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977
FXUS66 KSEW 162233
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
333 PM PDT Thu May 16 2024

.SYNOPSIS...
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Upper-level troughing through much of the upcoming
weekend. With it, cooler and showery conditions are in store.
Brief ridging is expected to start the upcoming week before
troughing rebounds through the middle of next week.
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.SHORT TERM /TONIGHT THROUGH SUNDAY/...
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As mentioned, upper-
troughing is currently positioned over the region. At the surface,
a frontal boundary is pushing towards western Washington out of
BC. With it, increased onshore flow and spotty precipitation is
being observed across the area. Light rain showers are in the
forecast this evening along with convergence activity. Most of the
precipitation will fall in higher elevations with aid of
orographic enhancement. High-res guidance has the PSCZ focused
mainly over Snohomish County before drifting southwards over King
County overnight tonight. With troughing overhead, cooler temps
aloft are expected with snow levels around 3,000-3,500 ft.
Overnight lows are to fall into the low to mid 40s.

Lingering showers are possible into Friday as we`ll be on the
backside of the upper-trough. Nevertheless, drier conditions are
expected but cooler temps are to remain with highs slightly below
average. Then, the next upper-low is on track to enter on Saturday
with another round of showers. However, a drying will try to set
up on later on Sunday as transient ridging moves overhead by the
nighttime hours. Weekend highs are to top out in the mid 50s to
lower 60s with overnight lows in the 40s.


.LONG TERM /MONDAY THROUGH THURSDAY/...Ridging to remain over the
region on Monday but it won`t be long lasting. Active weather
looks to resume around the Tuesday-Wednesday timeframe as another
upper-low out of BC dives south into the region. Temperatures are
to be around average for Monday but, cooler temps along with wet
weather looks to pick back up as the week continues.

McMillian
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&&

.AVIATION...
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West to northwesterly flow will persist aloft as an
upper level trough from British Columbia continues to dig and
slide across the Pacific Northwest. Surface flow generally remains
southerly this afternoon, with gusty winds across the area ahead
of an approaching frontal system. This system is also responsible
for light shower activity on radar this afternoon. Overall, expect
showers to remain light and rather spotty, except for a convergence
zone that looks to develop and persist across portions of the
central Sound tonight. Showers and the PSCZ look to dissipate
overnight. Cigs across the area are generally a mixed bag of MVFR
and VFR, with a few spots of IFR as well. Can expect a mix of high
end MVFR, low end VFR cigs to persist into this evening (with a
few spots of IFR cigs in showers), with gradual improvement
towards VFR expected. Latest NBM probabilistic guidance indicates
a 30-50 percent chance of cigs lowering back down to MVFR again by
Friday morning, likely between 12-15Z.

KSEA...Conditions MVFR with gusty southerly winds to 25-30 kt ahead
of an approaching frontal system. Expect PSCZ activity to remain
north of the terminal this evening and an improvement towards low-
end VFR conditions by tonight. Guidance showing a 30 percent
chance of cigs lowering back down to MVFR between 12-15Z. Winds
will remain breezy through tonight, but look to gradually ease
through the Friday morning hours. 14
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&&

.MARINE...
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An incoming frontal system will keep conditions breezy
across the area waters into Friday. Small craft advisories will be
in effect for all area waters as a result. Seas across the coastal
waters will build towards 10 ft on Friday, likely resulting in an
extension of small craft headlines for the coastal waters zones.
High pressure offshore looks to remain persistent into next week.
With lower pressure situated inland, expect onshore flow to
persist through the forecast period. Another frontal system looks
to move across the area waters early next week and may result in
another round of headlines.

Seas currently hovering at 4-6 ft over the coastal waters this
afternoon. Expect seas to build towards 9-12 ft on Friday before
gradually subsiding back to 5-7 ft over the weekend and into early
next week. 14
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&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
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WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 11 AM PDT
     Friday for Admiralty Inlet-West Entrance U.S. Waters Strait
     Of Juan De Fuca.

     Small Craft Advisory until 11 AM PDT Friday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca-Northern Inland Waters Including The
     San Juan Islands.

     Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Friday
     for Puget Sound and Hood Canal.

     Small Craft Advisory until 11 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-Coastal Waters From Point Grenville To Cape
     Shoalwater Out 10 Nm.
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&&

$$