textproduct: Portland

SYNOPSIS

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 the pattern remaining wet and cold weather next week, though exact details are unclear at this time.

LONG TERM...Monday through Thursday

A reinforcing trough is expected to drop south from northern AK, bringing much colder air aloft to the region early next week with subsequent disturbance through the end of the week. Morning lows fall to near or below freezing each morning, Monday through Thursday. 850 mb temperatures in the -3 to -6 C range are expected which is marginal for snow to the valley floor within onshore flow. If temperatures are cooler, closer to -8 to -10 C, chances will increase. The NBM has started to latch on to low probabilities for lowland snow at 5-10% overnight and early each morning with higher probabilities in the Western Portland hills, Salem hills, and the Chehalem mountains at 20-30%. Any snow that does accumulate would quickly melt as temperatures rise above freezing each day, thereby limiting potential impacts. Confidence in snowfall totals over the Cascades remain low confidence but trends support coinciding cold air and moisture which should bring healthy snowfall. Accumulation at pass level seems likely but exact timing and amounts are unclear so will continue to monitor the pattern for impacts. There is also a chance for snow to reach pass level in the Coast Range, mainly around highway 6 and 26. -19

AVIATION

As of 05z Fri, onshore flow has allowed for stratus to form along the coast as well as through much of the central and southern Willamette Valley and southwest WA lowlands. Expect MVFR ceilings to continue along the coast for the rest of the TAF period. For inland locations, ceilings could fluctuate between MVFR and VFR through around 15-20z Fri before an incoming frontal system will begin mixing out the stratus from north to south, with conditions returning to VFR. Rain associated with the frontal system will slowly spread into the region from northwest to southeast mainly after 18z Fri, though drizzle or light showers could begin around KAST as early as 10z Fri well ahead of the front. Showers impact inland terminals after 20-23z Fri. Inland conditions expected to deteriorate again after 00-04z Sat with MVFR ceilings behind the initial frontal passage. Winds generally light and variable overnight, increasing to around 5-10 kts after 18z Fri as the front approaches and passes through the region.

KPDX AND APPROACHES...A stratus deck around 25-35kft has formed across the Willamette Valley south of Portland, and there's a 40-60% chance it will impact KPDX and surrounding terminals between 06-15z Fri. Confidence is low in how long this stratus deck could linger around the Portland area, especially as broken high clouds begin streaming over the region ahead of a frontal system. If MVFR ceilings do form, expect conditions to improve to VFR by 16-18z Fri as the incoming frontal system will mix out the stratus. Rain returns around 21-23z Fri along the front with 60-80% chance of MVFR ceilings returning around 01-05z Sat behind the frontal system. Winds light and variable, becoming southerly 5-10 kts after 18z Fri. -03

MARINE

Winds around 5 to 10 kt have turned west to southwest this afternoon and will continue through tonight ahead of an approaching frontal system. Seas around 5 to 8 feet today will increase to 13 to 15 feet 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 10-30% chances that seas briefly exceed 15 ft between 1 AM and 7 AM PST Friday morning. Seas look to ease back to around 9 to 10 feet 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 be extended into Saturday night and/or Sunday if confidence increases for frequent northerly gusts above 20 kt. ~12/36

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.