Marine Weather and Tide Forecast for Scappoose, OR

SYNOPSIS
A weak cold front moving through the area will bring light rain chances through the morning with conditions drying out in the afternoon. High pressure returns later today, keeping conditions dry through Sunday. Low chances for rain on Monday as a low pressure system likely remains well offshore.
Seasonable temperatures and dry weather expected Tuesday and Wednesday before another chance for light rain returns Thursday.

SHORT TERM
Now through Sunday Night...An embedded shortwave trough passing to the north continues to move east across southern British Columbia, sending a cold front through the area. Satellite and radar imagery as of 3 AM depicts a shallow frontal precipitation band moving east across the coast range which is producing light rain. Mean QPF values are still expected to range from a trace to 0.10 inch, generally north of Lincoln City at the coast and from the Portland metro area northward. Conditions expected to dry out by the afternoon with northerly winds behind the front. Could see some breezy winds in the Willamette Valley, south of Salem with gusts around 20-25 mph after 10 pm. Highs this afternoon will be closer to normal, topping out in the mid to upper 60s across the interior valleys.
Clearing skies behind the front will allow for overnight lows to drop into the upper 30s to low 50s. Some sheltered locations could see temperatures briefly drop below 37 but these conditions are not expected to be widespread. The only exception will be the Upper Hood River Valley where temperatures are expected to drop between 33 and 36 degrees for several hours between 11 PM tonight and 9 AM Sunday morning. A Frost Advisory has been issued for this zone for the aforementioned timeframe.

Dry weather expected on Sunday as flow aloft becomes more zonal with the passage of the shortwave trough. Highs a degree or two cooler compared to the day prior, peaking in the mid 60s for most interior lowlands and mid 50s to low 60s along the coast.
Sunday night into Monday morning will bring another chance for frost in the Upper Hood River Valley and the southern Willamette Valley as lows could drop into the mid to upper 30s. -19

LONG TERM
Monday through Friday Night...Looking at the start of next week, ensembles continue to show good agreement in a robust low pressure system developing over the northeast Pacific. Model trends continue to keep this low well offshore, moving almost parallel to the PacNW coast and just offshore along California into the middle of the week. Chances for rain have plummeted to less than 25% and even then, only a small portion of the forecast area has that high of a chance for rain.
Ensemble clusters remain in decent agreement for the upper level low to persist near the California coast on Wednesday, while shortwave ridging nudges into the PacNW. There is high confidence for dry conditions to persist across the area Tuesday through mid Thursday, with temperatures warming back into the mid to upper 60s. More uncertainly returns later next week as another upper level trough begins to drop out of the Gulf of Alaska. Chances for rain increase on Thursday, though currently remain less than 40%. -19/DH

AVIATION
Through 12Z Sunday...A weak cold front continues to move across the area, bring low chances for light rain. Conditions across the airspace vary as KAST is already on the backside of the front and has started to mix out the low clouds in the area. KONP remains IFR and could hang onto those conditions through 16-18z or so. As for inland terminals, there is a 30% chance of rain and 30-60% chance of MVFR CIGs through 16Z. VFR conditions return by the afternoon with high clouds through the rest of the TAF period. Light southerly winds ahead of the front will turn northwest along the coast and northerly inland behind the cold front. Speeds along the coast 8-12 kt with gust to around 15 kt at KONP. Inland speeds 5-8 kt. KEUG could see some gusts up to 20 kt late this evening into early tonight.

KPDX AND APPROACHES...Mostly VFR conditions with increasing high cloud cover through the TAF period. A passing front will bring chances for MVFR CIGs and light rain through 16Z. Light southerly winds turn northwest behind the cold front around 5 kt. -19

MARINE
West winds will veer to the northwest today behind a weak cold front. Seas 5 to 7 feet at 11 to 12 seconds build toward 8 to 9 feet tonight. Chances for significant wave heights to build to 10 feet remain low at 10-15% beyond 30 NM. This swell will also pose a moderate risk for sneaker waves along the coast while overall seas remain relatively benign; caution should be used by those in or near the water along coastal beaches through this weekend.

As another weather system looks to track southward well offshore of the Oregon and Washington coasts early next week, and may bring a period of steeper seas Monday into Tuesday although the newest guidance has decreased significantly, bringing seas of 7 to 9 feet at 11-12 seconds Monday afternoon and evening. Chances for wave heights above 10 feet are 20-40% for waters beyond 20 NM. -19/36

PQR WATCHES/WARNINGS/ADVISORIES

OR...Frost Advisory from 11 PM this evening to 9 AM PDT Sunday for ORZ121.

WA...None.

PZ...None.