textproduct: Portland

SYNOPSIS

Dry weather is expected through Saturday with overnight and early morning frost/freeze conditions across much of the region. Rain chances increase early Sunday morning as a broad upper level low moves over the region. An semi-active pattern continues through the middle of next week, with a brief period of dry conditions expected Tuesday with another round of light precipitation expected Wednesday. Beyond Wednesday, uncertainty increases as models ensembles diverge significantly from each other.

DISCUSSION...Today through Friday

Transient upper-level ridging continues through this evening bringing clearing skies and light, offshore flow to the region. However, by tonight a broad upper level trough from the Gulf of Alaska will bring precipitation back into the forecast through at least early Monday morning. Current, high resolution ensemble guidance has rain beginning at the coast early Sunday morning and reaching inland locations through the afternoon, with the bulk of the precipitation expected to cease by Monday morning across the region. At this point, the chances for 0.25 inches of rain or more from 5 AM Sunday through 5 AM Tuesday are 80-90% along the coast and Coast Range, 70-80% along the I-5 corridor, and 60-70% in the Cascades and foothills. Even with the influx of precipitation into the region, seasonable conditions with milder overnight temperatures are expected to persist through at least the middle of next week. As the middle of next week approaches, forecast confidence decreases as the early week low pushes eastward, although long-range guidance does continue to support additional chances for rain, with 30-40% of ensemble members bringing another weather system to the Northeast Pacific Wednesday/Thursday, this system is not expected to be as impactful as the Sunday/Monday one. Overall, seasonable temperatures are favored to continue into the final week of October. As for those wondering what is expected for the final Saturday in October, ensemble guidance is pointing towards a drier solution with overnight lows above freezing. /42-36

AVIATION...Through 18Z Sunday

Satellite and surface weather observations from 18Z Saturday depicted broken high clouds with ceilings above 20 kft and light surface winds, resulting in widespread VFR conditions. One exception is at KAST where a low stratus deck continues to bring LIFR conditions, however this stratus deck is localized and shallow and should scatter out by 19Z Saturday. Expect high clouds and light winds to continue through this evening.

Between 09-14Z Sunday, a front will approach the coast and bring light rain and lowering ceilings. This front will slowly move towards inland terminals between 15-23z Sunday, with chances for ceilings below 3000 ft increasing to 30-50% towards the end of the 18Z TAF period. Lowering ceilings will be accompanied by the beginning of light rain.

KPDX AND APPROACHES...Expect high clouds above 20 kft through this evening with light and variable winds less than 5 kt. Southeast winds around 5-10 kt develop towards 10-12Z Sunday ahead of an incoming front. This front will bring increasing chances for rain and lowering ceilings towards the end of the 18Z TAF period. CHances for ceilings below 3000 ft increase to 30-40% by 17-18Z Sunday. -23

MARINE

A slow-moving low will approach the outer waters late tonight into Sunday, bringing a transition to southerly winds. This system will also result in building seas towards 8 to 10 ft with southerly wind gusts approaching 25 kt. These conditions are expected to start in zone PZZ271 before spreading south and eastward through tonight. As a result, have issued a series of Small Craft Advisories across all waters through at least late Sunday night. By the start of next week, conditions look to subside below Small Craft Advisory thresholds. However, another system is expected to impact the waters by mid- week and result in around a 20%-30% chance for Small Craft conditions to return. /42

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 11 PM this evening to 11 PM PDT Sunday for PZZ251.

Small Craft Advisory from 2 AM to 11 PM PDT Sunday for PZZ252- 272.

Small Craft Advisory from 8 AM to 11 PM PDT Sunday for PZZ253- 273.

Small Craft Advisory from 8 PM this evening to 11 PM PDT Sunday for PZZ271.