Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 121100

Area Forecast Discussion
National Weather Service Seattle WA
400 AM PDT Mon Mar 12 2018

.SYNOPSIS...Low level offshore flow increasing today as a frontal
system stalls offshore. Today will be the warmest day of the year
with possible record highs in many locations. The front will
slowly move inland on Tuesday with rain spreading over the area
from the southwest during the day. A cool upper level low behind
the front will remain off the coast Wednesday then move southeast
into Southern Oregon/Northern California later Thursday into
Friday keeping showers in the forecast.


.SHORT TERM...Satellite imagery shows clear skies over Western
Washington this morning. The front offshore near 134w has gone
nowhere overnight as the cold upper level trough behind the front
digs south. Wide variety of temperatures at 3 am/10z with mid 30s
in Olympia and Shelton with calm winds to upper 40s to near 50 in
Everett and at Sea-Tac airport with east winds.

Everything in place for a record breaking warm middle of March day
in Western Washington. Low level offshore flow increasing this
morning with the cross Cascade gradient down to -5 to 6 mb and
getting lower every hour. Sandpoint profiler shows temperatures
aloft have warmed by 3 to 5 degrees C in the last 24 hours. This
combined with the increasing offshore flow will result in high
temperatures 5 to 10 degrees warmer than Sunday, in the 60s and
lower 70s.

Front offshore will move east and become more negatively tilted
as it approaches the area tonight. Model solutions are a little
slower with the approach of the front with the ECMWF being the
slowest one of the bunch. With the front becoming negitively
tilted slower is the way to go. Have cut back on the pops for
tonight and confined them to west of the Puget Sound. Offshore
flow peaking tonight with gusty easterly winds in the foothills
near gaps in the terrain. There was some concern about possible
mountain wave activity but model soundings are showing very little
flow reversal in the lower levels which cuts down the chances of
this happening significantly. increasing clouds along with the
offshore flow will keep low temperatures in the 40s and lower 50s
Tuesday morning. It is possible some record high minimum
temperature records will be set.

Front weakening as it slowly moves into the area on Tuesday with
rain spreading inland from the southwest during the morning and
early afternoon hours. Little change in the temperatures during
the day with highs in the lower to mid 50s. Front still hanging
over the central and eastern portion of the area tonight keeping
rain in the forecast although with the front continuing to weaken
rainfall amounts will be light. Much cooler air mass slowly moving
inland behind the front with low temperatures dropping down in the
upper 30s to mid 40s.

Cool upper level trough offshore on wednesday with the air mass
somewhat unstable with southwesterly flow aloft. Nothing really
organized spinning out of the trough over the area but the
unstable air mas will keep showers in the forecast. Highs will be
a couple of degrees either side of 50.

.LONG TERM...Models showing good consistency both run to run and
model to model early on the extended with a cool upper level low
off the coast moving down into Southern Oregon/Northern California
for later Thursday into Friday. The air mass over Western
Washington will remain slightly unstable keeping a chance of
showers in the forecast but with the upper level low that far
south the bulk of the shower activity will be south of the area.
Highs will remain in the upper 40s and lower 50s.

Model consistency falls apart later Friday into the weekend with
the ECMWF keeping a broad trough over the area on Saturday with
the trough dissipating on Sunday. The GFS has dry northwesterly
flow over the area on Saturday with a front moving down the
British Columbia coast still north of the area on Sunday. With the
lack of any consistency in the models will stay with the chance
of showers forecast for next weekend.


.AVIATION...The air mass is dry and stable over Western
Washington this morning as a upper ridge axis shifts east of the
Cascades and southerly flow aloft increases. Low level offshore flow
will increase today as low pressure approaches the offshore waters
and a ridge remains over the northern Rockies. VFR conditions will
continue through the next 24 hours with some increase in high level
moisture after 00Z ahead of a front well offshore.

KSEA...VFR through 15Z Tuesday. Northeast wind 6 to 12 knots then
shifting to easterly tonight with some gusts of 20 knots possible as
the cross-Cascade easterly gradient strengthens ahead of an offshore
front. 27


.MARINE...Offshore flow will continue today. Small craft advisory
winds are likely at times near the west entrance. An approaching
front will also bring winds up to small craft advisory levels over
the outer coast.

The front will turn winds southerly on Tuesday. Small craft advisory
strength winds are likely on the coast and possible over some inland
waters. Models have been trending stronger with this system and now
gale force winds are possible on the coast. A gale watch is in
effect on the coast for Tuesday. Flow will turn onshore Wednesday
and Thursday. CHB


.HYDROLOGY...River flooding is not expected in the next 7 days.


.CLIMATE...Record highs for today Seattle 68/1998, Olympia
67/1994, Bellingham 64/1965, Hoquiam 68/1965 and Quillayute
67/1992. All of these records could be broken today.

The forecast high for paradise on Mount Rainier today is 61
degrees. This would make it the warmest March day on the mountain
in 23 years. The last time it was this warm in March was a 65
degree day on March 31st, 1995. Felton


PZ...Gale Watch from late tonight through Tuesday 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.

     Small Craft Advisory until 5 PM PDT 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 Point Grenville To Cape
     Shoalwater 10 To 60 Nm-West Entrance U.S. Waters Strait Of
     Juan De Fuca.


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