Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 212319
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
332 PM PDT TUE JUN 21 2016

.SYNOPSIS...Weak ridging tonight will give way to a cold front
approaching the coast early Wednesday morning. The cold front will
move inland on Thursday, bringing showers. An upper low will move
overhead late Thursday night into Friday morning for continuing
instability and showers through Friday evening. A ridge will build
over the weekend and into early next week for drier conditions.

&&

.SHORT TERM...Extremely light precipitation detected by the KLGX
radar off the Olympic Peninsula (PIC1) should not make landfall
until early Wednesday morning with a cold front approaching the
coast. Skies should remain partly to mostly cloudy tonight over the
area with lows in the upper 40s to mid 50s, fairly typical for this
time of the year.

On Wednesday, with the arrival of the cold front, expect some
precipitation on the coast and a brief wind shift from light
southerly to more northwesterly. Precipitation from the front is
unlikely to start impacting the interior of Western Washington until
late Wednesday night or Thursday morning (PIC2). Highs on Thursday
will be cool for this time of the year- in the lower to mid 60s.

Showers will continue Thursday and Friday as an upper low makes its
way directly overhead (PIC3). Temperatures will also remain below
normal. Snow levels on Friday will likely drop to around 5000 feet
in the mountains, and some of the higher passes and recreational
areas could see a few inches of summer snow. Any remaining showers
will taper off Friday night as the upper low moves further out of
the area. Smith

.LONG TERM...Models are in relatively good agreement that an upper
ridge will build in over the weekend and into early next week for
warmer and drier weather, with no precipitation in sight for the
lowlands and Seattle metro (PIC4). Based on the GFS forecast (PIC5),
I went ahead and put in a chance of showers in for the Cascades on
Sunday afternoon and evening. However, the most recent runs of the
ECMWF and Canadian are not showing any precipitation so this
forecast is uncertain. Smith

&&

.AVIATION...Weak upper level ridging (PIC10) will bring dry weather
to Western Washington tonight. The flow aloft is westerly. The low
level air mass is drying with SCT-BKN ceilings 2500-4000 ft. Low
level clouds will remain scattered this afternoon with some areas of
broken CIGS into the late afternoon for mainly VFR conditions. Low
clouds will reform tonight with onshore flow. A cold front will
bring light rain to the coast on Wed. 33/13

KSEA...Scattered low clouds around 4k will remain for VFR conditions
late this afternoon.  WNW/W winds veering to N 00-03z. CIGS near
3000 ft overnight.

&&

.MARINE...Low level onshore flow (PIC11) will continue this evening
with highest wind/waves through the Central and East Strait and the
Northern Inland Waters - a Small Craft Advisory remains in effect. A
weak cold front will cross the Coastal Waters on Wednesday then move
inland Wednesday night. High pressure over the NE Pacific will
maintain onshore flow through the end of the week. 33/13

&&

.SEW Watches/Warnings/Advisories...
WA...None.
PZ...Small Craft Advisory until 5 AM PDT Wednesday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory until 2 AM PDT Wednesday for Northern
     Inland Waters Including The San Juan Islands.

&&

$$

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