Cape Shoalwater WA to Cascade Head OR from 10 to 60 NM Marine Forecast
|Tonight...Se Wind 30 To 35 Kt With Gusts To 45 Kt. Combined Seas 16 Ft With A Dominant Period Of 13 Seconds. Rain.|
|Sun...S Wind 30 To 35 Kt With Gusts To 45 Kt. Combined Seas 16 Ft With A Dominant Period Of 17 Seconds, Building To 19 Ft With A Dominant Period Of 17 Seconds In The Afternoon. Showers And A Chance Of Tstms. Waterspouts Possible.|
|Sun Night...S Wind 35 To 40 Kt With Gusts To 50 Kt. Combined Seas 31 Ft With A Dominant Period Of 16 Seconds. Showers And A Chance Of Tstms. Waterspouts Possible.|
|Mon...Sw Wind 25 To 30 Kt. Gusts To 40 Kt, Becoming 35 Kt In The Afternoon. Combined Seas 26 Ft With A Dominant Period Of 15 Seconds. Showers And A Slight Chance Of Tstms.|
|Mon Night...Sw Wind 25 To 30 Kt With Gusts To 35 Kt, Easing To 20 To 25 Kt With Gusts To 30 Kt After Midnight. Combined Seas 25 Ft With A Dominant Period Of 15 Seconds In The Evening. Showers And A Slight Chance Of Tstms.|
|Tue...Sw Wind 20 To 25 Kt With Gusts To 30 Kt. Wind Waves 7 Ft. W Swell 18 Ft. Rain.|
|Tue Night...Sw Wind 15 To 20 Kt With Gusts To 25 Kt. Wind Waves 5 Ft. W Swell 12 Ft. Chance Of Rain.|
|Wed...S Wind 15 To 20 Kt. Wind Waves 4 Ft. W Swell 15 Ft.|
|Thu...Sw Wind 10 To 15 Kt. Wind Waves 4 Ft. W Swell 12 Ft.|
| Area Forecast Discussion|
...UPDATED National Weather Service Portland OR
417pm PDT Sat Oct 23 2021
Updated aviation and marine discussions.
A strong fall storm will impact the region tonight through Monday night with strong winds, high surf, locally heavy rain, and chances for thunderstorms on Sunday. The worst conditions will be found along the coast, with hazardous conditions also expected in the adjacent coastal waters. The active pattern will continue through next week, with temperatures staying near normal.
.SHORT TERM...TONIGHT THROUGH TUESDAY...Currently, a shortwave trough spawned from the upper low near Kodiak Island is passing overhead, with instability behind the front allowing for isolated to scattered showers this afternoon. These will dissipate this evening. However, as water vapor shows, an expected strong low is going under explosive cyclogenesis near 45N 145W under a near 180kt upper level jet. The mean sea level pressure is expected to rapidly fall, even near 40 mb in the next 12 hours (smashing the 24mb/24hrs required to be named a "bomb cyclone" by definition). High clouds from this feature have already raced eastward and moved inland along the western US coast. While small model differences still exist, including the GFS still being slightly slower than the other models, this low will generally reach about 350 miles off the OR/WA border coast before lifting north toward Vancouver Island by Monday evening.
Getting into higher detail, winds throughout the atmosphere will be increasing, with winds veering as you move up in height. This, as well as the higher theta-e advected into the area ahead of the storm, will set the stage for low-topped thunderstorm formation, and the ability for some of the storms to become severe strong damaging winds, hail and tornadoes as the hazards. CAPE values of 150-400 J/kg are expected to push into the coasts in the late morning through the afternoon. Right ahead of the CAPE really increasing, shear values will be 50-80 kts moving into the coast, resulting in a very favorable hodograph. As the models sometimes are too cool with ocean surface temperatures, CAPE could be modeled too low for the morning. Therefore, in terms of potential for strong storms, the potential may exist even by mid morning. Further east inland, the warm frontal rainband will have spread across the forecast area, with winds increasing as well. With a slightly slower track, easterly winds rushing offshore to fill in the low will likely delay the stronger winds moving into the coasts and inland. Therefore we delayed the coastal warnings to now start at 3pm. Gusts of up to 65 mph along the coasts and up to 40 mph in the Willamette Valley starting earlier are expected. The thunderstorm potential will move inland Sunday afternoon, with a lower threat of severe strength storms with lower CAPE values. However, with the strong winds just above the surface, mixing in a storm could bring this stronger winds downward. This low will then track towards Vancouver Island, and its occlusion front will rotate back around to bring an additional frontal rain band across the area on Monday. through Monday evening as it slowly fills and weakens. In terms of rainfall, expect the Coast Range to pickup another 2-3 inches with locally higher amounts through Tuesday morning while interior valley locations stay closer to 1 inch. Hydro concerns still look to be rather minimal given the progressive nature of the pattern and the current state of the mainstem rivers. Still will have to watch for localized ponding of water and things of the nature, especially with any convective cells Sunday into Sunday night. Snow levels should remain relatively high through the duration of the event, with potential accumulations likely limited to areas above 5000 feet and not significantly impacting area passes. /Kriederman
