textproduct: Portland

SYNOPSIS

Light rain showers continue through Monday morning, then a passing ridge will support drier conditions Tuesday and Wednesday. The next impactful system arrives during the latter half of the week, and while its evolution remains uncertain, lowland rain and mountain snow are possible.

LONG TERM...Wednesday through Sunday

Dry conditions continue into Wednesday afternoon before the next frontal system moves onshore. Some uncertainty persists in the evolution of this system, particularly whether the bottom of the approaching trough again pinches off to form a closed upper low moving into California, or if the trough remains more coherent as it tracks over the Pacific Northwest. In the former case, much of the region would be left with weaker forcing for precipitation and a weaker push of cold air, leading to both lower lowland rainfall and mountain snowfall. In the latter case, increased support for precipitation along with colder air aloft could support more impactful mountain snows, however the chances for significant accumulations of 6 inches or more at pass level are 10% or less. Chances for even light accumulations of one inch at pass level are only 45-55% at Santiam and Willamette Passes, and 10-15% along US-26 near Government Camp. Otherwise, near to slightly above normal temperatures in the low to mid 50s and overnight lows in the upper 30s to mid 40s. -36

AVIATION

Largely MVFR flying conditions continue as light rain showers linger behind an earlier frontal passage. Cigs at 2-4 kft and vis of 5-7 SM will likely (60-80% chance) continue through 15-18z Mon as skies trend clearer and cigs lift above 4 kft. Showers will dwindle in coverage through the afternoon, ending by 21-24z Mon without further impacts to area terminals. North to northwest winds at 5-10 kt continue across the region with gusts to 15 kt along the coast, easing to 5 kt or less after sunset. There are low probabilities of fog late in the period, most likely at KEUG after 09z Tue.

KPDX AND APPROACHES...MVFR conditions expected to trend to VFR by 15-16z Mon as cigs lift to 4 kft. Light rain showers linger through the morning with limited terminal impacts, then dissipate after 21z Mon. Northwest winds at around 5 kt ease to 3 kt or less after sunset. -36

MARINE

North-northwesterly winds with gusts up 25 knots persist across the waters behind the recent frontal passage while seas have built to 10-14 ft at 12-13 seconds. Winds and seas alike will continue through this afternoon before easing below 10 kt and 10 ft, respectively this evening. Small Craft Advisories therefore remain in effect through 7 PM PST for the Columbia River Bar, and through 10 PM PST elsewhere.

A brief reprieve from the active weather is expected Tuesday and Wednesday as seas subside to 5-8 ft at 11-12 seconds. Winds will similarly ease while remaining out of the northwest through Tuesday night. Late Wednesday through the weekend, a more active pattern returns as another frontal system moves into the region increasing wind gusts to 20-30 kt. A building westerly swell will see a 60-75% chance of seas reaching 15 ft or higher beyond 20 NM, and lesser chances nearer to the coast. There is roughly a 10% chances seas reach 20 ft beyond 20 NM. Seas are expected to peak Thursday evening or early Friday morning, then will be slow to subside, remaining above 10 ft into the weekend. -36/42

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 7 PM PST this evening for PZZ210. Small Craft Advisory until 10 PM PST this evening for PZZ251>253-271>273.