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Area forecast discussion 
National Weather Service Seattle Washington
330 am PDT Sat Apr 25 2015

Synopsis...an upper low will move through the area today for more
showers. High pressure will build on Sunday but a warm front will
reach the area late in the day. Temperatures will warm on Monday
with the ridge over the region. A cold front will bring rain back to
western Washington on Tuesday.

&&

Short term...the air mass will remain cool and unsettled with an
upper level low spinning overhead. Expect scattered showers across
the region today as this low shifts into eastern Washington. The highest
instability is over the Cascades with a chance of thunderstorms in
the afternoon. Temperatures will remain in the 50s but we should see
sunbreaks. The upper low will weaken and exit tonight with showers
tapering off.

A warm front will clip western Washington on Sunday for a little light
rain...mainly over the olympic peninsula. There is a chance of rain
in the interior as the front moves north into b.C. But precipitation
will remain light.

Monday will be warmer and drier with upper level ridging over the
Pacific northwest. What is left of the warm front may clip the coast Sunday
morning...otherwise expect dry weather as we head into the
afternoon. The warmer air mass will boost temperatures with highs in the
low to middle 70s in the interior.

The upper level ridge will shift farther inland toward Idaho on
Tuesday while a trough digs offshore. Models show a cold front
passing through western Washington for a chance of showers. It is looking
wetter and cooler over this period with the GFS and European model (ecmwf) now
aligned. 33

Long term...a mean long wave trough will persist over the Pacific northwest
through the long term period. There is a chance of showers through
the forecast with temperatures close to normal. No major changes
were made from the previous forecast. 33

&&

Aviation...upper level low over northwest Washington this morning
drifting southeast into eastern Washington by tonight. Light flow
aloft will become northerly this afternoon. Air mass moist and
somewhat unstable.

Multiple cloud layers today between 4000 and 8000 feet with ceilings
as low as 2000 feet in scattered showers through this afternoon. The
shower activity will decrease this evening.

Ksea...southerly winds 4 to 8 knots becoming northwesterly in the
late afternoon or evening hours. Ceilings between 4000 and 8000 feet
with a chance of brief ceilings near 2000 feet with isolated
showers. Felton

&&

Marine...weak high pressure will build over the waters today and
remain over the waters tonight giving lighter winds to the area. A
weakening front will move through the area Sunday afternoon and
evening. This should bring Small Craft Advisory winds to the coastal
waters...and possibly parts of the northern interior waters.

A second frontal system will reach the area Tuesday. Models are
continuing to have trouble settling on the timing and strength of
this system so confidence remains low for the wind forecast on
Tuesday. High pressure will build in behind the front on Wednesday.
Felton

&&

Sew watches/warnings/advisories...
Washington...none.
Pz...none.

&&

$$

You can see an illustrated version of the forecast discussion at
www.Weather.Gov/Seattle/gafd/latest_webafd.Html

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