textproduct: Portland

SYNOPSIS

An early-season frontal system will bring widespread rain and gusty winds to the region this evening through much of Friday. The progressive pattern will see dry weather quickly return late Friday through the weekend, before chances for rain increase again early next week.

LONG TERM...Saturday through Thursday

The progressive pattern aloft will see upper-level ridging and surface high pressure support dry weather through the weekend, although moderating temperatures are still likely to remain below seasonal norms. Cool overnight lows may favor further chances for frost in the Upper Hood River Valley, with decreasing confidence after Saturday morning. The majority of long-range ensemble members favor troughing to return to the Pacific Northwest early next week, although there remains much spread in its intensity and location. Chances for rainfall therefore increase again to 20-40% Monday through Wednesday, generally higher to the north and within areas of terrain. -36

AVIATION...Through 00Z Friday

Satellite imagery and terminal observations as of late Thursday morning depicts widespread high clouds ahead of the next system. Radar also shows rain approaching KAST as a weak shortwave ahead of the next system passes through. This evening, an approaching frontal system will bring widespread rain to the coast beginning 00-02z Fri, spreading into the Willamette Valley by 02-04z Fri. Will see more moderate rain as the front moves inland, resulting in potential VIS reductions to 4-5SM between 03-06z Fri along the coast and 06-09z Fri for Valley terminals. By this time, there is high confidence for CIGs dropping to IFR/MVFR along the coast. By 09-10z Fri, rain will transition into on-and-off showers, and it will be then that we see high confidence for CIGs dropping to MVFR across most of the Valley. Will also see winds increasing this evening and turning more southerly to southwesterly. The breeziest winds are expected behind the front after 10-12z Fri, when we could see gusts to 30-40 kt along the coast and 20-30 kt across the Willamette Valley through the end of the TAF period.

By Friday afternoon, increasing instability will result in a 10-20% chance for thunderstorms. Any passing thunderstorms may produce lightning, heavy rain leading to VIS reductions, gusty and erratic winds, and small hail.

KPDX AND APPROACHES...VFR conditions with high clouds through this afternoon. This evening, CIGs drop to low-end VFR with return of rain as the front approaches. As the front moves through late this evening, will see moderate rain with potential VIS reductions to 4-5SM. Post-frontal conditions with MVFR CIGs after 10-12z Fri. Southerly to southwesterly winds under 10 kt through this evening, increasing to 10-15 kt with gusts to 25-30 kt after 10-12z Fri. -10

MARINE

A strong low pressure system will move over the coastal waters tonight into Friday, bringing rapidly increasing winds and seas along with widespread rain. Gale Warnings are in effect beginning 5 PM Thursday for the waters south of Cape Foulweather, and 11 PM Thursday for the waters north of Cape Foulweather including the Columbia River Bar. These Gale Warnings are followed by Hazardous Seas Warnings that last through Friday afternoon/evening.

Given that the low pressure system will be coming from the southwest, will see winds ramp up across the southern waters at first, then gradually increase towards the northern waters heading into tonight. Expect widespread wind gusts as high as 40-45 kt with a 30-50% chance for brief and isolated storm-force wind gusts to 50-55 kt. Expect steep and choppy seas that are wind-driven. Seas build to around 9-11 ft at 10 sec tonight into early Friday morning, peaking late morning around 15-17 ft for the waters beyond 10 NM, and peaking early afternoon around 14-16 ft for the inner waters up to 10 NM offshore. Seas will gradually subside Friday afternoon as winds quickly weaken. By late Friday evening, seas fall to around 7-9 ft at 9 seconds. Northerly winds increase over the weekend, strongest Saturday afternoon and evening when wind gusts increase to 20-25 kt. -10

PQR WATCHES/WARNINGS/ADVISORIES

OR...Wind Advisory from 8 AM to 8 PM PDT Friday for ORZ121.

WA...None.

PZ...Gale Warning from 11 PM this evening to 2 PM PDT Friday for PZZ210-251-252-271-272.

Hazardous Seas Warning from 2 PM to 8 PM PDT Friday for PZZ210- 251-252-271-272.

Gale Warning from 5 PM this afternoon to 11 AM PDT Friday for PZZ253-273.

Hazardous Seas Warning from 11 AM to 5 PM PDT Friday for PZZ253-273.