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Area Forecast Discussion (AFD)

Issued by Seattle/Tacoma, WA (SEW)

                            
000
FXUS66 KSEW 230420
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
920 PM PDT Sat Jun 22 2019

.SYNOPSIS...Onshore flow will increase tonight and there will be 
a chance of showers--mainly north of Seattle and in the Cascades 
through Monday. An upper trough will move over the area by the 
middle of the week for a good chance of showers. Weak high 
pressure might build into the area around the end of the week.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...A few weak echoes are
popping up in the interior this evening, where there's
convergence. These light showers may linger in the interior and
Cascades due to strong onshore flow. The current forecast is on
track. 33

Previous discussion...Onshore flow will pack the clouds back into
Western Washington overnight with an increasing chance of showers
--mainly north of Seattle. The low level moisture will remain deep
through Sunday and Monday, with a chance of showers persisting-- 
especially in the PSCZ area and into the Cascades. An upper low 
will approach the area Monday and Tuesday. Winds aloft will back 
from westerly tonight and Monday to southerly Tuesday as the low 
drops down from the northwest. There are chance POPs in the 
forecast with plenty of clouds--especially for the Cascades and 
PSCZ area. The exception to that is Monday night and Tuesday 
morning when it looked reasonable to leave the chance of showers 
out of the forecast and cut back on the clouds a bit.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Previous discussion...Cool
showery weather is a good bet for Wednesday and Thursday as the 
upper low comes ashore. The low will move inland at the end of the
week with just a few showers lingering later Friday and into 
Saturday-- with the best chance of showers in the Cascades. A weak
ridge might build into the area around Saturday so forecast high 
temps warm up a bit.

&&

.AVIATION...Onshore flow continues across western WA tonight. The
flow aloft is W/NW. The low level air mass is moist with MVFR cigs
likely. Showers may develop in the Cascades and possibly the
central interior where there's convergence. Expect gradual
improvement in the cigs on Sunday but only in low-end VFR range
(cigs 3000-4000 ft). 33

KSEA...MVFR cigs likely overnight. Light S/SE winds becoming SW to
10-15 kt by 09z. Light showers possible with a convergence zone. 
33

&&

.MARINE...A Gale Warning continues for the central/east Strait of
Juan de Fuca tonight. Winds will ease early Sunday morning. High 
pressure over the NE Pacific will maintain onshore flow through 
next week. Highest wind and waves will be found through the Strait
of Juan de Fuca during the afternoon and evening hours, with 
Gales or Small Craft Advisory winds possible each day. 33

&&

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

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 AM PDT Sunday for Admiralty Inlet-
     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-Northern Inland 
     Waters Including The San Juan Islands.

     Small Craft Advisory from 5 AM Sunday to 5 AM PDT Monday for 
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance 
     U.S. Waters Strait Of Juan De Fuca.

     Gale Warning until 5 AM PDT Sunday for Central U.S. Waters 
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of 
     Juan De Fuca.

&&

$$

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