Mount Vernon, WA Weather

Synopsis

Mostly clear conditions are present this afternoon outside of some scattered clouds throughout Puget Sound. An area of low pressure will be dropping south from the British Columbia coast late Saturday night into Sunday for a round of light rain. Drier conditions resume by the middle of next week as the low offshore progresses inland and east.

Short Term

Mostly clear skies this afternoon and evening will give way to mostly cloudy skies overnight. With low pressure and cooler temperatures approaching, overnight lows will dip into the mid 30s in the Cascades and adjacent foothills with low 40s throughout Puget Sound. A frontal system dropping south from B.C will introduce rain along the coast tomorrow afternoon, spreading inland overnight into Sunday morning. The bulk of the rain will be focused along the Olympic Peninsula and generally west of the Cascades. Up to three quarters of an inch of rain is expected along the coast and windward slopes of the Olympics with only a few hundredths to a tenth of an inch in the Puget Sound region.

Showers will taper off late Sunday morning, leaving cloudy skies and highs in the mid to upper 50s.

Long Term

The pattern is becoming more consolidated in the models for early next week. It is suggestive of broad troughing remaining offshore through the middle of the week, which will keep cooler and cloudier conditions in the forecast. A weak impulse moving through will generate some slight chance PoPs for the area Tuesday afternoon through late Tuesday night. Significant rain is not expected beyond another few hundredths of an inch. Colder overnight lows will accompany this system and bring temperatures overnight back down the upper 30s and low 40s. Wednesday through Friday look to be more on the drier side as the low and associated weak front move inland, leaving the area in an onshore flow regime. Afternoon highs will consistently be in the mid to upper 50s through the week.

The 8-14 day hazards outlook still suggests a 20-40% chance of heavier rain, stronger winds and possibly mountain snow in the October 31 to November 6 timeframe. Stay tuned to the forecast as more details on emerge on a possibly more active pattern.

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Aviation

Generally VFR with some lingering clouds around 3000-4000 feet causing localized pockets of MVFR east of the Puget Sound. Conditions across western Washington are expected to reach VFR as clouds continue to erode into the evening. Mostly clear skies will be short-lived, with high clouds building in from the northwest later tonight. The increased cloud cover may work to inhibit fog and low cloud development for most areas, although IFR/LIFR is possible for more fog-prone terminals early Saturday morning including KHQM, KOLM, and KPWT. An approaching frontal system will bring increasing light showers into western Washington generally north of KPWT-KBFI Saturday afternoon, with a frontal system on track to sweep across the area late Saturday into Sunday, bringing more widespread MVFR conditions in rain.

Surface winds generally northerly around 5-10 kt this afternoon, becoming light and variable overnight. Light south to southeast winds will develop Saturday in the wake of an approaching frontal system.

KSEA...VFR this afternoon with lingering clouds right around 3000 feet. Clouds expected to gradually erode into the evening, with increasing clouds into early Saturday morning. The high clouds will likely limit the development of fog and low clouds around SeaTac, with VFR expected through the TAF period. Surface winds generally northerly 5 to 9 kt this afternoon, becoming light overnight and switching to the southeast to southwest early Saturday.

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