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 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

548
FXUS66 KSEW 060525
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
925 PM PST Tue Dec 5 2017

.SYNOPSIS...A strong upper ridge will bring dry weather to Western
Washington for at least the next week. The air will be stable and
increasingly stagnant by the end of the week.

&&

.SHORT TERM...There were clouds near the north slopes of the
Olympics near the Strait of Juan de Fuca this evening, and patchy
low clouds in the San Juans--but otherwise it is clear. There will
be some fog in the south part of Western Washington by morning, but
with pretty decent northerly flow only a few patches of fog
elsewhere. Air quality across the Puget Sound region was good today
with excellent visibility. However, as we move through the week
ahead the inversion resulting from high pressure aloft will limit
vertical mixing and, eventually, ventilation--especially as surface
flow weakens Friday through the weekend. So we can expect air
quality to worsen eventually, and there is a chance that an air
stagnation outlook could be issued in the next couple of days.

.LONG TERM...The upper ridge will remain east of the Cascades and
weaken a bit more Saturday, as a frontal system moves northeast
over the distant offshore waters into northern British Columbia.
Then the ridge will rebuild over the area Sunday through Tuesday.
The dry streak should continue, with limited mixing and
ventilation, through early next week. McDonnal

&&

.HYDROLOGY...There will not be any river flooding in the next
week.

&&

.AVIATION...An upper level ridge will remain over the area tonight
and Wednesday with northerly flow aloft. Offshore flow will continue
at the lower levels. The air mass is stable and dry except for
patchy low level moisture.

Clear skies across the area tonight with the exception of some
upslope stratus along the northern slopes of the Olympics. Strong
offshore and northerly gradients with nearly -5 mb KUIL-KBLI and
KOLM-KBLI gradient as low as -3 mb. With the gradients this strong
will be hard for much fog to form Wednesday morning leaving just
clear skies. The upslope stratus along the north slopes of the
Olympics will continue into Wednesday.

KSEA...Have taken the fog out of the terminal for Wednesday morning.
Local fog study shows fog very unlikely with KOLM-KBLI gradient
lower than -2 mb at 06z the night before. Clear skies through
Wednesday. North northeast wind 10 to 15 knots. Felton

&&

.MARINE...High pressure will remain over the area through the week
with low level offshore flow. Small craft advisory easterlies will
continue at times near the west entrance to the Strait of Juan de
Fuca and over most coastal waters near gaps in the coastal terrain
through mid week. Small craft advisory northerly winds over the
Puget Sound and Hood canal will ease Wednesday morning. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 4 PM PST Thursday 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 Point Grenville To Cape Shoalwater 10
     To 60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater Out 10 Nm-West Entrance U.S. Waters Strait Of
     Juan De Fuca.

     Small craft advisory until 6 AM PST Wednesday for Puget Sound
     and Hood Canal.

&&

$$

www.weather.gov/seattle



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.