textproduct: Portland

SYNOPSIS

Conditions remain cool and wet today as an upper level low and surface fronts move over the region. A warming and drying trend is expected Thursday and through the start of next week as high pressure builds over the eastern Pacific.

DISCUSSION...Now through Tuesday Night

Shower activity has dropped off over much of the area as the upper level low shifts eastward. Radar imagery as of 2 am does show scattered showers persisting over the Cascades and Cascade Foothills along westerly surface flow. Precipitation is expected to increase as a weak cold front drops in from the northwest, bringing another round of light rain through the day. Rain is expected to enter the northern portion of the forecast area around 5 am and spread southward through the morning. Conditions trend drier from north to south through the afternoon and evening, though showers linger over the Cascades and Cascade Foothills into the overnight hours. Rainfall totals are expected to be light west of the Cascades ranging from a few hundredths in the for rain shadowed portions of the Willamette Valley to around 0.35 inches over parts of the Coast Range. Higher totals between 0.25-0.50+ inches over the Cascades are expected with terrain enhancement supporting more forcing. There is a low (10-15%) chance for thunderstorms over the Lane and Linn count Cascade Foothills this afternoon.

Showers may linger over the Cascades Thursday morning but conditions are expected to trend warmer and drier through the day and into the weekend. Highs bounce back into the low 60s inland and mid to upper 50s along the coast. Upper level ridging over the eastern Pacific tries to build into the PacNW heading into the weekend but a large upper level low over central Canada and the northern Plains will hinder its eastward momentum. There is some uncertainty in what the upper level pattern looks like over the region by Saturday, split between the pinch point of the upper level features or possibly shortwave energy coming more overhead. Either way, conditions are expected to remain dry with relatively minor differences in high temperatures Friday through Monday. Highs in the mid 60s to low 70s inland and upper 50s to low 60s each day can be expected. The Cascades could see light scattered rain showers each day, mainly during the afternoon and evening hours. -19

AVIATION

Currently MVFR along the coast and VFR inland with cloud cover hovering around 3-5 kft with light west to northwest winds around 5 kt. Scattered showers continue over the Cascade. Expecting conditions to trend toward MVFR inland and possibly IFR along the coast as a week cold front drops through the area starting early this morning. Precipitation will be light but lower clouds should lower to 1500-2500 ft as the front passes through. Winds are also expected to increase from the southwest after 12z. Gusts for all terminals could reach 20 kt between 15z Wed and 03z Thu, slightly earlier along the coast with gusts up to 25 kt possible. KTTD and the western Columbia River Gorge will also see higher winds up to 30-35 kt due to the enhanced pressure gradient in the area. Winds all appear to be unidirectional and therefore LLWS is not a threat at this time.

KPDX AND APPROACHES...VFR conditions with light northwesterly winds around 5 kt. Another cold front is expected to move through the area beginning around 12-15z, bringing MVFR CIGs and gusty southwest winds. CIGs are expected to drop to between 1500-2500 feet. Wind gusts of 20-25 kt possible after 16-18z today with higher gusts to around 30 kt at KTTD. -19

MARINE

A cold front approaching from the northwest will bring increasing seas and westerly to northwesterly winds. By early to mid morning, a northwest swell will push seas up to 7 to 8 ft with westerly winds around 15 to 20 kt with gusts up to 25 kt over the central and northern waters. The southern waters will see winds and seas increase a bit later in time, beginning this afternoon. Seas peak between 9-13 ft Wednesday evening into tonight at 10 to 12 seconds, bringing steep and hazardous seas. The highest seas are expected over the northern outer waters beyond 20-30 nm. Winds decrease tonight behind the frontal passage, however seas will remain elevated until significant wave heights fall below 10 ft by late Thursday afternoon.

A Hazardous Seas Warning will be in effect for PZZ271 from 2 PM PDT today through 5 AM PDT Thursday, following a Small Craft Advisory that begins at 5 AM PDT today. The remaining marine zones have Small Craft Advisories in effect from 5 AM today until 5 PM PDT Thursday, except 5 PM today until 5 PM PDT Thursday for the southern waters as winds and seas take longer to increase south of Cape Foulweather. Note there is a 10-25% chance seas will peak near 14-15 ft over the northern outer waters, which represents a reasonable worst case scenario.

A strong ebb current will occur in the Columbia River Bar this morning, peaking around 9 AM and pushing seas up to 7 to 8 ft with steep ebb chop over the main channel. Seas then increase to around 9 to 10 ft over the main channel late today and remain elevated tonight into Thursday. In addition, westerly winds will increase to 15 to 25 kt with gusts up to 25 kt. Winds will become southwest around 10 kt with gusts up to 15 kt Thursday morning. A Small Craft Advisory has been issued from 5 AM PDT today to 5 PM PDT Thursday for the Columbia River Bar to cover these hazards. A second strong ebb current is expected Thursday morning, peaking around 10 AM. -19/23

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 5 AM early this morning to 5 PM PDT Thursday for PZZ210-251-252-272. Small Craft Advisory from 5 PM this afternoon to 5 PM PDT Thursday for PZZ253-273. Small Craft Advisory from 5 AM early this morning to 2 PM PDT this afternoon for PZZ271. Hazardous Seas Warning from 2 PM this afternoon to 5 AM PDT Thursday for PZZ271.