Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 241747
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
1030 AM PDT TUE MAY 24 2016

.SYNOPSIS...Weak high pressure aloft will be over the area today and
Wednesday. Clouds should break up a bit this afternoon and evening
but then fill back in overnight into Wednesday. An upper low will
bring an increasing chance of showers Thursday through Saturday.

&&

.SHORT TERM...Morning satellite imagery shows the highest peaks and
volcanos sticking up above the clouds in the Cascades. The clouds
over the Olympics are more broken up. There is also an area of lower
marine stratus on the coast. Through tonight there will be low level
onshore flow continuing with weak high pressure aloft. After a
little clearing in the afternoon and evening the clouds will fill
back in overnight. Onshore flow will increase Wednesday in response
to an upper level low beginning to dig south along the British
Columbia coast. The increasing onshore flow will limit the amount of
afternoon sunshine on Wednesday and give slightly cooler max
temperatures versus today. As the upper level low sags south
Thursday and Friday there will be an increasing chance of showers
with stronger onshore flow.

.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.

&&

.AVIATION...A long wave trough remains over the West today 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
this morning but ceilings are mainly VFR. The stratus should break
up this afternoon for SCT040-060. Patchy low clouds will re-
develop overnight. 33

KSEA...VFR conditions today with SCT040-060 this afternoon. Light
N/NW winds at the surface becoming S this afternoon, then back to
N between 00Z-03Z. 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...
WA...None.
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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You can see an illustrated version of this discussion at
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