textproduct: Portland

SYNOPSIS

High pressure will maintain dry weather through Friday. Offshore flow will bring unseasonably warm temperatures Thursday and Friday along with gusty east winds in the western slopes of the Cascades and Columbia River Gorge. A weak cold front will bring chances for light rain late Friday night into Saturday, before high pressure brings a quick return to dry weather Saturday night into Sunday. Chances for widespread rain return Monday into early Tuesday with an approaching low pressure system, although model guidance has been trending drier.

LONG TERM...Saturday through Tuesday Night

There is high confidence among ensemble guidance for cooler temperatures this weekend as a weak cold front swings through the region and brings chances for light rain. Light rain begins at the coast Friday night, mainly from Lincoln City northward. Rain chances spread inland Saturday morning, peaking around 40-60% across the south Washington and north Oregon Cascades, 25-50% along the I-5 corridor from Salem northward, and 10-20% south of Salem. Rain amounts, if any, will be light. Conditions quickly dry out Saturday night to Sunday as transient shortwave ridge passes through. Expect seasonable temperatures in the 60s across interior valleys and 50s along the coast and Cascades.

Monday to Tuesday, the majority of ensemble members are in agreement that an upper-level trough from the northeast Pacific will approach the Pacific Northwest, bringing increased chances for widespread rain between early Monday morning and Tuesday morning. This system has the potential, albeit low, to bring a more meaningful amount of rain considering how dry conditions have been thus far this October. The NBM currently shows a 20-35% chance for at least 0.25 inches of rain between 5 AM PDT Monday and 5 AM PDT Wednesday. Probs continue to come down as there are an increasing number of ensemble members showing a solution where the upper-level trough remains farther offshore or progresses farther south into California, limiting the amount of rain in our area. Chances for impactful wind gusts over 40 mph are currently less than 10% with this system. DH/10/23

AVIATION...Through 06Z Friday

VFR conditions across the airspace with mostly clear skies. Strengthening offshore pressure gradients between KTTD and KDLS will result in increasing easterly winds after 06Z Thu. East winds across the Cascades with the strongest winds through the Columbia River Gorge with gusts up to 35 kts. These stronger east winds reach KTTD around 12Z Thursday with gusts up to 30 kts, followed by KPDX around 18Z Thursday with gusts up to 25 kt. Gusty east winds could also manifest for areas near the gaps and flows of the coast range, thus locations near KONP could experience gusts up to 20 kt starting around 17Z Thursday. For other terminals across the central and southern Willamette Valley, winds generally remain north/northeasterly under 10 kt.

KPDX AND APPROACHES...VFR conditions with mostly clear skies through the TAF period. Northwesterly winds 3-4 kt through 12-15Z Thursday, then turning easterly with gusts up to 20-22 kt through the rest of the TAF period. -42/10

MARINE

Benign marine conditions continue. Southerly winds are turning northerly to northeasterly this afternoon, continuing through the end of the week. Winds turn southerly again over the weekend and into early next week as a series of fronts pass through the waters. Seas remain around 4-7 ft this week with periods of 12-14 seconds.

A steeper northwesterly swell arrives this weekend, building seas to 7-9 ft by Sunday and 10-12 ft early next week. There is a 10-20% chance for seas exceeding 15 ft on Monday, with the highest chances north of Cape Falcon and beyond 30-40 NM. Will also note that the long periods from the swells will result in a moderate sneaker wave threat this week. Caution should be used when in or near the water. -10/03

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...None.