Marine Weather and Tide Forecast for Cedar Mill, OR

SHORT TERM
Now through Monday night...There has been minimal change to the forecast. Satellite and radar observations from early Friday afternoon depicted a slow-moving cold front draped across western Washington and extending into the coastal waters off the north Oregon coast, with a narrow band of light rain along and ahead of the front. This frontal boundary was finally beginning to show more noticeable movement towards the southeast as of Noon-2 PM PDT Friday, which seems to be on track with the latest suite of hi-res model guidance. This will allow the aforementioned band of rain to gradually push southward across northwest Oregon from the Columbia River down to Lane County late Friday afternoon through Friday night.
Rain rates and amounts will be much too light for impacts to occur, with most locations picking up anywhere from a trace to 0.15 inches of rain.

Rain is expected to end quickly Saturday morning as models and their ensembles remain in agreement for surface high pressure and zonal flow aloft behind the frontal passage for the Saturday through Monday time frame. This will bring drier weather and relatively cooler temperatures with highs close to average for this time of year (mainly in the mid to upper 50s). Winds will also be light, especially during the overnight hours each day. The light winds will be in conjunction with clearing skies Saturday afternoon into Saturday night, resulting in an ideal set-up for radiational cooling.
As such, forecast low temperatures remain coldest Saturday night with widespread lows in the low to mid 30s. Widespread frost will likely develop as a result. Sunday night into Monday morning will be chilly once again, though low temperatures will be a few degrees warmer in the mid to upper 30s with less widespread frost development. Those with sensitive outdoor plants should take precautions to protect vegetation from frost this weekend. Note that NWS Portland will not begin issuing Frost Advisories and Freeze Watches/Warnings for agricultural purposes until April 1st when the growing season begins to ramp up more and impacts from frost and freeze conditions become more significant. -23

LONG TERM
Tuesday through Thursday night...Confidence remains high for widespread rain and breezy winds Tuesday into Wednesday as a stronger Pacific cold front moves inland. Model ensemble guidance continues to show uncertainty on timing and exact precipitation amounts. However, confidence is high that river flooding is not expected, even in the wettest possible scenario. This front could arrive as early as early Monday night or as late as Tuesday evening, with the most likely arrival time being sometime between Tuesday afternoon and Tuesday evening. As a result of these timing differences, the NBM 10-90th percentile for snow levels continues to show large spread on Tuesday, ranging from 5000-10000 ft. Large model spread is evident for surface temperatures as well, with highs potentially ranging anywhere from the lower 50s to upper 60s. The outcome will be dependent on the cold frontal timing; if the front holds off until late in the day, surface temperatures will be well into the 60s with snow levels well above pass level. If the front arrives Monday night or Tuesday morning, temperatures will be in the lower 50s with snow levels approaching pass level. Regardless of the exact arrival time, confidence is high that snow levels will drop considerably behind the cold frontal passage, bottoming out Wednesday night into Thursday morning well below the Cascade passes. That being said, ensemble guidance for QPF clearly shows precipitation beginning to end by that time, meaning conditions will trend colder and drier with little accumulating snow and travel impacts at pass level.
NBMv5.0 probabilities for 6 inches of snow or more in a 48-hour period ending at 5am PDT Thursday continue to back this expectation up, as chances are only around 5% at Willamette and Santiam Passes, and 15% along highway 26 near Government Camp. Note that lowland snow is NOT expected given conditions will be drying out by the time temperatures become colder.

By Thursday afternoon, the weather system is expected to move out of the area with upper level flow becoming more zonal. Expecting dry conditions with clearing skies by midday Thursday, which could allow for temperatures to warm into the upper 50s. -23/03

AVIATION
The front continues to move southward, spreading light rain over the central/southern Willamette Valley and central Oregon coast. Specifically, radar imagery currently shows the rain band stretched from KONP to KSLE.

Expect chances of MVFR CIGs at inland terminals around 40-60% through 12Z Sat (highest chances KSLE southward), then VFR through the rest of the TAF period. As for the coast, MVFR/VFR conds at KAST and LIFR/IFR conditions at KONP are expected to end at different times. While KAST will likely improve to predominantly VFR by 10-12Z Sat, KONP wont improve to VFR conds until 19-21Z Sat (30-50% chance of LIFR conditions before 19Z Sat at KONP). Expect northerly winds at most terminals through the TAF period, with the exception of northwesterly winds at terminals near the Columbia River. Wind will remain under 10 kt for most terminals, with the only exception of gusts up to 20 kt at KONP through majority of the TAF period.

KPDX AND APPROACHES...There is a 30-50% chance for MVFR CIGs before 12Z Sat, then VFR through the rest of the TAF period.
Northwesterly winds under 8 kt through the TAF period.
~12

MARINE
High pressure will gradually build tonight, turning winds more northerly over the waters and remaining under 20 kt. A brief northwesterly swell will move in tonight, bringing marginal small craft seas of 8-9 ft at 10 sec. Therefore, a Small Craft Advisory has been issued for all waters from 11 PM Friday to 8 AM Saturday. An exception is the Columbia River Bar, where a Small Craft Advisory is in effect between 5-10 AM Saturday for a very strong ebb current that will bring seas around 9 feet. Outside of the period with the very strong ebb, seas along the Main Channel of the bar are slightly lower (7-8 ft), so this zone was excluded from the Small Craft Advisory that starts late Friday evening.
Benign marine conditions continue through Monday as high pressure persists. Seas fall to 5-7 ft at 10 sec by late Saturday night, but re-build to 8-9 ft heading into Monday.

The next robust weather system returns Tuesday into Wednesday.
This system will bring a return of breezy southerly winds across all waters. Current guidance suggests high confidence (60-80% chance) for widespread and frequent small craft wind gusts of 21 kt or greater, and a 10-30% chance for widespread and frequent Gale force wind gusts of 34 kt or greater on Tuesday. Chances for isolated Gale force wind gusts are around 50-75%, with the highest chances beyond 20 NM offshore. Seas on Tuesday and Wednesday are also expected to build to around 14-16 ft in response to increasing wind waves along with an increasing westerly swell.
There's a 30-60% chance seas could exceed 15 ft with a 5-15% chance for seas exceeding 20 ft. Chances increase from south to north, peaking across the waters north of Cape Falcon. -10

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.
WA...None.
PZ...Small Craft Advisory from 5 AM to 10 AM PDT Saturday for PZZ210.

Small Craft Advisory until 8 AM PDT Saturday for PZZ251>253- 271>273.