711
FXUS66 KSEW 070347
AFDSEW

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

.UPDATE...No changes made here in this evening`s update. Scattered
showers and convergence zone activity is still ongoing but
thunderstorm chances will diminish with loss of diurnal heating.
For tonight, overnight lows are forecast to fall into the upper
30s to lower 40s with continued rain showers and snow for passes.
The previous discussion remains below along with an updated
marine/aviation section.

&&


.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 FRIDAY/...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...Onshore flow will continue throughout the day as a surface
cold front continues to move inland. Small Craft Advisories will
continue 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 thanks to strong onshore flow behind
yesterday`s cold front. 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 9 to 11 ft tonight through Tuesday as
high pressure amplifies towards the coast. A Small Craft Advisory
remains in effect 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 ft Wednesday and beyond.

Davis/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 until 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 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.

&&

$$