000
FXUS66 KSEW 202202
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
300 PM PDT Thu Jun 20 2019

.SYNOPSIS...An upper level low will exit to the east keeping showers
confined to the Cascades. Dry weather expected for Friday and
Saturday as weak high pressure builds in. Another trough will
approach the area late Saturday and settle over the region through
early next week.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...Current satellite shows that
skies continue to clear over the western half of the CWA this
afternoon...with some gaps starting to form over the eastern half as
well...though not nearly as prominent. This is supported with a look
out the window here at the NWS office and...lo and behold...there
are indeed some patches of blue sky present. Current radar is not
terribly impressive in the shower department...with some weak echoes
present over the Cascades as well as over portions of Mason and
Lewis counties. Precip amounts associated with these are expected to
be light.

PoPs will continue to diminish the remainder of today and tonight as
the upper level low responsible for the activity the past couple of
days pushes further east...allowing for cloud cover to diminish and
drier conditions to set up. Models remain in pretty good agreement
for the near term...with an upper level ridge starting to assert its
influence starting Friday and continuing into Saturday. This will
result in clearing skies and interior high temps right around 70 for
both days while the coast is slow to warm up...temps there lingering
right around 60. This ridge flattens out by Saturday evening as an
upper level low starts to approach from the Gulf of Alaska.

Minimal changes made to inherited forecast...mostly just a touch up
here and there to incorporate latest model runs.  SMR

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...As the aforementioned upper
low starts to slowly sink southward...will likely see clouds fill in
Saturday night with first chances of associated precip hitting the
coast and northern portion of the CWA on Sunday...becoming more
widespread Sunday night and into Monday. Models agree that late
Monday night/early Tuesday morning may afford a bit of a break as
the track of the low pulls it away from the coast some...the ECMWF
not quite as far out as the GFS. As such...the ECMWF shows a shorter
break with showers kicking back into the area early Tuesday
afternoon while GFS shows showers waiting until Tuesday evening.
Models realign some moving the system eastward to bring chance PoPs
over much of the area. The ECMWF is more aggressive with the
system...having it further east Wednesday night than the GFS which
actually hangs the low up along the coast. The end result is
effectively the same in the forecast...even though the reasons why
differ. And with the difference in these solutions being felt mostly
on Thursday...which falls out of the scope of this discussion...it
feels appropriate to end this on a bit of a cliffhanger.  SMR

&&

.AVIATION...Moist but drying northerly flow aloft will continue
tonight and Friday. At the surface, moderate onshore flow will
continue. The air mass is slightly unstable, with a cumulus field
over most of the land areas, but after sunset the air mass will
stabilize, the cumulus will disappear, and late tonight stratus will
form over most areas. VFR or no ceilings this evening will become
MVFR overnight.

KSEA...Discussion above applies. Wind will be southerly 4-8 kt
increasing to 8-12 kt this evening. Wind will make a run at turning
northerly for a few hours this evening, but will probably only get
to westerly. CHB

&&

.MARINE...Onshore flow of varying degrees of strength will continue
through early next week. Westerly flow in the strait will reach high
end small craft advisory levels this evening, and gale force winds
are not out of the question. There will be outflow advisory level
wind in Admiralty Inlet and the northern inland waters as well.

Onshore flow will continue into the weekend as high pressure remains
offshore. Westerly advisory level winds are possible each day in the
strait. Gales are possible Saturday evening. CHB

&&

.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...
WA...None.
PZ...Small Craft Advisory until 5 PM PDT Friday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm.

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

&&

$$

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NWS SEW Office Area Forecast Discussion