881
FXUS66 KSEW 062111
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
211 PM PDT Mon May 6 2024

.SYNOPSIS...Cool and showery conditions will continue across the
region into Tuesday with lowland rain and mountain snow expected.
A Puget Sound Convergence Zone will develop later on today with
isolated thunderstorms possible across most of the area. The
pattern will shift starting around midweek as a upper level ridge
builds over our region, bringing dry and much warmer temperatures
into the weekend.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...A upper level trough
will sweep through western Washington this afternoon into the
evening which will provide instability and some lift for
widespread rain showers and isolated thunderstorms across the
area. Brief gusty wind, small hail, and isolated lightning will
be the main hazard associated with any thunderstorm that develops
this afternoon. Recent radar imagery already shows post-frontal
rain showers moving onshore through the interior. Afternoon
temperatures will remaining in the mid 50s.

Along with widespread showers and isolated thunderstorms, a Puget
Sound Convergence Zone will develop this afternoon across
Snohomish into Central Skagit County, moving southward into King
county by this evening. Meanwhile, snow levels will start to fall
to around 3000 feet this evening and around 2500 feet by Tuesday
morning. Light snow is possible down to around Stevens Pass and
Snoqualmie Pass into this evening. Amounts look generally light,
but with the Puget Sound Convergence Zone shifting southward into
the Cascades, there is a chance that the PSCZ may enhance the
snowfall totals near the passes. Overall, best chance for
accumulating snowfall would be on the higher mountain elevations
of the Cascades. NBM probabilities generally show a 25-35% chance
of 3 to 5 inches at Snoqualmie Pass this evening into early
Tuesday morning, with amounts most likely ending up on the 1 to 2
inch scale (mainly due to road temperatures as well).

Showers will linger into Tuesday but will be mainly confined to
the mountains, with the thunderstorm threat also diminishing.
Temperatures will continue to stay in the mid to upper 50s.

A pattern shift will become clear on Wednesday as the upper level
trough moves off to the east to make room for an upper level
ridge to build just offshore western Washington. Cloud cover will
begin to decrease with temps starting to warm into the lower 60s.

The warm up continues into Thursday, with temperatures reaching
into the the low to mid 70s, and possibly even upper 70s in the
Southwest Interior. Areas near the water will likely experience a
temps a little bit cooler, in the upper 60s/lower 70s. A more
significant warm up will continue into the weekend.

.LONG TERM /FRIDAY THROUGH MONDAY/...Ensemble guidance remains in
a quite strong agreement with the aforementioned upper level ridge
shifting closer to the Pacific Northwest and taking residence
there through the long term period. There is still some details to
iron out regarding exact location and placement of this ridge,
but confidence is high that most areas will see the first 80
degree day this year on Friday and Saturday - which seem to be the
warmest days of the week. While the precise temperature will
likely fluctuate in the coming days, it is worth noting that this
is our first significant warm up of the year and it is heading
into a weekend. Many folks will want to be outside and take
advantage of the nice weather and want to be around bodies of
water. Keep in mind that local waters and rivers are still quite
cool, with hypothermia risk possible even with the warm air
temperatures. Be sure to adhere to safety practices if you are out
in or around the water during this time.

Mazurkiewicz

&&

.AVIATION...Mainly VFR with areas of localized MVFR/IFR in scattered
post-frontal shower activity and areas of low ceilings. Shower
activity will continue through the evening with southwest to west
surface flow generally 5-15 kt with gusts 20-30 kt this afternoon.
Convergence zone shower activity will develop this afternoon
generating MVFR ceilings and the potential for a few lightning
strikes and locally heavier rain, and will slowly drift between
Snohomish and King Counties into the early morning Tues. Shower
activity will decrease but continue into Tuesday afternoon with
improving ceilings.

KSEA...Generally VFR with S/SW winds 12-17 kt with gusts 23-28 kt.
Scattered showers and SCT/BKN ceilings this afternoon. Low (10% to
15%) chance of lightning through Tues/06z. Convergence zone showers
will drift southward later this evening, lowering ceilings to MVFR.
Convergence zone will likely cause variable winds and a brief shift
to northeasterly winds between Tues/00z-05z.

15

&&

.MARINE...Onshore flow will continue throughout the day as a surface
cold front continues to move inland. Small Craft Advisories will
continue for the Puget Sound and Hood Canal through this evening and
for the Central and East Entrance to the Strait of Juan de Fuca
and Admiralty Inlet through tonight.

Winds up to 25 to 30 kt will continue through the Strait of Juan de
Fuca, Admiralty Inlet, and southern side of the San Juan Islands
through Tuesday as high pressure begins to develop to the west over the
open ocean. Winds will turn westerly then northwesterly and slowly
decrease as high pressure moves into the region towards the middle of
the week, and high pressure is expected to linger through the weekend.

Combined seas will build to 10 to 11 feet tonight through Tuesday as
high pressure amplifies towards the coast. A Small Craft Advisory has
been issued for the coastal waters through Tuesday evening. Seas will
gradually subside as high pressure continues to increase over the
region, lessening between 5 and 7 feet Wednesday and beyond.

15

&&

.HYDROLOGY...No river flooding expected in the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 8 PM PDT Tuesday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory from 8 PM this evening to 5 AM PDT Tuesday
     for Admiralty Inlet.

     Small Craft Advisory from 11 AM to 8 PM PDT Tuesday for
     Admiralty Inlet.

     Small Craft Advisory until 6 PM PDT this evening for Puget Sound
     and Hood Canal.

     Small Craft Advisory from 11 PM this evening to 8 PM PDT 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.

&&

$$