631
FXUS66 KSEW 282014
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
114 PM PDT Tue May 28 2024

.SYNOPSIS...Rain showers will continue to spread inland today as a
frontal system moves across Washington. Convergence zone activity
east of the Puget Sound will continue through the evening with
continued shower activity on Wednesday. A shortwave ridge and
surface high to the south will bring warmer and drier conditions
for the rest of the week. A series of systems will cross the
Pacific Northwest over the weekend and into early next week,
bringing more rounds of wet weather.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...Stratiform rain spreading
inland will continue to destabilize this afternoon and transition
to showers. Skies will stay mostly cloudy today, limiting high
temperatures to the 50s for most areas. While mean model
instability is fairly limited at 100 J/kg or less, a lightning
strike cannot be ruled out this afternoon. Confidence is high
that convergence zone activity will form this evening over the
Puget Sound which will slowly propagate eastward, lingering
through the early morning hours on Wednesday. Short range
ensembles keep most of the PSCZ shower activity north of Stevens
Pass Highway before dissipating. More post-frontal showers will
spread inland on Wednesday as an upper level trough axis passes
overhead, and models continue to show another round of PSCZ
showers developing in the evening. A few lightning strikes are
possible once again on Wednesday afternoon in any stronger showers
that develop, with slightly more instability available.
Temperatures will peak a couple degrees higher on Wednesday,
closer to 60 degrees for most areas.

High pressure will build inland on Thursday and Friday, allowing
conditions to dry out. Any lingering showers will be limited to
the northern Olympic Peninsula and North Cascades. Temperatures
will warm towards the end of the week, reaching a degree or two
below normal by Friday in the mid to upper 60s for most lowland
locations.

.LONG TERM /SATURDAY THROUGH TUESDAY/...Ensembles show good
agreement that cooler and wetter conditions will return throughout
the long term. A weak shortwave trough is on track to move across
the region on Saturday, cooling temperatures off a few degrees
and bringing in scattered showers. The region will have little
time to dry out with a series of deeper storm systems following
close behind. Long range ensembles continue to show much wetter
conditions entering the region Sunday through Tuesday, especially
over the western Olympic Peninsula and Cascades, where up to 4
inches of rainfall is currently forecast to fall over the span of
three days. However, models continue to show a wide range of
possible solutions with GFS precipitation amounts nearly double
that of the ECWMF. Uncertainty remains in terms of rainfall totals
and the placement of heaviest rainfall through the period.
Temperatures will return to near- normal with highs in the low to
mid 60s through the weekend and into early next week.

Lindeman

&&

.AVIATION...An upper level trough will pass through today with a
weakening cool front/surface trough. Flow aloft is southwesterly and
will transition to west/northwesterly once the trough passes early
Wednesday. Light rain bands continue with the low feature passing
through western Washington this afternoon. Some of the showers have
been able to knock visibilities and ceilings down to IFR briefly at
times. Otherwise, ceilings remain MVFR and improvement to VFR is
still expected late this afternoon and evening. However MVFR
ceilings will return for Wednesday morning for the majority of the
terminals.

Convergence zone activity remains possible, which if one
does form, winds will flip to the west northwest from KPAE, south to
potentially KSEA. The time span for this wind flip is expected to
last roughly 3 to 5 hours, from 21-22Z through around 04-05Z.
Variable winds from other directions are possible during this time
span. Wind speeds are expected to remain around 5 to 10 kt, but a
couple gusts to 20 kt cannot be ruled out.

KSEA...Mix of MVFR/VFR ceilings this afternoon improving to VFR as
shower activity ends. MVFR ceilings will return tomorrow morning.
Possible convergence zone activity to the north may bring variable
winds from 23Z-05Z (flipping from southwest to north & east, and
then back to southwest). Potential exists for gusts out of these
variable directions. Otherwise winds outside of this window will be
out of the southwest at 8 to 12 kt.

HPR

&&

.MARINE...An upper level trough is swinging a front through this
afternoon, with shower activity over much of the waters. Increase in
onshore flow will follow the trough. The push is strong enough for
gusty winds of 15 to 25 kt in the Central/East Strait of Juan de
Fuca. The small craft advisory will remain in effect for the rest of
the day. A similar push is expected Wednesday night into Thursday.
Otherwise winds will remain light and predominately onshore for the
forecast period. Waves will remain at 4 to 6 ft in the outer coastal
waters, with a system early next week bringing waves up to 6 to 8 ft.

HPR

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 2 PM this afternoon to 2 AM PDT
     Wednesday for Central U.S. Waters Strait Of Juan De Fuca-
     East Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$