textproduct: Portland

SYNOPSIS

Rain returns this weekend with a weak atmospheric river on Saturday and again on Monday into Tuesday. Breezy easterly winds near the mouth of the Gorge are possible on Saturday into Sunday morning but confidence is low. Storm and Gale Force Winds over the waters on Saturday. Showers persist on Wednesday through the remainder of the week.

LONG TERM...Sunday Night through Friday

As we move into early next week, things become a bit more complicated. Models suggest another round of rain on Monday into Tuesday - this time associated with a slightly stronger atmospheric river. Still on the weaker side, there will be the potential for more widespread precipitation. The challenge is that the precipitation will fall within a narrow band (as is common with atmospheric rivers) and where that band falls is still to-be-determined. Models continue to fluctuate between impactful rainfall, to our typical rainfall totals based on the location of the atmospheric river. Currently it is trending further south, but it easily could shift northward over the next few days. Model ensembles help paint this picture well. The 24-hour rainfall totals in Newport for example range from 1.5 inches to 2.5 inches on Monday into Tuesday, and for Portland Airport span from 0.75-1.5 inch in 24-hours. Given the long duration of the rain in the atmospheric river, the previous days of rain, and the snowfall from the last several days, we cannot rule out isolated flooding. Confidence is incredibly low as there is less than a 10% chance of our most prone rivers reaching action or minor flood stage on Tuesday. However, if this band shifts northward then those probabilities may rise as we will see more of the accumulation. We will continue to monitor, but if you see a widely fluctuating rainfall forecast, the location of the atmospheric river is to blame.

Showers persist through Wednesday then the flow becomes zonal as a weak area of high pressure forms late in the afternoon. Some rain potential remains through Friday but overall it resembles that of our typical rain forecast. -27

AVIATION

Generally VFR conditions across the airspace with pockets of MVFR conditions within the Willamette Valley. Flight conditions are expected to continue to improve over the next few hours towards VFR. Winds generally southerly across the airspace, but will become more easterly through 00Z Sat as an offshore pressure gradient sets up. This offshore gradient combined with increasing high clouds will help to maintain VFR conditions across the airspace through at least 10Z-14Z Saturday.

A weak frontal band starting around 08Z Sat looks to bring a mixture of VFR/MVFR conditions as it moves northward across the airspace. This frontal band will impact areas around KPDX 12Z Saturday. Rain is expected with this front. South/southeasterly winds will also return to the coast with gusts around 25 kt for areas around KONP. The front will also aid in increasing the easterly winds around the western end and the mouth of the Columbia River Gorge with gusts around 25 kt. These gusts are expected to impact KTTD starting around 13Z Sat with a 35% chance of gusts up to 35 kt.

KPDX AND APPROACHES...Lingering MVFR conditions should improve to VFR through 22Z Fri. Afterwards, VFR conditions expected to persist with light, southerly winds through at least 10Z Saturday. A weak frontal band towards the end of the TAF period brings a mixture of VFR/MVFR conditions starting around 12Z Sat in addition to light rain. Around 13Z-15Z Sat, easterly winds from the mouth of the Columbia River Gorge are expected to increase, but these increasing winds will likely (75-85% chance) not impact KPDX. -42

MARINE

Largely benign conditions tonight across all waters. However, a robust system, moving into the region from the south will bring elevated winds and seas across all waters through the weekend. Expect Gale Force gusts across the outer waters, starting late tonight with gusts up to 40 kt. Inner waters will also see an increase in winds, but should remain below Gale Force, but cannot rule out some isolated gusts up to 35 kt. As the main body of the system continues to track northward, Storm Force gusts up to 50 kt are expected for zones PZZ272 and PZZ273 starting Saturday morning through very early Sunday morning. Zone PZZ271 could see isolated gusts up to 50 kt from Saturday morning through very early Sunday morning. Seas will also build across all waters, peaking Saturday night/Sunday morning in the upper teens for the inner waters and 20-23 ft for the outer waters. Therefore, have upgraded the Gale Watch to a Gale Warning and Storm Warning, with the Hazardous Seas Watch for the inner waters and the Columbia River Bar being upgraded to a Hazardous Seas Warning. On Sunday, winds and seas will start to slowly subside with wind gusts below 20 kt and sub 12 ft seas expected by Monday. Conditions expected to continue to subside further as the middle of the week approaches. -42

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Hazardous Seas Warning from 1 AM Saturday to 7 AM PST Sunday for PZZ210-251>253. Gale Warning from 1 AM Saturday to 7 AM PST Sunday for PZZ271. Gale Warning from 1 AM to 10 AM PST Saturday for PZZ272-273. Storm Warning from 10 AM Saturday to 1 AM PST Sunday for PZZ272-273.