Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 261543

Area Forecast Discussion
National Weather Service Seattle WA
843 AM PDT Thu Apr 26 2018

.SYNOPSIS...One last day of warm and dry conditions over Western
Washington with high temperatures well above seasonal normals. An
upper level low will approach from the southwest, allowing for
showers to creep back into the forecast starting Friday and
persisting through the weekend. Temperatures will be much cooler
Friday and this weekend, returning to near or below average
values for this time of the year.


.SHORT TERM...Today will be the warmest day of the stretch with
increasing offshore flow and the ridge overhead. Temperatures
aloft are a few degrees warmer compared to yesterday. The interior
will see highs in the mid 70s to lower 80s. A few daily records
will be in jeopardy. The cool spots will be the Strait of Juan de
Fuca and the San Juans with temps in the 60s. The current
forecast is on track.

A flip to onshore flow will bring cooler conditions on Friday.
There`s already a stratus deck along the coast. This marine push
will knock temperatures back into the 60s - closer to normal.
There`s moisture wrapping around an upper level low that will
spread north into Western WA Friday afternoon and evening for a
chance of showers. The upper level low will slowly drift inland
this weekend for additional showers and cooler conditions. Highs
on Saturday and Sunday are a few degrees below normal with
temperatures mainly in the mid 50s. 33

.LONG TERM...Previous discussion...Models remain in agreement
regarding the start of next week with a secondary system right on
the heels of the exiting weekend system...allowing for POPs to
linger into Monday. In the wake of this...models start to drift
apart...with the GFS ejecting the moisture out quicker and
allowing for another upper level ridge to build while the ECMWF
keeps enough moisture for the prospect of showers into Tuesday
afternoon. Opted for a compromise between the two models and
decided on a slight chance for showers to linger into Tuesday. The
second half of next week looks to be dry with temperatures
climbing once again. SMR


.AVIATION...An upper ridge over the area will shift slowly inland
today and tonight with light southerly flow aloft. At the surface,
offshore flow will peak this morning, weaken this afternoon and
turn onshore tonight and Friday morning. The air mass is dry and

Stratus along the Central Coast will gradually spread north
but remain confined to near the coast today. The stratus should
push inland tonight as onshore flow develops, penetrating at
least partially into the central and south Puget Sound area and
down the Strait of Juan de Fuca by Friday morning.

KSEA...Clear today and tonight. Stratus should reach the terminal
a little after sunrise Friday morning. Northerly wind 5-10 knots
will ease tonight and become south 4-8 knots Friday morning.


.MARINE...Offshore flow will peak this morning and then ease this
afternoon. Onshore flow will develop tonight and strengthen on
Friday with gales possible in the Strait of Juan de Fuca Friday
evening. Onshore flow will continue into early next week with high
pressure offshore and lower pressure inland. Small craft advisory
strength west winds are likely each evening in the Strait.


PZ...Gale Watch from Friday afternoon through late Friday night for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 2 PM PDT this afternoon for Coastal
     Waters From Cape Flattery To James Island Out 10 Nm-West
     Entrance U.S. Waters Strait Of Juan De Fuca.


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