Forecast Discussion for SEW NWS Office
000
FXUS66 KSEW 252231
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
231 PM PST Sat Jan 25 2020

.SYNOPSIS...A front will move through Western Washington tonight.
The associated low pressure center will bring windy weather to
the coast and north part of the area later tonight and Sunday
morning. A trough will move through the area Sunday evening. A
parade of additional weather systems will affect the region
through next week.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...The next frontal system
is coming together just offshore and will arrive tonight and Sunday
morning for a round of rather blustery weather and full gales to the
normally windier marine areas like the coast and north. Wind
advisories will be in effect for the adjacent land areas. That
system will be followed quickly by a trough Sunday evening. Yet
another system arrives Monday--with the heavier rain probably
heading more into northwest Oregon and southwest Washington around
Monday evening and than that system splits somewhat, weakens, and
moves ashore Tuesday with a little shot of cooler air aloft in
its wake and perhaps a break in the weather around Tuesday night.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...A frontal system on
Wednesday--perhaps timed for Wednesday afternoon and night--looks
fairly progressive but a little bit warmer. Upper heights rise a
bit through Thursday--and Thursday might see a break in the
precip. Friday and Saturday are likely to be wet and mild--the
atmospheric river pattern. That might mean a more significant
round of river flooding is possible around the end of next week.

&&

.AVIATION...Westerly flow aloft backing to southwesterly tonight
and becoming strong as potent frontal system approaches from the
southwest. Surface gradients are light this afternoon and this has
allowed ceilings to deteriorate to low MVFR and IFR. As the low
level flow becomes increasingly offshore late this afternoon and
evening, a short term improvement to general VFR ceilings is
expected. Ceilings will drop back to MVFR early Sunday morning as
rain spreads inland from the coast with the next system. Low level
wind shear will become a factor by 09Z-12Z Sunday morning as winds
near 2000 feet rapidly rise to southerly 40-45 knots.

KSEA...Low MVFR and IFR ceilings expected to gradually improve to
VFR this evening as low level easterly flow increases and dries the
low levels of the atmosphere. Ceilings will drop back to MVFR 09Z-
12Z Sunday with rain spreading back into the terminal. As mentioned
above, low level wind shear expected to be a factor 09Z through
perhaps 18Z before winds aloft ease with passage of frontal system.
Surface winds light southerly backing to easterly 5 to 10 knots this
evening...then veering southerly 15 gusting 25 knots by 14Z-16Z
Sunday morning.   27

&&

.MARINE...A strong front associated with a 995 mb low moving into
Vancouver Island Sunday morning will reach Western Washington late
tonight into Sunday morning. Gale force winds are likely for the
coastal waters as well as the Northern Inland waters, East Entrance
to the Strait and Admiralty Inlet Sunday morning easing to small
craft in the afternoon. Small craft advisory winds over the
remainder of the waters late Saturday night into Sunday. Another
strong system will move through the area Sunday evening. Active
weather pattern continuing next week with a significant system
possible Monday night or Tuesday.  27

&&

.HYDROLOGY...Although there are several weather systems that will
move through Western Washington through midweek the pattern is
fairly progressive with period of rain turning to scattered
showers periodically. The river forecasts do not look too bad at
all through the middle of the week. Naturally the Skokomish river
will remain high, probably remaining above flood stage most of the
time. But it might not be til late in the week that a more
general river flood event becomes possible--the 12z GFS and ECMWF
both had a rather wet scenario Fri/Sat so that bears watching.


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 3 AM to 11 AM PST Sunday for Admiralty Inlet
     Area-Central Coast-North Coast-San Juan County-Western
     Skagit County-Western Whatcom County.

PZ...Small Craft Advisory until 6 PM PST this evening for Grays
     Harbor Bar.

     Small Craft Advisory until 6 AM PST Sunday 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.

     Gale Warning from 6 AM to noon PST Sunday for Admiralty Inlet-
     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-East Entrance U.S.
     Waters Strait Of Juan De Fuca-Northern Inland Waters
     Including The San Juan Islands.

     Small Craft Advisory from 1 AM to 6 PM PST Sunday for Central
     U.S. Waters Strait Of Juan De Fuca-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 6 AM to 6 PM PST Sunday for Puget
     Sound and Hood Canal.

&&

$$

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NWS SEW Office Area Forecast Discussion