684 
fxus66 ksew 060951 
afdsew 


Area forecast discussion 
National Weather Service Seattle Washington 
300 am PDT sun Jul 6 2008 


Synopsis...the blanket of clouds over the area will gradually burn 
off and give way to sunny skies over the western Washington interior 
this afternoon. An upper ridge will build offshore early next week 
for mostly sunny and warmer days. A weak upper trough will approach 
the forecast area late in the week. 


&& 


Short term...we have westerly flow aloft over the forecast area... 
and the weak upper trough that followed the front Saturday is 
heading east of the Cascades. Onshore low level flow is quite weak. 
There is lots of low level moisture over western Washington though 
..and cloud cover based around 4000-5000 feet has been filling in 
early this morning. So the day will start cloudy...but we will have 
gradual clearing over the interior as the low level flow takes on a 
northerly component. There will still be a low end chance of showers 
in the Cascades today. 


An upper ridge will start building along 130w tonight...resulting in 
a warming trend and clearer skies for western Washington through at 
least Tuesday. The ridge will remain rather flat...but upper heights 
will gradually rise. The 500 mb heights will eventually climb into 
the 585-590 dam range over western Washington late Tuesday as the 
ridge axis crosses the area. Given the flat nature of the ridge... 
the thermally induced trough along the northern California and 
southern Oregon coast will not extend north to our coast. Instead 
the low level flow will remain weakly onshore and northerly. But 
there will be only minor marine influence...and the night and 
morning will be pretty much limited to the coast. High temperatures 
will be a bit above early July normals under sunny skies. Mcdonnal 


Long term...the ridge will progress east of the Cascades Wednesday 
..but upper heights will remain fairly high -- around 580 dam at 
500 mb. Likewise low level onshore flow will increase somewhat 
behind the ridge passage...but it will probably result in only a 
minor increase in marine influence rather than a big marine push. 
The longer range models have been indicating that a weak upper 
trough will arrive Thursday or Friday. They are not in strong 
agreement with regard to this feature...and model solutions diverge 
badly beyond Friday. The current extended forecast does not hit this 
feature very hard...and that looks like the way to go. There is a 
good chance it will not bring precipitation...and it may only result 
in slightly cooler temperatures and a slightly stronger marine 
influence. Mcdonnal 


&& 


Aviation...a stratus deck has filled in a bit higher than 
previously expected with most ceilings around 035. A slightly lower 
deck has developed over the Kitsap peninsula and lower clouds are 
being observed along the north coast and against the Cascades. 
Expect ceilings to lower 500-1500 feet during the morning hours with 
nocturnal cooling. A stabilizing air mass will combine with strong 
July insolation to bust clouds out around 19z...leaving little more 
than a few cumulus clouds over the mountains. Mainly clear 
conditions will continue tonight with only isolated pockets of River 
Valley stratus or fog after 10z. 


Ksea...ovc035 with scattered-bkn020 developing underneath 13z-19z. Clouds 
will bust out around 19z leaving little more than few040 mainly over 
the distant mountains. Wind today S-SW 4-6 knots through 19z...turning 
to north/northwest 20z Onward 5-8 knots. Wind will turn to NE 10kt later tonight. 
Albrecht 


&& 


Marine...a ridge of high pressure around 130w will combine with lower 
pressure east of the Cascades to give onshore flow through the upcoming 
week. After another afternoon and evening of moderate onshore pressure 
gradients today...expect gradients to relax a bit Monday-Tuesday as a short 
wave ridge of high pressure aloft passes across the area...followed by 
strong onshore pressure gradients Wednesday/Thursday as pressures fall east of the 
Cascades with the passing of an upper level trough. Expect typical 
diurnal small craft advisories in the central/east Strait through 
Tuesday due mainly to daytime heating in the interior. Small Craft 
Advisory northwest winds are also expected at times on the coast Monday Onward 
with the ridge offshore. Stronger pressure gradients Wednesday/Thursday will 
give the opportunity for gale force winds in the Strait during the 
afternoon and evening hours. 


The 10-11 feet swell train that reached buoys 46036 and 46005 Sat 
afternoon and evening has yet to reach the coastline...but should 
decay onto the coast during the morning hours. At this time it is 
expected to reach the coastline at 9 feet 13 seconds about 9 am . The 
timing of the arrival of the swell train does not appear to coincide 
with the strong maximum Ebb current at Grays Harbor bar this 
morning...so combined seas at The Bar should stay around 8-9 feet this 
morning. But The Bar may experience rough conditions during the 
evening Ebb. Albrecht 


&& 


Sew watches/warnings/advisories...none. 


$$ 


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