Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 260324
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
824 PM PDT SAT JUN 25 2016

.SYNOPSIS...High pressure aloft will build into Western Washington
on Sunday the shift east on Monday. High pressure at the surface over
the offshore waters will combine with lower pressure east of the
Cascades will give light low level onshore flow, resulting in
temperatures rising into the 70s to mid 80s by Monday. An
increase in onshore flow Tuesday onward will result in
temperatures falling to only a couple of degrees above normal, but
conditions will remain dry.

&&

.SHORT TERM...Short wave ridging aloft over the offshore waters
will shift eastward into Western Washington on Sunday. The ridge
will build as it moves into Eastern Washington Sunday night then
into Western Montana on Monday. After some patchy morning low
clouds that form below a low level inversion early Sunday morning
burn off, expect light low level onshore flow to result in nice
warming on Sunday and further warming on Monday. Current NAM
guidance temperatures in the upper 70s in the Seattle area on
Sunday and in the lower to mid 80s on Monday look reasonable and
are consistent with the current forecast.

The latest NAM12 solution is similar to the 18Z GFS and the 12Z
ECMWF in showing a weak short wave trough moving northeast across
the area Monday afternoon. This trough will result in some
increase in onshore flow late Monday afternoon and may produce
some isolated thunderstorms in the Cascades.

Cloud cover in the forecast for Sunday morning was refined to
provide some patchy morning low clouds to portions of the
interior, and to make low clouds more patchy on the coast.
Otherwise the going short term forecast is in good shape. Albrecht

.LONG TERM...Onshore flow may increase somewhat Tuesday onward as
ridging retrogrades from the Great Plains into the Four Corners
region of the Desert Southwest and amplifies somewhat northward
into Montana. Weak shortwave troughs will rotate northeastward
across Washington. Heights aloft are expected to remain rather
high, around 580 DAM at 500 mb, but low level flow will be
onshore. So expect temperatures to be near or 2-3 degrees above
normal through the period and the air mass to be quite stable.
There may be some increase in late night and morning clouds along
the immediate coastline, but very pleasant early-summer weather
can be expected during the upcoming week or more. Albrecht

&&

.AVIATION...An upper ridge will build over the region tonight and
Sunday with westerly flow aloft. At the surface, onshore flow will
prevail with high pressure offshore and lower pressure inland. The
air mass is dry and stable. There will probably be a little
stratus at the coast Sunday morning. Otherwise, skies will be
clear.

KSEA...Clear. Northerly wind 5-10 knots. Schneider

&&

.MARINE...Onshore flow will prevail for the next five days with
high pressure offshore and lower pressure inland. There will be
small craft advisory west winds in the Central and Eastern Strait
most evenings. There will also be small craft advisory northwest
winds for the coastal waters at times. Schneider

&&

.SEW Watches/Warnings/Advisories...
WA...None.
PZ...Small Craft Advisory until 3 AM PDT Sunday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory until midnight PDT tonight for Coastal
     Waters From James Island To Point Grenville Out 10 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater Out
     10 Nm.

&&

$$

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