Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 182146

Area Forecast Discussion
National Weather Service Seattle WA
246 PM PDT Thu Apr 18 2019

.SYNOPSIS...Showers will continue through Friday as a frontal
system moves across the area. Dry weather and warmer temperatures
expected for the weekend into early Monday. Another system will
bring rain later Monday into mid-week.


.SHORT TERM /TONIGHT THROUGH SUNDAY/...Warm front lifting north
through the area with dry weather from about Seattle southward
this afternoon with a few sunbreaks. Chehalis has warmed up to 72
degrees in the past hour under one of these. Scattered showers
continue elsewhere. Totals so far range from a few hundreths
around the sound to a quarter to half inch up north and across the
mountains. Cold front currently offshore will move across the
area tonight into early Friday with more steady rainfall. A few
post-frontal showers will linger into the day Friday with the
possibility of a convergence zone band somewhere near Snohomish
County as onshore flow returns. This activity should wind down
towards evening.

Ridge will then build in for Friday night into early Monday with
clearing skies and warming temperatures. Should turn out to be a
rather nice weekend for holiday activities! Temperatures on
Saturday will top out near the 60 degree mark and warm several
degrees for Sunday with highs in the low to mid 60s. CEO

.LONG TERM /MONDAY THROUGH THURSDAY/...As mentioned by previous
shift, models slowed down the arrival of next frontal system on
Monday. Still, differences remain between GFS and ECMWF solutions. ECMWF
stalls the wave offshore, leaving most of the area dry through
Tuesday night. GFS has showers arriving Monday night into Tuesday
with secondary wetter wave on Wednesday. For now, have cut back
precipition changes until later in the day Monday and will
continue to monitor solutions. Past Wednesday, looks like ridging
will return for the end of the week. CEO


AVIATION...A frontal system will reach the coast tonight and
dissipate over the area Friday. Flow aloft will remain west to
southwest. The air mass is moist and stable. At the surface,
moderate southerly flow tonight will become moderate onshore Friday.

Ceilings remain good VFR this afternoon. Expecting them to become
MVFR by 03Z or so and remain MVFR Friday as the front works its way
through the region. Pockets of IFR are possible tonight.

KSEA...Discussion above applies. The terminal will be somewhat rain-
shadowed in westerly flow aloft. Ceilings should lower tonight as
the front pushes through. Southerly wind 5-10 kt. CHB


.MARINE...A weak front will reach the coast tonight and dissipate
over the area Friday. Strong onshore flow may develop behind the
front Friday night, with gales possible in the strait. A gale watch
is in effect Friday night for the strait.

Onshore flow will diminish Saturday and Sunday with high pressure
offshore and lower pressure inland. Another frontal system will
reach the area on Monday. CHB


.HYDROLOGY...Rivers coming out of the North and Central Cascades
will rise significantly later today through Friday but are
expected to remain below flood stage. River flooding not expected
across the area for the next 7 days. JBB


PZ...Small Craft Advisory for hazardous seas until 5 AM PDT Friday
     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.

     Small Craft Advisory for rough bar from 2 AM to 8 AM PDT Friday
     for Grays Harbor Bar.

     Gale Watch from Friday afternoon through late Friday night for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 11 PM PDT this evening for Admiralty
     Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca.

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