textproduct: Seattle/Tacoma

SYNOPSIS

Unsettled and cooler temperatures expected into next week as Western Washington remains under the influence of an upper level trough, resulting in additional weather systems to move over the area. An upper level ridge may develop over the region next week, bringing warmer temperatures to the region.

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/

An upper level low continues to move south across Western Washington this afternoon, bringing scattered showers to the region. While most showers have remained light, some have produced moderate radar returns, indicating brief downpours. Shower chances will continue this afternoon and will gradually diminish for most of the area, with the exception of the Cascades, where shower chances will linger into early Sunday morning. Additionally, there is a slight chance for thunderstorms this evening. The highest chances are from Olympia southward, with probabilities at 25-30%. Any thunderstorm that does develop will be accompanied by heavy rain, small hail, gusty/erratic winds, and lightning. Lighting chances will diminish late this evening.

Western Washington will remain under the influence of an upper level trough into next week. As a result, this will give way for multiple systems to traverse the region, keeping rain chances in the forecast. Sunday and Monday looks to remain mostly dry, with the exception of the Cascades, where there is a 40-60% chance of showers. Breezy conditions will develop for locations south/southwest of Seattle Sunday evening with gusts 15-20 mph possible. Winds will subside early Monday morning. In addition to rain, temperatures will be on the cooler side. High temperatures will be in the low 60s along the coast and mid to upper 60s along the interior.

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LONG TERM /TUESDAY THROUGH SATURDAY/

There is good agreement between long term guidance that the upper level trough will remain over Western Washington through at least Friday, keeping cooler temperatures and rain chances in the forecast. On Saturday, the majority of ensemble members suggest conditions will become warmer and drier with an upper level ridge will building offshore and moving inland.

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AVIATION

Mostly VFR cigs so far this evening with the exception of KHQM where MVFR cigs are observed. MVFR cigs will become more widespread between 08-12z Sunday morning. There is a 30% chance for IFR cigs at the coast between 10z-14z. Improvement to VFR expected for interior terminals after 19z-21z. Showers will decrease in coverage tonight and will become spotty at best. WNW winds this evening will transition back S-SW after 06z.

KSEA...VFR this evening and into most of the night. There is a 40- 50% chance for MVFR cigs to return after 11-12z. Improvement to VFR likely after 19z Sunday. Surface winds with some degree of westerly component through 06z between 6-8 kt. Winds will then shift back SW and become breezy Sunday evening with gusts to 15 kt possible.

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MARINE

The dominant weather feature will involve broad high pressure over the Pacific and lower pressure over the interior that will help promote onshore flow through next week. This will lead to gusty northwesterlies over the outer coastal waters and steep, choppy seas. In addition, the central and east portions of the Strait of Juan de Fuca will likely see diurnally driven increases in westerlies that may reach small craft advisory strength. There is a small craft advisory in effect for this afternoon's westerlies and it is very likely (85-95%) another advisory will be needed Sunday evening. The offshore ridge looks to weaken late next week, resulting in lighting winds and subsiding seas.

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FIRE WEATHER

Little in the way of fire weather concerns remain in the picture well into the week ahead with upper troughing maintaining cool conditions, high RH, and periodic chances for shower activity. Conditions will warm up and dry toward the end of the week as an upper level ridge builds over the area.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 5 AM PDT Sunday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 11 AM PDT Monday 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.