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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

FXUS66 KSEW 151018

Area Forecast Discussion
National Weather Service Seattle WA
315 AM PDT Sat Jun 15 2019

.SYNOPSIS...No significant weather systems will affect the area into
the first part of next week. Marine layer clouds will occasionally 
spread into Western Washington. An upper trough will reach the 
area around the middle of next week for a chance of showers, mainly 
in the Cascades.


.SHORT TERM /TODAY THROUGH MONDAY/...There will be some areas of 
night and morning clouds for the next few days. It will be cloudiest 
on the coast with not much breakout there, but inland areas will 
have sunny skies--at least for the afternoon and evening hours. 
Highs temps will range from the lower to mid 60s on the coast to the 
mid and upper 70s in the warmer inland areas. 

.LONG TERM /TUESDAY THROUGH FRIDAY/...An upper trough will likely 
move through the region Wed and Thu, and then another trough 
will reach the area for the weekend. The ECMWF and GFS are in better 
agreement now. So, the air mass will cool aloft, some showers will 
probably develop at times, and skies should be partly to mostly 
cloudy. The best chance of showers will be over the Cascades and we 
might see some PSCZ activity at times. There isn't anything very 
specific in the forecast yet but I'd take some rain gear if I was 
planning on hiking in the north Cascades after the middle of next 


.AVIATION...Satellite imagery shows stratus along the coast, Lower 
Chehalis Valley, Southwest and Northwest Interior and over the 
Cascade foothills at 3 am/10z. Ceilings heights vary from 1000 feet 
or less from the Hood Canal westward to 1500-2500 feet in the 
Southwest Interior and Cascade foothills to near 5000 feet over the 
Northwest Interior. The remainder of the area has just partly cloudy 

Expect the stratus along the Cascade foothills to spread back over 
the Puget Sound area this morning. While the cross cascade gradient 
is still plus 7 millibars the remainder of the gradients over the 
area are flat. With the lack of onshore flow to reinforce the marine 
layer expect the stratus over the interior to dissipate late 
morning/early afternoon with a late afternoon breakout along the 
coast. Stratus reforming over the coastal sections tonight moving 
inland overnight but with only weak onshore flow Sunday morning 
expect the stratus to remain west of the Puget Sound. 

KSEA...Stratus moving into the terminal by 13z with ceilings 
near 2000 feet. Stratus lifting late morning and dissipating 
around 19z. Just scattered clouds this afternoon through Sunday 
morning. Light and variable winds becoming northwesterly 4 to 8 
knots this afternoon. Felton


.MARINE...High pressure over the coastal waters with lower
pressure inland will result in varying degrees of onshore flow
through the middle of next week. Small craft westerlies developing 
in the late afternoon/early evening hours in the central and eastern 
Strait of Juan de Fuca each day. Small craft advisory winds also in 
Admiralty Inlet in the evening hours and over the Coastal Waters out 
to 10 nm in the evening hours as well for the next couple of days. 


.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 from 6 PM this evening to 5 AM PDT Sunday 
     for Central U.S. Waters Strait Of Juan De Fuca-Coastal 
     Waters From Cape Flattery To James Island Out 10 Nm-Coastal 
     Waters From James Island To Point Grenville Out 10 Nm- 
     Coastal Waters From Point Grenville To Cape Shoalwater Out 
     10 Nm-East Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 6 PM this evening to 2 AM PDT Sunday 
     for Admiralty Inlet.