161
FXUS66 KSEW 232220
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
320 PM PDT Thu May 23 2024

.SYNOPSIS...Brief high pressure will pass through the region
today, leading to some cloud breaks for the afternoon, and warmer
temperatures. A disturbance will pass through the region Friday
into Saturday, brining cooler temperatures and the return chance
of showers. Sunday looks to dry out some before additional
disturbance pass through next week.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...Upper level analysis shows
a ridge passing over Washington today. Down at the surface, a
surface low/trough sits east of the Cascades, with another surface
system northwest of Washington. Satellite imagery shows quite a
bit of cloud cover still to be cleared out for the afternoon, with
low stratus over all areas except the Olympics. Model guidance
was suggesting expansive cloud breaks in Puget Sound up to the
Canadian border this afternoon, but confidence is low in there
being complete sunshine. Most likely will see some breaks. With
temperatures also still in the mid 50s today, extended cloud
coverage will likely keep highs from climbing far above 60. Areas
that do clear out substantially will however have a shot of mid
60s. Winds out of the west/southwest will decrease overnight to
around 5 mph.

The next disturbance is quickly wrapping down into Washington from
Canada. An upper level trough is expected to pass through Friday
into Saturday. The main surface low will arrive on Friday, with a
surface low pressure tracking southeastward over Washington. This
will bring a weakening occluded front through the region, with
onshore westerly flow into Washington. Moisture is limited with
this round of showers, but the best chance of seeing anything over
a tenth of an inch of QPF is from Snohomish to Skagit County
(possible convergence zone late Friday night). If convection is
able to form, amounts may exceed a quarter of an inch with the
heaviest showers. A rumble of thunder is possible but not likely
at this point (given increased temperatures aloft). Temperatures
cool down into the 50s Friday and Saturday. Winds remain light out
of the southwest 5-10 mph.

Upper level ridging Sunday appears to dry out most of the region.
Only caveat is a surface low will pass to the northwest of
Washington well into Canada. This will keep shower chances Sunday
confined to the coast, West Olympics and North Cascades. There is
also a slight warm up to the 60s during the day as well.

.LONG TERM /MONDAY THROUGH THURSDAY/...Agreement is good between
ensemble/deterministic models for troughing to continue through
much of next week. This is as upper level ridging in the
Rockies/Great Plains keeps us influenced by a trough off the coast
of B.C. Canada. This will stop the pattern from progressing for
the first part of the week, with the blockage of the ridge
eastward. Overall, shower chances will continue for much of the
extended forecast with a slow moving cold front passing through
Monday into Tuesday. Monday appears to be the warmest day with
highs potentially topping out in the upper 60s to low 70s
(depending on how much warm air advection is brought in behind the
ridge before the trough). Remainder of the week brings a lot of
mid 60s for high temperatures across western Washington.

HPR

&&

.AVIATION...Weak high pressure will move inland for dry conditions
tonight. Ceilings remain around 3500 ft and VFR conditions will
prevail overnight. Clouds will lower Friday morning with a return
to MVFR conditions as the next frontal system moves in. Showers
mainly along the coast 12-20z with vicinity showers in the
interior. 33

KSEA...VFR conditions tonight with S wind around 5-10 kt. MVFR
conditions return by 12z with showers in the vicinity through the
afternoon. 33

&&

.MARINE...Generally light winds across the waters tonight as weak
high pressure moves in. A frontal system will cross western WA on
Friday with a brief westerly push down the Strait of Juan de
Fuca. High pressure over the NE Pacific maintains onshore flow
through Saturday with N/NW winds near Small Craft Advisory
criteria over the the Outer Coastal Waters. The next frontal
system will move into B.C. on Sunday with south flow increasing
over the waters. 33

&&

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

$$