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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

FXUS66 KSEW 170357

Area Forecast Discussion
National Weather Service Seattle WA
857 PM PDT Sun Jun 16 2019

.SYNOPSIS...Weak ridging will set up over western Washington
Monday, with morning clouds making way for afternoon sunshine. 
Tuesday will see more clouds and perhaps a few showers or some 
morning drizzle. An upper level trough will reach the area after 
the middle of the week and bring back some chances for showers at


.SHORT TERM /TODAY THROUGH TUESDAY/...Current satellite imagery
indicating mostly cirrus over portions of Puget Sound this evening,
with stratus starting to push in along the coast. Expect the 
stratus to push into the Sound during the overnight hours.
Overnight lows will be in the low to mid 50s. SB

.From previous discussion...Weak ridging resumes Monday with very
little change in conditions. Tuesday sees a switch as the area 
starts to feel the presence of an upper level low approaching the 
area from northern BC. While conditions will remain dry...temperatures
will fall to the lower 70s over the interior lowlands...lower 60s
along the coast. All that said...very few changes made to 
inherited forecast. SMR

discussion...Models are coming more in line with regards to 
approaching upper level low as it dips southward from northern BC 
Wednesday. Both models suggest that there may be some precip for 
northern portions of the CWA Wednesday...but as the upper low 
dives east of the CWA Thursday will likely see best chance for 
widespread precip then. PoPs with this feature still less than 
impressive...topping out in low-end chance category. This feature 
does not linger and dry conditions are expected to resume Friday. 
A second upper level low looks to arrive Saturday bringing another
chance...albeit small...for showers. This switch to a more active
pattern will bring temps over the area down some...with interior 
lowland temps dropping into the upper 60s to lower 70s while 
locations on the coast will hover around 60. SMR


.AVIATION...A weak upper level shortwave to the north will move 
to the east, allowing for another upper level ridge to build 
offshore late tonight into Monday. Westerly flow aloft will become
northwesterly overnight. Increasing low level onshore flow will 
allow for stratus to move inland quicker tonight. That could lead 
to IFR or low MVFR ceilings across the area from later this 
evening through midday Monday. With mainly cirrus over Puget 
Sound, current conditions for all interior terminals remain VFR 
at this hour. However, satellite imagery has indicated that 
stratus has already started to move inland along the coast and has
resulted in IFR ceilings at HQM.

KSEA...VFR conditions will prevail through late tonight. Stratus
should return tonight between 10Z and 13Z and is likely to be 
slightly higher and thicker than what occurred this morning. 
Stratus should dissipate a little later on Monday-around 21Z. 
Surface winds NW 3 to 8 knots this evening...becoming light 
variable overnight. 27/14


.MARINE...High pressure over the coastal waters with lower
pressure inland will result in varying degrees of onshore flow 
through the week. A gale warning remains in effect through 5 AM 
for the central and eastern waters of the Strait of Juan de Fuca
as observations in the central Strait continue to report winds of
30-40 knots within the last hour. Gales will be likely in the 
central and eastern Strait of Juan de Fuca each night through 
Tuesday. Small craft advisory winds will likely bleed into Admiralty
Inlet and the Northern Inland waters during the same time. Onshore
flow should become weaker as a weak trough sets up over the 
coastal waters near midweek. 27/14


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


PZ...Gale Watch from Monday afternoon through late Monday night for 
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance 
     U.S. Waters Strait Of Juan De Fuca.

     Gale Warning until 5 AM PDT Monday for Central U.S. Waters 
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of 
     Juan De Fuca.

     Small Craft Advisory until 5 AM PDT Monday for Admiralty Inlet-
     Northern Inland Waters Including The San Juan Islands.