National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
252
FXUS66 KSEW 162219
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
319 PM PDT Sat Jun 16 2018

.SYNOPSIS...A weak upper level low will stall over southern
Oregon and northern California tonight with a chance of showers
or thunderstorms over the Cascades. High pressure will build
offshore Sunday and Monday with ridge shifting inland Tuesday
night and Wednesday. High temperatures will trend around 10 to 20
degrees warmer than normal. Increasing onshore flow will result
in cooler temperatures over the interior on Thursday and Friday.

&&

.SHORT TERM...An upper level low is spinning over southern Oregon
this afternoon. Satellite shows some wrap-around moisture
associated with the low and thunderstorms are popping up along
the Cascades. Showers and thunderstorms will diminish this
evening as the low exits.

A strong upper level ridge will build offshore on Sunday then
nudge inland early next week for a warming trend. Dry northerly
flow will prevail Sunday and Monday with skies mostly clear.
The warm air mass will lead to above normal temperatures with
highs reaching the mid to upper 80s in the interior, around 10-20
degrees warmer than normal. Along the coast, surface pressure
gradients remain onshore with a tight temperature gradient
expected. Temperatures along the beaches will be in the 60s to
lower 70s with 80s inland.

Models are showing a marine push Monday night into Tuesday with
stratus clouds possibly pushing into the interior. The stratus
deck will be shallow and will burn back to the coast during the
early afternoon. Models are showing a few showers developing over
the Cascades where the air mass will be warm and unstable.
Isolated thunderstorms are possible. 33

.LONG TERM...Wednesday will be the last day of the warm spell as
the ridge moves overhead. Temperatures in the interior will peak
in the mid to upper 80s with a few low 90s possible. Showers and
isolated thunderstorms are possible in the mountains again,
especially the Cascades. A strong onshore push will bring cooler
conditions as we move into Thursday with highs mainly in the mid
60s to 70s. An upper level ridge will cross the Pac NW Friday and
Saturday for more dry weather. 33

&&

.AVIATION...An upper level ridge offshore will continue expanding
E over the area thru tonight while the upper level low over OR
drifts S. This will result in nly flow aloft over wrn WA. Low
level onshore flow will become offshore overnight.

Meanwhile, the tstm threat over the Cascades will end this
evening as the air mass stabilizes. There may be patchy IFR CIGs
late tonight or Sunday morning.

KSEA...VFR. Expect northerly winds thru Sunday afternoon. Wind
speeds will be the strongest during the afternoon. Please see the
TAF for specific details.

&&

.MARINE...The flow will become light offshore or northerly tonight due
to a 1020 mb high briefly setting up over British Columbia.
Onshore or NW flow will return Sunday afternoon before becoming
offshore Sunday night. Onshore or westerly flow will return Monday
afternoon and then strengthen for the possibility of gale force
winds over parts of the Strait of Juan de Fuca. Anticipate onshore
flow of varying strength Tuesday through Thursday.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening 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 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 11 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 9 PM PDT this evening for Northern
     Inland Waters Including The San Juan Islands-Puget Sound
     and Hood Canal.

&&

$$

www.weather.gov/seattle