Marine Weather Net

Cape Shoalwater WA to Cascade Head OR out 10 NM Marine Forecast


REST OF TODAY

SW
WINDS
5 KNOTS

TONIGHT

W
WINDS
TO 5
KNOTS

WED

N
WINDS
5 - 10
KNOTS

WED NIGHT

N
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
PZZ250 Forecast Issued: 847 AM PDT Tue Sep 13 2022

DENSE FOG ADVISORY IN EFFECT UNTIL 10 PM PDT THIS EVENING
Rest Of Today...Sw Wind 5 Kt. Wind Waves Sw 1 Ft At 4 Seconds. Nw Swell 2 Ft At 9 Seconds. Widespread Dense Fog In The Morning. Areas Of Dense Fog In The Afternoon.
Tonight...Nw Wind To 5 Kt. Wind Waves Nw 1 Ft At 4 Seconds. Nw Swell 2 Ft At 9 Seconds. Areas Of Dense Fog In The Evening. Patchy Dense Fog After Midnight.
Wed...N Wind 5 To 10 Kt. Wind Waves N 1 Ft At 4 Seconds. Nw Swell 2 Ft At 9 Seconds.
Wed Night...N Wind 5 To 10 Kt. Wind Waves N 2 Ft At 4 Seconds. Nw Swell 3 Ft At 9 Seconds.
Thu...Ne Wind To 5 Kt, Backing To Nw In The Afternoon. Wind Waves Ne 1 Ft At 4 Seconds, Shifting To The Nw At 4 Seconds In The Afternoon. Nw Swell 3 Ft At 10 Seconds.
Thu Night...Nw Wind 5 Kt. Wind Waves N 1 Ft At 4 Seconds. Nw Swell 3 Ft At 10 Seconds.
Fri...Nw Wind 5 To 10 Kt. Wind Waves 2 Ft. Nw Swell 4 Ft.
Sat...Nw Wind 5 To 10 Kt. Wind Waves 2 Ft. Nw Swell 4 Ft.
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Area Forecast Discussion
...Update National Weather Service Portland OR
821pm PST Monday Feb 6 2023

Made some changes to forecast winds, as well as seas for the coastal waters. The incoming front appears likely to develop a southerly coastal jet while the front approaches the coast after midnight tonight. This will lead to solid Gale Force winds within the coastal jet, particularly 5 to 20 NM offshore where gusts of up to 45 knots are possible. The coastal jet will also clip the beaches and headlands with localized south wind gusts of up to 60 mph Tue morning, but these gusts shouldn't be persistent or widespread enough to warrant a High Wind Warning. Gusts should peak in the 40-50 mph range for the coastal communities Tuesday. Inland valleys will be close to Wind Advisory criteria, especially Salem northward. The 12z HREF probabilistic guidance shows the highest chance for advisory level wind gusts of 45+ mph in the lowlands will be in the Silverton/Scotts Mills/Molalla area, where the HREF is showing a 30-50% chance of such gusts occurring between 8am and 2pm Tuesday. Most of the Willamette Valley should just have a breezy day, with gusts 30-40 mph developing around sunrise and continuing through midday before gradually decreasing later in the afternoon and evening.

More significant changes were made to the forecast seas across our coastal waters, which have been underforecast consistently in our waters by the GFS (Global Forecast System) wave model, and thus by extension the NWPS. The 18z GFS wave spectral guidance suggests seas peaking around 16 ft around 7am Tuesday at the entrance to the Columbia River Bar. For the last two or three events (and possibly more), seas have generally peaked at or above NBM 90th percentile wave guidance, which even includes members from the ECMWF (European Centre for Medium-Range Weather Forecasts) wave model. The NBM 90th percentile guidance is showing 16 ft, so it appears the spectral wave guidance may NBM is catching on to the fact that models are consistently under-doing seas with this dynamic series of frontal systems. Our forecast is essentially a 50/50 blend between the NBM 90th percentile and NWPS wave heigheights derived from our wind forecast, with about a 10-15% boost from that within the coastal jet (roughly 5-20 NM offshore). This brings seas into the mid to upper teens, which seems more appropriate for a middling gale than the peak of 12-15 ft shown by the NBM and GFS wave deterministic guidance. Would put the chances of seas reaching 20 feet at the Columbia Bar Entrance at around 15 percent; this would occur between roughly 5am and 10am Tuesday. Weagle

Synopsis
Overall looking at a moist pattern as several passing fronts move inland through the week. The first more robust front will arrive tomorrow which will bring gusty southerly winds and ample precipitation to the region. Will see snow along the Cascades, and rain elsewhere. Periods of rain breaks on Wednesday and Thursday.

