Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 241611

Area Forecast Discussion
National Weather Service Seattle WA
911 AM PDT Sun Jun 24 2018

.SYNOPSIS...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.


.SHORT TERM...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

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.


.AVIATION...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


.MARINE...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


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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