textproduct: Portland

SYNOPSIS

Periods of light rain today as a frontal boundary lifts northward across the area. Mostly dry on Sunday as low pressure stalls off the northern California coast. A deeper upper level trough will bring more unsettled weather to the region early next week as snow levels lower to around 1500 ft. Cool and showery weather likely continues through the end of next week as troughing persists over the region, but confidence remains low in exact details regarding higher elevation snowfall amounts.

LONG TERM...Tuesday through Friday

There remains very good agreement among ensembles for an anomalously deep upper level trough over the Pacific NW on Tuesday. Cooler air aloft will be ushered in as ensembles suggest 850 mb temperatures are likely to fall to around -4 to -6 C. Low pressure becomes vertically stacked off the north Oregon coast which should maintain showery, unsettled weather. At this time, QPF amounts do not appear too impressive with some light snow accumulations above 1500 ft.

Active weather is expected to continue through next week as upper level troughing remains likely over the region. The highest probabilities for more substantial Cascade snow remain later in the week, Thursday into Friday with around a 30-50% chance of exceeding 12 inches in 24 hours. There is also around a 10-20% chance of exceeding 4 inches of snowfall Thursday through Thu night at pass level in the Coast Range, including highway 6 and 26. Colder temperatures in the morning and overnight could also allow a few snow showers to reach the valley floor later in the week, but accumulating snow is very unlikely. /DH

AVIATION

Moist, southwest flow aloft continues today as a frontal boundary remains over southern parts of the forecast area. As of 10z, a line of showers moving onshore is producing MVFR conditions at the coast. By 12z, expect conditions to improve to predominately VFR as cooler temperatures mix the environment. Conditions inland remain a mix of MVFR and VFR, with a few pockets of shallow LIFR fog where clearing has generally occurred, including at KHIO. This frontal boundary will begin to lift northward, spreading light rain across more of the area later today. Chances for MVFR at KONP increase to around 40-50% by 18z.

KPDX AND APPROACHES...VFR conditions as of 10z Saturday. But, with clearing occurring, this brings a 10-20% chance for fog or low stratus to develop, potentially dropping conditions into IFR toward the 14-18z time period this morning. Light rain returns after 18z, with CIGs more likely (60-70% chance) in lower-end VFR. Probabilities for MVFR increase after 00z Sunday. Light and variable winds generally becoming northwest this afternoon. /DH

MARINE

Low pressure develops off the northern California coast today while high pressure builds well offshore. This will turn winds north to northeasterly across the coastal waters today. Winds around 15 kt or less this morning will increase through this evening with gusts up to 25-30 kt across the outer coastal waters, strongest south of Cascade Head. Northerly winds continue on Sunday, gradually easing through Sunday night. A west- northwesterly swell producing seas of around 13 ft early this morning will continue to gradually subside, falling to around 9 to 10 ft this afternoon and continuing into Sunday. Will maintain the Small Craft Advisory for all waters through this afternoon, with the outer coastal waters continuing through tonight.

A cold front will approach the waters early Monday bringing more westerly winds and active weather. Weak low pressure drops south toward the north Oregon coast on Tuesday. Winds likely remain below advisory thresholds, but another northwesterly swell is expected to build seas again to around 13 to 15 ft on Tuesday. Active weather continues with around a 20% chance of marginal gale force wind gusts late next week. /DH

BEACH HAZARDS

A high threat for sneaker persists 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.

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 4 PM PST this afternoon for PZZ210- 251>253.

Small Craft Advisory until 4 AM PST Sunday for PZZ271>273.