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fxus66 ksew 191525 
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Area forecast discussion 
National Weather Service Seattle Washington 
825 am PDT Wed Jun 19 2019 


Synopsis...a relatively deep trough will slide southward later 
today into Thursday bringing some shower activity through 
Thursday. Weak high pressure will build in Friday and Saturday. 
Another trough approaches the area late Saturday into Sunday and 
settles over the region into early next week. 


&& 


Short term /today through Friday/...the first of a pair of 
systems is passing by to our north this morning. Aside from some 
weak convergence zone shower activity extending from the olympic 
peninsula across Admiralty Inlet into Snohomish County, it's 
generating little more than some cloud cover across the interior of 
western Washington. A secondary, deeper trough digging southward 
near haida gwaii this morning will shift into the region late this 
evening. Along with increased onshore flow, the trough will 
generated the necessary lift to get more widespread shower activity 
going this evening and overnight. The uw-WRF model has a couple of 
convergences zones forming by late tonight...one downwind of the 
Olympics and the other downwind of Vancouver Island. An initial 
convergence zone looks to get started over the central Puget Sound 
this evening with shower activity becoming more widespread through 
the night across the interior and Cascades. The coast will only get 
spotty showers at best with this system. Temperatures to remain on 
the cool side today...mostly in the 60s. 


Showers will be dissipating on Thursday and should be confined to 
the Cascades by afternoon. Weak high pressure aloft begins nosing 
into the region on Friday with temperatures returning to something 
that resembles normal for the time of year. 27 


Long term /Saturday through Tuesday/...from previous 
discussion...dry conditions will continue for the majority of 
Saturday with weak high pressure over the area. Guidance is in 
agreement of the chance for pops late Saturday night through Sunday 
as an upper level low approaches the region. Both GFS and European model (ecmwf) 
suggest showers will be around on Monday with the upper level low 
off the coast. The upper level low will slide south off the coast on 
Tuesday, though the exact track will determine if there will be any 
showers in West Washington on Tuesday, kept slight pops for now on Tuesday. 
Temperatures will generally be seasonable on Saturday with cooler 
than average temperatures into early next week. Jd 


&& 


Aviation...an upper trough will be over the area today and 
tonight with westerly flow aloft. At the surface, onshore flow 
will continue with high pressure offshore and lower pressure 
inland. The air mass is moist and relatively stable. 


Low clouds are fairly prevalent across the area this morning with 
ceilings a bit higher over the northwest interior. Ceilings should 
lift a bit diurnally today with daytime heating then lower again 
tonight in continued low level onshore flow. 


A Puget Sound convergence zone is possible tonight over northern 
King County. 


Ksea...low clouds this morning should lift this afternoon then 
lower again tonight. A Puget Sound convergence zone will probably 
form just north of the terminal this evening. Southerly wind 5 to 
10 knots will become more southwest to west this afternoon and 
increase to 10-15 knots but a switch to northerly is not expected. 
Schneider 


&& 


Marine...onshore flow will continue through the weekend with high 
pressure offshore and lower pressure inland. At least Small Craft 
Advisory strength west winds are likely each day in the Strait. 
Gales are expected in the Strait tonight and are possible again 
Saturday night. For the coastal waters, there will be marginal 
Small Craft Advisory strength northwest winds at times through 
Thursday. There will also be Small Craft Advisory level short 
period steep west swell through Thursday. Schneider 


&& 


Hydrology...the daily hydrology discussion has ended until the 
start of the next rainy season; it will only be updated as needed 
until then. 


&& 


Sew watches/warnings/advisories... 
Washington...none. 
Pz...Small Craft Advisory until 6 PM PDT Thursday for coastal waters 
from Cape Flattery to James Island 10 to 60 nm-coastal 
waters from Cape Flattery to James Island out 10 nm-coastal 
waters from James Island to Point Grenville 10 to 60 nm- 
coastal waters from James Island to Point Grenville out 10 
nm-coastal waters from Point Grenville to Cape Shoalwater 
10 to 60 nm-coastal waters from Point Grenville to Cape 
Shoalwater out 10 nm. 


Small Craft Advisory until 6 PM PDT this evening for central 
U.S. Waters Strait of Juan de Fuca-East Entrance U.S. 
Waters Strait of Juan de Fuca. 


Gale Warning from 6 PM this evening to 5 am PDT Thursday for 
central U.S. Waters Strait of Juan de Fuca-East Entrance 
U.S. Waters Strait of Juan de Fuca. 


Small Craft Advisory from 6 PM this evening to 5 am PDT Thursday 
for northern inland waters including the San Juan Islands. 


Small Craft Advisory from 2 PM this afternoon to 5 am PDT 
Thursday for Admiralty Inlet. 


Small Craft Advisory from 6 PM this evening to 2 am PDT Thursday 
for Puget Sound and Hood Canal. 






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