Brier Weather Station

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 Latitude N 47° 46' 49"    Longitude W 122° 16' 48"    Elevation 341 ft

000
FXUS66 KSEW 211544
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
844 AM PDT Mon Oct 21 2019

.UPDATE /THIS MORNING/...Mostly light rain falling across the
northern coast and northern interior this morning, with a few
light rain showers over the central Cascades as well. Expect rain
to increase in coverage and sag southward this afternoon and
evening. Rain, heavy at times, could cause sharp rises in Cascade
and Olympic rivers during the evening and overnight hours. Will
continue to watch river monitors closely. SB

&&

.SYNOPSIS...From previous discussion...A wet frontal system will
cross the area today and tonight. Rain chances will end from the
northwest on Tuesday as the system exits. High pressure aloft will
bring dry weather Wednesday and Thursday. An upper trough will
bring showers on Friday. Dry weather will return next weekend.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...A wet warm-frontal system
will bring rain, heavy at times, coast and mountains today and
tonight. The central Puget Sound area will get lighter rain in a
rain shadow under strong west flow aloft. Snow in the mountains
should not be a concern as snow levels rise well above pass
levels. It will also be locally windy at the coast and north
interior but not enough for any headlines.

The frontal system will sag south and east of the area on Tuesday
with rain tapering from the north and ending entirely by Tuesday
night. An upper ridge will build in from the west on Wednesday for
a dry day. Temperatures will be near normal each day. Schneider

.LONG TERM /THURSDAY THROUGH SUNDAY/...An upper ridge will keep
the weather dry on Thursday although there will be some moisture
coming over the top and probably some clouds at times.

An upper trough will drop down from the northwest on Friday,
bringing showers and cooler air. Western Washington will be under
the influence of dry northerly flow aloft next weekend as a strong
and high amplitude blocking upper ridge develops over the
Northeast Pacific. Schneider

&&

.AVIATION...No major changes to the aviation forecast this
morning. Mixed bag of mainly MVFR and VFR ceilings out there
currently /15z/ but with rain increasing later this morning into
the afternoon, ceilings are still expected to drop noticeably to
the IFR and lower MVFR category where they will then likely remain
into the overnight hours. Locally moderate to heavy rainfall will
be possible late this afternoon and evening, which will likely
impact vsbys: vsbys may drop to the IFR category in the heavier
rain. Breezy southerly winds are also expected to develop this
afternoon, potentially peaking late this evening into the early
overnight hours where gusts to 20- 25kts appear possible. Winds
overall should remain sustained out the south in the 10-15kt
range.


KSEA...VFR ceilings generally dominate this morning but that will
quickly change later this morning as rainfall coverage increases.
Cigs should drop down to MVFR and potentially IFR later in the
afternoon as heavier rain moves in. Winds will continue out of the
south today at generally 10-15kts, with the potential for gusts
in the 20-25kt range later this evening through early overnight.

Kovacik

&&

.MARINE...The only adjustment to the marine forecast this morning
was to push the SCA for Puget Sound up a few hours as some
observations indicate winds just under criteria as of 15z.

A warm front will move across the area through the day today,
followed quickly by a cold front overnight tonight into early
Tuesday. These frontal systems will be responsible for breezy
conditions across most waters of western Washington. Current
headlines include a Small Craft Advisory for wind for the Coastal
Waters, Eastern Strait of Juan de Fuca, Northern Inland Waters,
Admiralty Inlet, and Puget Sound where wind speeds out of the
south are expected to be at least 21kts. Wind and waves will be
quieter across the western and central Strait of Juan de Fuca
today given dominant wind direction from the south. With southerly
gradients increasing later this evening ahead of the cold front,
may have to extend some of these headlines for the interior waters
with the afternoon package. Otherwise, waters relax on Tuesday,
except for the central and eastern Strait where a somewhat strong
westerly push is likely behind the cold front. Will evaluate
whether SCA or Gale headlines are more appropriate with the
afternoon package.

Kovacik

&&

.HYDROLOGY...Two to four inches of rain is likely over the west
slopes of the Olympics and the central Cascades today and tonight.
Snow levels will also rise to 7000-9000 feet today. This
combination could be enough to push some rivers to flood stage
tonight or Tuesday. Since this is the first big rain event of the
season, confidence is not high on exactly how the rivers will
react as some of the rain will likely soak into the ground rather
than runoff like later in the season. A flood watch remains in
effect for the areas of concern.

Less rain is expected over the north and south Cascades but these
areas will also need to be monitored.

Otherwise, river flooding is not expected for the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch from 6 PM PDT this evening through late Tuesday
     night for Admiralty Inlet Area-Bellevue and Vicinity-
     Cascades of Snohomish and King Counties-East Puget Sound
     Lowlands-Eastern Strait of Juan de Fuca-Everett and
     Vicinity-Hood Canal Area-Lower Chehalis Valley Area-North
     Coast-Olympics-Seattle and Vicinity-Western Strait of Juan
     De Fuca.

PZ...Small Craft Advisory until 5 AM PDT Tuesday 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 8 PM PDT this evening for Admiralty
     Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca-
     Puget Sound and Hood Canal.

     Small Craft Advisory until 11 PM PDT this evening for Northern
     Inland Waters Including The San Juan Islands.

&&

$$

www.weather.gov/seattle

NWS SEW Office Area Forecast Discussion

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