textproduct: Seattle/Tacoma

SYNOPSIS

A return to cooler and cloudier conditions as showers rotate through the region around an upper low to the south. Isolated thunderstorms are possible this afternoon in the Cascades. Drier and warmer conditions return late in the week through next weekend with a stronger ridge of high pressure building offshore.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

An upper low remains positioned off of southern Oregon and northern California, spreading increasing cloud cover and mid level moisture across the region. We'll see continued showers across the region, with increasing coverage across Western Washington. This will bring temperatures down to considerably cooler values than the last few days. With increasing instability this afternoon, we'll have the potential for a few isolated thunderstorms across the Cascades through the evening hours. Little change to the pattern into Wednesday as the upper low slowly progresses eastward across the western U.S. Temperatures remain on the cooler side, toping out mostly in the upper 50s tomorrow. Moving into Thursday, heights begin to rise on the back side of the system as the upper low drifts further eastward. This will have the impact of both cutting off support for additional showers and bring about another warming trend as clouds begin to decrease.

LONG TERM /FRIDAY THROUGH TUESDAY/

Ensemble guidance remains in good agreement for a return of high pressure over the region late in the week. This should bring a return of Minor HeatRisk as temperatures again climb into the upper 60s to near 70 in the warmest locations. However, the location of the ridge axis - specifically, how far offshore or over the region it remains - remains a key bit of uncertainty in the forecast with a decent amount of spread. This could leave the door open to the opportunities for some light showers late in the weekend or early next week with a few embedded impulses rotating within the flow across the region

AVIATION

South to southeasterly flow aloft will turn east to northeasterly tonight as a broad upper trough moves onshore over northern California and southwest Oregon. The low level flow is onshore. Ceilings will deteriorate late this afternoon as moisture associated with the area of low pressure spreads northward into the region. MVFR ceilings in scattered showers are expected most areas by this evening with shower coverage increasing overnight. Predominantly MVFR ceilings in showers will persist into Wednesday with minor improvement late in the day as shower activity diminishes.

KSEA...Ceilings on are track to deteriorate late this afternoon as a band of deeper moisture lifts northward into the area. MVFR ceilings in showers this evening will continue into Wednesday morning with improvement to low end VFR expected near or after 00Z Thursday. Surface winds S/SW 8 to 12 knots this afternoon/evening will increase Wednesday morning to 10 to 15 knots gusting to around 20 knots at times.

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MARINE

Weak low pressure will remain over the inner coastal and interior waters into Thursday with broad high pressure remaining well offshore for an onshore flow pattern. The flow will turn more northerly over area waters Friday into Saturday with a broad surface ridge over the western Canadian provinces and lower pressure over the Pacific Northwest.

Small craft advisories remain in effect for the central/east strait today and for the coastal waters and Puget Sound tomorrow. Seas will build and steepen over the coastal waters on Wednesday with seas nearing rough bar criteria at Grays Harbor by Wednesday night. Seas will then gradually subside later Thursday into the weekend.

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HYDROLOGY

No river flooding is expected during the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

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

Small Craft Advisory from 11 AM Wednesday to 11 AM PDT Thursday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.