Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
000
FXUS66 KSEW 101044
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
244 AM PST Tue Dec 10 2019
.SYNOPSIS...An upper level ridge will slide east of the area this
morning. A weak front will move through Western Washington this
afternoon through this evening. Stronger weather systems will move
through Wednesday night into Friday with wet, breezy weather along
with mountain snow.
&&
.SHORT TERM /TODAY THROUGH THURSDAY/...Satellite imagery shows low
clouds across much of the Puget Sound and coastal areas this
morning with widespread high clouds ahead of the next system. The
frontal system will move through Western Washington through today
with light rain reaching Puget Sound later this afternoon. Snow
levels with this system will be around 4000 feet, however there is
limited precipitation as the front is weakening. An inch or two is
possible at Stevens Pass and higher elevations later today into
tonight. High temperatures will be in the upper 40s.
Wednesday morning will be generally dry across the area with the
next system on approach. This second system will be stronger and
be more December-like bringing more widespread Lowland rain,
breezy/windy conditions, and mountain snow. The initial front
will slide onshore midday Wednesday and move east through the day.
Along with widespread rainfall, southeasterlies will be rather
noticeable for portions of the North Interior with gusts up to
35-40 MPH Wednesday night. Breezy conditions elsewhere across
Western Washington with a decent BLI-YZT pressure gradient.
Another element with the late Wednesday-Thursday frontal systems
will be mountain snow. Snow levels at the onset of the
precipitation Wednesday evening will be in 3500-4000 foot range
for accumulating snowfall for the higher passes, including Stevens
Pass. Snow levels will not vary much through Thursday for decent
snow accumulations above 3500 feet, at least advisory level.
Snoqualmie Pass should see a rain/snow mix at points through
Thursday, however snow levels are not too far off for more snow
than rain at the Pass.
One other aspect to this system will be the rather cool air aloft
on Thursday following the front. Precipitation will become more
showery in nature during the afternoon. Instability appears to be
rather limited (100-300 J/kg), but with lifted indices to -2 would
at least suggest the chance for thunderstorms for coastal areas,
so have added for Thursday afternoon.
Showery weather for Thursday night as the system slides east of
Western Washington. Temperatures Wednesday and Thursday will be
in the upper 40s to low 50s across the area. JD
.LONG TERM /FRIDAY THROUGH MONDAY/...The wet weather should be
around through Friday as the upper trough slides east of the area.
Deterministic guidance suggests a brief upper level ridge is
possible Saturday afternoon into Sunday morning as an upper trough
stays south of the area. However, given the proximity of the
trough and ensemble guidance, have slight chance of POPs. Active
weather for Sunday afternoon through Monday as another system
moves through. Temperatures in the 40s through the weekend across
Western Washington. JD
&&
.AVIATION...Upper level ridge over Western Washington shifting
east early this morning. Front moving through the area this
evening. southwesterly flow aloft becoming westerly behind the
front.
Widespread ceilings below 1000 feet with local visibility aob 1sm.
Visibility restrictions ending around 20z. Ceilings slowly lifting
in the afternoon with ceilings 1000-1500 feet around 00z. Local
visibility 3-5sm in light rain 00z-08z.
KSEA...Ceilings below 500 feet with visibility less than 1sm in
fog until around 18z. Ceilings slowly lifting in the afternoon to
1000-1500 feet around 00z. MVFR ceilings continuing into Wednesday
morning. South southeasterly wind 6 knots or less. Felton
&&
.MARINE...A weakening front will move through the area today with
small craft advisory strength southeast winds for the Coastal
Waters and West Entrance Strait of Juan de Fuca.
A stronger frontal system crosses the area Wednesday and
Thursday. Gale force southeast winds are possible for the Coastal
Waters, East Entrance Strait of Juan de Fuca, and Northern Inland
Waters with the strongest winds expected Wednesday evening. Small
craft advisory strength winds are expected elsewhere with this
frontal system. Onshore flow will follow into Friday then weaken
and turn southeasterly by Saturday.
West swell 14-17 feet are expected to reach the area Wednesday
night and continue into Friday before subsiding on Saturday.
&&
.HYDROLOGY...River flooding is unlikely for the next 7 days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Watch from Wednesday afternoon through late Wednesday night
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 2 PM PST this afternoon 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-West Entrance U.S. Waters
Strait Of Juan De Fuca.
Gale Watch from Wednesday afternoon through late Wednesday night
for East Entrance U.S. Waters Strait Of Juan De Fuca-
Northern Inland Waters Including The San Juan Islands.
&&
$$
www.weather.gov/seattle
NWS SEW Office Area Forecast Discussion