Marine Weather and Tide Forecast for Cedar Mill, OR

SHORT TERM
Now through Sunday Night...Efficient radiational cooling, calm winds, and a moist surface will support additional fog and low stratus development across the Willamette Valley this evening through mid-morning Saturday.
Based on high resolution guidance, there is a 50-80% chance for visibilities falling below 1/2 mile across the Valley, with the highest chances in the southern Willamette Valley (our typically foggiest spot). Will note that any locations that don't clear out this afternoon and maintain low stratus will likely maintain the stratus deck through tonight rather than develop fog. An inversion aloft from the high pressure will keep the clouds low.
Guidance suggests most of the fog and low stratus will dissipate by early Saturday afternoon as the upper level ridge moves over head, making way for some brief afternoon sunshine.

Saturday night into Sunday, the next frontal system will move into the Pacific Northwest, returning clouds and chances for rain. Snow levels briefly fall to 6000-7000 feet, so it's still looking like rain will be falling at pass-level with this system. Rainfall totals are not expected to be nearly as robust as we saw earlier this week. 24 rainfall totals will be highest along the coast with the most likely scenario favoring around 0.25-0.75 inches on Sunday. There is a 10% chance of rainfall totals closer to 0.75-1.25 inches. If these rain amounts are received, hydrological concerns are heightened for coastal rivers. For inland sites, locations north of Salem have a 10% chance of seeing rain as high as 0.5 inch while locations from Salem southward to Lane County have a 10% chance of seeing up to 0.30 inch. Will note that this system is taking a northerly track which is keeping the central and southern Willamette Valley and central Oregon Cascades drier than other locations more north. -99/10


LONG TERM
Monday through Thursday...While this weekend looks to be drier, it's not time to put away your rain boots as yet another strong series of persistent atmospheric rivers are in store. Confidence is increasing that the first stronger frontal system will arrive Monday into Tuesday. The upper level synoptic pattern is showing the frontal system taking a northerly track with a broad ridge still present aloft over much of the west. This means that we may be on the southern edge of the main rain band on Monday. But don't let that sway you - we still have the potential to be very wet with impactful rainfall totals. The coast and southwest Washington will be the most susceptible to the heaviest rain. Current rain forecast from 4 AM Monday to 4 AM Wednesday shows around 1-2 inches along the coast, 1.5-3.5 inches of rain across the Coast Range and Willapa Hills, and 2.5-4.5 inches across the Cascades. Now if the frontal system shifts northward precipitation totals will be much less ranging from 0.75-2 inches along the coast with up to 1-2.5 inches across the Cascades (10% chance for this drier scenario). If the system makes a direct hit though, we could see rain totals around 2.5-5 inches along the coast and 3.5-5.5 inches across the Cascades (10% chance for this wettest scenario) along the Cascades. 48 hour rainfall totals ending Wednesday at 4 AM for 2 inches or more of rain is 20-30% along the coast, around 50-70% across the Coast Range and Willapa Hills, and 70-80% across the Cascades. The Willamette Valley is around 10-20% chance, and the valleys of southwest Washington around 30-40%.

Another concern with this first system on Monday and Tuesday are winds. Winds gusts greater than 40 mph are likely coast at 80%+ chance, near 60-70% across the Coast Range, and 20-30% for interior lowland valleys chance (breeziest on Tuesday). The southwesterly flow though is a more gusty wind prone scenario for coastal areas and the interior valleys so it is something to watch for. The combination of yet another wet system with gusty winds will increase probability for downed trees.

While the Monday and Tuesday system look to be the most robust at this time, we aren't out of the water so to speak as there will be wave after wave of additional precipitation Wednesday through the end of the week. At this point confidence is incredibly low as it will greatly depend on the overall flow.
There appears to be around a 50-60% chance of IVT values greater than 500 kg/m*s. This value is a fair representation for the potential of moisture transport. From an impact perspective, it will be a very wet week with each day after Monday offering the potential for impactful rainfall.

