Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 132329
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
326 PM PST Tue Nov 13 2018

.SYNOPSIS...Weather over Western Washington will transition today as
high pressure aloft weakens while a warm front begins to enter the
area. A secondary front will keep conditions wet Thursday and into
Friday. Upper level ridging is expected to resume over the weekend
allowing for dry conditions as well as overnight and morning fog. A
front may approach the region early next week with a chance of rain.

&&

.SHORT TERM...Current satellite and the old trusty window show high
clouds continuing to push eastward in advance of the approaching
warm front. Current radar shows most of the rain with this front is
still predominantly over the coastal waters still...although a stray
shower or two look like they may be trying to sneak in ahead of
everyone else. That said...forecast continues to look in good shape
as models agree that this system will steadily move
eastward...likely bringing more steady rainfall to locations east of
Puget Sound this evening. Once it gets here...precip is expected to
remain over the area throughout the day on Wednesday.

Models suggests a brief break in the action Wednesday night and into
Thursday morning before a secondary system Thursday afternoon and
evening...tapering off by midday Friday. Timing for the start of
this second round of precip is lining up as models are falling into
agreement...but the usual biases typical to each model show
themselves regarding solutions pertaining to the cessation of
rainfall...the GFS ending things by late Friday morning while the
ECMWF keeps it around through the afternoon...ending things in the
evening. Models remain agreed that another upper level ridge
building over the Pacific will allow dry conditions to return
Friday.  SMR

.LONG TERM...Models keep the upper level ridge in place for much of
the weekend...although the GFS kind of dirties things up a bit by
introducing a shortwave disturbance into the ridge Sunday. It does
not show any precip with this feature...so will be something to keep
an eye on in future solutions. This minor feature aside...models
once again fall prey to their typical dispositions as the GFS
maintains a dry forecast into Wednesday while the ECMWF brings in a
frontal system late Monday night into Tuesday. As has been the case
for forecasting this fall...have opted to split the difference in
the model solutions and went with slight to low-end chance POPs for
Monday into Tuesday with better chances for Wednesday.
However...since this discrepancy falls in the days 7-9 time
frame...to read any degree of confidence into the forecast that far
out would be utter folly.  SMR

&&

.AVIATION...Broken to overcast high clouds present across the
area this afternoon with VFR conditions. Light rain is approaching
the coast with ceilings beginning to lower for coastal locations.
Rain will continue to spread east/southeast across the area this
evening into the overnight hours as a weak front moves inland with
showers continuing on Wednesday. Conditions will likely bounce
around from VFR to MVFR during this period as rain moves in with
widespread MVFR conditions likely Wednesday morning. Aloft,
southwesterly flow today will shift to the west tonight into
Wednesday. Southerly winds at the surface.

KSEA...Above discussion applies. VFR conditions through early
Wednesday with lowering ceilings. Showers will move in after 4-5Z
this evening, continuing through about 18-20z Wednesday. MVFR
ceilings likely Wednesday morning and possibly through the end of
the current TAF periods. Winds will be southerly to 6 to 12 kts
through the period. CEO

&&

.MARINE...A weak front will move inland tonight into Wednesday.
Small craft advisory conditions expected across most of the coastal,
Strait, and inland waters with the exception of the central Strait.
A brief period of onshore flow likely in its wake with winds
relaxing slightly during the day Wednesday. A second weak system
will then clip the area on Thursday. Offshore flow will return this
weekend. CEO

&&

.HYDROLOGY...A frontal system will bring rain at times to most of
Western Washington later this afternoon through late Wednesday. The
initial warm front will produce moderately strong southwest flow
aloft which will enhance rain amounts in the mountains. Meso models
indicate 1-2 inches at most over roughly a 36 hour period. This
amounts to a nice rain, but not much more than that. Area rivers
will see a bit of a bump up from the storms. Bottom line is that
flooding is not expected on area rivers through the next 7 days.
Mercer/JBB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 2 AM PST Wednesday 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.

     Small Craft Advisory until 10 AM PST Wednesday for Admiralty
     Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca-
     Puget Sound and Hood Canal.

     Small Craft Advisory until 10 AM PST Wednesday for Northern
     Inland Waters Including The San Juan Islands.

&&

$$

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