Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 302210
Area Forecast Discussion
National Weather Service Seattle WA
310 PM PDT THU JUN 30 2016
.SYNOPSIS...Onshore flow will result in seasonable temperatures
with night and morning clouds and partly to mostly sunny
afternoons for the next several days. Weak upper troughs will
bring a slight chance of showers at times.
.SHORT TERM...A broad upper trough and the remnants of a weak
front will bring a chance of rain to the area Friday. The main
precipitation threat will be at the north coast with lesser
chances for the north interior and a negligible threat elsewhere.
A weak upper trough will remain over the area Saturday and low
level onshore flow will continue. It should be a mainly dry day
but there could be a little drizzle in the morning near the coast
and then a few showers over the interior in the afternoon.
Another weak front will reach the area Sunday for a small chance
of rain. The ECMWF is wetter than other models but this seems a
bit overdone for now. Highs will be near normal Friday through
.LONG TERM...An upper trough will keep a small chance of showers
in the forecast Independence day through Wednesday. An upper low
could bring an increase in the showers activity Wednesday but
models are still struggling with the details. An upper ridge is
expected to bring a return to dry weather Thursday. Schneider
.AVIATION...Moderate westerly flow aloft will prevail through
tonight. An upper trough and weak front will brush the area Friday
with increasing onshore flow. The air mass is stable and moist in
the lower levels due to onshore flow. Generally dry air in the mid
and upper levels but becoming somewhat moist aloft as the decaying
front pushes across the area Friday. Sprinkles or spotty light rain
is possible Friday as the weak front moves into Western Washington.
Patchy stratus mainly along the coast this evening will fill back in
overnight with cigs gradually lowering. Widespread MVFR ceilings
appears likely again at most terminals by 10-12z through midday
Friday. Cigs should then lift to VFR with sct-bkn clouds
at multiple levels associated with the weak frontal band.
KSEA...light w-nw wind 3-6 kt becoming n-ne during the late evening
and becoming light by morning. Stratus will develop in place
overnight, with MVFR cigs likely by 11 or 12Z through midday Friday.
Patchy drizzle or spotty light rain is possible Friday as a decaying
front moves through the area. Expect multiple sct-bkn VFR cloud
layers Friday afternoon.
.MARINE...Higher pressure offshore with low pressure inland will
maintain moderate to strong onshore flow through Tuesday. Gale force
winds are likely in the strait tonight. Small craft winds are likely
in portions of the northern inland waters and admiralty inlet near
the east entrance to the strait. A front on Friday could bring
enhanced onshore flow Friday/Friday night. Another system on
Saturday night and Sunday could bring another bout of stronger
onshore flow. dtm
PZ...Gale Warning until 5 AM PDT Friday for Central U.S. Waters
Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
Juan De Fuca.
Small Craft Advisory until 5 AM PDT Friday for Admiralty Inlet-
Northern Inland Waters Including The San Juan Islands.
You can see an illustrated version of this discussion at