There may be some positive signs next week for snow and winter sport lovers. Snow levels drop behind the Monday-Tuesday system, potentially bringing snow back down to pass-level. NBM chances for a foot of snow or greater in 48 hours from 4 AM Tuesday to 4 AM Thursday are 40-50% through Highway 26 and Santiam Pass, and 20-30% through Willamette Pass. These chances have fallen since yesterday. Will note that if the system early next week shifts northward, then we'll end up on the warm side of that system and snow levels will rise significantly. -10/27

AVIATION
Satellite and surface observations show a rather pervasive fog and low stratus across Western Oregon and Southwest Washington late this evening leading to prevailing IFR to LIFR CIGS/VIS at most sites. Confidence is high these degraded flight conditions stick around through the remainder of the overnight hours into Saturday morning through at least 15-16z as a ridge of high pressure overhead sharpens a temperatures inversion at the surface. After mid morning, any LIFR visibility should begin to improve as fog transitions to more of a low stratus deck although CIGs likely hold around IFR through midday. Come the afternoon hours the big question is whether we'll actually be able to break out of the low stratus across the interior valleys which can be hard to do this time of year. Due to the development of weak easterly flow, confidence is highest for a return to VFR conditions along the coast and KTTD. But for spots like KSLE, KUAO, and KHIO, the continuation of a IFR to a low-MVFR cloud deck is favored through the day. Much tougher call KPDX and KEUG, would assign a 30-40% chance for clearing but overall a persistent stratus deck is favored. At least winds outside of KTTD and the coast should remain fairly light, generally less than 5-8 knots.

KPDX AND APPROACHES...Low stratus has developed overhead with CIGs already dropping to a mix of MVFR to IFR as of 05-06z. Expecting CIGs and VIS to continue to degrade overnight with a 60-70% chance for LIFR conditions by 12-13z. Slow improvement to eventually a IFR or low-MVFR deck by 17-20z with a 30-40% chance to break out to VFR after that point. Winds expected to remain light less than 5-10 kt. -99

MARINE
Overall relatively calm conditions are in place across the coastal wasters a ridge of high pressure holds overhead through much of Saturday. Winds remain 10 kt or less while seas hover around 4 to 6 ft through the morning hours. That said, southerly winds return Saturday afternoon as a decaying front approaches the coastal waters before increasing into Sunday morning. The latest models guidance still project a 60-70% chance to exceed Small Craft Advisory wind gust thresholds (22+ kt).
Seas build slightly to around 7 to 8 ft through Sunday evening due to the wind waves and a fairly fresh WSW Swell.

Then all eyes turn to Monday as a much stronger front moves into the waters bringing increasing winds and hazardous seas. There remains high confidence for southerly gale force wind gusts with this second frontal system. Also worth noting there is a scenario where a strong coastal jet is able to push wind gusts towards Storm Force (48kt+) for a period of time but the probabilities to jump across the 48kt threshold remains low, only around 15-20%.
Steep and hazardous seas peaking in the mid to upper teens late Monday. There is a 10-15% chance of significant wave heights exceeding 20 ft - something to keep an eye on. Seas are expected to remain elevated in the teens through the middle of next week as an active weather pattern continues. -99/DH

HYDROLOGY
Minimal changes to the flood headlines. There continues to be two rivers currently at and forecast to be at minor flood stage through at least the 13th of December. The Pudding River at Aurora and the Cowlitz River at Kelso will remain elevated for at least the next 24 hours, and then will slowly fall below flood stage. However, confidence in the easing of the rivers is low due to the incoming rain and how they have responded. The Cowlitz for example may fall just below minor flood but it's proximity to that stage will prompt the warning to remain until further notice. The Pudding, in a similar way, is forecast below but on the upper end of action stage.
Therefore there is a chance that this river specifically may have the warning extended.

Looking forward to the next week, there continues to be the threat for flooding due to swollen rivers, saturated soils, and the potential for more robust rain. It won't take much to get our rivers back into action or flood stage. There still remains uncertainty with exactly which rivers will flood and by how much, but something to keep an eye on. For specific flood forecasts for area rivers, please visit www.water.noaa.gov.
-10/27

PQR WATCHES/WARNINGS/ADVISORIES
OR...Dense Fog Advisory until 10 AM PST Saturday for ORZ118.
WA...None.
PZ...Small Craft Advisory from 10 PM Saturday to 10 AM PST Sunday for PZZ210-253-273.
Small Craft Advisory from 7 PM Saturday to 10 AM PST Sunday for PZZ251-252-271-272.