National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KSEW 250943
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
243 AM PDT Thu Apr 25 2024

.SYNOPSIS...A wet finish to the work week is in store as multiple
disturbances pass through western Washington. A surface system
will stall over the region Thursday into Friday, which will
produce widespread stratiform rain across the region. A couple
more disturbances will produce lighter showers across the region
this weekend into next week as the upper level pattern remains
unsettled. Expect high temperatures to remain below normal with
temperatures climbing into the 50s.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...Upper level analysis
showers a deepening upper level low/trough beginning to dig down
along the west coast today. A jet core to the west aids in the
deepening of the trough. The pattern is also slowed down by a
ridge over the Great Plains that will begin to move east on
Friday/Saturday (as well as the system itself slowing down as it
arrives onto land). A surface warm front sits just off the
Washington coast west of Hoquiam this morning, with moist air
advection making its way into the region via southwesterlies
aloft. As the surface low drops down from off the coast of B.C.
Canada, the trailing cold front is expected to occlude and stall
over the region through Friday.

Radar imagery this morning already shows bands of rain moving
inland along the coast, and up into Victoria Canada. As the system
drops down into the region, rain chances will increase region-wide
Thursday morning through Friday. Precipitation is expected to be
in the form of rain (with snow levels increasing to around 5,000
feet Thursday/Friday keeping wintry precipitation generally above
this level). Coverage of the activity will be widespread - with
multiple bands of rain moving across the region during the
remainder of today and into Friday morning (then tapering down to
showers). As a result, total QPF from this system will be
significant higher compared to the garden-variety showers that
have been seen so far. Most likely amounts for regions include
around 1.5 to 2.25 inches in the coast/Olympics, 1 to 2 inches in
the north Cascades, and around half an inch for remaining lowland
areas. If the system over-performs (i.e. convective banding with
limited CAPE) - amounts will increase 0.25 to 0.50 inches for
totals through Friday afternoon.

Remainder of Friday/Saturday stays wet with shower activity
expected to continue via a weakening stalled surface trough over
the coast, and a weak upper-level trough. Amounts remain light
from second half of Friday through Saturday. Temperatures will
remain cool with highs in the 50s (Friday appearing to be the
warmest of the short term forecast with a couple 60s possible).
Lows will hover in the mid and upper 40s with the rain activity.
Wind will remain light out of the south at 5 to 10 miles per hour.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...The long range models show
good agreement of the cool and wet weather pattern continuing into
next week across western Washington (as well as the majority of
the Pacific Northwest). There`s disagreement after Wednesday as
for how deep the low will go down the west coast (which may depend
on how strong the ridge over the Great Plains is when it sets up
mid week next week). For now, the chance of showers will continue
Sunday through Wednesday in the forecast. The wetter days appear
to be on Sunday in the North Cascades, and along the coast Tuesday
into Wednesday, where more stratiform rain is possible via
weakening/slow surface systems. Again, confidence is low in timing
of the synoptic features after Monday - expect amounts to change
in future updates. Winds will remain light out of the south, and
temperatures will remain cool with highs in the 50s, and lows in
the 40s.

HPR

&&

.AVIATION...Moist S/SW flow continues over western WA with rain
spreading over the region. Ceilings will be mostly within MVFR
range through much of the day. Surface winds southerly around 10.
Little changes overnight as rain and MVFR cigs persist. 33

KSEA...Rain throughout the day with MVFR conditions. S winds
around 5-10 kt. 33

&&

.MARINE...A cold front will move inland today with strongest
winds over the southern Coastal Waters, Admiralty Inlet and
the eastern Strait of Juan de Fuca - Small Craft Advisories are
in effect. Winds will ease tonight. Active conditions look to
continue with several systems moving through western WA this
weekend and early next week. 33

&&

.HYDROLOGY...No river flooding expected in the next 7 days.
However heavy rain over the south slopes of the Olympics Thursday
into Thursday night could push the Skokomish River in Mason
county close to action stage Friday. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for Admiralty
     Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 5 AM early this morning to 5 PM PDT
     this afternoon for Coastal Waters From Point Grenville To
     Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater Out 10 Nm.

&&

$$