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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

FXUS66 KSEW 220915

Area Forecast Discussion
National Weather Service Seattle WA
215 AM PDT Wed May 22 2019

.SYNOPSIS...Dry weather the next two days outside of
afternoon/evening showers and thunderstorms over the mountains.
The next system will arrive Friday into early Saturday bringing a
chance for showers. Dry weather for the rest of the weekend into
early next week in the lowlands with mountain showers.


.SHORT TERM /TODAY THROUGH FRIDAY/...Upper level low has pushed
into NorCal this morning with high pressure building into the area
for the next few days. Morning fog/clouds possible each morning, 
mainly along the coast and portions of the southwest interior. 
This will gave way to mostly sunny days today and Thursday in the 
lowlands. Some diurnally-driven afternoon and evening showers are
possible in the mountains with enough instability to suggest a 
thunderstorm or two, especially near the Cascades crest. Daytime 
highs will warm into the 70s with Thursday a few degrees warmer 
than today. 

Shortwave will drop south from BC on Friday and then into western
Oregon by Saturday. This will bring a chance for more widespread 
showers across the area, but still doesn't look like it will 
amount to much. Will continue to monitor the chances for
thunderstorms as low closes off overhead. Temperatures will cool
back into the 60s. CEO

.LONG TERM /SATURDAY THROUGH TUESDAY/...System exits on Saturday
with high pressure then building back in for the rest of the
weekend. Will continue to see the chance for afternoon/evening
showers and possible thunderstorms in the mountains each day. By
Sunday, large model differences remain with flip-flopping from run
to run. The ECMWF now drops another low down the West Coast for 
the start of next week while GFS holds onto ridging. Have held
onto mostly dry forecast until details become clearer. CEO


.AVIATION...Northeasterly flow aloft today. Some moisture will 
linger although the trend is for drying conditions with clearing 
skies. Cigs over W WA generally VFR except for HQM with IFR 
conditions there. Some low level moisture...particularly in 
locations more prone to lower cigs such as in the SW interior...may 
allow for momentary MVFR or IFR conditions overnight. Expect mostly 
dry weather today and into Thursday as weak high pressure moves in.

KSEA...VFR ceilings will prevail. Variable wind 3-6 kt this 
morning before becoming northerly 8-12 kt by afternoon. SMR


.MARINE...Winds fairly benign this morning...although SCA winds will 
remain in place over the outer coastal waters over the next 24 
hours. Onshore flow increasing this evening will give rise to SCA 
winds in the strait tonight. High pressure over the NE Pacific will 
maintain onshore flow through the remainder of the week so SCA winds 
may be routine in the strait each night. The outer Coastal Waters 
may see N/NW gales on Friday. SMR


.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 5 AM PDT Thursday for Coastal Waters 
     From Cape Flattery To James Island 10 To 60 Nm-Coastal 
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10 
     To 60 Nm.

     Small Craft Advisory from 5 PM this afternoon to midnight PDT 
     tonight for Central U.S. Waters Strait Of Juan De Fuca-East 
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 11 PM this evening to 5 AM PDT 
     Thursday for Northern Inland Waters Including The San Juan