Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

FXUS66 KSEW 272200

Area Forecast Discussion
National Weather Service Seattle WA
300 PM PDT FRI MAY 27 2016

.SYNOPSIS...An upper level low will remain over British Columbia
this weekend. A series of weak upper level shortwave troughs will
bring scattered showers at times to western Washington. Warmer and
drier weather is expected beginning Memorial day and continuing into
the middle of next week as an upper level ridge builds offshore then
moves over western Washington.


.SHORT TERM...Clouds filled in today and showers have become a
little more widespread. There is still no real Puget Sound
convergence zone but models continue to insist it will form in the
usual area, so the forecast for tonight is for chance pops
everywhere except a swath of likely pops from the central Cascades
to the Kitsap peninsula.

A weak front will reach the coast Saturday morning and spread rain
inland during the day. Models are mainly dry over Puget Sound but
have rain in the Cascades Saturday afternoon. Have forecast
categorical pops on the coast with chance or likely pops inland.
Highs will continue to be on the cool side...mid 50s to lower 60s.

The last in the series of shortwaves moves into western Washington
on Sunday, keeping a chance of showers in the forecast. The surface
pattern is somewhat favorable for a convergence zone over Snohomish
and northern King counties in the afternoon. Highs will rise a
bit but remain below normal...mid 50s to mid 60s.

The upper trough will move east Sunday night and a major warming
trend will begin Monday. Heights build into the 570s as an upper
ridge sharpens offshore. Skies will gradually clear. Highs on Monday
will be in the mid 60s to mid 70s. Burke

.LONG TERM...Warming continues Tuesday as heights build further. A
thermal trough will develop along the coast. High temperatures
Tuesday will be in the 70s and low 80s. The 12Z models kept this
pattern going on Wednesday which may turn out to be the warmest day.
Have forecast mid 80s inland with 70s on the coast. The surface flow
turns onshore around Thursday though the upper ridge remains nearby.
This will likely bring some cooling Thursday and Friday with highs
in the 70s inland and 60s coast. Burke


An upper level low over the southeastern Alaska panhandle will
drop southeast into southwestern British Columbia tonight and
Saturday. Moist and stable northwest flow aloft will become
westerly later tonight into Saturday. At the surface, a weak but
developing low well offshore will deepen to near 1013 mb as it
moves to central Vancouver Island Saturday afternoon. An
associated cold front will move through the coastal waters
Saturday morning and through the interior of western Washington
Saturday afternoon.

A scattered to broken cloud layer sits around FL035-040 while a
more broken deck is seen between FL060-080. Scattered showers are
seen over the mountains and along the coast, and in a weak area of
convergence between the Hood Canal Bridge and central Snohomish
county. Cigs are expected to lower to around 035 this evening then
fall to 020-030 after 06z as the frontal system develops offshore
and approaches the region. Visibility will likely fall to 2-4sm in
light rain and fog along the coast with heavier precipitation
ahead of the front 10-18Z Saturday. Conditions are expected to
return to VFR Saturday behind the front that will move onto the
coast about 18Z and through the interior by 22Z. Albrecht

SCT-BKN035 and BKN070-080 through 04Z with showers mainly
remaining SW and N of the terminal. Ceilings will fill back in to
BKN035 about 04Z and lower to OVC020 after 08Z. Southwest winds
8-10KT will shift to south 7-10 kt after 08z. Winds 20012g20kt can
be expected Saturday afternoon as a mesoscale low develops around
the Hood Canal Bridge. Albrecht


Flow is onshore with Small Craft Advisory conditions expected
through about midnight in the central and eastern portions of the
Strait of Juan De Fuca. Conditions will relax later this evening
as a frontal system approaches from the west.

A 1017 mb low well offshore will deepen to about 1013 mb as it
approaches central Vancouver Island midday Saturday. A frontal
system to the south and east of the low will move through the
coastal waters during the morning hours on Saturday then will push
eastward through the inland waters Saturday afternoon. Small Craft
Advisory conditions are expected to develop over the coastal
waters by 12Z Saturday and continue until the front passes. Small
craft advisories have also been issued for the Northern Inland
Waters, Admiralty Inlet, and the East Entrance to the Strait of
Juan De Fuca ahead of and with the front from mid morning through
mid afternoon Saturday. Models continue to show the development of
a mesoscale low around Hood Canal during the afternoon hours on
Saturday behind the front, so there is a 50 percent chance that
southerly winds could reach Small Craft Advisory criteria in the
central Puget Sound from Alki Point to West Point Saturday
afternoon and early evening. At this time the forecast will be
held at 20 knots there. Onshore flow and convergence zone
activity will likely continue Saturday evening through Sunday
afternoon behind the front.

High pressure will increase over the offshore waters on Memorial
Day. This will give the potential for 20-25 kt nwly winds over the
coastal zones Monday afternoon and evening. Moderate to strong
inflow is also possible Monday evening through the strait during
the late afternoon and evening hours.

The offshore ridge will likely shift east into the coastal and
inland waters mid week resulting in winds becoming more north to
northeast Tuesday through Wednesday. Albrecht


.SEW Watches/Warnings/Advisories...
PZ...Small Craft Advisory from 5 AM to 3 PM PDT Saturday 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 3 AM PDT Saturday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory from 8 AM to 3 PM PDT Saturday for
     Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De
     Fuca-Northern Inland Waters Including The San Juan Islands.



You can see an illustrated version of this discussion at is the U.S. government's official web portal to all federal, state and local government web resources and services.