Cape Shoalwater WA to Cape Lookout OR between 150 and 250 NM Offshore Forecast
|Tonight...Nw Winds Less Than 10 Kt. Seas 3 To 4 Ft.|
|Sun...Variable Winds Less Than 10 Kt. Seas 3 To 5 Ft.|
|Sun Night...E To Ne Winds 5 To 10 Kt, Becoming N To Ne 5 To 15 Kt. Seas 4 To 5 Ft.|
|Mon...N To Ne Winds 10 To 20 Kt, Becoming N To Nw. Seas 4 To 6 Ft. Scattered Showers.|
|Mon Night...Nw Winds 5 To 15 Kt, Becoming W To Sw. Seas 4 To 6 Ft.|
|Tue...Sw Winds 10 To 20 Kt, Becoming S 20 To 30 Kt. Seas 6 To 9 Ft.|
|Tue Night...S Winds 30 To 40 Kt, Becoming S To Sw 20 To 30 Kt. Seas 9 To 15 Ft.|
|Wed...Sw Winds 20 To 30 Kt. Seas 11 To 17 Ft.|
|Wed Night...Sw Winds 15 To 25 Kt. Seas 13 To 20 Ft.|
|Thu...Sw Winds 15 To 20 Kt. Seas 16 To 19 Ft.|
|Thu Night...Sw Winds 10 To 20 Kt, Becoming W 15 To 20 Kt. Seas 15 To 17 Ft.|
| Area Forecast Discussion|
National Weather Service Portland OR
825pm PDT Sat September 19 2020
Decreasing showers today leading to more settled weather through Tuesday. A pattern shift in store Tuesday evening through Friday with more rain expected.
Today through Monday...No changes. Previous discussion follows. The first day of fall is nearing, leaves are beginning to change, and the weather is following suit. Satellite is showing widespread patchy clouds with a few well needed glimpses at the sun today. For the first time in what feels like weeks, expect calm weather with very little change through Monday as zonal flow persists aloft, and very few surface based disturbances are expected. Onshore flow will continue through the start of the week which will help to keep conditions moist with higher relative humidities. Westerly winds will also aid in keeping much of the smoke out of the area, but could still experience some reductions in air quality at times. On Sunday and Monday morning, there is a chance for some patchy fog with lower marine stratus building in - especially along the coast and the southern Willamette Valley. With a small dewpoint depression and residual moisture from the rain the last few days, fog may become more widespread and dense at times.
While conditions are expected to be dry, some models are hinting at a slight shortwave within the zonal flow on Monday afternoon. This shortwave could bring some rain showers to southwest Washington and the Oregon north of Salem but chances are below 20%. Any rain accumulation will be slight, and likely will not be measurable. Enjoy this break as more active weather expected later in the week. -Muessle
Monday night through Thursday...No changes. Previous discussion follows. Settled weather will remain into early Tuesday morning as the flow remains zonal and onshore. On Tuesday night, a deepening Gulf of Alaska low with upper level support from the jet stream will begin to advance towards the area. This low will likely bring strong southerly winds along the coastal areas and has the potential to bring significant rainfall. The onset of this stronger system will be slow starting late Tuesday night, spreading eastward through Wednesday. At this time, there is still some model variability regarding precipitation amounts and the overall speed so stayed a bit more conservative. This system has the potential to bring an inch or more of rain along the Coast Range and the north Oregon/south Washington Cascades through Thursday morning. The heaviest rainfall is expected on Wednesday afternoon but based on the low progression, that could easily be delayed or sped up.
The broad area of low pressure will remain relatively stationary sitting over southeast Alaska. As it continues to spin, a second disturbance that is embedded in the low will move over the area on Friday. This will likely bring another shot of rain to the area. One thing to note is that freezing levels are staying around 8000-9000 ft. There is a chance, especially with the Friday system that there could be some snow at the ridgetops. However, it is too far into the future to have any amount of certainty so it was left out of the forecast. -Muessle
No changes. Previous discussion follows. Weak high pressure across the waters will result in rather benign conditions through early next week with winds generally less than 15 kt and seas around 2-3 ft. Strong frontal system will drop south Tuesday and move across the waters Wednesday. Increasing chances of southerly gale force gusts are expected. Expect seas to build to around 7-9 ft as the front approaches the waters Tuesday, then into the mid teens on Wednesday as the front moves across the waters. Winds will subside behind the front with winds generally 20 kt or less through the rest of the week, but a large westerly swell will likely keep seas around 12-14 ft. -BPhillips/64
.PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None.