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Area forecast discussion
National Weather Service Seattle Washington
303 PM PDT Fri Jun 22 2018 upper trough will move inland tonight. A Puget
Sound convergence zone is likely tonight. An upper ridge will
bring sunny and somewhat warmer weather this weekend. An upper
trough will arrive Monday for a return to slightly cooler weather.


Short term...a Puget Sound convergence zone is possible tonight
as an upper trough moves inland. An upper ridge will move over
the area on Saturday for dry weather. Morning clouds should give
way to some afternoon sunshine and highs will creep up a few
degrees. The upper ridge will shift inland on Sunday with an upper
trough offshore and an approaching weak frontal system. It should
be a mostly sunny day with highs warming a few more degrees. The
aforementioned frontal system will move through the area Sunday
night. It will be weakening as it moves onshore and rain will be
spotty. A few showers will linger into Monday as an upper trough
settles over the area. Onshore flow will keep skies mostly cloudy
and highs will cool 10-15 degrees. Schneider

Long term...weak high pressure aloft will move over the area
Tuesday and Wednesday followed by a weak upper trough Thursday and
Friday. Onshore flow will continue through the period. Night and
morning clouds are likely each day with some afternoon sunshine.
Temperatures will be near or slightly above normal. Isolated
showers are possible at times but no organized systems area
expected. The general trend will be for showers to increase late
in the week. The GFS is wetter than the European model (ecmwf) and Gem Thursday
and Friday. The forecast leans more to the drier European model (ecmwf) for now.


Aviation...a weak upper level trough will move east of the region
tonight, and an upper level ridge will build offshore Saturday. Flow
aloft will be northwesterly. Moderate to strong low level onshore
flow will continue tonight and Saturday. The air mass is stable with
low level moisture. Radar shows isolated light showers which will
continue into tonight. A convergence zone is forecast to form over
mainly King County tonight.

Ceilings this afternoon are mostly around 3.5k ft with clear areas
mainly south part. Marine stratus will increase later tonight with
ceilings forming again and falling back to 1-2k ft. Scattered
showers are forecast, mainly in the mountains and in a convergence

Ksea...discussion above applies. Model solutions have a convergence
zone over south King County tonight so will keep showers in the taf.
Southwest wind 4-8 kt though there could be a few hours of northerly
wind this evening associated with the convergence zone. There will
be good VFR Saturday afternoon. Chb


Marine...onshore flow will continue through the period. Westerlies
will continue in the Strait of Juan de Fuca--rising to at least 20-
30 kt each evening, but possibly reaching gale force for a few
hours. Forecast gradient tonight for kuil-kbli is more than 3 mb so
have issued a Gale Warning for 25-35 kt tonight. Chb


Sew watches/warnings/advisories...
Pz...Gale Warning until 5 am PDT Saturday for central U.S. Waters
Strait of Juan de Fuca-East Entrance U.S. Waters Strait of
Juan de Fuca.

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