Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 240355
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
855 PM PDT Sat Mar 23 2024

.SYNOPSIS...An upper low offshore will continue to bring unsettled
conditions through the weekend. A series of weather systems will
move through the area into the first half of next week, bringing
periods of lowland rain and light mountain snow with temperatures
near normal.


&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Satellite imagery shows
upper level low just west of Florence, Oregon off the Central
Oregon coast. Deformation zone over the Northwest Interior has
almost completely dissipated with what is left of the zone along
the Central and Western Strait of Juan de Fuca and over the North
Coast. What is left of the zone will be done by early Sunday
morning. Doppler radar shows some shower activity still left in
the Southwest Interior. Temperatures at 8 pm/03z were in the mid
40s to lower 50s.

Forecast on track this evening with the upper level low drifting
south overnight and a weak upper level ridge building into British
Columbia. Flow aloft becoming northwesterly which will bring some
drier air aloft decreasing the shower chances through Sunday
morning. By Sunday afternoon what little showers chances that
remain will be confined to the Central and Southern Cascades. Even
with the upper level ridge building inland the low level flow is
light and becomes weakly onshore Sunday afternoon. This combined
with plenty of low level moisture left over from today`s rain will
keep skies mostly cloudy/partly sunny Sunday. Brief break Sunday
night with another system making its way into the area Monday.

Upper level troughing looks to be reintroduced back into Pacific
Northwest on Tuesday for increased shower chances and onshore
flow, opening the door for more stronger systems to move through
the area. JD/Felton

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Ensemble and cluster
guidance depicts a stronger deep upper low approaching the area
on Wednesday from the northwest. Steadier lowland rain, mountain
snow, and breezy conditions definitely look to be possible
starting midweek. The exact timing and track of the low is still
uncertain and thus impacts may vary, but the overall message is
that the weather pattern looks to become active in the long term.
Troughing looks to continue through the week, with cool and wet
conditions before possibly becoming more drier into the weekend.

Mazurkiewicz

&&

.AVIATION...An upper level low over the Pac NW will continue to
produce showers across western WA tonight. The flow aloft is
westerly. Cigs generally VFR as of 8 PM PDT with some sites
reporting MVFR due to persistent showers such as along the Strait
and portions of the SW interior. More widespread MVFR conditions
expected to emerge around 11 PM PDT thanks to plenty of low level
moisture present over W WA. Showers will linger in the interior and
Cascades Sunday morning with improving conditions toward the
afternoon as high pressure moves in. 18/33

KSEA...VFR conditions currently with showers in the vicinity tonight
and MVFR conditions developing around 06Z. Winds light N turning
more W to SW by 09-12z. 18/33

&&

.MARINE...Winds are generally light across western WA, turning
onshore tonight as a weak surface low off Oregon moves inland. Light
winds continue on Sunday with high pressure. Will see increasing
onshore flow through the Strait of Juan De Fuca Sunday night with
Small Craft Advisory Winds possible. A weak warm front will clip the
region on Monday with winds likely remaining below SCA criteria.
Winds and seas will increase Tuesday night and Wednesday as a
stronger Pacific frontal system moves in. Winds and seas remain
elevated through the end of the week as this system slowly churns
offshore. 18/33

&&

.HYDROLOGY...No river flooding is expected over the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$


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