Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 281017
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
317 AM PDT SAT MAY 28 2016

.SYNOPSIS...An upper level low will remain over British Columbia
this weekend bringing mostly cloudy and cool weather to western
Washington, with showers at times. A strong upper level ridge will
bring mostly sunny and warmer weather beginning on Memorial Day and
continuing through next week.

&&

.SHORT TERM...Upper level low pressure over British Columbia will
continue to keep conditions cool and showery over W WA. Not helping
matters any are a couple of additional factors. First...a surface
level ridge of high pressure will keep onshore flow in
place...adding more cool and moist air into the mix. Second...a weak
warm front looks to reach the coast a bit later this morning and
move east through the area as the day progresses. Do not let the
name fool you...this warm front is about as pseudo as it gets...with
high temperatures today running right at or just a degree or two
under what was observed on Friday. This front brings with it a
better chance for precip over the coast...with some chance for
precip inland. In the wake of the front Sunday...could see temps go
up a degree or two...but sufficient moisture from the plodding upper
level low will remain in the area for a continued chance for showers.

Now for the good news. Upper level ridging looks to set up over the
area starting as early as Sunday night...putting the kibosh on any
additional precip just in time to save any Memorial Day plans in W
WA. This will allow temps to rebound rather quickly as well...with
many locations seeing right around 70 degrees.  SMR

.LONG TERM...But wait...there is more. In fact...maybe too much of a
good thing...since temps on Tuesday continue to climb...with the
Seattle metro area poised to hit 80. The hits keep coming as
Wednesday climbs into the lower 80s. This will prove to be the peak
as the ridge starts to move eastward and thus...temps start to
slowly decline afterward. An upper level trough over the Pacific
will start to try and nudge its way in...but it looks like
conditions will remain dry more at least the first half of next
weekend before said trough finally makes its way into W
WA...bringing with it another round of precip.  SMR

&&

.AVIATION...An upper level trough will remain over Washington
through Sunday before moving eastward. Light to moderate westerly
flow aloft. Moist in the mid to lower levels and generally stable. A
1013 mb surface low will move into central Vancouver Island around
midday. The associated trailing front will reach the coast by late
morning and move through the interior including Puget Sound in the
afternoon. Light rain at times today...especially north and west of
Puget Sound. Areas of MVFR stratus and vis 4-5 SM with -RA this
morning...otherwise VFR stratus.

KSEA...South winds 7-11 KT...rising to 10-14 KT w/ gusts 22 KT this
afternoon. The front is expected to pass the terminal around 22z.
Cigs mostly MVFR this morning...then VFR in the afternoon. Light
rain at times...with scattered showers by late afternoon.

&&

.MARINE...A 1013 MB surface low will reach central Vancouver Island
around midday. The trailing front will move through the coastal
waters this morning...then push through the inland waters this
afternoon. Small craft southwesterly winds will develop ahead of and
along the front affecting all waters...except the Central Strait and
Puget Sound. However...winds in the north part of Puget Sound could
potentially reach low-end small craft with frontal passage this
afternoon.  Onshore flow and convergence zone activity will likely
continue this evening through Sunday afternoon behind the front.

High pressure will increase over the offshore waters on Memorial
Day. This will give the potential for northwesterly winds up to 25
KT over the coastal zones Monday afternoon and evening. Winds
becoming northerly inland. Offshore flow will likely prevail Tuesday
through mid week.

&&

.SEW Watches/Warnings/Advisories...
WA...None.
PZ...Small Craft Advisory coastal waters...North Inland waters...Admiralty
     Inlet and the Eastern Strait of Juan de Fuca.

&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html


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