Cape Shoalwater WA to Cape Lookout OR between 60 and 150 NM Offshore Forecast
|Today...Variable Winds Less Than 5 Kt, Becoming S. Seas 3 To 4 Ft. Scattered Showers.|
|Tonight...Variable Winds Less Than 5 Kt. Seas 4 To 5 Ft.|
|Mon...S To Se Winds Less Than 10 Kt, Becoming W To Nw. Seas 4 To 6 Ft.|
|Mon Night...Nw Winds 10 To 20 Kt, Becoming W To Nw 5 To 15 Kt. Seas 4 To 6 Ft. Scattered Showers.|
|Tue...S To Sw Winds 5 To 15 Kt, Becoming S 15 To 25 Kt. Seas 6 To 7 Ft.|
|Tue Night...S Winds 25 To 35 Kt. Seas 8 To 13 Ft.|
|Wed...S To Sw Winds 20 To 30 Kt. Seas 12 To 14 Ft.|
|Wed Night...Sw Winds 20 To 25 Kt. Seas 12 To 17 Ft.|
|Thu...W To Sw Winds 15 To 25 Kt. Seas 15 To 18 Ft.|
|Thu Night...W To Sw Winds 15 To 25 Kt. Seas 15 To 17 Ft.|
| Area Forecast Discussion|
National Weather Service Portland OR
303am PDT Sunday September 20 2020
Weak high pressure will lead to mainly dry weather and near average temperatures through Tuesday before a more active storm track brings a period of wet weather beginning Wednesday.
Today through Tuesday...Water vapor satellite imagery this morning reveals weak shortwave ridging pushing across the eastern Pacific and Pacific Northwest. Closer to the surface, marine clouds continue to linger across the northern half of the CWA while clear skies to the south have led to areas of valley fog developing in the Coast Range and Willamette Valley. For those socked in fog or marine clouds this morning, expect clearing towards midday with high temperatures topping out in the mid 70s across the Willamette Valley.
A shortwave trough apparent on satellite imagery near 40N and 155W will move across the area Monday into Tuesday. Our sensible weather shouldn't change too much, but there will likely be an increase in marine clouds spreading inland. Most model scenarios keep the area dry, but there are a few scenarios that result in some light rain/drizzle along the coast Monday night. Otherwise, expect a continuation of pleasant fall weather. /Neuman
Tuesday night through Saturday...Models remain in good agreement a large shortwave trough will settle into the Gulf of Alaska and result in a front and attendant atmospheric river pushing across the CWA from northwest to southeast on Wednesday. Models also generally agree it will weaken a bit as it does so. As a result, NBM1D guidance suggests there is a 50% chance 24 hour rainfall amounts will end up somewhere between 2/3-1 1/3" of rain at Portland while the interquartile range for Eugene looks to be between 1/4- 3/4" on Wednesday at this point. In addition, gusty southerly winds will increase ahead of the front Tuesday night into early Wednesday, but details in how strong they will be remain uncertain. Post frontal instability should keep additional showers going into Thursday. Another shortwave trough skirting the region late Thursday into Friday should keep unsettled wet weather going into Friday and early Saturday as well. However, models seem to be coming around to the idea that shortwave ridging will begin to shift over the Pacific Northwest Saturday, which should begin to dry the area out. /Neuman.
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 2-4 ft. Guidance continues to show a strong frontal system dropping south Tuesday and moving across the waters Wednesday. Southerly gales appear likely Tuesday night into Wednesday with gusts to 40 kt possible. Expect seas to build to around 7-9 ft as the front approaches the waters Tuesday, then into the mid teens 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 moving into the NE Pac will allow seas to build into the mid to upper teens late next week. /64
.PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None.