790
FXUS66 KSEW 292135
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
235 PM PDT Wed May 29 2024

.SYNOPSIS...Convergence zone activity with embedded thunderstorms
are likely to persist into the evening hours before dissipating.
Weak high pressure will impact the region from the south for drier
and slightly warmer temperatures on Thursday and Friday.
Additional frontal systems and an increase in moisture is likely
to return early next week.


&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...Convergence zone showers
and isolated thunderstorms are occurring along the I-90 corridor
and along the King and Snohomish county lines. The threat for
thunderstorms will persist until sundown as solar heating and
resultant instability wanes. The storms will be capable of
producing heavy rain and brief spurts of graupel. Additional
showers are moving in along the coast, but are generally just
light rain at the time of this writing.

A shortwave ridge is expected Thursday and Friday ahead of the
next frontal system, but it is only expected to return the
temperatures to seasonally normal, upper 60s and low 70s. Some
shower activity associated with the next front may arrive at the
coast by Friday afternoon, but Puget Sound and the rest of the
interior will have to wait until early Saturday morning to see
that wave of precipitation arrive.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Long range cluster
analysis is in good agreement on troughing lingering in the area,
favoring cooler temperatures and increased precipitation. Sunday
through Tuesday will feature a parade of systems, some taking on
atmospheric river levels of moisture and high snow levels,
bringing up to 4 inches of rain on the windward slopes of the
Olympics and Cascades, amd over an inch of rain throughout much of
Puget Sound over those three days. While some may digress that
this is not the type of late spring weather most desire, receiving
moisture like this at this point in the year is incredibly
beneficial in providing some breathing room on fuel receptiveness
to fires. While it won`t nix the threat of a fire season
completely, the region is far better off with receiving this
moisture than not.

That tidbit aside, high temperatures through Wednesday will likely
only be in the upper 50s and low 60s. With ongoing precipitation
over three days, the Skokomish, Snohomish and Skykomish rivers
will need to be monitored as they are likely to rise into Action
stage flood levels by Monday and Tuesday.

For what its worth, and much further in the distance, it is worth
noting that in the 8-14 day outlook from the Climate Prediction
Center, there is a signal for a heat event centered over
California, but western Washington is in the slight risk of
excessive heat category. This is something that will be closely
watched and at this time, no projections on exact temperatures can
be made, but rather something to think about if you still need to
get air conditioning units put back in windows, etc.

Kristell


&&

.AVIATION...An upper level trough is over western Washington this
afternoon. Flow behind the trough will quickly become northwesterly.
Unstable airmass (aided by some sunshine late this morning and
afternoon) has sparked the convergence zone from Kitsap County into
King County, primarily along the I-90 corridor. Activity is expected
to continue primarily in this area through the afternoon as it
slides eastward. Heavy rain (reducing visibilities and ceilings),
along with gusty winds, possible lightning and small hail are all
possible with the convergence zone. Showers are still possible at
northern and southern terminals, but are not expected to be as
strong as the convergence zone. Precipitation will wrap up this
evening, with some partial VFR clearing occuring this evening. MVFR
ceilings will roll in for Thursday morning (primarily along I-5
corridor in Puget Sound to the Canadian border). Surface winds out
of the west at 8 to 12 kt decreasing overnight to under 5 kt (winds
out of the north for areas under the convergence zone through early
evening.

KSEA...Convergence zone activity continuing through the afternoon
(vicinity showers and possibility of a heavy shower/thunderstorm).
Winds have begun to shift to the north at KSEA and KBFI (with a few
gusts to 25 kt observed), but will quickly turn to the northeast as
the showers move out to the east, before turning back to the
southeast at around at 4 to 8 kt. For Thursday morning, MVFR
ceilings possible early to mid/late morning, winds transitioning to
the northwest 4 to 8 kt after 18Z.

HPR


&&

.MARINE...An upper level trough has moved inland, with ridging
taking place offshore, maintaining onshore flow. A strong push of
westerlies will persist through the Strait of Juan de Fuca this
afternoon and evening (will continue the small craft advisory).
Expect the ridge to weaken Friday with systems to follow this
weekend into next week potentially bringing gusty winds and higher
seas. Seas through the end of the week will hold around 4 to 6 ft.

HPR


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 2 AM PDT Thursday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

&&

$$