textproduct: Portland

SYNOPSIS

A frontal system continues impacting the region with gusty winds and showers for far northern Oregon and SW Washington. Dry weather is favored again by Wednesday, likely lasting into early next week with temperatures trending warmer day to day.

DISCUSSION...Tuesday afternoon through Monday

A frontal system continues moving southeast toward SW WA and NW OR this afternoon. Gusty winds with gusts up to 25-35 mph have been observed this morning and will continue through this afternoon, mainly for the coast north of Lincoln County and adjacent terrain as well as for the far northern OR Cascades. Showers are also occurring in the same area and portions of the SW WA lowlands north of the Vancouver metro. As the cold front moves inland this evening, winds and showers will quickly decrease.

Ensemble members are in very good agreement through the weekend that dry weather returns on Wednesday and will continue through at least Sunday. High pressure over the eastern Pacific will move inland over the next few days then peak over the PacNW on Saturday and Sunday. This will lead to a warming trend for the area through the week. Temperatures tomorrow will be a few degrees warmer than today for locations that see cloud cover today, with another few degrees of warming for Thursday. The interior lowland are expected see temperatures in the low to mid 70s tomorrow and the mid to upper 70s for Thursday and Friday. Temperatures then warm to the upper 70s to low 80s for Saturday and Sunday for the interior lowlands, with upper 60s to low 70s along the coast and terrain. By Monday, the vast majority of ensemble members indicate the ridge axis shifts east of WA and OR, allowing temperatures to begin lowering again into the 70s for the interior valleys with dry weather continuing.

Ensembles indicate a thermal trough will develop along the coast at the surface under the high pressure aloft Friday through this weekend. This pattern is expected to cause winds to shift from the onshore (westerly) pattern the area has generally been observing over the past couple of weeks to offshore (easterly to northerly). At this time, pressure gradients don't look to be very high, so winds aren't expected to be strong. Instead, expect to see a typical diurnal behavior of winds becoming easterly on the west side of terrain in the overnight to morning hours and increasing to peak gusts up to 20-25 mph. Then, winds decrease over the terrain during the day and increase through the valley from the north in the afternoon hours, also peak gusts up to 20 mph. The probability of wind gusts peaking above 30 mph is less than 10% everywhere except for through the western Columbia River Gorge and surrounding terrain at 50-65%, which is generally the windiest location during offshore flow. -03

AVIATION...Through 18Z Wednesday

Westerly flow aloft continues with moist onshore flow in the lower levels. This will maintain mostly cloudy skies with IFR to MVFR stratus at the coast, and a mix of MVFR and low-end VFR inland. Probabilities for widespread VFR inland increase after 00-02z Wed. But, CIGs are expected to lower again late tonight into Thu morning with around a 60-70% chance of MVFR after 09-14z Thu. At the coast, IFR conditions are favored through 00z Thu with more uncertainty in the forecast after the cold front pushes inland, as some guidance suggests conditions improve while others suggest conditions worsen. Southerly winds will be strongest along the north Oregon coast today with gusts to around 25 kt through this afternoon near KAST. Winds become light behind the front and overnight.

KPDX AND APPROACHES...Cloudy skies with CIGs jumping between MVFR and low-end VFR this morning, likely becoming predominately MVFR this afternoon. Then CIGs are expected to lift back to VFR by 00-01z Thu. Chances for MVFR CIGs again increase to above 60% after 10z Thu as the front sags through the area. Southerly winds around 5-9 kt become light later this evening. /DH

MARINE

This afternoon a frontal boundary is slowly dropping south across the waters with southerly wind gusts in the 20-30 knot range peaking north of Cape Falcon, especially right along the coastline. A Small Craft Advisory remains in effect for coastal waters north of Cape Foulweather, including the Columbia River Bar, into the late afternoon and early evening hours. Behind the front, winds are expected to abruptly shift to the northwest, transitioning to a somewhat lighter northerly wind pattern Wednesday. Another weak system may approach the northern waters from the west on Thursday, but it likely holds north as it moves toward the Washington coast then out of the region to the east. Northerly winds then return Friday, likely persisting over the weekend.

A mid-period west-northwesterly swell of 6 to 8 ft at 11-12 seconds continues to move through the coastal waters through tonight, increasing significant wave heights into the 8 to 10 ft range. Seas then gradually subside to around 4 to 6 ft later in the week with no other prominent swells of note at this time. -99/DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ210.

Small Craft Advisory until 5 PM PDT this afternoon for PZZ251- 252-271-272.