Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000 FXUS66 KSEW 241611 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 911 AM PDT Sun Jun 24 2018 .SYNOPSIS...
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Low clouds will burn off this morning with mostly sunny skies expected. A low pressure system offshore will approach the area during the day today. Look for the cold front to move across the region tonight. Low pressure aloft will keep the area cool and unsettled on Monday. Weak high pressure aloft will prevail on Tuesday for near normal temperatures.
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&& .SHORT TERM...
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Low level stratus clouds formed early this morning across much of the lowlands. The stratus clouds are shallow, around 500 ft thick, and should burn off late this morning for sunny skies. Temperatures will trend a few degrees warmer than normal with weak upper level ridging over the Pac NW. Highs will reach the mid 70s to lower 80s in the interior with 65-70 degrees along the coast. Clouds will increase this evening as the ridge exits and a cold front approaches from the west. The cold front will track through Western WA late this evening with showers expected. The trailing upper level trough will keep the air mass cool and moist through Monday. Heights will build on Tuesday as the trough moves east but the flow is nearly zonal. Low level onshore flow will prevail with temperatures near normal. 33 .LONG TERM...Previous discussion...No major changes to the previous forecast. Overall, it looks like the Pacific Northwest will be mainly under the influence of upper level troughs during much of this period. This, coupled with continued low level onshore flow, will result in below normal temperatures.
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&& .AVIATION...
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A weak front will move toward the coast today, then move inland tonight. Southwesterly flow aloft will continue today and tonight. At the surface, weak gradients today will become strongly onshore tonight. The air mass is stable and dry except for low level stratus over marine areas and most of the lowlands. High clouds are apparent offshore and these will move inland today. Stratus brought IFR ceilings to most terminals. The stratus is shallow and rapidly diminishing; most should be gone 17Z-19Z. High clouds will arrive this afternoon, and as the front moves in the clouds will lower and thicken. MVFR ceilings will develop 06Z-12Z. KSEA...Discussion above applies. Clouds are dissipating over KSEA faster than other places and ceiling should be gone 17Z. Northerly wind 5-10 kt will become southwest 03Z-06Z. CHB
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&& .MARINE...
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Light gradients today will turn strongly onshore tonight. A gale warning is now in effect for the strait, and small craft advisory strength winds are likely in outflow areas near the strait. Onshore flow will continue through the week. Small craft advisory level westerlies are likely each afternoon and evening in the strait, with gale force winds possible at times. On Tuesday and Wednesday, small craft advisory northwest winds are possible on the central and south coast. CHB
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&& .SEW WATCHES/WARNINGS/ADVISORIES...
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WA...None. PZ...Small Craft Advisory until 5 PM PDT this afternoon for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. Gale Warning from 5 PM this afternoon to 5 AM PDT Monday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Monday for Admiralty Inlet-Northern Inland Waters Including The San Juan Islands.
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