Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 291019
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
318 AM PDT SUN MAY 29 2016

.SYNOPSIS...Showers will gradually diminish today as an
upper level low over British Columbia moves slowly east. A strong
upper level ridge will build over the region Monday, bringing mostly
sunny and warmer weather for Memorial Day and continuing through the
middle of next week.

&&

.SHORT TERM...The upper level low over B.C. that has been
influencing weather in W WA the past few days does not seem to be in
much of a hurry to go and pester some other geographic location for
a while...as models prog it to remain nearly stationary today...only
starting to shuffle on late this afternoon and early evening. This
will be enough to keep pops in for points from the Puget Sound
east...but will also allow for some clearing along the coast and
even sneaking into the north interior and San Juans. By
tonight...the influence of an upper level ridge will start to be
felt all over the CWA as conditions start to dry. Some overnight
clearing might be possible...emphasis on the might...as lingering
low level moisture may cancel that out with some low clouds.

This upper level high makes the remainder of the short term
discussion rather easy...as clear and sunny skies with warmer
temperatures are expected for much of the week...and it certainly
does not waste any time warming things up. Highs on Memorial Day
leap up to mid to upper 60s...with 70 expected in the Seattle metro
area...so cookout plans are go. Tuesday will make a good push for 80
while temps will peak on Wednesday...with highs generally in the
upper 70s to low 80s. The heating of those two days looks to set up
a thermal pressure trough...turning flow offshore and helping to
ratchet up the heat.  SMR

.LONG TERM...The thermal pressure trough moves on by the time
Thursday rolls around...allowing for onshore flow to return and
providing a more moderating influence on temps. The ridge also looks
to flatten out around this time...allowing for the emergence of pops
Thursday afternoon...mainly for the Olympic peninsula and for points
from Marysville north. Models start to disagree somewhat after this.
The ECMWF wants to keep pops in for Friday...while the GFS dries
things out quickly as the ridge reamplifies. Opted to split the
difference with slight chance pops for the locations mentioned when
discussing Thursday. The two models flip positions for the start of
next week...with GFS proving the wetter solution as it wants to move
an upper level trough into the area...while the ECMWF keeps W WA
under the ridge. Kind of leaned toward the drier solution at this
time...but plenty of time and reason to change.  SMR

&&

.AVIATION... An upper level trough over b.c. extending south across
Washington will shift eastward through tonight. High pressure aloft
will build over the northeast Pacific. Light northwesterly flow
aloft becoming northerly tonight and Monday. Generally stable and
moist in the lower levels. Air mass becoming drier later tonight and
Monday with northerly flow developing in the low levels.

Cigs will vary across the area today. Predominate MVFR stratus
expected this morning with isolated pockets of IFR...lifting to
mostly VFR in the afternoon. Scattered showers can be expected
through this evening...especially over higher terrain and in a
possible central Puget Sound convergence zone which may affect the
KSEA/KBFI/KPAE terminals. A switch from southerly to northerly wind
is expected this afternoon in greater Puget Sound including
KSEA/KBFI.

KSEA...South to Southwest wind 8-12 KT...becoming northerly 7-10 KT
this afternoon...easing tonight. Mainly MVFR cigs this morning
before improving to mostly VFR stratus. A Puget Sound convergence
zone could form today producing showers as the winds switch from
southerly to northerly this afternoon.

&&

.MARINE...Post-frontal onshore flow will prevail through tonight but
gradually ease. Small Craft Advisory westerly winds in the Central
and East Strait of Juan De Fuca is likely through tonight. Winds
will generally stay below 20 KT all other waters in the near-term.

High pressure will build offshore on Memorial Day. This will give
the potential for northwesterly winds up to 25 KT over portions of
the coastal waters Monday afternoon and evening. Winds will become
northerly inland and dominate on Tuesday as a thermally induced
trough of low pressure nudges northward along the western Oregon and
south Washington coasts. The trough will push inland Wednesday with
a marine push likely in the evening. DTM

&&

.SEW Watches/Warnings/Advisories...
WA...None.
PZ...Small Craft Advisory Central and East Strait through late tonight.

&&

$$

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