textproduct: Seattle/Tacoma

SYNOPSIS

A ridge will bring dry and warm conditions into Friday with highs in the mid 70s. The pattern flips back to trough dominant over the weekend with a weak system bringing light rain on Saturday. Additional rainfall is expected early next week.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

Skies have cleared this afternoon with sunny skies and temperatures around the region in the mid to upper 60s. Winds will become breezy overnight from the east. The winds will be most elevated in the Cascades and adjacent foothills, easing by Friday morning. Gusts in these locations will likely be between 25-30 mph. Given the offshore flow, fog potential will be limited tomorrow morning. Isolated patchy fog in the south Sound and fog prone valley locations may still occur. Friday will be slightly warmer, with anticipated highs in the mid to upper 70s. Residual influence of the offshore flow will also dry things out with afternoon relative humidity values dipping into the upper 30 to low 40 percent ranges across western Washington.

Onshore flow resumes Friday afternoon and by Saturday, the next weak frontal system will traverse the area. This will bring a few hundredths of an inch to most lowland locations and around a quarter of an inch to the Cascades. Areas of central Puget Sound may end up more rainshadowed given the weak moisture profile and southwesterly flow. Elevated westerly winds will move through the Strait of Juan de Fuca and Admiralty Inlet Saturday afternoon and evening behind the front.

LONG TERM /SUNDAY THROUGH THURSDAY/

Sunday will be cool and mostly dry as the trough offshore lingers. Highs will be in the upper 50s and low 60s. Most model guidance regarding the low pressure system on Monday actually take the feature to the south of the CWA. With that prognosis, the area generally stays dry, but cool into Monday. That trough will continue moving south, but Gulf of Alaska troughing builds back in through the middle of the week. A weak front moving off that low may arrive Wednesday into Thursday but does not look particularly strong and may produce isolated showers through Thursday.

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AVIATION

High pressure aloft over the region this afternoon will shift inland on Friday. Flow aloft will remain southwesterly through the period. Latest satellite imagery shows fog and low clouds have largely scattered across the area this afternoon, leading to mostly sunny skies across western Washington. Conditions across the area terminals have rebounded to VFR as a result. A system approaching the region offshore will bring increasing high cloud cover to the area tonight into Friday. High cloud cover and continued offshore flow in the low levels tonight will likely limit widespread fog development on Friday morning, with hi-res guidance showing minimal development expected for the area terminals. However, a shallow layer of moisture remains present and could lead to some fog development at more fog- prone terminals. East/northeasterly winds will persist at 5-10 kt through the evening hours, before easing tonight. Winds will then transition to the southeast overnight into early Friday and then become more southerly through the morning hours.

KSEA...VFR conditions. Northerly winds persisting between 5-10 kt will ease later tonight and become 5 kt or less. Winds will then gradually shift to the southeast overnight and then become more southerly through the morning hours on Friday. Fog development will likely be more limited overnight due to offshore flow and high cloud cover streaming in overhead, however areas of patchy fog may develop within the vicinity of the terminal. 14

MARINE

High pressure over the offshore waters with a thermal trough along the coast will promote offshore flow across the area waters into Friday morning. The trough will push inland on Friday ahead of an approaching frontal system, allowing for winds to switch back to onshore. Winds will increase Friday night into Saturday, with the strongest winds expected along the central and eastern Strait of Juan de Fuca, where latest hi- res guidance continues to show roughly a 35-50% likelihood of gusts exceeding gale force. Winds will become breezy as the frontal system approaches, with other locations such as the outer coastal waters and waters of Puget Sound and Hood Canal likely seeing wind gusts exceed small craft criteria. Winds will decrease as the system exits the area Saturday evening and will remain relatively light on Sunday. A low pressure system will track southward offshore on Monday, just skirting the coastal waters. This system will then likely bring another round of offshore flow to the area waters Monday night into Tuesday.

Seas will persist between 3-6 ft into Friday, before building to 8-10 ft over the weekend. Seas could even build further early next week, but will be dependent on the track of the system offshore. The most likely scenario shows seas building to 9-12 ft on Monday, however the GEFS does continue to highlight a 40-50% of seas exceeding 12 ft.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...None.