Cape Shoalwater WA to Cape Lookout OR between 60 and 150 NM Offshore Forecast
|Tonight...S Winds 20 To 30 Kt, Becoming W To Nw 25 To 35 Kt, Then Becoming W 15 To 25 Kt. Seas 9 To 13 Ft. Chance Of Rain And Areas Of Fog With Vsby 1 Nm Or Less.|
|Sun...W To Sw Winds Diminishing To 10 To 15 Kt, Then Becoming S 15 To 25 Kt. Seas 11 To 13 Ft.|
|Sun Night...S Winds 20 To 30 Kt. Seas 10 To 12 Ft, Building To 10 To 18 Ft.|
|Mon...S Winds 20 To 30 Kt. Seas Building To 15 To 25 Ft. Chance Of Rain With Vsby 1 Nm Or Less.|
|Mon Night...S To Sw Winds 20 To 30 Kt. Seas Becoming 20 To 24 Ft.|
|Tue...Winds Becoming W 10 To 20 Kt, Then Diminishing To 5 To 15 Kt. Seas Subsiding To 16 To 20 Ft.|
|Tue Night...W Winds 10 To 15 Kt, Becoming W To Nw 10 To 20 Kt. Seas Subsiding To 13 To 16 Ft.|
|Wed...Nw Winds 10 To 20 Kt, Becoming N To Nw 5 To 10 Kt. Seas Subsiding To 11 To 13 Ft.|
|Wed Night...Winds Becoming S 10 To 20 Kt, Then Increasing To 20 To 30 Kt. Seas Subsiding To 9 To 11 Ft.|
|Thu...Winds Becoming W To Nw 20 To 25 Kt. Seas Building To 10 To 15 Ft.|
|Thu Night...W To Nw Winds Diminishing To 10 To 20 Kt. Seas Becoming 13 To 15 Ft.|
| Area Forecast Discussion|
National Weather Service Portland OR
232pm PST Sat Dec 5 2020
A weakening frontal system will bring light precipitation to much of the forecast area, with rain developing along the coast this afternoon then spreading inland overnight. Temperatures may be cold enough for some spotty freezing rain in the Central Columbia River Gorge and Hood River valleys, but any accumulation would be light. Gradual drying is likely Sunday, with dry weather likely Monday. Next decent chance for rain comes Tuesday with our next Pacific frontal system.
Tonight through Tuesday...Current radar shows the stratiform rain from a negatively tilted trough making its way northeast up the southern Oregon coast. The system will continue to weaken as high pressure over the Columbia Basin restricts its progression east, but there is still a good chance that most of the CWA will see some precipitation by late this evening. Precipitation accumulations will be generally light with the heaviest precip occurring overnight in the Cascades.
Winds are expected to weaken overnight but light east winds will continue across the central Columbia River Gorge and in the Hood River Valley. The primary forecast challenge will be tonight as cold air continues to move east out of the Gorge coupled with light precipitation from the weakening system. The primary concern will be freezing rain in the two areas mentioned. According to the 18Z NAMNest, a warm layer around 800mb will move over K4S2 creating an atmospheric profile favorable for freezing rain. A mix of rain, snow, and freezing rain is possible between 10pm and 9 AM. It is likely that the temperatures will drop below freezing for an extended period of time, but whether we get the precipitation is another story. The freezing rain in these two areas has been left as a slight chance during the overnight hours due to lowered confidence in Quantitative Precipitation Forecast. No headlines will be issued but those traveling should be cautious.
Lingering low-level moisture and poor mixing will probably keep plenty of clouds and some precipitation around into Sunday morning, but high pressure will reestablish by Sunday afternoon bringing mostly clear skies Sunday evening. Sunday night into Monday morning will be a prime setup for fog formation as the subsidence inversion strengthens Sunday night. The next shortwave to bring precipitation to the area will be Monday night into Tuesday.
There is also the potential for another period of hazardous beach conditions early next week when large, long period swell may result in breakers up to 25 feet Monday afternoon. This large and energetic swell will create an elevated threat of sneaker waves or otherwise dangerous surf conditions along the beaches Monday and Tuesday. BPhillips/Weagle
Tuesday night through Saturday...With minimal spread in the ensemble members, there is pretty high confidence that the Pacific Northwest will remain under a high pressure pattern Tuesday night into Wednesday. Thursday night into Friday brings greater uncertainty as solutions begin to diverge. EOF analysis shows high spread in ensemble solutions based on the position and timing of an approaching shortwave. There is a high chance that the CWA will see precipitation during this time but where and when is hard to say. There is little to no agreement in the models past Friday night, most are trending towards high pressure rebuilding over the area but it's too uncertain at this time.
A cold front approaching the waters from the southwest early Saturday afternoon will move northeast across the coastal waters early tonight. Expect the front to reach the coast around 7 PM near Newport, and around midnight at the mouth of the Columbia. Pressure gradients suggest peak wind gusts may reach 30kt, mainly over the outer waters and the nearshore waters south of Cascade Head, through early evening. Steep seas dominated by wind waves will slowly build through this evening, then a westerly swell arrives tonight which should push seas a little above 10 ft for later tonight through Sunday.
Another cold front slowly sags into the northern outer waters Sunday night and Monday, pushing wind gusts back into the range of 20 to 30 kt for the northern outer waters. the front is then expected to move southeast across the coastal waters Monday night and early Tuesday, potentially brings wind gusts up to 20 to 25 kt for the rest of the coastal waters.
An intense low pressure system Saturday south of the Aleutians is generating large seas today well to the northwest of the coastal waters. A fairly large long period swell is expected to arrive over the waters Monday, potentially building seas to near 20 ft.
.PQR WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory until 7pm PST Tuesday for Central Columbia River Gorge-Upper Hood River Valley.
WA...Air Stagnation Advisory until 7pm PST Tuesday for Central Columbia River Gorge.
PZ...Small Craft Advisory until 4am PST Monday for coastal waters from Cape Shoalwater WA to Florence OR out 60 NM.
Small Craft Advisory from 6pm to 10pm PST this evening for Columbia River Bar.
Small Craft Advisory from 7am to 11am PST Sunday for Columbia River Bar.