oakridge.
Probabilities for rain amounts over 1" have increased slightly to 10-20% in the Willamette Valley and Portland/Vancouver metro.
Meanwhile, the coast, Cowlitz Valley and lower Columbia have a 50-75% chance. In the Cascades, precipitation will eventually fall as snow down to around 3000 feet. Snow levels start off high Saturday morning at over 9000 ft before lowering to around 5000 ft Saturday afternoon and then down to 3000 ft Saturday night. Snow levels should remain nearly steady thereafter, at least through Sunday night. Confidence is high for a solid 6-10 inches of snow in the south WA/north OR Cascades above 3000 feet (80% chance for 6 inches or more). The period of heaviest snowfall is expected to occur late Saturday night through Sunday morning. With travel impacts expected at pass level, have decided to issue a Winter Weather Advisory for the south WA/north OR Cascades above 3000 feet. Minimal impacts and snow amounts are expected for Santiam Pass and Willamette Pass where only 1-3 inches of snow is likely to fall.

High pressure starts building into the area again Sunday night, bringing an end to any lingering post-frontal showers and a return to calm winds. With high pressure in place and recent rainfall, expect areas of dense fog to develop over inland valleys Sunday night. -TK


LONG TERM
Monday through Friday night...Models and their ensemble continue to suggest ridging over the northeast Pacific will begin building into western WA/OR Monday into Tuesday, bringing a return to dry weather. With a 1030-1032mb surface high in place during that time, winds will be light aside from the redevelopment of breezy east winds in the western Gorge. Chances for max wind gusts over 40 mph are around 20% in Troutdale and 50% in Corbett. Overall the strength of east winds early next week looks to be noticeably weaker than what has been observed over the past several days. Skies will likely clear out as well, aside from the Willamette Valley and Upper Hood River Valley where areas of dense fog and low clouds will develop overnight and likely persist through the day. No air stagnation concerns with this high pressure system as these conditions will be fairly short-lived. Chances for precip return late Wednesday and increase to 75-85% Wednesday night. Chances for rain then remain in that range through Friday night. These probabilities are up a bit from last night. Still no concerns in particular with the two frontal systems late in the week. Overall the weather pattern looks fairly typical for this time of year. -TK



AVIATION
Recent observations have reported light freezing rain in the Upper Hood River Valley and in eastern Skamania County which includes K4S2. Be aware that ice may accumulate on outside surfaces. Previous discussion follows.

A frontal system continues to push inland today with a stream of precipitation falling over the forecast area. VIS and CIGs have been variable bouncing between IFR and MVFR but not necessarily at predictable time frames. Models struggle with this system overall so confidence is on the lower side with the break out of the clouds and VIS. There is a trend that behind the front conditions will become more showery and lift to VFR CIGs . At the same time, winds will shift slightly more southerly and become breezy along the coast and the Willamette Valley.

Based on soundings, the lower atmosphere will saturate if skies clear overnight. Fog once again is possible though not expecting significant density unless skies really clear out. However, could still see some patchy fog and reduced VIS after 08Z Sun. Showers will persist through Sun.

PDX AND APPROACHES...A mix of VFR and MVFR CIGS/VIS today as heavy showers move through. Still waiting on some of the heaviest bands to move over the Coast Range. Rain will ease becoming more showery, and CIGs will begin to thin and lift slightly. Low confidence in returning to VFR CIGs so have maintained a low-end VFR forecast in the long term. One thing to note is a return to a more southerly wind direction. These winds will cause a slight increase tomorrow. Note that LLWS has been removed from the forecast and winds have become unidirectional though winds at 1000 ft or so are gusting to 20-25 kt. -Muessle

MARINE
A front this morning will continue to bring Small Craft Advisory conditions to the north and central waters, then all waters by 7 AM. Expect wind gusts up to 30 kt and seas around 9 to 12 feet through early today. Seas will continue to build towards 16 to 19 ft (70%-80% probability) by late tonight/early Sunday. Seas will then settle into the 11 to 14 ft range by late Sunday/early Monday and likely fall below 10 ft by Monday afternoon. Next disturbance will arrive late Tuesday, likely to bring more Small Craft Advisory conditions. ~Hall

PQR WATCHES/WARNINGS/ADVISORIES
OR...Winter Weather Advisory from 4 PM this afternoon to 4 PM PST Sunday for ORZ126.
WA...Winter Weather Advisory from 4 PM this afternoon to 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.