947
FXUS66 KSEW 170341
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
741 PM PST Sun Feb 16 2025
.SYNOPSIS...Low pressure and a frontal system will continue to
produce precipitation across the region Sunday into Monday.
Accumulating snowfall will also continue in the Cascades through
this time. The pattern remains wet and unsettled, with more
widespread precipitation expected Wednesday and next weekend. High
temperatures will slowly warm through the week, reaching low 50s
by the end of the week.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY/...No updates to the
forecast this evening, with the following discussion still on
track.
Snow coverage is expected to increase again tonight with activity
passing through from the southwest. Snow rates may approach 1/2
an inch per hour tonight/Monday morning. Most likely another 5 to
10 inches of snow will fall during this window, so will keep the
winter storm warning through 10 am Monday for elevations above
2,500 ft. After that time, any new additional snowfall
accumulations are not expected to produce any travel impacts over
the Cascades., with potential
Tuesday will see a modest ridge dry most of the region out. Only
caveats will be any convergence zone activity that lingers into
the Cascades Tuesday morning, and the next frontal system
approaching late Tuesday with a shortwave trough. It will be
challenging to get rid of any cloud cover in between systems on
Tuesday (due to RH`s aloft being nearly saturated with moisture
with southerly flow just aloft).
The shortwave trough Tuesday into Wednesday will bring an
organized frontal system into western WA. The warm air will bring
snow levels above 4,000 ft for most areas outside of the Cascades
(Cascades will just get above 3,000 ft). This will most likely
keep snow chances (depending on how ensembles resolve the warmer
air intruding in Wednesday). Will keep an eye for potentially
advisory level snow accumulations at Snoqualmie/Stevens Passes
Wednesday into Thursday. Most of the QPF with this system will be
concentrated in the Olympics. While there is a significant range
in potential outcomes at this point, NBM has a over a 50% chance
of at least 1 inch of QPF along the coast/South Interior/Olympic
and Cascades region. Check back for updates on this system and any
potential hydrologic concerns through the week.
High temperatures will reach upper 40s today, with a few low 50s
possible on Tuesday. Lows will drop into the low 40s. THere may be
some breezy east winds in the Cascades with the system Wednesday,
but at this time winds are expected to remain well below advisory
thresholds.
.LONG TERM /FRIDAY THROUGH MONDAY/...Precipitation chances will
decrease Thursday into Friday as the trough exits the region, and
is replaced with a brief transient ridge before another shortwave
trough returns precipitation chances Friday, primarily along the
coast. Ensembles/IVT analysis shows potential for an atmospheric
river event next weekend. QPF amounts will likely change between
now and next weekend, but this will be an area of potential
concern for flooding (see hydrologic discussion below). Expect
temperatures to remain mild, approaching the mid 50s by next
weekend.
HPR
&&
.AVIATION...A weak upper level trough is over the region with SW/W
flow aloft. The flow will turn more NW as the trough moves east on
Monday. The low level air mass remain moist with light showers.
Ceilings are mostly MVFR to low-end VFR. Low clouds and MVFR
conditions are likely to persist into Monday with light winds. 33
KSEA...Ongoing showers and possible MVFR conditions tonight. The
air mass remains moist Monday morning with little change in
conditions. S winds around 5 kt. 33
&&
.MARINE...A surface trough will shift inland tonight while seas
remain elevated - a Small Craft Advisory remains in effect. High
pressure brings generally light winds Monday night into Tuesday.
S/SE flow increases Tuesday night and Wednesday with the next
incoming Pacific frontal system. 33
&&
.HYDROLOGY...A series of storm systems will move across western
Washington this week bringing several rounds of modest precipitation
to the area. Snow levels will remain in the 3000-4000 ft range until
late in the week. A warmer and wetter system next weekend could
result in more widespread river rises and the possibility of
flooding along the Skokomish River. Until then, no flooding is
forecast, but the Skokomish may rise into action stage by mid-
week.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Warning until 10 AM PST Monday for West Slopes
North Cascades and Passes-West Slopes North Central
Cascades and Passes-West Slopes South Central Cascades and
Passes.
PZ...Small Craft Advisory until 10 PM PST Monday for Grays Harbor Bar.
Small Craft Advisory until 6 AM PST Tuesday for Coastal Waters
From Cape Flattery To James Island 10 To 60 Nm-Coastal
Waters From Cape Flattery To James Island Out 10 Nm-Coastal
Waters From James Island To Point Grenville 10 To 60 Nm-
Coastal Waters From James Island To Point Grenville Out 10
Nm-Coastal Waters From Point Grenville To Cape Shoalwater
10 To 60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm.
&&
$$
NWS SEW Office Area Forecast Discussion
Discussion Script by Ken True at Saratoga Weather - WFO Script by SE Lincoln Weather
