textproduct: Seattle/Tacoma

SYNOPSIS

An upper ridge offshore will bring dry, warmer conditions on Wednesday. Troughing develops over the Pacific Northwest Thursday with an upper low bringing cooler conditions and precipitation potential into the weekend. More benign weather appears favorable into the beginning of next week.

SHORT TERM /TODAY THROUGH FRIDAY/

Transient upper-ridging today in concert with a surface thermal trough just off the PNW coast. As a result, dry conditions are favored as light offshore flow and subsidence rise temps into the upper 70s to lower 80s across the interior - slightly above average. Coastal areas are to stay put in the mid to upper 60s. Aforementioned ridging and surface thermal trough will push eastward on Thursday as the pattern progresses. Upper-troughing will develop as low-level flow switches onshore, ushering in marine stratus and cooler temperatures. Troughing further develops over the Pacific Northwest on Friday with a continued cooling trend. Ensembles are in general agreement that an upper low moves southwards offshore Friday with an increase of areas PoPs. Highs forecast in the 60s and 70s on Thursday before settling mainly in the 60s on Friday. Overnight lows in the 40s and 50s throughout the short term.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

The upper-low will move inland over WA/OR during the weekend. Rain potential increases as the upper low moves inland, particularly Saturday into Saturday night. There is also a 10 to 15 percent probability for thunderstorms Saturday afternoon. Some uncertainty in the ensembles as to how quickly the troughing moves eastwards Sunday into Monday. However, lingering precipitation is likely at least over the Cascades on Sunday before a slow warming trend begins early next week with ridging offshore.

AVIATION

VFR conditions will continue across western Washington through the morning hours with passing high clouds and light winds. Marine stratus and fog are expected to develop along the Pacific Coast this morning, but are not favored to develop over most inland terminals. The exception is for KOLM/KPWT, where patchy fog may develop over these terminals in the early morning. All inland terminals are expected to return to VFR conditions by 19z, with high clouds beginning to build in from the north. Northerly winds will generally remain light through the period at 10 kt or less.

KSEA...VFR conditions through the TAF period. Northerly winds between 3-6 kt overnight, increasing slightly tomorrow afternoon at around 5 to 9 kt with increasing high clouds later in the day.

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FIRE WEATHER

A drying and warming trend will peak today, with light easterly flow through the Cascade gaps causing moderate overnight humidity recoveries along the western crest of the Cascades. Daytime relative humidities along the ridges of the Cascades and Olympics will bottom out in the low to mid 20s, causing brief elevated fire weather concerns for these areas. However, this will be short lived, with onshore flow returning on Thursday as a weak and mostly dry frontal system crosses to the north. Cooler and more moist conditions will return over the weekend, with periodic chances for light precipitation.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 11 PM this evening to 11 AM PDT Thursday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 5 AM Thursday to 5 AM PDT Friday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.