.SHORT TERM /THROUGH THURSDAY NIGHT/...The synoptic pattern will feel a bit like a rinse and repeat as the jet stream "ebbs and flows" between quickly advancing troughs and passing ridges. Each trough will energize a surface front which will bring rain and breezy winds to the area. The first system, which happens to be the most robust of the week, will arrive on Tuesday. A low pressure system will drop down from the Gulf of Alaska and skirt the Alaska Panhandle before pushing inland and decaying over Washington late Tuesday. Ahead of this low though will be a cold front which will be the main weather maker on Tuesday. Winds will become southerly with the frontal passage and will build. Will see gusts upwards of 45 mph along the coastal beaches, and around 35 mph in the Willamette Valley. Areas most at risk for those gusty southerly winds will be along the coast, the central Willamette Valley and the Cascades. Gusts around 60 mph are possible along the very highest peaks of Mt Hood. More widespread gusts of 40-50 mph are expected through southerly wind susceptible Cascades. Do not have any wind advisories out at this time as forecasts are falling below criteria, however, cannot rule out an isolated gust or two that exceed 40 mph in the Cascade Foothills of Marion County.

With the influx of cold air (around -6C at 850 mb), snow levels will rise slightly right ahead of the front, then drop to around 2000 ft in the post frontal environment. In combination with the significant amount of precipitation expected, will see heavy snow to fall Thursday morning through Thursday afternoon. Areas between 3500-5000 ft will see anywhere from 2-9 inches of snow with the lower amounts falling the central Oregon Cascades and higher amounts in the south Washington Cascades. Above 5500 ft though could see near two ft of snow, especially along the volcanos. Ensemble guidance shows less than a 20% chance of seeing snow in excess of 6 inches in 12 hours along the south Washington Cascades. Have decided to transition the Winter Storm Watch into a Winter Weather Advisory as any warning level snow will fall along the highest peaks of the Cascades. If you add in the gusty winds and the heavy snow, blowing snow conditions are possible - generally in the most exposed areas at higher elevations. Visibility may be reduced at times during those stronger showers but as the precipitation dissipates and winds ease, will see any reductions to visibility improve.

By Wednesday morning, most of the precipitation will have weaned as high pressure rebuilds over the region. One thing to note is that in the transitional period from the low to the ridge, the NBM is projecting around a 10 to 15% chance of thunderstorms along the north coast. This will greatly depend on the intensity of the low and the timing. Cannot rule out this very slight chance, but confidence is low so have not included in the forecast at this time. With drier conditions in store, overnight lows will dip/ there is around 60-80% chance of seeing temperatures around 30-35 degrees in the central and southern Willamette Valley, and around 10-30% chance of seeing temperatures sub 30 degrees from Corvallis southward. Will continue to monitor, but given the available moisture from the previous days and lingering clouds, could be a bit more difficult to get that chilly.

Another shortwave trough will arrive late Thursday which will bring yet another round of rain to the region. -Muessle

Long Term
Friday through Sunday
500 mb vorticity advection shows a slight slow pressure system and digging shortwave trough that stretches along the Pacific Northwest coast. This system will bring another round of rain on Friday which will likely persist through Saturday. This system will be a bit more showery so accumulation wise not expecting anything overly significant at this point. Ensembles show a variety of solutions with the Cascades seeing most of the long-persisting precipitation with accumulations ranging from 0.01" (10th percentile) to 0.35" (90th percentile). At this point, trending on more of the mean solution of around 0.10 inches for the highest accumulations. Will say though that the Canadian model is a bit more robust in precipitation than the others. Residual showers expected through Sunday with minimal impact. -Muessle

Marine
The next system will start to impact the coast as a low and associated cold front brings southerly wind gusts up to 45 kt across all waters by this evening. Models are showing the development of a coastal jet primarily focused on the northern Oregon coast from about Cape Mears northward to Cape Disappointment and inside of 20 NM. As the system pushes eastward, the highest winds are expected during the late Tuesday morning/early Tuesday afternoon. Some guidance is showing that there could be isolated gusts up to 50 kt, but confidence is low at this time.

Seas during the time will build under a combination of increasing 10-12 ft westerly swell and southerly 9-12 ft wind waves that will result in a very chaotic seas state through Tuesday night. Combined seas generally peak at 14-17 feet. Seas could build higher late Tuesday morning as the strongest winds could push seas towards 19 ft, but there is some uncertainty as models have backed off slightly on the strength of the incoming system. Will monitor the system over the next 24 hours and adjust the forecast as needed.

Behind the front winds will become westerly, which will result in winds and seas to start subsiding. Winds will fall below 20 kt by late Tuesday/early Wednesday. Seas will be slower to subside and will be around 10 ft by Wednesday afternoon.

Thursday/Friday the next large scale low will start to impact the region and send a fresh westerly swell into the region. Guidance is suggesting that seas will build towards the mid-teens at this time. However, each model run brings varying degrees of winds and seas, do not have solid confidence for the latter part of this week at this time. -42

NOAA Portland OR Office: Watches - Warnings - Advisories
OR...None. WA...Winter Weather Advisory from 4am Tuesday to 10am PST Wednesday for South Washington Cascades.

PZ...Gale Warning until 1pm PST Tuesday for Columbia River Bar.

Hazardous Seas Warning from 1pm to 10pm PST Tuesday for all waters.

Gale Warning until 1pm PST Tuesday for coastal waters from Cape Shoalwater WA to Cape Foulweather OR out 60 nm.

Small Craft Advisory until 4am PST Tuesday for coastal waters from Cape Foulweather OR to Florence OR out 60 nm.

Gale Warning from 4am to 1pm PST Tuesday for coastal waters from Cape Foulweather OR to Florence OR out 60 nm.