Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 301010
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
310 AM PDT MON MAY 30 2016

.SYNOPSIS...Upper level ridging will move slowly east across
western Washington today and Tuesday bringing sunny skies and a
short warming trend. A weak weather system will bring increasing
clouds Wednesday and a chance of showers Thursday and Friday.
Another upper level ridge will build next weekend for sunny and
warmer conditions.

&&

.SHORT TERM...After a bit of a preview yesterday...looks like today
W WA will get a full day with that missing-in-action orb of light
and heat typically referred to as the sun. Thanks to upper level
ridging starting to enter into the area...that sunshine is expected
to stick around into Tuesday. This will result in a short but sharp
warming trend...with highs today in the mid to upper 60s...near 70
in the Seattle metro area and interior lowlands...and highs tomorrow
almost 10 degrees warmer than that.

Latest model runs have introduced a weak front pushing into the area
on Wednesday...which erases any earlier mentions of a potential
thermal pressure trough. While 24 hours ago...the forecast was for
temps to peak on Wed with a resulting thermal pressure trough and
offshore flow...now...not so much...as highs Wed look to be down a
degree or two from Tue. This new solution with the weak front has no
real time for offshore flow to develop and onshore flow
increasing...aiding in keeping temps in check. In addition...said
front is expected to dissipate as it enters into W WA but does so
slowly enough that a secondary front has time to catch up
to it bringing better chances for precip into the area by Thu
afternoon...although there are some chance pops for locations north
and west of the Seattle metro area for after midnight Wed night.  SMR

.LONG TERM...Late Thursday and into Friday...models agree that
ridging will rebuild of W WA...but there is some discrepancy on the
timing. GFS proves to be progressive as usual...wrapping up any
potential for precip by Thu night...while the ECMWF likes to cling
to the moisture into Fri before allowing the ridge to rebuild into
the area. The Canadian tends to follow the slower ECMWF solution.
Have opted to take a compromise of these solutions...keeping very
low end chance pops in the forecast for Thu night and Fri morning
with slight chance pops in for Fri afternoon and drying things out
by Fri night. This ridge should linger long enough to provide a dry
start to the weekend and a return to warmer temps.  SMR

&&

.AVIATION...
An upper level ridge building offshore will shift over Washington
tonight and Tuesday. Light northerly flow aloft. The air mass is
stable and dry. VFR conditions through Tuesday.

KSEA...Northeast wind 5-9 kt. Winds will shift to more northerly
around 19z. VFR skies. DTM

&&

.MARINE...
Thermally induced low pressure along the Oregon coast will nudge
northward along the southern Washington coast tonight and Tuesday.
This will maintain northerly flow over the waters with the strongest
winds up to 20 kt over the south part of the coastal waters tonight.

The low pressure trough near the coast will shift inland
Tuesday...and east of the Cascades Tuesday night. Onshore flow is
expected to resume Tuesday night and continue through the week.
Winds are likely to reach Small Craft Advisory criteria in the
central and east portions of the Strait of Juan de Fuca during the
late afternoon and overnight hours Tuesday and Wednesday.

A weak front will reach the coastal waters late Wednesday night and
dissipate over the inland waters Thursday.  DTM

&&

.SEW Watches/Warnings/Advisories...
WA...None.
PZ...None.

&&

$$

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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