858
FXUS66 KSEW 171613
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
913 AM PDT Mon Jun 17 2024

.SYNOPSIS...Light shower activity will linger today as an upper
level trough shifts eastward. High pressure aloft will gradually
build through the week, allowing conditions to dry out and warm
up. A pattern change is on track for the end of the week as a
trough brings wetter and cooler conditions to western Washington.


&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...No planned updates to the
forecast this morning and current trends are on track. 33

previous discussion...Light shower and virga activity will
continue to push southward throughout the day today as moisture
wraps around an exiting trough to the east. Combined with onshore
flow, cloudy skies will stick around today and limit temperatures
to the low to mid 60s for most areas. Instability will be lacking,
so thunderstorms are unlikely to form this afternoon. Shower
activity will taper off over the Cascades through the evening and
early morning hours as drier air moves inland.

High pressure will build into the region on Tuesday and Wednesday,
allowing conditions to warm up and dry out. Clearing skies and a
transition to more zonal flow aloft will allow temperatures to
return to near-normal on Tuesday. Thermal troughing to the south
and weak onshore flow will allow most inland lowland areas to
reach the mid to upper 70s on Wednesday, while coastal areas peak
a bit cooler near the 70 degree mark.

.LONG TERM /THURSDAY THROUGH SUNDAY/...Warming will continue
through the end of the week as low amplitude ridging continues to
build across the region on Thursday and Friday. Most lowland areas
apart from the coast will reach 80 degrees on Thursday, and
temperatures are on track to peak on Friday. Temperatures Friday
are slated to reach the mid 80s, roughly 10 to 15 degrees above
normal. This may be the warmest day of the year so far for inland
areas. However, the current forecast is still several degrees
below daily records, and ensembles maintain a low (10% or less)
chance of reaching record temperatures. The latest HeatRisk shows
a moderate risk of localized urban heat stress that may impact
vulnerable populations for the Seattle, Tacoma, and Olympia metro
areas and will continue to be monitored.

Ensembles are in good agreement over a pattern change by the
weekend, with cooler and wetter weather on tap. Temperatures are
favored to return to near-normal by Sunday, with a return of
cloudy skies and a chance (20% to 30%) of light precipitation for
most areas.

Lindeman


&&

.AVIATION...Northerly flow aloft today as a departing upper level
trough continues eastward over the Rockies. A few lingering showers
remain across western Washington, mostly confined to over the
Cascade mountains. A few scattered showers remain possible across
the region throughout the day today, diminishing this evening.
Recent hi-res guidance is indicating the possibility for a
convergence zone over northern King County this afternoon. Ceilings
across the region are mostly MVFR, locally lower/higher in other
locations. Ceilings look to slowly rise up to low-end VFR late
morning into early afternoon with widespread clearing not expected
today. Convergence zone development may keep ceilings locally lower.
Ceilings look to lower back into widespread MVFR this evening
through tomorrow morning. Southerly winds will continue across the
area today, increasing up to 8 to 12 kt today. Winds will decrease
this evening, becoming light southerly to variable.

KSEA...Light showers east of the terminal this morning with IFR
becoming MVFR ceilings. Ceilings should continue to rise to low-end
VFR early this afternoon. A convergence zone north of the terminal
may keep ceilings locally lower into the afternoon. VFR conditions
should continue through this evening before lowering back to MVFR
early tomorrow morning. Southerly winds continue through this TAF
period, increasing to 5 to 10 kt this afternoon before decreasing
this evening.

LH

&&

.MARINE...High pressure over the NE Pacific will maintain onshore
flow over western WA this week. Highest winds and waves will be
through the Strait of Juan de Fuca, mainly during the afternoon and
evening hours. A Small Craft Advisory remains in effect beginning
this afternoon through early Tuesday morning. Winds remain light
through much of the forecast with high pressure remaining just
offshore. The next frontal system is not expected until this weekend.

Seas 4 to 6 ft are expected to persist through the remainder of this
week.

18/LH

&&

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

&&

$$