Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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236
FXUS66 KSEW 251637
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
937 AM PDT Thu May 25 2017

.SYNOPSIS...Temperatures will slowly rebound today with enough
moisture and instability for a few afternoon showers and
thunderstorms over the Cascades. A warm and dry upper ridge axis
off the coast on Friday will pass directly over Western Washington
on Saturday. Its warm and dry influence will continue from Sunday
through Tuesday, including Memorial Day.

&&

.SHORT TERM...Slightly cyclonic northerly flow aloft will prevail
today with an upper ridge offshore and an upper trough over the
Intermountain West. This is not a classic thunderstorm pattern
but there is enough lingering instability and moisture for a
slight chance of thunderstorms near the Cascade crest from about
mid afternoon to early evening today. Otherwise, it looks like a
mostly sunny day with highs warming to a few degrees above normal.

The offshore upper ridge will move closer to the region on Friday
and then overhead this weekend. At the same time, low level
onshore flow will weaken slightly and turn a bit more northerly.
All of this means there will be an extended warm and dry period.
Highs should climb into the 70s most areas on Friday. Highs in
the lower to mid 80s will be common this weekend with mid 60s and
70s near the coast and water. Schneider

.LONG TERM...Previous discussion...Beyond the holiday...the first
half of next week seems to want to transition a bit. Starting
with late Monday night...models remain consistent on some degree
of instability and scattered precip signatures possibly signaling
a bit of a marine push...though not nearly as intense as the
previous one. Still looks to be enough to start cooling temps with
afternoon highs Tue falling back into the upper 70s for the
interior. This downward trend will continue as an upper level
trough starts to approach the area by midweek...where we finally
start to see the prospect of showers re-enter the forecast. SMR

&&

.AVIATION...Light northerly flow over Western Washington through
Friday with a trough over the Rockies and high pressure aloft over
the northeast Pacific. Light low level onshore flow. The air mass is
somewhat moist in the lower and mid levels and dry above 10k ft.
Generally stable conditions except weakly unstable over the Cascades
this afternoon and early evening leading to a chance of isolated
thunderstorms. These are not expected to reach the lowlands or
affect any terminals. Any thunderstorms will dissipate after sunset.

Patchy low clouds and fog around the southwest interior will scatter
out by 17-18z. MVFR stratus near the coast and affecting HQM
may briefly scatter after 22z.

KSEA...VFR. Light and variable winds will become NW near 10 knots
this afternoon. dtm

&&

.MARINE...High pressure centered over the northeast Pacific along
with lower pressure east of the Cascades will result in light
onshore flow through Friday. The offshore high will weaken and
redevelop farther west on Saturday, causing the flow to become light
northerly. Diurnally driven small craft winds are expected in the
central/eastern Strait late this afternoon and evening. Hazardous
seas around 10 feet over the coastal waters will subside to 7 to 8
ft during the afternoon. dtm

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory for hazardous seas until 3 PM PDT this
     afternoon 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.

     Small Craft Advisory from 3 PM this afternoon to midnight PDT
     tonight for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html



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