Cape Shoalwater WA to Cape Lookout OR between 150 and 250 NM Offshore Forecast
|Today...N To Ne Winds 10 To 20 Kt. Seas 5 To 7 Ft.|
|Tonight...N Winds 15 To 25 Kt. Seas 6 To 9 Ft.|
|Sat...N Winds 15 To 25 Kt. Seas 7 To 10 Ft.|
|Sat Night...N Winds 15 To 25 Kt. Seas 6 To 10 Ft.|
|Sun...N Winds 10 To 20 Kt, Becoming W To Nw 10 To 15 Kt. Seas 5 To 9 Ft.|
|Sun Night...W To Nw Winds 10 To 15 Kt. Seas 4 To 7 Ft.|
|Mon...W To Nw Winds 5 To 15 Kt. Seas 5 To 9 Ft.|
|Mon Night...Nw Winds 5 To 15 Kt, Becoming W To Nw 10 To 20 Kt. Seas 7 To 9 Ft.|
|Tue...W Winds 5 To 15 Kt. Seas 8 To 9 Ft.|
|Tue Night...N To Nw Winds 5 To 15 Kt. Seas 7 To 8 Ft.|
| Area Forecast Discussion|
...UPDATED National Weather Service Portland OR
925am PDT Fri September 29 2023
Updated aviation discussion
Weak low pressure off the southern Oregon coast will spread light to moderate rain across the southern half of the forecast area today, with less - if any - rain expected north of Salem. High pressure will lead to a drying trend over the weekend with seasonable temperatures. Next cold front will lead to cool and unsettled weather Monday, then it appears increasingly likely that a more robust warming and drying trend will take hold for the remainder of next week.
.SHORT TERM...Today through Sunday...The active weather pattern that has brought beneficial rains to the region over the past week appears to be winding down as what was once a strong Pacific jet stream buckles and weakens. Currently have weak low pressure off the southern Oregon coast, but this system has enough moisture and forcing to spread light to moderate rain across much of southwest and west-central Oregon today. Most of this rain should remain south of Salem, as that is where the best forcing is. Areas north of Salem will still see plenty of clouds, but less widespread rain as an upper trough swings onshore this afternoon and evening. Models show reasonable agreement that a weak upper low will form at the base of the upper trough tonight and Saturday, taking most of the precipitation with it as it moves across the Sierra Nevada and into the Great Basin.
After a somewhat damp and cool day today, drier northerly flow will lead to a gradual drying and warming trend over the weekend. Aside from some lingering showers in the Cascades, the forecast area should be mostly dry during the day Saturday. With some shear vorticity still overhead, will still see some cloudiness Saturday but the trend will be for decreasing clouds. There is still a little bit of uncertainty as to how much the air mass will warm from Saturday to Sunday, with the 00z EPS mean suggesting 850 mb temps climbing from around +6 deg C Saturday to +8 deg C Sunday over Portland. Meanwhile, the 00z GEFS mean stays flatter around +6 deg C. Either way, temperatures will be seasonable this weekend, with a chilly night and possible valley fog as skies above clear out. Will likely see some of the cooler outlying valleys dip into the upper 30s again Saturday night, but we are not expecting frost at this time. That said, NBM v4.2 probabilistic guidance is currently suggesting a 38% chance of Parkdale reaching 35 deg F or cooler Saturday night, and a 50% chance for Vernonia. Fortunately, these chances are generally 10% or less for the Willamette Valley. Weagle
Monday through Thursday...High pressure begins to flatten Sunday night as a shortwave trough shifts southward from the Gulf of Alaska. How fast and significantly the ridge weakens will greatly depend on the track of this shortwave. At this point it appears this system will be moisture-starved, just producing mostly scattered showers while moving across the forecast area. This is a fast moving front that will have limited impact on the area.
Most models/ensembles continue to trend toward stronger ridging next week, with latest cluster analyses suggesting a 75% chance of strong ridging over the region by the middle of next week. The other 25% maintain northwest flow with more shortwave energy riding over the northern periphery of the upper ridge and digging into the northwestern USA. The stronger signal for ridging next week is having an impact on NBM temperatures - the interior lowlands are currently showing a 50/50 chance of seeing highs in the 70s by Wednesday, with about a 60% chance on Thursday. Weagle
East to southeast winds on the waters early today will gradually turn more northerly as the day progresses. Low pressure well west of Astoria this am will drop southeast towards Calif through tonight. As such, will maintain northerly winds on the waters, with gusts 20 to 25 kt on the outer waters, mainly to south of lat 45 N. Will maintain Small Craft Advisory on the outer waters for today through Sunday am. Seas mostly staying in the 5 to 8 ft range, with highest seas over the outer waters.
NOAA Portland OR Office: Watches - Warnings - Advisories
OR...None. WA...None. PZ...Small Craft Advisory until noon PDT Sunday for Coastal waters from Cape Shoalwater WA to Florence OR from 10 to 60 NM.