TUESDAY NIGHT THROUGH SATURDAY...The pattern will start to de-amplify and calm down at least somewhat by Tuesday in the wake of the upcoming system, but still generally looks to stay on the wet side through much of next week as mean upper level troughing continues to reside over Alaska and the North Pacific. Flow will briefly come more up from the southwest for the Wednesday system, looking like another atmospheric river event setting up, yet in no means being very strong at this point. And the exact track has been going further north and may only end up affecting WA. Continued to utilize an ensemble heavy approach and maintained chance Probability of Precipitation through much of the period given relatively large model spread. One similarity that looks to be developing is ridging for next weekend which may end up bringing a dry Halloween to the forecast area. However, this spooky time still remains a week out. /Kriederman
As expected, details on the very strong surface low continue to evolve with each model cycle. Latest ECMWF (European Centre for Medium-Range Weather Forecasts) and NAM have brought the lowest central pressure up the the 947-948 mb range while the GFS dips as low as 941 mb. Regardless, the overall location and track of the low keep our waters away from the worst of the storm.
Given the current minimum pressure data and the resulting wind fields, winds will be a bit slower to ramp up into storm force gusts. The first round which was previously expected to arrive Sunday morning, is now coming in weaker with gusts peaking 40-45 kt. The second round for Sunday night remains just as strong as previously expected with gusts around 50 kt. That said, have left the overall Storm Warning timing as is to avoid issuing multiple warning products and thus avoid creating potential product confusion. Winds now appear to start easing a bit sooner on Sunday night with the primary 45-50 kt gust threat ending before daybreak Monday.
Winds then remain gale worthy with gusts 35-40 kts through Monday and Monday night as the surface low fills as it moves toward Vancouver Island. Tuesday and Wednesday, South to southwest winds gust 20-30 kts as winds slowly ramp down.
Seas will continue.nue to slowly subside this afternoon and evening, but remain near 10 ft. Combined seas will become more wind wave/fresh swell driven as winds increase through the next 24 hours. By mid-evening Sunday, the dynamic fetch generated higher swell will arrive to the waters. Then a SW swell around 25 feet will arrive to push combined seas to 30-32 feet. Given recent past performance of the wave models, have already increased these swell trains by a couple feet to account. Peak combined seas are still expected to arrive shortly after midnight Sunday night into Monday. Seas will slowly subside Monday, not falling below 20 feet until daybreak Tuesday. Seas will then remain above 10 feet through Thursday. -JBonk
.BEACH HAZARDS...The powerful low and associated storm force winds expected over the next few days will also generate rough and hazardous seas and produce significant coastal impacts through Monday night. A Coastal Flood Warning remains in place as swell heigheights will build to 20-25 feet by Sunday night into Monday, with breakers may exceed 30 feet in the surf zone. Exercise extreme caution on area beaches and do not venture out onto outcroppings or jetties. /CB
NOAA Portland OR Office: Watches - Warnings - Advisories
OR...Wind Advisory from 11am Sunday to 5am PDT Monday for Central Willamette Valley-Greater Portland Metro Area-Lower Columbia-South Willamette Valley.
High Wind Warning from 3pm Sunday to 9am PDT Monday for Central Oregon Coast-North Oregon Coast.
Coastal Flood Warning from 8pm Sunday to 5am PDT Tuesday for Central Oregon Coast-North Oregon Coast.
WA...Wind Advisory from 11am Sunday to 5am PDT Monday for Greater Vancouver Area-I-5 Corridor in Cowlitz County.
High Wind Warning from 3pm Sunday to 9am PDT Monday for South Washington Coast.
Coastal Flood Warning from 8pm Sunday to 5am PDT Tuesday for South Washington Coast.
PZ...Storm Warning from 3am Sunday to 8am PDT Monday for coastal waters from Cape Shoalwater WA to Florence OR from 10 to 60 nm.
Small Craft Advisory until 11am PDT Monday for Columbia River Bar.
Storm Warning from 7am Sunday to 8am PDT Monday for coastal waters from Cape Shoalwater WA to Florence OR out 10 nm.