Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 021642

Area Forecast Discussion
National Weather Service Seattle WA
942 AM PDT Sat Jul 2 2022

.UPDATE /0945 AM/...No updates to the forecast this morning.
There remains the chance for thunderstorms this afternoon. The
primary location of concern will be the Cascades.

The previous forecast discussion with updated aviation and marine
sections is below.


.SYNOPSIS...An upper low off the coast will gradually push over
the area Sunday and Monday before dissipating. This will bring
cooler weather with showers at times. A second upper low will
develop off the coast in the middle of next week.


.SHORT TERM /TODAY THROUGH MONDAY/...Satellite imagery shows
interior filling up with stratus this morning from about Skagit
county southward. Still mostly clear skies over Whatcom and san
Juan county. Temperatures at 3 am/10z were in the 50s.

Weak upper level low remaining offshore today. In the lower levels
onshore flow increasing. This will keep the cloud cover intact
longer today with just some partial clearing over the interior in
the afternoon. Southerly flow aloft and a slightly unstable air
mass over the Cascades could produce an afternoon shower or two
especially near the crest. Highs today with the cloud cover will
be below normal, in the 60s and lower 70s.

Upper level low continuing to drift southeast overnight and
Sunday with the low centered off the Northern Oregon coast late
Sunday afternoon. Increasing mid level moisture and instability as
the low moves closer to the area. Flow aloft becoming
southeasterly pushing shower activity off the Cascades and into
the interior from about Puget Sound eastward tonight and over the
entire area Sunday. Deformation zone forming near the Canadian
border Sunday making the precipitation type rain over Whatcom and
San Juan counties. If this rain was happening today Bellingham
would have a chance to break the daily rain record ( 0.48 inches
in 1962 ) but the record Sunday is the wettest day on record in
July for Bellingham ( 1.78 inches in 1990 ). Thunderstorms will
remain possible over the Cascades and with the southeast flow
aloft there is a chance they could get as far west as the Cascade
foothills. Lows tonight in the 50s. Highs Sunday will only be in
the upper 50s to mid 60s.

Low weakening and moving over the top of Western Washington
Sunday night into Monday keeping showers in the forecast. The low
will dissipate north of the area Monday evening. Showers Sunday
night into Monday decreasing from the south Monday afternoon and
evening. Looks dry Monday night from about Olympia southward.
Lows Monday morning in the 50s. Highs Monday only in the 60s.

.LONG TERM /TUESDAY THROUGH FRIDAY/...Extended models in good
agreement with another upper level flow forming off the coast
Tuesday and remaining offshore at least into Thursday with
southwesterly flow aloft over the area. In the lower levels
varying degrees of onshore flow. Air mass slightly unstable
especially in the afternoon and early evening hours combined with
mid level moisture embedded in the southwesterly flow aloft will
keep a slight chance of showers in the forecast in the afternoon
or evening hours all three days. Ensembles in line with this idea
with no real dry spell in the forecast but also just a few
solutions with light precipitation. Models differ on Friday with
the ECMWF lifting the low north of the area while the GFS is a
little slower with this process. Even the slower GFS has only 2
out of the 30 ensemble members with light rain. Will keep the
slight chance of showers out of the forecast Friday. Highs will
be near normal for the entire period with mid and upper 60s on the
coast and mid 60s to mid 70s inland.



.AVIATION...Southwesterly flow aloft will turn more southerly by
this afternoon and into Sunday as an upper level low sits just off
the coast.

Mix of cigs this morning as marine stratus remain in place over W
WA. IFR conditions mostly concentrated around Puget Sound and in the
South Sound area. MVFR conditions present along the coast while VFR
conditions in place over the San Juan Islands and northern portions
of the CWA, such as BLI. While the expectation is that these clouds
will eventually recede and give way to VFR conditions during the
afternoon, this will likely be delayed from previous thinking by at
least a couple of hours, in the early to mid afternoon time frame.
MVFR/IFR cigs expected to return later tonight. Mainly W/NW winds
through this evening.

KSEA...IFR cigs in place with gradual improvement. VFR conditions
expected to emerge around 20Z, but that may need to be re-evaluated
should satellite trends remain stubborn. MVFR conditions expected to
redevelop overnight tonight after 09Z. Winds W/NW through the
evening before turning SW overnight. 18


.MARINE...An upper low with mainly westerly flow through early next
week with increasing westerly winds across the central and eastern
Strait of Juan de Fuca during each afternoon/evening. Small Craft
Advisory winds for the central and eastern Strait of Juan de Fuca
through today, with winds potentially decreasing below Small Craft
Advisory briefly late morning, and increasing through the afternoon.
Gale winds are possible through the central and eastern Strait this
evening, but expected mainly to be Small Craft Advisory winds, only
reaching gale speeds via an occasional gust. SCA winds for the
Admiralty Inlet and northern inland waters this evening and tonight
with increasing westerly/southerly winds. Winds a bit lighter into
next week. Seas 1-3 feet through the weekend and into next week.


.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.


PZ...Small Craft Advisory until 5 AM PDT Sunday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Sunday
     for Admiralty Inlet-Northern Inland Waters Including The
     San Juan Islands.


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