textproduct: Seattle/Tacoma

SYNOPSIS

Dry weather will continue tonight through Sunday, with cool/cloudy mornings giving way to afternoon sun. A low pressure system on Monday will bring widespread rain and breezy conditions, with a slight chance of thunderstorms in the afternoon. Unsettled conditions continue into Tuesday, with drier and warmer weather possible by midweek.

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/

Stratus is continuing to slowly thin out and scatter across western Washington. The coast is starting to clear, but clouds will be slower to give way through the Puget Sound interior where the layer remains the thickest. Once the afternoon sun arrive, expect highs to rise into the mid to upper 60s, with areas with earlier clearing potentially reaching near 70. A similar pattern is expected on Sunday with stratus rebuilding, giving way to afternoon sun. Highs again in the upper 60s and low 70s given a slightly earlier clearing time forecast.

The weather will become active on Monday as a low pressure system approaches and moves across the area. Rain will begin to arrive at the coast early Monday morning, slowly spreading into the interior though the morning. Winds will also begin to increase, peaking late morning/early afternoon as the front moves through. Gusts for most will likely be in the 20 to 30 mph, but locations along the coast and through the north interior may see gusts up to 35 to 40 mph. These winds will not produce much in the way of widespread impacts, but unsecured/temporary items outside such as tends may be impacted. Rain will devolve into more scattered showers behind the front and persist through the afternoon and evening. With the upper level low not far to the west, that will give some upper level support for a few isolated to scattered (15-20%) thunderstorms in the afternoon. Temperatures will be much cooler, down into the upper 50s to low 60s.

LONG TERM /TUESDAY THROUGH SATURDAY/

Showers and perhaps a few isolated thunderstorms look to continue into Tuesday as the system continues to depart. Chances for thunder are again in the 15-20% Tuesday afternoon, through more so over the interior areas than along the coast. On the coast, however, waves will increase late Monday into Tuesday, which may bring high surf conditions with waves reaching up to 15 ft before slowly easing throughout the day.

The upper level trough continues to dig into the southwestern U.S., which will allow for warmer and drier conditions to return to the area, with highs climbing back into upper 60s and low 70s. Models are showing the potential for another trough to move into the area late next week, which may bring the potential for slightly cooler weather and chances for scattered showers. Long period swell arriving to the coast on Thursday may pose a threat to beachgoers with significant wave runup possible.

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AVIATION

Onshore flow will continue in the low levels through the TAF period, with northwesterly flow aloft becoming more westerly into Sunday. Latest satellite imagery shows stratus has largely scattered along the coast, but continues to linger across portions of the interior this afternoon. Conditions are primarily MVFR for terminals in stratus and VFR for terminals elsewhere. Stratus is expected to continue to lift and scatter over the next few hours for a more widespread return to VFR ceilings by mid-afternoon. Another round of stratus is likely to push into the interior between 10-12Z on Sunday. Ceilings will likely lower to MVFR for a few hours in the morning, before improving back to VFR by 18-19Z. Surface winds remain out of the west/ southwest for KBLI, KCLM, and KHQM and have been gusty at times between 15-25 kt. Surface winds may briefly become northerly for central Puget Sound terminals this evening, though will remain light at 6 kt or less, before shifting back to the south late tonight into early Sunday.

KSEA...MVFR conditions with stratus slowly lifting and scattering at the terminal this afternoon for a return to VFR conditions between 22-23Z. Winds remain out of the southwest at 5-8 kt this and may briefly switch to the north this evening between 03-06Z. Winds will likely remain light at 6 kt or less, before shifting back to the south by early Sunday. Another round of stratus will likely move into the terminal between 10-12Z Sunday, with probabilistic guidance indicating a 30 percent chance of ceilings lowering to MVFR by 12Z. Expect stratus to scatter by 18Z for a return to VFR. Winds will be out of the south, increasing to 6-9 kt Sunday afternoon.

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MARINE

Surface high pressure well offshore will result in continued onshore flow through the weekend. A strong westerly push is expected through the Strait of Juan de Fuca this evening, for which a Gale Warning will remain in effect for the central and eastern portions of the Strait through late tonight. This will also push into Admiralty Inlet, for which a Small Craft Advisory will continue through late tonight as well. Winds will ease Sunday as high pressure weakens. A low pressure system will approach and move through the area waters on Monday which will bring stronger southwesterly winds. Winds will increase to SCA level early Monday morning through the coastal waters, later in the morning through Puget Sound up into the East Strait and Northern Inland Waters. Winds will switch to more west/southwesterly following the frontal passage mid-day, but winds will not ease until late in the day. High pressure then rebuilds Tuesday into Wednesday, bringing back the previous regime of Small Craft Advisory winds and steep seas in the outermost coastal waters.

Seas remain steep, especially through the outer coastal waters, with waves 6-10 ft with a dominant period of around 8 seconds. Seas will ease to around 5-7 ft Sunday before waves increase on Monday as the low moves through the area. Waves peak Tuesday morning at around 14 to 16 ft before slowly easing throughout the day to around 8 to 10 ft. Long period swell looks to arrive Thursday, which pushes seas up to 8 to 12 ft.

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HYDROLOGY

The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Gale Warning 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 from 5 PM this afternoon to 5 AM PDT Sunday for Admiralty Inlet.

Small Craft Advisory until 2 AM PDT Sunday 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.