textproduct: Portland

SYNOPSIS

Unseasonably warm and dry weather will give way to cooler temperatures and chances for light rain as an upper trough moves over the region Friday into Saturday. Cool nights will bring chances for morning frost in rural valleys away from urban cores this weekend into early next week. Dry conditions with seasonable temperatures are expected Sunday and Monday before another round of light rain is possible on Tuesday.

LONG TERM...Sunday through Wednesday Night

Ensemble guidance is in good agreement that the elongated upper trough drops south over California on Sunday and eventually splits into a cutoff upper low early next week. Weak upper level ridging of the NE Pacific will nudge back over the region, leading to dry and more seasonably warm temperatures into the mid to upper 60s. Sunday morning will feature a near-repeat of Saturday morning, if not cooler under more clear skies, with widespread chances for frost in sheltered valleys away from urban areas and chances for a freeze within the Upper Hood River Valley. There is increasing consensus among long-range ensemble members in additional upper-level troughing moving into the region Tuesday into Wednesday. At this point, low to moderate (35- 55%) chances for rain are assessed during this period until confidence in the evolution of this feature increases. DH/36

AVIATION...Through 06Z Saturday

VFR conditions persist inland while marine stratus has moved in along the entire coast, supporting MVFR or lower CIGs. Upper level clouds are streaming in along westerly flow ahead of an approaching trough and frontal system. The trough is expected to bring rain to KAST around 12Z and then interior lowland terminals around 15-20Z as the front moves southward (KPDX: around 15Z, KEUG: around 19Z). Additionally, this trough will bring a 40-70% chance of MVFR CIGs.

Light north to northwest winds around 5 kt will ease overnight. Winds inland are expected to increase ahead of the front, initially out of the south around 5 kt but will quickly turn westerly with the passage of the front along with increasing to around 10 kt and gusts. Winds along the coast will remain northwesterly through the period but will increase behind the front to 10-15 kt with gusts around 20 kt.

KPDX AND APPROACHES...VFR with high cloud cover through most of the period. A trough approaching will bring a chance of rain to around 16Z Fri and a 40-60% chance of MVFR CIGs. Additionally, winds will likely increase tomorrow afternoon, to around 8 to 10 kt. -19

MARINE

High pressure at the surface over the northeastern Pacific today continues to bring afternoon/evening wind gusts of 20-25 kt. As a result, Small Craft Advisories for the waters south of Cape Falcon remain in effect until 11 PM tonight. Anticipate largely wind-driven seas of 6-9 ft with an underlying west-northwest swell during the advisories. While weakening high pressure aloft would continue to support areas of fog in the morning hours tomorrow, an approaching weather system that will bring rain and wind will likely inhibit fog from becoming dense.

This weather system on Friday and through the weekend, which is a trough over the Gulf of Alaska pushing southward, will generate a northwest swell in addition to the arrival of a frontal boundary. Winds out of the northwest associated with the frontal boundary will increase to around 20 to 25 kt on Friday, especially north of Cape Falcon, while seas peak at 8-12 ft Friday evening into Saturday. By Sunday, winds ease and veer out of the north to north-northeast while seas fall back to 5-7 ft through early next week. ~12/36

PQR WATCHES/WARNINGS/ADVISORIES

OR...Frost Advisory from midnight Friday night to 9 AM PDT Saturday for ORZ121.

WA...None.

PZ...Small Craft Advisory from 11 AM to 6 PM PDT Friday for PZZ210.

Small Craft Advisory from 8 AM to 2 PM PDT Friday for PZZ251.

Small Craft Advisory until 11 PM PDT this evening for PZZ252- 253-272-273.

Small Craft Advisory from 5 AM to 2 PM PDT Friday for PZZ271.