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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

FXUS66 KSEW 190306

Area Forecast Discussion
National Weather Service Seattle WA
806 PM PDT Sun Aug 18 2019

.SYNOPSIS...Onshore flow into Monday as a weak weather system
passes to the north of Western Washington. An upper level ridge
will build into the area Monday with warmer temperatures and more
sun into Tuesday. A front will move through Western Washington the
middle of the week with a chance for showers and cooler
temperatures. Generally dry weather expected Thursday.


evening shows mostly clear skies across much of Western 
Washington with areas of stratus across the Olympic Peninsula. A 
system will slide north of the area tonight with just a slight 
chance for a shower along the Olympic Peninsula. Otherwise, 
morning stratus expected on Monday with onshore flow. 

An upper level ridge will strengthen over the area Monday
afternoon with low level flow becoming light or even weakly 
offshore by Tuesday afternoon. Mostly sunny skies expected Monday
afternoon with temperatures in the upper 60s to upper 70s. Higher
heights with additional sunshine will boost temperatures on 
Tuesday into the low to mid 80s in spots. 

Clouds will increase Tuesday evening ahead of the next frontal
system approaching the Pacific Northwest. Showers will likely
spread along the coast late Tuesday night into Wednesday morning 
with the upper level trough offshore. Rain will move east across 
Western Washington during the day on Wednesday as the front slides
through. Showers chances through Wednesday night, especially for
the Cascades as the front weakens as it moves east. Plenty of
cloud cover expected Wednesday with cooler temperatures generally
in the mid 60s to low 70s.

.LONG TERM /THURSDAY THROUGH SUNDAY/...Drier conditions expected 
for Thursday into Friday with zonal flow aloft. Guidance suggests
another frontal system looks to possibly brush portions of 
Western Washington Saturday into Sunday. The GFS remains a tad 
wetter than the generally dry ECMWF, so have a chance for POPs in
the forecast generally for northern areas. Temperatures will
generally be near normal in the 70s.


.AVIATION...Low level onshore flow will become light on Monday
with westerly flow aloft. Substantial clearing occurred this
afternoon with just a bit of stratus lingering across the NW
corner of the Olympic Peninsula. VFR conditions rule. Stratus will
move back inland overnight with MVFR ceilings. Improvement
expected by late morning into early afternoon. 

KSEA...VFR conditions this evening with MVFR stratus returning
early Monday morning. Improvement expected again by late morning
to early afternoon. South to southwest winds around 5 kts. CEO


.MARINE...Small craft advisory westerlies present throughthe
central and eastern Strait this evening. Lighter onshore flow
expected for Monday and Tuesday. The next system will move through
the waters on Wednesday with small craft advisory winds possible
across portions of the area. High pressure returns behind the
front Thursday. CEO


.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.


PZ...Small Craft Advisory until 2 AM PDT Monday for Central U.S. 
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters 
     Strait Of Juan De Fuca.