Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

000
FXUS66 KSEW 251004
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
304 AM PDT Mon Mar 25 2024

.SYNOPSIS...Cloudy conditions with periodic showers will continue
through Tuesday as a series of weak fronts cross the region. A
stronger and wetter system will bring in more widespread lowland
rain and mountain snow alongside breezy winds through at least
Thursday. Drier and warmer conditions are on track to return by
the weekend.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...Clouds will continue to
increase early this morning as an approaching weak cold front
generates onshore flow. Showers will move inland throughout the
morning, filling in across western Washington by the afternoon
with snow levels hovering between 2500-3500 ft. A weak impulse in
the northwest flow aloft will maintain scattered shower activity
across the area on Tuesday ahead of brief drying Tuesday evening.
Lower elevations will see up to a quarter of an inch of rainfall
over the next two days while the mountains see light accumulating
snowfall. Snoqualmie Pass will see periods of transitioning
precipitation with a low (20% to 30%) chance of over an inch of
snow accumulation through Tuesday evening, while Stevens Pass
will see a moderate (50% to 60%) chance of 2 inches of snow or
more. Temperatures on Monday and Tuesday will peak in the low to
mid 50s across the lowlands with cloudy skies sticking around.

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...Unsettled conditions will
continue through the remainder of the week as a stronger storm
system moves into the Pacific Northwest. A front stemming from a
deepening offshore low will swing across western Washington on
Wednesday, spreading another round of widespread lowland rain and
mountain snow into the region. Southerly flow aloft will allow
temperatures to warm up a few degrees, lifting snow levels above
4000 ft Wednesday afternoon. South to southeast winds will become
breezy as the front passes, and weak instability to allow for an
isolated lightning strike or two in stronger showers that develop.
The low will continue to inch towards the coast on Thursday, with
continued southerly flow advecting ample moisture northward. The
bulk of the moisture with this storm system will be focused over
the Olympic Peninsula, with preliminary snow totals of 1 to 2 feet
over the Olympics between Wednesday and Thursday. The Cascade
passes are on track to see 2 to 6 inches of snow, with up to a
foot or more over the higher peaks, while much of the lowlands
will see an inch or less of rainfall.

Diffluence aloft will allow for conditions to start to dry out on
Friday as showers exit to the northeast. A positively tilted ridge
will build into the Pacific Northwest over the weekend, bringing
in warmer temperatures and dry conditions. Temperatures across the
lowlands are favored (60% to 80% chance) to reach 60 degrees or
higher by Sunday.

Lindeman

&&

.AVIATION...North to northwesterly flow aloft today as an upper
level ridge begins to move towards western Washington. Widespread
low to mid level cloud cover across the region with ceilings at low-
end VFR to MVFR. Sufficient low-level moisture will allow ceilings
to remain or lower to MVFR through the morning as a frontal system
approaches the region. Ceilings may lift back up to VFR late morning
into the afternoon, but will lower back to MVFR area-wide early this
evening as the front makes its way across the region. Scattered
showers will also accompany the front, though light and limited in
coverage. These conditions will persist through the end of the TAF
period.

Southwesterly flow this morning, becoming breezy up to 10-15 kt
through the Seattle area terminals. Winds will ease up tonight but
remain southwesterly to westerly along the coast.

KSEA...VFR conditions this morning. Ceilings may further lower,
potentially reaching high-end MVFR after 12-15Z, but should return
to VFR into the afternoon. Ceilings becoming MVFR after 21-00Z as a
frontal system moves through the region, also bringing light
scattered showers. Southwesterly winds 12-15 kt gusting to 20 kt on
occasion this morning, easing this afternoon into tonight into the 5-
8 kt range and remaining southwesterly.

LH

&&

.MARINE...Southwesterly onshore flow continues as a frontal system
moves through the coastal waters later today. Winds will be most
breezy through the Strait of Juan de Fuca, where a Small Craft
Advisory remains in effect this morning. Weak high pressure will
fill in behind this system on Tuesday, leaving similar conditions to
yesterday with a push of westerlies through the central Strait of
Juan de Fuca. Winds look to top out just below Small Craft Advisory
criteria. A more substantial frontal system will pass through the
region Tuesday night into Wednesday that will likely bring gale
force winds to the coastal waters. The system slowly moves westward,
keeping conditions breezy on Thursday before easing into the end of
the week.

Seas 5 to 7 ft at 15 seconds build tomorrow night to around 10 to 12
ft, increasing again Wednesday night into Thursday to 13 to 15 ft
before easing below 10 ft by the end of the week.

LH

&&

.HYDROLOGY...A frontal system entering the area on Wednesday will
bring moderate rain over the Olympics which may cause the
Skokomish River to rise above action stage into Thursday.
Fortunately other rivers will likely not see much of a rise.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 AM PDT early this morning for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

&&

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.