Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 242141

Area Forecast Discussion
National Weather Service Seattle WA
240 PM PDT TUE MAY 24 2016

.SYNOPSIS...Clouds might break up a bit late this afternoon and evening
but then they will fill back in overnight into Wednesday. An upper low
will bring an increasing chance of showers Thursday through Saturday.
Another upper level trough will reach the area Sunday night or Monday.


.SHORT TERM...After some sunbreaks later this afternoon and evening
the clouds will fill back in overnight. Onshore flow will increase
Wednesday in response to an upper level low digging south along the
British Columbia coast. The increasing onshore flow will limit the
amount of afternoon sunshine on Wednesday and give slightly cooler
max temps. As the upper level low sags south Thursday and Friday
there will be an increasing chance of showers with stronger onshore

.LONG TERM...The 12z gfs takes the center of the low from the
central B.C. coast on Thursday and drops it SE into Eastern
Washington Friday morning. That track keeps the best chance of
showers over Western WA in the mountains and perhaps a PSCZ but also
suggests a chance for some wrap around rain in the north Cascades at
first. By Saturday morning the low is opening up to more of a trough
and is near the Idaho Panhandle--but some PSCZ precip could still
be going over Western WA. The 12z GFS has a second trough arriving
around daybreak Monday for another round of shower activity.
Camping this holiday weekend may require blue tarps in the mountains
and in the PSCZ, but might not be too bad overall in the lowlands.


.AVIATION...A long wave trough will remain over the West tonight while
an upper level low spins over MT. The air mass over western WA is
stable. The flow aloft is northerly with low level onshore flow at
the surface. Low level stratus clouds cover much of western WA but
ceilings are mainly VFR. The stratus may break up late this
afternoon then reform overnight. MVFR ceilings are possible early
Wednesday morning. 33

KSEA...VFR conditions through this evening. Light N winds
developing 00-03Z then flipping back to S 09-12Z tonight. Ceilings
near 2000 ft early Wednesday morning. 33


.MARINE...Onshore flow will prevail this week with high pressure
over the NE Pacific. Small Craft Advisory winds are likely in the
Central and East Strait of Juan de Fuca during the afternoon and
evening hours each day. 33


.SEW Watches/Warnings/Advisories...
PZ...Small Craft Advisory until 5 AM PDT Wednesday for Central U.S.
     Waters Strait Of Juan De Fuca-Coastal Waters From Cape
     Flattery To James Island 10 To 60 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-East
     Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland
     Waters Including The San Juan Islands.



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