textproduct: Portland

SYNOPSIS

A steady warming trend will continue through the weekend as high pressure strengthens across the region. Inland temperatures will rise into the 80s this weekend, then into the upper 80s to mid 90s early next week. Hot and dry weather is expected to persist through at least midweek, with increasing heat impacts possible across the interior lowlands.

DISCUSSION...Now through Friday

A large-scale pattern early this morning continues to favor warming and drying across southwest Washington and northwest Oregon. Upper-level ridging is building inland while surface onshore flow lingers just enough to temper the rate of warming, especially near the coast. Even so, heights aloft will continue to rise through the weekend as the ridge becomes more firmly established over the Pacific Northwest. In response, inland temperatures will trend upward day by day, while coastal areas remain noticeably cooler under continued marine influence.

For today, inland highs should climb into the lower to mid 80s, warmest across the interior valleys. By Sunday, most inland locations are expected to reach the mid to upper 80s. Along the coast, highs will remain much more seasonable, generally in the 60s to lower 70s today and Sunday. Higher terrain will also warm through the weekend, with afternoon temperatures rising into the upper 70s to mid 80s.

Attention then turns to the hotter portion of the forecast from Monday through Wednesday, when the ridge is expected to peak in strength. Confidence remains highest in Monday's forecast, with interior lowland highs generally in the upper 80s to lower 90s. Beyond that, uncertainty grows for Tuesday and Wednesday. Much of the uncertainty appears tied to how a low off the California coast evolves and whether some monsoonal moisture is able to lift northward into the region. Even modest increases in cloud cover or moisture could influence afternoon temperatures, and ensemble guidance reflects that with a broader spread in the forecast by midweek.

Despite that uncertainty, the overall message remains the same: Tuesday and Wednesday still appear likely to be the hottest days of the period for many inland locations. Probabilistic guidance continues to support a moderate to high chance of 90-degree temperatures across much of the interior lowlands, with the higher odds on Tuesday and Wednesday. There is also a meaningful chance (20-30% chance on Monday, 30-50% chance on Tuesday and Wednesday) that some of the traditionally warmer valleys push into the mid 90s. With several consecutive hot afternoons and only limited overnight cooling, Moderate HeatRisk appears increasingly likely for portions of the interior lowlands, especially for those without effective cooling or for anyone spending extended time outdoors. There is also a lower-end chance (15-35%) for pockets of Major HeatRisk if temperatures end up on the warmer side of the forecast envelope.

By Thursday and Friday, guidance still favors a slight easing of the heat as a broader upper-level low begins to shift east into the Pacific Northwest. Even so, temperatures may remain above normal, and confidence in the exact magnitude of cooling remains lower than average given the spread that develops by the middle of the week. Overall, the forecast continues to support an extended stretch of dry weather with the most notable hazard being the building heat inland. ~12

AVIATION

West to southwesterly flow aloft continues through the TAF period as an upper low moves through British Columbia. Expect VFR conditions inland and a mix of IFR/MVFR/VFR conditions along the coast through the TAF period. From now until 19-21Z Sat, expect MVFR CIGs at coastal terminals with a 30-50% chance of IFR CIGs anytime before 18Z Sat. Additionally, there is a 10-20% chance of LIFR CIGs before 16Z Sat. While conditions at coastal terminals will likely return to VFR by 19-21Z Sat, expect conditions to once again deteriorate to IFR/MVFR CIGs by 04-07Z Sun as marine stratus pushes back into the coast. Otherwise, expect light northwesterly winds early this morning, then increasing in the late morning/afternoon to around 8-12 kt with gusts up to 20 kt inland and 12-18 kt with gusts up to 20-25 kt along the coast.

KPDX AND APPROACHES...VFR with clear skies through the TAF period. There is a 10-15% chance of MVFR CIGs until 18Z Sat. Light northwesterly winds early this morning increase to around 8-12 kt with gusts up to 20 kt between 20Z Sat and 05Z Sun. ~12

MARINE

A typical summertime pattern will continue through early next week with persistent north to northwest winds over the coastal waters. Winds will be strongest during the afternoon and evening hours each day, especially through weekend for the waters south of Cape Falcon. Expect wind gusts up to 25 kt over the central and southern waters this weekend, with seas becoming steep on Sunday due to a fresh northwest swell around 6-7 ft at 7-8 seconds. By Sunday afternoon, these gusty winds and steep seas will expand into the waters north of Cape Falcon. Between the increasing winds and steepening seas, conditions will become hazardous to small craft. As such, Small Craft Advisories are in effect from Saturday afternoon through late Sunday.

Steep seas early Monday are expected to become less steep through the day as northerly winds decrease. Seas and winds decrease even more on Tuesday, bringing benign conditions. ~12/23

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 2 PM Sunday to 2 AM PDT Monday for PZZ251-271.

Small Craft Advisory from 5 PM this afternoon to 2 AM PDT Monday for PZZ252-272-273.

Small Craft Advisory from 11 AM this morning to 2 AM PDT Monday for PZZ253.