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562
FXUS66 KSEW 231632
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
932 AM PDT Tue Jul 23 2024

.SYNOPSIS...Upper level trough over Western Washington through
Thursday. The trough will move off to the northeast Friday. A
weaker trough will take its place over the weekend into the first
part of next week. Temperatures will remain near or just a little
below normal through the period.

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.SHORT TERM /TODAY THROUGH THURSDAY/...
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The current forecast
remains on track with no planned updates this morning. 33

Previous discussion...Cloud cover over the interior not the
result of a marine push overnight. Instead the cloud cover is
being caused by weak convergence over the area. Surface gradients,
which were onshore yesterday, have gone flat overnight. Weakening
convergence combined with the lack of onshore flow will not
maintain the cloud cover much past the mid to late morning hours
leaving sunny skies across the area for the afternoon. 500 mb
heights even with the trough in the vicinity in the lower to mid
580 dms. Morning cloud cover will cut the high temperatures back a
few degrees with 70s inland and mid to upper 60s along the coast.

Upper level trough remaining over the area tonight and Wednesday
with the trough axis offshore. Surface gradients going briefly
onshore this evening with the onshore flow dissipating by
Wednesday morning. It will be a touch brisk for July out there
Wednesday morning with lows in the upper 40s to mid 50s. With
sunshine from the get go highs will be a little warmer but still
in the 70s inland and mid to upper 60s along the coast.

Upper level trough axis approaching Western Washington Wednesday
night with the axis moving through Thursday morning. Weak
shortwave with the trough axis could produce a shower over the
northern portion of the area especially in the Cascades.
Increasing onshore flow behind the trough axis will keep skies
partly sunny/mostly cloudy Thursday. Highs a little cooler, in the
mid 60s to mid 70s. Lows Thursday morning again on the cool side,
upper 40s to mid 50s.

.LONG TERM /FRIDAY THROUGH MONDAY/...Extended models in good
agreement with the upper level trough kicking out to the
northeast Friday and northwesterly flow aloft over the area.
Weaker trough settling over Western Washington for the weekend
into the first part of next week. While the operational runs don`t
show much, a portion of the ensemble solutions for Monday ( and
Tuesday ) have light precipitation over the northern portion of
the area. 500 mb heights in the mid to upper 570s dms, not
impressive but enough to confine the shower chances Monday to near
the Canadian border. Low level flow remaining onshore for the
most part. This combined with the weak trough aloft will keep
temperatures near normal. Highs in the 70s over the interior and
mid 60s to lower 70s for the coast. Lows each morning in the 50s.
Felton
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.AVIATION...
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Westerly/southwesterly flow aloft as a low pressure
churns in the northeast Pacific, with light onshore flow in the
lower levels. Expect any lingering OVC MVFR ceilings to gradually
lift and break apart late this morning into the afternoon, leading
to VFR for all terminals throughout the remainder of the day. N/NE
winds 5 to 10 knots will back to N/NW late this afternoon and
increase to around 8 to 12 knots throughout the interior.

KSEA...Expect VFR to prevail by late morning as clouds gradually
lift and scatter out. NE winds this morning 4 to 8 knots will turn
more N/NW after 20z and increase to 8 to 12 knots. VFR will persist
through the TAF period.

Mazurkiewicz/Kristell
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&&

.MARINE...A surface high pressure will remain over the offshore
waters with lower pressure inland. Additional weak systems look to
cross over the waters over the next several days with varying
degrees of onshore flow.

Latest guidance suggest a 30% chance of westerly winds reaching
small craft strength through the Central and Eastern entrance of
the Strait of Juan De Fuca this afternoon. With onshore flow
being a touch weaker than previous days, did not hoist up an
advisory for this afternoon. Will continue to monitor if one is
needed later on in the day.

Additional onshore pushes of westerly winds will be likely through
the Strait over the next couple of days and could yield additional
headlines at times.

Coastal seas 3 to 5 feet will generally remain through the rest
of the week.

Mazurkiewicz

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.SEW WATCHES/WARNINGS/ADVISORIES...
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WA...None.
PZ...None.
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$$