textproduct: Portland

SYNOPSIS

The low pressure system that has brought scattered showers today continues to spin over the OR/CA border. A frontal system is traversing northern Oregon bringing rain to the lowlands and snow to the mountains. High pressure builds on Saturday which will lead to clear and dry weather through much of next week.

LONG TERM...Tuesday through Friday

Cold weather persists through at least Wednesday as high pressure lingers. Transitioning into Thursday is when conditions get a bit more complicated. The upper air pattern suggests a dirty ridge continuing over the area, while some of the ensembles suggest a long wave trough moving in bringing precipitation and slightly warmer air. While at the mid-levels the trough looks more likely, aloft the ridge is better supported. Given the lack of vertical support, the change in the pattern will be harder to support. Given the pervasive nature of the ridge, the low must be robust enough to erode it completely on Thursday. At this point, that does not look to be the case but there is still ample time for consensus to form. -27

AVIATION

A frontal system continues moving east through NW Oregon and SW Washington as of 22z Friday, and should move east of the Cascades by 00-02z Sat. A widespread band of stratiform showers is moving through the region ahead of the front. Conditions will fall to predominately MVFR ceilings as the band of showers moves over the terminal. Scattered showers will continue through the rest of the TAF period behind the front, less stratiform in nature. Conditions return to predominately VFR after behind the front, with periodic brief drops to MVFR if heavier showers move overhead. Winds currently shifting from southerly to westerly as the front approaches. Along the coast, winds 12-15 kts with gusts up to 20-25 kts, decreasing after 18z Sat. Winds at inland terminals will remain mainly less than 10 kts, except over the Cascades where winds will also increase after 00z Sat with gusts up to 25-30 kts, also decreasing after 18z Sat. There's about a 10-20% chance that low stratus or fog could develop and produce MVFR/IFR conditions in the southern Willamette Valley between 12-18z Sat. However, surface temperatures will be in the mid to low 30s deg F, which is likely cold enough to limit fog/stratus formation.

KPDX AND APPROACHES...A mix of VFR and MVFR conditions with light rain showers through around 00z Sat. Scattered rain showers continue through the rest of the TAF period with mainly VFR conditions, occasional brief drops to MVFR in heavier showers. West winds less than 10 kt. -03

MARINE

A front continues moving through the waters this afternoon with winds shifting northwesterly behind it. Winds continue increasing with gusts up to 25-30 kts north of Depoe Bay. Seas also build to 11-15 ft at 10 to 12 sec across all waters, highest north of Cascade Head. A Hazardous Seas Warning remains in effect for all outer water zones and a Small Craft Advisory for all inner waters and the Columbia River Bar through at least Saturday afternoon for a combination of winds and seas.

Winds begin decreasing early Saturday morning, along with seas slowly subsiding through the day Saturday, with conditions falling below Hazardous Seas and Small Craft thresholds by late Saturday afternoon. A ridge of high pressure builds overhead late Saturday into Sunday. Winds decrease to less than 15 kts by Saturday night and seas settle in the 4-6 ft range, continuing into Sunday. -03

PQR WATCHES/WARNINGS/ADVISORIES

OR...Winter Weather Advisory until 4 PM PST Saturday for ORZ126>128. WA...Winter Weather Advisory until 4 PM PST Saturday for WAZ211. PZ...Small Craft Advisory until 3 PM PST Saturday for PZZ210- 251>253. Hazardous Seas Warning until 3 PM PST Saturday for PZZ271>273.