textproduct: Portland

SYNOPSIS

High pressure overhead is keeping northwest Oregon and southwest Washington warm and dry today. Out over the Pacific, a storm system is organizing and is expected to become a slow-moving closed low late this weekend into early next week. That will gradually bring more clouds on Monday, then a better chance for cooler, wetter weather by the middle of the week. Confidence is increasing that showers become more likely late Monday into Tuesday as the system begins to spread moisture inland. Wednesday still looks like the coolest and most showery day overall.

LONG TERM...Monday through Friday

On Monday, the offshore low pressure system will start to have more influence on our weather. Expect more cloud cover and slightly cooler temperatures compared to the weekend. Highs should generally be in the upper 60s to near 70 inland, and upper 50s to low 60s along the coast. Rain shower chances increase late Monday into Tuesday as the system begins to move closer and spread moisture inland, with the first steadier showers most likely over the higher terrain and the southern Willamette Valley. Even so, precipitation through Monday looks light overall, generally around 0.05 to 0.15 inch where showers occur.

Tuesday is still the trickiest day. While exact timing still needs refinement, confidence is higher that at least scattered showers will reach more of the area sometime late Monday into Tuesday, rather than staying largely offshore. If showers do begin Tuesday, they would most likely show up first along the coast and in areas farther south and west, then spread inland later.

Confidence is higher for Tuesday night into Wednesday: this is the most likely period for a more widespread cooler, and showery pattern across the area. The Coast Range and Cascades will be favored for more persistent showers due to terrain enhancement. While rain amounts remain uncertain, expect around 0.25 to 0.75 inches in the lowlands and around 1 to 1.75 inches in the Coast Range and Cascades from 5 PM Tuesday to 5 PM Wednesday.

By Thursday and Friday, the pattern looks like it will trend drier again with temperatures slowly warming back up into the mid 60s and maybe 70s by Friday. A few leftover showers near the mountains are possible early in that period, but overall conditions should improve late week. ~12

AVIATION

High pressure will maintain widespread VFR flight conditions through 00Z Monday with scattered to broken high clouds around 20-25 kft. Winds will remain light and variable less than 5 kt, with one exception. Easterly winds at KTTD will remain breezy through at least 22Z Saturday with occasional gusts up to 20-25 kt before east winds gradually decrease in strength between 22-00Z. Expect easterly winds to restrengthen a bit between 12-18Z Sunday.

KPDX AND APPROACHES...Scattered to broken high clouds with cigs above 20-25 kft will maintain VFR flight conditions through 00Z Monday. Variable winds around 5 kt or less are expected to become easterly towards 17Z Sunday with sustained wind speeds approaching 10 kt. -23

MARINE

Benign conditions continue through the weekend. Southerly to southwesterly winds between 5-15 kt continue today with seas under 5 ft. Winds will weaken and become east to southeast by early Sunday morning. Winds then remain light through early next week with seas increasing by a few feet, but staying under 10 ft.

An area of low pressure sitting off the coast will move inland during the middle of next week. This will bring onshore flow, showers, and increasing winds and seas. However, uncertainty remains regarding exact wind speeds and wave heights. The placement of the low will determine what conditions materialize across the waters. The current forecast favors a period of increasing west to northwest winds late Tuesday into Wednesday with wind gusts reaching 20-25 kt or stronger by Wednesday afternoon. In fact, there is a 50-75% chance for max wind gusts over 25 kt. The highest probabilities are beyond 30 NM offshore. Seas are expected to reach at least 10-12 ft by late Wednesday, however there is a 40-70% chance seas will peak over 12 ft over the northern and central outer waters. There is a 1-5% chance seas will peak as high as 15 ft, which represents the worst case scenario.

Very strong ebb currents will continue across the Columbia River Bar each morning through Tuesday. With seas expected to build slightly by early next week, a steep ebb chop may necessitate Small Craft Advisories in the hours around peak flow each day. -23

PQR WATCHES/WARNINGS/ADVISORIES

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