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Area forecast discussion 
National Weather Service Seattle Washington
915 am PDT sun Aug 2 2015

Synopsis...a strong upper ridge will persist today...then weaken
tonight and shift eastward on Monday. Onshore flow will gradually
return Monday and Tuesday with moderating temperatures through middle
week. Weak upper troughs will bring a chance of showers to the
mountains Wednesday and also toward next weekend.


Short term...middle and high clouds from convection off the Oregon
coast overnight cover much of southern Washington. These clouds will
drift northeast today and by afternoon sunny skies will return over
most of the area. Have already updated the grids and forecasts for
more cloud cover this morning. Lowered the high temperatures a bit
in deference to the cloud cover. Still looking for 80s and low 90s
over the interior today.

Rest of forecast remains unchanged. Expecting some intrusion of
marine stratus Monday morning but this will rapidly retreat to the
coast. The upper level trough in British Columbia will be affecting
the area with considerably lower heights so high temperatures Monday
will be in the 80s inland and near 70 on the coast under more
persistent stratus. There is a chance of high based thunderstorms in
the Cascades on Monday.

A stronger marine push Monday night appears to be in the cards. This
will bring clouds into Puget Sound sound Tuesday morning. Though they will
probably evaporate back to the coast in the afternoon...highs on
Tuesday will be lower than they have been for a the 70s
and low 80s. Burke

Long term...previous discussion...upper level low pressure over the
Pacific northwest will begin to shift eastward Tuesday night and Wednesday. Models
have trended toward much less moisture so there is little threat of
precipitation over the area. Left the showers in over the mountains
but if any rain does fall it will be quite light. Highs will again
top out mostly in the 70s.

Model solutions begin to vary more starting Thursday...although the
trend is toward weak ridging. This may be transitory but the rising
heights and weaker onshore flow should allow highs to reach back
into the low to middle 80s. This may carry over into Friday but another
trough may approach the region and the affects could begin to be
felt Friday or over the weekend. Given the uncertainty of the timing
and strength of the trough...showers will remain in the forecast for
the mountains. Highs will probably start to moderate by Saturday...
falling back to the 70s or low 80s...which is near or slightly above
average. However...confidence in the forecast this next weekend is
low. Mercer


Aviation...a broad upper ridge will remain over the region through
tonight with light westerly flow aloft. The air mass will be stable
and dry...except for shallow marine moisture mainly along the coast.

There is patchy fog this morning along the coast and in the lower
Chehalis valley and south interior of western Washington. It should
burn off this morning...and stratus and fog could return to those
areas again tonight. Otherwise there will be no significant clouds
below 12000 feet.

Ksea...north wind 4-10 knots becoming northwest this afternoon...then
becoming variable 6 knots or less tonight. Mcdonnal


Marine...high pressure offshore and low pressure east of the
Cascades will result in increasing onshore flow through early
next week. Small Craft Advisory northwest winds will continue
over most of the coastal waters zones through tonight...and then
again at times early next week. Brief westerly gales occurred in the
central Strait of Juan Delaware fuca and East Entrance Strait Saturday
evening...and conditions look similar again this evening. For now I
will stay with our forecast of high end Small Craft Advisory winds
of 20 to 30 knots there tonight...but I may decide to upgrade that to a
Gale Warning this afternoon. Gale force westerlies are a good bet
there Monday night...and possibly Tuesday night and Wednesday night
as well. Mcdonnal


Sew watches/warnings/advisories...
Washington...heat advisory remains in effect until 8 PM this evening for parts
of the Puget Sound sound region and southwest interior.

Pz...Small Craft Advisory coastal waters except zone 150...central
Strait of Juan Delaware fuca...East Entrance Strait. Gale watch
central Strait of Juan Delaware fuca...East Entrance Strait for
Monday night.



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