Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS66 KSEW 200415 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 915 PM PDT Tue Sep 19 2017 .SYNOPSIS...
-- Changed Discussion --
Low pressure aloft will remain over the region through Wednesday for cool and unsettled conditions. High pressure aloft will gradually move over the area from the west the latter part of the week for a drying and warming trend. An upper ridge will remain over the area into early next week.
-- End Changed Discussion --
&& .SHORT TERM...
-- Changed Discussion --
Showers and a few thunderstorms moved over the area this afternoon and evening. Thunderstorms have ended and showers are on the downswing. An upper trough will be over the area tonight, keeping scattered showers in the forecast. An upper short wave will move onshore late tonight and Wednesday morning, brushing the southern part of the forecast area and bringing another shot of organized showers to the south. The mountains above 5000 feet will probably pick up more snow tonight and Wednesday. Paradise will probably get the most with maybe 2-4 inches. Further north, showers will be more isolated later tonight and Wednesday. Highs will be near 60. Drier northerly flow aloft will develop Thursday and Friday as the upper trough shifts inland. A few showers will linger, mostly over the mountains, especially by Friday. Highs will rise a few degrees each day but remain a little below normal. Schneider/Burke .LONG TERM...Previous discussion...An upper ridge will be just offshore Saturday through Tuesday. The ridge is looking more dirty compared to yesterday. The GFS is dry but the ECMWF brings some precipitation over the top of the ridge and into Western Washington at times. The forecast is dry for now but some PoPs may need to be introduced if models continue to trend the direction of the EC. Temperatures should warm back to near normal during this period. Schneider
-- End Changed Discussion --
&& .AVIATION...
-- Changed Discussion --
An upper level trough over Western Washington shifting east late Wednesday. Light flow aloft becoming northerly Wednesday afternoon. The air is moist and unstable with onshore flow and scattered showers. The mountains will remain mostly obscured. Puget Sound convergence zone over northern Snohomish county moving into Cascades overnight. KSEA...Scattered to broken layer around 2500 feet with multiple layers between 4000 and 7000 feet. Lower deck dissipating late Wednesday morning. Scattered showers into Wednesday morning. Convergence zone staying north of the terminal. Variable winds 5 knots or less. Felton
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Trough over inland waters will continue to shift east tonight. Next trough will move inland over Oregon on Wednesday. High pressure will build into the area Friday and Saturday. Swell over the coastal waters around 13 feet will subside to around 8 feet Wednesday. Felton
-- End Changed Discussion --
&& .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory for hazardous seas until 2 AM PDT Wednesday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-West Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory for rough bar until 2 AM PDT Wednesday for Grays Harbor Bar. && $$ www.weather.gov/seattle You can see an illustrated version of this discussion at www.wrh.noaa.gov/sew/gafd/latest_webafd.html

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.