059 FXUS66 KSEW 121616 AFDSEWArea Forecast Discussion National Weather Service Seattle WA 916 AM PDT Fri Sep 12 2025
.UPDATE...No changes made to this morning`s update. Stratus and patchy fog is persisting but is still expected to burn off as the day progress. Area temperatures range between the lower 50s to near 60 at this hour. The previous discussion is below along with an updated aviation section:
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.SYNOPSIS...Weak high pressure builds over the interior with dry conditions through early Saturday. A cold front likely moves through the region late Saturday through Sunday, with widespread rain. Warmer and drier conditions develop early next week.
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.SHORT TERM /TODAY THROUGH SUNDAY/...High pressure is over western WA today with light winds and weak gradients. The low level air mass remains moist with low clouds and fog over the lowlands. Expect a slow burnoff today with the coast remaining partly to mostly cloudy. Expect highs in the 60s to lower 70s this afternoon.
High pressure remains over the region on Saturday while the next incoming Pacific frontal system stalls offshore. The air mass will be a little warmer with highs in the interior reaching the mid to upper 70s.
Wetter conditions are in store for Sunday as an upper level trough moves inland. Total rainfall amounts range from 0.25-0.50" along the coast and in the mountains to around 0.10-0.25" in the interior. The air mass will be slightly unstable with a chance of thunderstorms too. Temperatures will trend cooler with highs in the 60s. 33
.LONG TERM /MONDAY THROUGH THURSDAY/...Showers will linger into Monday but will taper down as this system exits east. Drier weather is favored moving toward midweek as high pressure returns. Highs Tuesday and Wednesday will reach the mid to upper 70s with a few low 80s possible. Critical fire weather conditions remain low with higher humidities. A trough may bring cooler and wetter conditions moving toward the end of the week. 33
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.AVIATION...An upper level ridge will briefly build over Western Washington through late Friday with flow aloft becoming more westerly. Stratus across much of Western Washington early this morning with a mix of MVFR/IFR to LIFR cigs for most areas. Slow improvements are expected to begin around 18z, with cigs improving into VFR likely late afternoon (21 to 23z) for the interior. Vsby reductions also possible this morning with lower stratus. Stratus expected to continue through the afternoon for most of the coast. Cigs will then lower again Friday night into Saturday morning, with increasing chances of IFR/LIFR conditions in the interior Saturday morning. Light W/SW winds this morning with more of a NW component this afternoon - will be light and variable tonight and become more WSW ahead of a front passing through this weekend.
KSEA...MVFR cigs early this morning - with a few SCT010 or BKN010 cigs lingering up to 18Z intermittently. Slow improvements then expected late morning into the afternoon. VFR cigs around 21 to 22z. Light SW winds this morning with more of a NW component late afternoon and evening, with winds generally under 6 kts. Increasing chances of low stratus Saturday morning (down to LIFR). JD/HPR
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.MARINE...Weak high pressure over the waters will result in a continued onshore flow pattern through Friday night. A front will move into the coastal waters on Saturday and move inland on Sunday. West to northwest winds will increase on Sunday for the Coastal Waters, and will need to monitor the potential for SCA wind gusts for the outer Coastal Waters during this period. In addition, increasing onshore flow Sunday night may result in SCA winds through the Strait of Juan de Fuca. Offshore flow is then expected to develop on Tuesday, with another potential weather system midweek.
Seas will range 6 to 8 feet through early next week. Seas then will subside briefly Monday to 3 to 5 feet before building to 5 to 6 feet midweek. JD
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.SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. &&
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NWS sew Office Area Forecast Discussion