Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 241656

Area Forecast Discussion
National Weather Service Seattle WA
856 AM PST Fri Feb 24 2017

.SYNOPSIS...Snow showers will continue this morning with
additional light accumulations in some areas of Western Washington
before changing over to rain. After a dry Saturday, another
weather system will affect the area Saturday night into Sunday for
a good chance of snow showers on higher hills. Showers will
continue through much of next week with snow levels rising mid-


.SHORT TERM...Snow showers are moving through parts of Western
Washington this morning. Parts of Lewis County, the lower Chehalis
River valley, and the east Puget Sound lowlands could see
additional light accumulations before showers change over to
liquid form this afternoon. Showers will taper off by this evening
as an upper low and its associated surface disturbance move south
out of the area.

On Saturday, an upper ridge will take hold over Western Washington for
partly to mostly sunny skies. The air mass will remain cool and

Saturday night into Sunday, a second upper level low, associated
with a surface low, will drop southeast through the Washington
coastal waters. The ECMWF and GFS operational solutions support
snow levels 300-500 feet on Sunday and give the potential of a few
inches of snow to the higher east Puget Sound Lowlands, the
terrain above a couple hundred feet in Snohomish County, and the
higher terrain in Skagit, Whatcom and San Juan counties. The
current forecast for snowfall is the model consensus of an inch or
two on the higher hills north and east of Seattle. JSmith

.LONG TERM...Weaker upper level troughs will move across the area
Sunday night through Tuesday. Snow levels will remain low during
the night and morning hours during this period, but precipitation
amounts will generally be light.

Strong west to northwest flow aloft combined with somewhat higher
500 mb heights and low level temperatures will give wet weather to
the area Wednesday onward. Precipitation will be in the form of
rain showers in the lowlands with temperatures a bit closer to
normal. The mountains will see snow showers and potentially could
see heavy amounts of snow by late in the week if the GFS solution
verifies. The ECMWF is drier than the GFS. Will play middle
ground for now. Albrecht/JSmith


.AVIATION...An upper level trough will move south today over the
coastal waters with light flow aloft over Washington. The air mass
is cool, moist, and slightly unstable. Radar shows scattered
showers. These showers will diminish tonight as the low moves away
and cool dry northerly flow aloft begins. At the surface moderate
southerly winds today will become light northerly tonight.

Most ceilings are VFR 3k-5k ft with some outliers. In showers
ceilings have typically fallen to MVFR. There are snow flurries
around Puget Sound, and somewhat heavier snow showers on the north
coast and in southern Lewis County. Mostly VFR conditions will
continue today as snow showers turn to rain showers. Tonight a slow
clearing from the north will occur, with KBLI clearing around 00Z,
KSEA around 03Z, and KOLM around 06Z.

KSEA...Discussion above applies. Snow flurries this morning with no
significant accumulations. Clearing tonight. SE wind 4-8 KT this
morning will become NE by 03Z. CHB


.MARINE...Surface low pres will move south well off the coast today.
Winds will turn from moderate southeast to light northerly as the
low passes. On Saturday winds are forecast to be light. Another low
will move south closer to the coast on Sunday, then remain over the
area into Monday. Offshore flow will develop later Monday. A front
will approach the region Tuesday. CHB


.HYDROLOGY...No flooding is expected during the next week.


WA...Winter Weather Advisory until noon PST today for North Coast-
     Western Strait of Juan De Fuca.



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