273
FXUS66 KSEW 011638
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
938 AM PDT Wed May 1 2024

.SYNOPSIS...Another weak system will slide to the south late
Wednesday into Thursday, bringing in light shower activity. Drier
and warmer conditions are expected Thursday and Friday before more
precipitation arrives in time for the weekend and beyond.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...A chilly start to the morning
with lows around the south sound and foothills in the 30s. The
Frost Advisory ended a few hours early as temps have risen into
the 40s (for the most part). Otherwise, no major changes or
updates expected. 33

Previous discussion...Dry conditions will continue on into the
afternoon for much of the region as weak ridging builds inland
ahead of an approaching low. A weak shortwave will cross the
region Wednesday afternoon, which may stir up scattered showers
mainly over the Olympic Peninsula. Temperatures for much of the
lowlands will peak in the mid to upper 50s.

A weak low pressure system will slide south of the region late
Wednesday into Thursday, bringing more light precipitation over
the Olympic Peninsula and Chehalis Valley. Showers will linger
over southwest Washington into Thursday morning with some wrap-
around moisture triggering light showers over the Cascades
Thursday afternoon. Continued warming will allow temperatures to
return to normal for early May, with highs in the mid 60s.

A deeper low pressure system will drop along the Pacific Coast on
Friday, lifting a warm front across the region and allowing
temperatures to continue to warm. While ensembles continue to show
disagreement in the evolution of this storm system, models
continue to highlight the potential for highs near 70 degrees on
Friday. Uncertainty also remains over the intensity of
precipitation that enters the region Friday afternoon and evening
with this system. Ensembles focus the bulk of the incoming
moisture over the Olympic Peninsula, with widespread precipitation
continuing into the weekend and snow levels above 4000-5000 ft.

.LONG TERM /SATURDAY THROUGH TUESDAY/...While uncertainty remains
throughout the extended forecast period, a wetter and cooler
pattern is favored to continue through the weekend and into next
week. Ensemble members continue to show different solutions over
the path of the low along the coast, with some members pulling the
system southward through the weekend and other members bringing
the low across Washington which would result in heavier
precipitation. Moist zonal flow is favored to develop by the end
of the weekend and into next week, maintaining showery conditions
with below-normal temperatures.

Lindeman

&&

.AVIATION...An upper level trough will continue to shift eastward
into Wednesday as upper level ridging resides across the northeast
Pacific. An upper level low will then sink into the area along the
periphery of the ridge tonight. Northerly flow will continue
aloft and low level flow has shifted back to the south overnight.
Most terminals are VFR this morning, except for those in the
vicinity of patchy fog. With ample moisture still present in the
low levels, can expect fog development to briefly drop conditions
down to MVFR to IFR for terminals within its vicinity at times
through this morning. Latest guidance shows fog mainly persisting
across areas of the south Sound and southwest interior. Low
clouds and fog look to scatter by 18Z, allowing for more
widespread return to VFR conditions. Otherwise, expect for
streaming mid level clouds likely to increase after 16Z
Wednesday. Winds in the low levels will generally persist from the
south at 3-7 kt through the day, before shifting to the north
tonight.

KSEA...VFR conditions this morning. Winds will persist out of the
southeast at 3-6 kt. Increasing middle level clouds expected
after 17Z, but VFR conditions are likely to continue. Winds look
to transition to the north tonight, but look to remain light at 5
to 7 kt or less into Thursday. 14/Maz

&&

.MARINE...Onshore flow will continue through the day with high
pressure residing over the coastal waters. A low pressure system
offshore will then move southeast tonight and move into northern
Oregon on Thursday morning, allowing for southerly winds over the
outer coastal waters to pick up tonight. Weak high pressure will
then rebuild over the area waters Thursday night into Friday,
keeping conditions calm across the area waters. The next system
will then move into the waters Friday night into Saturday, likely
bringing another round of area headlines. This will then be
followed by another frontal system that looks to arrive late in
the weekend.

Seas generally hovering between 6-8 ft this morning will continue
to subside towards 3-5 ft throughout the day today. Seas look to
persist at this range into Friday, before building back over the
weekend as systems move across the area. 14

&&

.HYDROLOGY...No river flooding is expected over the next 7 days.

&&

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

$$