textproduct: Portland

SYNOPSIS

A weak front will bring chances for rain across southwest Washington and along the north Oregon coast over the weekend into early next week, while the Willamette Valley and Portland metro stays dry. Drier and warmer over the entire area early next week as high pressure moves slightly offshore and amplifies, with high temps nearing 60 degrees on Tuesday.

LONG TERM...Sunday Night through Friday

A noticeable warming trend develops Sunday through Tuesday as a quasi-stationary upper level ridge becomes anchored in place over California and the Pacific Northwest. By Tuesday, models and their ensembles show the ridge evolving into a large closed high pressure system at 500 mb with heights peaking near 590 dm over northern California and southern Oregon, which is around the 99th percentile compared to climatology. This will bring dry and calm weather with warmer than normal temperatures for this time of year, both overnight and during the day. The NBM suggests high temperatures in the low to mid 50s across the lowlands on Sunday and mid to upper 50s on Monday, warmest along the central Oregon coast and in the Lane County lowlands. By Tuesday, forecast highs reach the upper 50s to lower 60s for nearly all lowland locations across northwest Oregon and southwest Washington. Normal high temperatures for mid January are in the mid to upper 40s within the Willamette Valley and Portland metro, which means forecast temperatures are 10 to 15 degrees above normal. Overnight lows will likely be in the 40s each night, except upper 30s in the southern Willamette Valley.

The pattern likely persists the the middle and into late next week. However, there are signs that the pattern may waver slightly in the middle of next week when another large upper level trough digs across the eastern Pacific. Current solutions keep the area dry but there is potential that a weakening cold front could bring light precipitation to the southwest Washington counties late Wednesday. Regardless of whether this slight breakdown occurs, high pressure will either remain in control or quickly retake hold of the PacNW. -19/23

AVIATION

High clouds continue to stream overhead this afternoon as VFR conditions persist across the region. Expect similar conditions into the evening hours. We'll still need to watch the threat for patchy fog tonight into Saturday morning across portions of the Willamette and Tualatin Valley as calm winds and wet soils will be in place to provide 2 out of the 3 antecedent conditions needed. The big question remains whether the prevalence of high cloud cover through Saturday morning will be enough to inhibit radiational cooling (and thus fog formation), or at the very least limit the window for fog development. KHIO, KUAO, KSLE, and KEUG still all have a 20-40% chance for visibilities to drop below 1/2 SM or less at any time between 08-18z Saturday. At this point confidence is low regarding fog placement and timing. For now, have continued to hint at fog and low stratus development in the TAFs for those four sites. Fog is unlikely to occur at KPDX, KTTD, KAST, and KONP due to light offshore winds around 5-10 kt.

KPDX AND APPROACHES...Overall there is high confidence VFR conditions persist through the TAF period with CIGs AOA 10-15kft. Current guidance places the chance for degraded flight conditions due to fog at only 10-15% between 14-18z. Winds generally remain below 10 knots with an easterly component. -99

MARINE

Seas have been on the decrease today with current buoy observations showing wave heights around 9-11 feet at 14-15 seconds. We'll likely remain in a holding pattern with similar conditions into early Saturday morning. An area of high pressure just to our east coupled with an approaching frontal system offshore will produce a slight offshore component to the wind to start Saturday but winds become due south and strengthen a bit as days goes on. Expect widespread gusts up to 25-30 kt Saturday afternoon through the weekend. There is around a 20-40% chance of marginal gale force wind gusts up to 35 kt across the outer coastal waters beyond 20 NM, but that will depend on how far east the quasi-stationary front gets. Confidence in frequent gale force wind gusts materializing are still not currently high enough to justify the issuance of a Gale Watch - a Small Craft Advisory remains in effect.

Seas will build again on Saturday too as the southerly wind waves combine with a more southwest to westerly swell. Seas around 12 to 15 ft are likely by Saturday evening. However, seas likely build further into the mid to upper teens late Sunday into Monday with the arrival of a long period westerly swell. At least the chances for seas to exceed 20 ft on Sunday are very low at only 1-5%. High pressure strengthens Monday night into Tuesday, bringing much quieter marine conditions with light winds and seas under 10 ft for the middle of the week. -99/23

BEACH HAZARDS

A high threat of sneaker waves remains for the coast through early next week due to a continued long-period southwesterly to westerly swell. Sneaker waves can create potentially life-threatening conditions in the surf zone as waves may run farther up the beach than expected. These waves can easily catch people off guard and cause beachgoers to be knocked off their feet and pulled out into cold ocean waters. Never turn your back to the ocean. Caution should be used when in or near the water, and those with children should be especially watchful. Sneaker waves can lift or roll large, heavy logs or rocks which can lead to serious death or injury. Keep off rocks, logs, and jetties near the waterline on beaches. -23

PQR WATCHES/WARNINGS/ADVISORIES

OR...Air Stagnation Advisory until 10 AM PST Sunday for ORZ109>111- 114>118.

WA...Air Stagnation Advisory until 10 AM PST Sunday for WAZ205-206.

PZ...Small Craft Advisory until 4 PM PST this afternoon for PZZ210- 251>253-273.

Small Craft Advisory from 4 AM Saturday to 10 AM PST Sunday for PZZ210-251>253-273.

Small Craft Advisory until 10 AM PST Sunday for PZZ271-272.