textproduct: Portland

SYNOPSIS

High pressure will remain in place across the region through Friday, maintaining dry weather with mild temperatures, warmest in the Oregon Cascade foothills and along the central Oregon coast. Skies will remain mostly clear, aside from low stratus and areas of dense fog during the overnight/morning hours in the central and southern Willamette Valley. Meanwhile, strengthening easterly flow through the Columbia River Gorge will lead to windy conditions in the eastern Portland/Vancouver metro and adjacent higher terrain through early today. Widespread rain returns Saturday and continues into next week.

DISCUSSION...Now through Tuesday night

High pressure continues to dominate the region, maintaining dry conditions through Friday along with anomalously warm temperatures for early February. Many locations across northwest Oregon and southwest Washington will see afternoon highs in the 60s today and Friday, with the warmest readings favored in areas benefiting from downslope easterly flow and greater exposure to sunshine. Localized highs near the mid to upper 60s remain possible, most notably today in the Lane County Cascade Foothills, Cascade Foothills of Marion and Linn Counties, Central Oregon Coast, and Tillamook County Coast. These temperatures are well above seasonal normals and may approach daily records in a few locations.

In contrast, portions of the central and southern Willamette Valley are likely to remain cooler during the daytime due to recurring overnight and morning low stratus and dense fog. These cloud decks may be slow to erode each day, limiting solar heating. Air stagnation concerns continue in these areas, including the Cowlitz Valley, as light winds and strong inversions persist. Deteriorating air quality remains possible through at least tomorrow evening. Meanwhile, the central Columbia River Gorge and Upper Hood River Valley will stay relatively cooler as well, with highs generally in the low 50s and better mixing limiting stagnation concerns.

Easterly winds remain a primary impact today, particularly in the western Columbia River Gorge, Troutdale, and the Washougal area. Sustained east winds of 25 to 35 mph with gusts of 40 to 45 mph are expected through early afternoon, with stronger gusts possible at exposed locations such as Crown Point. Pressure gradients continue to tighten early this morning, with a difference of -7 to -8 mb from Troutdale to The Dalles as of 3 AM. Wind Advisories remain in effect for these areas, as isolated tree damage and localized power outages remain possible. Winds will gradually ease later today as gradients relax.

A notable pattern shift begins Saturday as an approaching Pacific frontal system pushes inland. Cloud cover will increase early Saturday, followed by rain developing along the coast by late morning or early afternoon, then spreading inland through the evening. Snow levels will remain quite high with this system, generally above 6000 to 7000 feet due to warm frontal influences, resulting in rain at the Cascade passes. Widespread rain continues into Saturday night and Sunday as a trailing cold front moves through.

Behind the cold front Sunday night into Monday, precipitation becomes more showery in nature while snow levels drop to around 3500 feet. This will allow some snow to accumulate at the Cascade passes, though overall snow totals are expected to remain modest due to decreasing moisture. Current guidance supports 1 to 3 inches of snow over 24 hours, with a low (10-15%) probability of totals exceeding 6 inches. Conditions trend cooler and somewhat drier Monday night into Tuesday night, though isolated light showers may linger, primarily near the coast. ~12/23

AVIATION

Dry south to southwesterly flow aloft as an upper level ridge of high pressure persists over the region. VFR conditions persist through much of the airspace during the TAF period, with the only exception being areas of fog or low stratus for KEUG, KSLE, and KHIO before 19-20Z Thursday and after 04-07Z Friday. Probabilistically, chances for LIFR fog are around 30-50% at KEUG, and 20-40% at KSLE and KHIO. A strong offshore pressure gradient through the Columbia River Gorge will maintain breezy east winds into the east Portland metro through the TAF period, keeping VFR conditions at nearby terminals. Expect gusts up to 35 kt at KTTD through this afternoon, weakening after 00-06Z Friday. ~12

KPDX AND APPROACHES...VFR conditions expected with scattered high clouds. Diurnally driven southeast winds around 5-10 kt expected at the terminal, while east approaches will see stronger east winds with gusts up to 35 kt near KTTD. ~12/DH

MARINE

High pressure inland will maintain light offshore winds across the waters through Friday. East winds with gusts up to 15-20 kt will be possible today near gaps in the coastal terrain. Winds turn southerly by late tonight and gradually increase Friday into the weekend as a front approaches the waters by Saturday. There is around a 60-70% chance for maximum wind gusts to exceed 34 kt on Saturday.

A persistent southwest to westerly swell at around 13-15 seconds will maintain seas around 9 to 12 ft through the end of the week, then shift more westerly and persist into at least early next week. Will maintain the Small Craft Advisory across all coastal waters including the Columbia River Bar through at least Friday. Overall, active weather continues into early next week. ~12/DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...Air Stagnation Advisory until 10 PM PST Friday for ORZ108- 115>118-123>125. Wind Advisory until 1 PM PST this afternoon for ORZ112. WA...Air Stagnation Advisory until 10 PM PST Friday for WAZ204-205. Wind Advisory until 1 PM PST this afternoon for WAZ207. PZ...Small Craft Advisory until 4 PM PST Friday for PZZ210-251>253- 271>273.