fxus66 ksew 270312 

Area forecast discussion 
National Weather Service Seattle Washington 
812 PM PDT Sat may 26 2018 

Synopsis...a flat upper ridge will be over the area for sunny and 
warmer weather Sunday. Onshore flow will increase Sunday into 
Memorial Day resulting in cooler temperatures and an increase in 
marine clouds. Upper level troughiness will keep the weather 
cloudier and a bit cooler much of next week. 


Short term...clouds have thinned out a bit this evening, but 
conditions remain rather cloudy in the interior of western 
Washington. While onshore flow is light, expect clouds to reform 
near the top of the marine layer late tonight then continue 
through mid morning on Sunday. 

Flat upper ridging will move across the area on Sunday resulting 
in warmer temperatures. Expect highs on Sunday in the mid 60s on 
the coast and in the lower to mid 70s inland. 

The upper level ridge will shift east of the area Sunday evening. 
The movement of the ridge to the east will induce stronger 
onshore flow Sunday night which will deepen the marine layer and 
result in an increase in clouds Sunday night into Monday morning. 
Memorial Day will see cooler high temperatures with morning clouds 
and partly sunny conditions in the afternoon. Some drizzle or 
light rain is possible over the olympic peninsula Memorial Day 
into Monday night. 

An upper level trough is forecast to approach the area Tuesday, and 
it will be centered near the coast by Tuesday afternoon. The 
coverage of drizzle or light rain will expand somewhat on Tuesday, 
and highs will be cooler ... inland and 55-60 coast. Albrecht 

Long term...from the previous long term discussion: it's 
difficult to pinpoint any periods in the extended forecast, 
Wednesday through Saturday, that will definitely be dry. An upper 
level trough is always over the area, near the area, approaching 
the area, or leaving the area in one or another model. So have 
applied a broad brush to the whole period, with 15-30 pops each 
period. For now, partly cloudy with a chance of showers seems like 
the best forecast. Burke 


Aviation...a flat upper level ridge will build into western 
Washington tonight and Sunday. Light to moderate northwest flow 
aloft will become westerly on Sunday afternoon. Low-level onshore 
flow will keep a moist marine layer in place, with dry and stable 
air above the marine layer. Cigs on Sunday morning should be 
similar to this morning, mainly in the 020-030 range during the 
hours after sunrise. Conditions will scatter out late morning with 
VFR conditions across the region Sunday afternoon. Albrecht 

Ksea...the stratocumulus deck has scattered out this evening. 
Expect VFR conditions to persist until about 10z when a bkn030 
deck will fill in and persist until about 18z Sunday. VFR 
conditions will dominate Sunday afternoon. Light NE wind this 
evening will turn to light southerly about 10z then become SW 5-7 
kt late Sunday morning. Wind will become more nwly Sunday 
afternoon. Albrecht 


Marine...onshore flow peaked earlier this evening and Small Craft 
Advisory westerly inflow has been limited to the central and 
eastern portions of the Strait of Juan de Fuca. Small craft 
advisories this evening have been cancelled for Admiralty Inlet 
and the northern inland waters. 

Onshore flow will increase late Sunday afternoon into Sunday 
evening in response to an upper ridge over western Washington 
moving eastward. Expect high end Small Craft Advisory conditions 
over the eastern two thirds of the Strait of Juan de Fuca later 
Sunday, and Small Craft Advisory conditions as well over Admiralty 
Inlet and the northern inland waters south of the San Juan 

Westerly gales are possible Monday evening as onshore flow 
increases further in response to a broad upper trough offshore. 

Otherwise, a diurnal rhythm of onshore westerlies will continue 
for the next week. 

Northwest winds are expected to increase to Small Craft Advisory 
criteria Monday and continue into Wednesday. A longer fetch of 
northwesterly winds from western Vancouver Island into the coastal 
waters will likely generate a steep and short-period northwesterly 
swell. Albrecht 


Sew watches/warnings/advisories... 
Pz...Small Craft Advisory until 6 am PDT Sunday for central U.S. 
Waters Strait of Juan de Fuca-East Entrance U.S. Waters 
Strait of Juan de Fuca. 

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