textproduct: Portland

SYNOPSIS

High pressure maintains dry weather through today with early morning fog and frost in interior valleys and weaker east winds through the Columbia River Gorge. Rain returns to the region tonight into Friday with lingering lowland rain and mountain snow showers diminishing through the weekend. There is moderate confidence in further wet and cold weather next week.

LONG TERM...Monday through Wednesday

By early next week, the closed low off of California will be reinforced as the first in a potential series of vigorous shortwaves rapidly drops out of the Gulf of Alaska. These features will both inject colder air into the region as well as increase the chances for widespread precipitation in the early and middle portions of next week. Snowfall totals in the Cascades are relatively low confidence at this point, but the coincident cold air and moisture could certainly support ample accumulations at and above pass level. With snow levels most likely between 1500-2500 ft, lowland snow is also not out of the question, particularly in the overnight and early morning hours when the atmosphere is at its coldest. Long-range guidance maintains mid-level temperatures around -3C to -5C overhead, which supports marginal chances for snow or rain/snow mix to the valley floor. Any snow that does reach the ground is most likely to melt on contact or within a few hours as daytime temperatures rise well above freezing, thereby limiting potential impacts. Altogether, chances for brief snow along the I-5 corridor in the early mornings next week are 10% or less, and 10-25% at elevations of 500-1000 ft, including the Chehalem Mountains and Eola/Salem Hills within the Willamette Valley, and the West Hills of Portland. -36

AVIATION

Primarily VFR conditions throughout the airspace through a majority of the TAF period. Another approaching frontal system will bring rainfall and deteriorated CIGs to the coast around 09-12Z Friday (30-50% chance for MVFR CIGs). Could see a return of fog at KEUG around 12-14Z Friday, with guidance suggesting a 10-30% chance of IFR/LIFR conditions. Otherwise, expect winds to remain around 5 kt or less through the period.

KPDX AND APPROACHES...VFR conditions with light southeast winds at 5 kt or less through the period. Scattered high clouds continue through today, with bases lowering after 09Z Friday as a frontal system approaches from the west. ~12

MARINE

Northerly winds will continue to ease to 5-10 kt this morning, before turning out of the west to southwest this afternoon through tonight ahead of an approaching frontal system. Despite relatively light winds, seas will rise dramatically from 5-8 ft today to 13-15 ft by Friday morning as a long-period westerly swell arrives. The highest seas are expected between Cape Shoalwater and Cape Falcon beyond 20-30 NM, where there are 30-60% chances of briefly exceeding 15 ft between 1 AM and 10 AM PST Friday morning. Seas look to ease back below 10 ft while modest high pressure will support increasing northerly winds through this weekend.

Small Craft Advisories are therefore in effect across the outer waters (beyond 10 NM) from 7 PM PST this evening through 1 PM PST Saturday, across the inner waters (within 10 NM) from 1 AM PST Friday through 1 PM PST Saturday, and for the Columbia River Bar from 1 AM PST Friday through 1 AM PST Saturday. These advisories may need to be extended into Saturday night and/or Sunday if confidence increases in frequent northerly gusts above 20 kt. -36

BEACH HAZARDS

A high threat for sneaker waves is likely Friday through Sunday evening due to a long period westerly swell. Waves can run up significantly farther on a beach than normal, including over rocks and jetties. Sneaker waves can suddenly knock people off of their feet and quickly pull them into the frigid ocean which may lead to serious injury or drowning. Caution should be used when in or near the water, especially those who will be razor clamming. Keep children and pets away from the surf zone. Keep off of jetties, rocks and logs near the surf zone. If you see someone swept into the sea do not swim in after them. Call 911 and keep an eye on them until help arrives. -10

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory from 1 AM Friday to 1 AM PST Saturday for PZZ210.

Small Craft Advisory from 1 AM Friday to 1 PM PST Saturday for PZZ251>253.

Small Craft Advisory from 7 PM this evening to 1 PM PST Saturday for PZZ271>273.