Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000 FXUS66 KSEW 171631 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 931 AM PDT Sun Jun 17 2018 .SYNOPSIS...An upper level ridge will build offshore with an upper level low remaining well east of the area through Monday. The upper level ridge will shift inland on Tuesday then shift east later Wednesday. High temperatures will be well above normal through Wednesday. A weak upper level trough will move through the area on Thursday inducing a push of marine air into the interior, cooling highs back down to near normal. A weaker upper level ridge will build into the area next weekend. && .SHORT TERM...A strong upper level ridge will build offshore today and Monday for dry, northerly flow over Western Washington. Expect plenty of sunshine with above normal temperatures. Highs will be mostly in the low to mid 80s today with 70s near the water. There is little change in the overall pattern for Monday for similar conditions. The GFS is showing an onshore push Monday night which may bring low level stratus clouds into the interior Tuesday morning. The stratus deck will be shallow and will burn back to the coast Tuesday afternoon. A few showers may develop over the mountains where heating and instability is the greatest. Isolated thunderstorms are possible, especially in the Cascades. 33 .LONG TERM...Previous discussion...Extended models in good agreement with the upper level ridge axis remaining over western Washington for most of Wednesday making it the warmest day in this warm spell by a couple of degrees. Onshore surface gradients increasing Wednesday night into Thursday resulting in a marine push for the interior. This will cool high temperatures back down in the mid 60s to mid 70s. Model solutions become inconsistent on Friday with the GFS bringing another weak upper level low like the one that moved through the area early Saturday morning into western Washington while the ECMWF starts to build another upper level ridge. Both models have decent low level onshore flow so will lower high temperatures back down normal, 60s and lower 70s for Friday. Model consistency returns on Saturday with another upper level ridge building into the region and 500 mb heights rising into the lower to mid 580 dms. Surface gradients still remain solidly onshore with the surface ridge axis south of the area so will go for a few degrees of warming on Saturday but keep highs in the 70s for the most part. Felton && .AVIATION...Wrn WA will be primarily under the influence of an upper level ridge centered offshore today. The flow aloft will remain nly. The low level flow will also be nly. VFR conditions will prevail today. KSEA...VFR. Winds will generally be northerly 7-15 knots today. There may be brief gusts near 20 knots this afternoon. Winds will become light and variable overnight. && .MARINE...Northerly flow will become light onshore or southerly Monday afternoon. Onshore or westerly flow will prevail on Tuesday. There is a possibility of brief westerly gales over parts of the Strait of Juan de Fuca Monday evening. It appears that there is a better chance of gale force winds over parts of the Strait of Juan de Fuca on Thursday. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.