Small Craft Advisory 150, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
927 PM PDT Sat Jun 30 2018

.SYNOPSIS...Moist northwest flow aloft and low level onshore flow
will continue through Monday for near or slightly below normal
temperatures. Look for dry and warmer conditions on Tuesday under
weak high pressure aloft.

&&

.SHORT TERM...
The low pressure system that brought scattered showers to the CWA
during the day was now east of the area. A low-topped convergence
zone over Snohomish County earlier has become disorganized during
the past couple of hours. It should mostly fall apart overnight
before redeveloping on Sunday.

From the previous discussion: On Sunday another weak impulse will
briefly enhance shower activity, again mostly over the north, in
the mountains and in a convergence zone. Highs on Sunday will be
in the 60s, except around 70 in the southwest interior.

Strong onshore flow Sunday night will probably bring gales to the
strait and keep a convergence zone going into Monday. An upper level
trough will swing through eastern Washington, keeping showers in the
Cascades. By Monday afternoon, flow aloft will become northerly and
the air mass will begin to dry. There will probably be more sun on
Monday, at least away from the convergence zone, and highs once
again will be in the 60s and lower 70s.

Tuesday should be dry with partly to mostly sunny skies. Highs will
reach well into the 70s, 60s on the coast. Burke

.LONG TERM...
The latest GFS solution still has the CWA under of the influence
of cyclonic flow aloft on Independence Day. Consequently, this
model generated precipitation over the mountains Wednesday
afternoon. If this models ends up verifying, there could be a
slight risk of thunderstorms over the mountains, too. However,
confidence in the forecast for Independence Day was not high due
to lack of continuity in the models. It will be interesting to see
what the 0000 UTC ECMWF and Canadian solutions show. For now, the
current forecast reflects a compromise between the drier/warmer
and cooler/somewhat showery scenarios.

From the previous discussion: Similarly the Euro keeps the low
offshore, with warm and dry weather over Western Washington
through the end of the week, while the GFS is fairly wet. Have
kept low chance pops Thursday through Saturday, with some dry
areas, and a slow cooling trend. Highs should still be in the 70s
all three days, normal or slightly above normal. Burke

&&

.AVIATION...Weak high pres aloft will prevail over the region
overnight for contd strong wly flow aloft. The low level flow will
remain onshore. Expect wdsprd MVFR CIGs overnight, with areas of
IFR CIGs/VSBYs.

KSEA...MVFR CIGs (generally 1500-2500 ft) are expected thru
Sunday morning. Winds will also remain southerly 8-13 knots thru
Sunday morning.

&&

.MARINE...
High pressure centered offshore with lower pressure east of the
Cascades will result in onshore or westerly flow of varying
strength through Tuesday. There is a high probability of westerly
gales over the central and eastern Strait of Juan de Fuca Sunday
evening.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Watch from Sunday afternoon through late Sunday night for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 3 PM 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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