962
FXUS66 KSEW 010433
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
933 PM PDT Sun Jun 30 2024

.SYNOPSIS...High pressure will build far offshore tonight into
Monday maintaining onshore flow keeping temperatures near normal
for the next few days. High pressure shifts over the region late
in the week about a sharp warm up starting around the
Independence Day holiday and continuing through the weekend.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...Shower activity has dried
up for the most part this evening. Skies have cleared a bit over
the southern portion of Western Washington. Will update the
forecast and get rid of the chance of showers tonight. Some light
showers are possible early Monday over the Cascades as another
weak disturbance slides by to the east. Otherwise, low stratus
along the coast tonight will try to make it inland Monday
morning. The building offshore ridge will remain in place Monday
through Wednesday. With it remaining offshore, this should
maintain some onshore low level flow that will hold temperatures
generally near seasonal normals through Wednesday with some
morning clouds giving way to afternoon sunshine. Felton

.LONG TERM /THURSDAY THROUGH SUNDAY/...Previous discussion
follows. Strong agreement in the global ensemble guidance for the
ridge to begin to build eastward over the Pacific Northwest
around the Independence Day holiday, ushering in a period of above
normal temperatures. The big question centers around how strong
the ridge gets and when it moves over the region. The most likely
scenario, which remains reflected in the forecast, brings
widespread Moderate HeatRisk to the lowlands Friday and Saturday
with temperatures climbing through the 80s and some local spots
around 90 degrees. It`s worth noting that for next weekend, the
spread in potential temperatures grows significantly, reflecting
some uncertainty between various camps of ensemble solutions.
There are subsets of each ensemble system that suggest either a
weaker ridge or less persistent ridge. As a result, the
deterministic NBM temperature values, which remain close to the
50th percentile of the distribution, continue to be used for the
forecast today. With the increased temperature and lower relative
humidities, it is expected that the grasses and other finer fuels
will have time to begin further drying ahead of the holiday
weekend. This may lead to elevated fire weather concerns in
addition to the potential heat impacts late this week.


&&

.AVIATION...Upper level ridge offshore with northwesterly flow
aloft. In the lower levels light onshore flow. VFR ceilings inland
with LIFR ceilings and reduced visibility along the coast. With
the light onshore flow ceilings lowering over the interior after
10z with MVFR ceilings over most of the interior by 13z. Ceilings
improving for the interior back to VFR 17z-19z. For the coast slow
improvement overnight into Monday morning with ceilings improving
to MVFR by 19z.

KSEA...VFR ceilings overnight into early Monday morning. Ceilings
lowering to MVFR around 13z. Ceilings improving to VFR 17z-19z
with VFR ceilings MOnday afternoon.

Variable wind 5 knots or less becoming southwesterly around 12z.
Winds trying to go northwesterly after 21z. Felton

Felton

&&

.MARINE...An upper level trough is exiting western Washington this
afternoon. There remains a weak surface low over the waterways, but
otherwise high pressure is expected to build over the Pacific
throughout the week, with stronger pushes of onshore flow this
afternoon and Monday. Flow will become northwesterly over the
coastal waters as the high begins to shift towards land.

Breezy west winds of 15 to 25 kt Central/East Strait of Juan de
Fuca through tonight (small craft advisory remains in effect).
For tonight and tomorrow: low marine cloud coverage and fog is
possible along the coastline. Some of the fog may be dense. A
stronger push is expected Monday evening. Sustained winds are
expected to reach 20 to 30 kt in the Central and Eastern Strait.
The gale watch will remain in effect. The northwest flow Tuesday
into Thursday over the outer coastal waters may approach 15 to 25
kt. Seas may also increase to 8 to 10 feet at 9 seconds during
this period (will be 4 to 6 feet outside of Tuesday - Thursday
period).

HPR/Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 3 AM PDT Monday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Gale Watch from Monday afternoon through late Monday night for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

&&

$$