FXUS66 KSEW 191640

AFDSEW



Area Forecast Discussion

National Weather Service Seattle WA

940 AM PDT Tue Aug 19 2025



.SYNOPSIS...Mild conditions through midweek as an upper low moves

east into British Columbia. High pressure will build over the 

Pacific Northwest this weekend for warm and dry conditions. 



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.SHORT TERM /TODAY THROUGH THURSDAY/...The forecast remains 

largely on track this morning, with no significant updates needed.

Conditions will remain cooler and cloudier across the region 

today with radar showing some light shower activity along the 

coast. The previous discussion follows below, with updates made 

to the aviation section. 14 



We're under SW flow today as an upper level low spins off B.C. 

Across western WA, a few light showers may clip the coast with dry

weather in the interior and Cascades, under partly sunny skies. 

With the proximity of the the low and lower heights, temperatures 

will track a few degrees cooler compared to yesterday. 



The upper level low shifts inland on Wednesday (over B.C.) with

weak troughing over wester WA. Overall, expect dry and mild

conditions with any showers associated with the trough remaining

to our north. 



High pressure builds over the Pac NW on Thursday with temperatures

climbing back toward normal. Highs will reach the upper 70s to

lower 80s with low to mid 70s along the coast. 33



.LONG TERM /FRIDAY THROUGH MONDAY/...High pressure will stall over

the Pac NW through the weekend and into early next week - leading

to warmer conditions. Temperatures will climb back into the 80s

for most interior lowlands (away from the water) with Moderate 

HeatRisk expected. On Saturday, temperatures will peak with 90s 

possible in SW Washington and in the Cascade foothills. Weak 

onshore pushes will cut temperatures back as we move into next

week, but we'll still track a few degrees warmer than average. 33



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.AVIATION...Southwest flow aloft will continue across Western 

Washington today as an upper trough moves onshore over British 

Columbia with a trailing front dissipating as it moves over Western 

Washington tonight. Varying degrees of mid and high level moisture 

will continue to stream across the region today with areas of MVFR 

stratus at times along the immediate coast. Increasing low level 

onshore flow tonight will pull MVFR stratus into portions of Puget 

Sound on Wednesday morning. Some disorganized IFR/LIFR stratus is 

possible along the coast. Clearing of all clouds should take place 

just past 18Z Wednesday. Light southwest winds 4-8 kt today will 

become northerly across much of the region this evening into 

tomorrow.



KSEA...VFR will continue today with varying degrees of high and mid 

level clouds of ahead of a weak front offshore. An increase in 

onshore flow is expected to bring some low MVFR stratus to the 

terminal for a period between 12Z and 17Z Wednesday morning before 

scattering out. Surface winds S/SW 7 knots or less will veer 

northerly near and after around 02Z this evening, and remain 

north/northeast tonight and due north on Wednesday. 27/HPR



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.MARINE...A weak front will dissipate as it moves onshore this 

evening. Surface high pressure will rebuild in its wake over the 

coastal and offshore waters tonight into Wednesday. Thermally 

induced low pressure will expand northward along the coast Thursday 

into Friday before shifting into the interior late in the weekend. 

Winds are expected to generally remain below advisory levels across 

area waters into this weekend.   27



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.SEW WATCHES/WARNINGS/ADVISORIES...

WA...None.

PZ...None.

&&



$$