textproduct: Portland

SYNOPSIS

High pressure will amplify over the region this weekend with low-level offshore flow, bringing dry conditions with well above normal temperatures for this time of year. Temperatures trend relatively cooler Tuesday through Friday with the return of onshore flow, however conditions will most likely remain dry.

LONG TERM...Tuesday through Friday night

The long term forecast is highlighted by relatively cooler temperatures that are closer to seasonal normals (highs in the low to mid 60s) with dry conditions most likely continuing (80-90% chance west of the Cascades). The cooler temperatures will be in response to a transition back to onshore flow and northwest to northerly flow aloft, which models and their ensembles are in good agreement on per WPC's cluster analysis for 500 mb heights as well as the GEFS/ENS/GEPS ensemble means. However, a closed upper level low moving into California from the Pacific may track just far enough to the north to bring light showers to the Oregon Cascades due to wrap-around moisture from the south. The best chance for showers to occur over the Oregon Cascades is between 5 PM Tuesday and 5 PM Wednesday when NBM PoPs peak between 30-45%. Probabilities for thunderstorms have decreased to below 5%, even along the Cascade crest. Do not expect any impacts with these light showers if they do occur.

It is also worth mentioning that some areas of early morning frost will be possible each day from Wednesday through Friday given the light winds and mostly clear skies in place, especially in the Upper Hood River Valley and central/southern Willamette Valley. These areas generally have the highest chance to see morning low temperatures of 36 degrees or colder (generally anywhere from a 15-35% chance each morning, except a 40-70% chance in the Upper Hood River Valley from Odell to Parkdale). Probabilities are less than 10% in the Portland metro, except 15-35% in Hillsboro, Forest Grove, Banks, and North Plains. Anyone with sensitive outdoor vegetation that is susceptible to frost damage should stay up-to-date on the temperature forecast over the coming days and monitor for potential Frost Advisories. -23

AVIATION

Widespread VFR flight conditions under mostly clear skies will continue through the majority of the TAF period. Expect some increasing high clouds starting around 00Z Sunday, but no impacts to flight conditions are expected. The only exception to this will likely be at KAST and KONP, which have a 50-60% chance of developing IFR/LIFR conditions starting around 10Z-14Z Sunday. KEUG could also see some IFR/LIFR conditions, but the chance of that occurring is only 10-20% chance starting around 13Z Sunday. Any lowered flight conditions that do develop, should scour out around 16Z-18Z Sunday

Calm winds this morning will become north/northeast 10 kt or less starting around 18Z-20Z Saturday. KTTD will maintain easterly winds with gusts as high as 20 kt starting around 12Z-15Z Sunday.

KPDX AND APPROACHES...VFR flight conditions under mostly clear skies through the TAF period. High clouds begin to increase after 00Z Sunday, with no impacts to flight conditions expected. Light winds will becoming northerly less than 10 kt around 20Z Saturday. /42

MARINE

High pressure remains in place over the waters and is resulting in rather benign conditions through the start of the weekend. Seas early Saturday morning were around 4 to 6 feet and are expected to remain within that range through at least Monday night. Northerly winds over the outer waters have increased to 15 to 20 kt and should increase to 20 to 25 kt by late Saturday morning and then hold steady through Saturday night.

Wind gusts will generally stay below 21 kt over the inner waters, but there could be isolated gusts up to 25 kt Saturday afternoon and evening. Despite the uptick in winds, seas are not expected to respond much, likely staying below 7 ft. Winds turn more offshore and weaken on Sunday before becoming northwesterly by Monday afternoon with seas remaining relatively low. -23

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 5 AM PDT Sunday for PZZ271>273.