Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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218
FXUS66 KSEW 230430
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
930 PM PDT FRI JUL 22 2016

.SYNOPSIS...Isolated showers will diminish this evening across
Western Washington. High pressure will bring dry and mild weather
this weekend. The ridge will strengthen over the region next week
for a warming trend.

&&

.SHORT TERM...An upper trough that brought showers earlier today
has departed to the east. Lingering moisture and low level onshore
flow behind the trough will result in a mostly cloudy night
tonight. A few showers currently over the Cascades and near the
coast should fade away by midnight.

An upper ridge will move over the area on Saturday for dry
weather. Morning clouds should give way to partly to mostly sunny
skies in the afternoon. Highs will be near normal.

Low clouds should be more limited Sunday morning with weaker
onshore flow and sunshine for most areas by afternoon. Highs will
warm several degrees with low 80s likely for parts of the
interior.

Monday looks like a near repeat of Sunday. A broad upper ridge
will be over the region with relatively light low level onshore
flow. Sunny weather should prevail except for areas of morning low
clouds near the coast. Highs will remain a bit above normal.
Schneider

.LONG TERM...Previous discussion...High pressure across the West
will lead to dry and stable weather through much of next week.
This pattern is dominated by a strong ridge anchored over the
Southwest, while arcing north through the Pac NW. The 500 mb
height field is in the lower 590s dam over the region. Expect a
warming trend through the period, likely peaking on Thursday and
Friday with highs in the 80s to lower 90s. The low level flow is
still onshore for mainly late night and morning clouds along the
coast, along with temperatures in the 60s to mid 70s. A weak
trough may break the ridge down next weekend with temperatures
trending back to normal. 33

&&

.AVIATION...An upper trough will exit across the northern Rockies
for the rest of tonight, and a somewhat flat upper ridge will
build in off the Pacific on Saturday PM. Low-level air mass will
remain moist due to moderate onshore flow, but gradual drying
expected on Saturday PM due to weak large-scale subsidence.
Otherwise, the air mass will become more stable over the next 24
hours. Light to moderate NW flow aloft.

KSEA...Moist low-level air mass will support a lowering of
ceilings overnight into the 010-018 range by early Saturday
morning. Lifting and scattering of the clouds expected around
mid-day, with clearing on Saturday evening. Light and variable
wind through Saturday morning, then a north breeze will gradually
develop around mid-day Saturday.Haner

&&

.MARINE...High pressure centered offshore with lower pressure
east of the Cascades will maintain onshore flow of varying
strength through early next week.Haner

&&

.SEW Watches/Warnings/Advisories...
WA...None.
PZ...Small Craft Advisory until 9 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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You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html



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