FXUS66 KSEW 272134

Area Forecast Discussion
National Weather Service Seattle WA
234 PM PDT Tue Oct 27 2020

.SYNOPSIS...Mainly dry conditions across the region this week with
high pressure. The exception is near the Canadian border where
there`s a chance of rain due to a front over southern British
Columbia. A cold front will bring showers to western Washington on
Friday. The weekend is looking dry with high pressure.


.SHORT TERM /TONIGHT THROUGH FRIDAY/...High pressure remains in
place offshore, keeping W WA under mostly dry northerly flow. The
rest of today should remain mild under a deck of mid to upper
level clouds.

The offshore ridge dampens slightly on Wednesday and a front
stalled over southern B.C. may lead to light showers in areas
along the International Border and Strait of Juan de Fuca. The
rest of W WA looks to stay dry, with temperatures in the mid to
upper 50s.

The ridge amplifies once again, slightly, by Thursday which will
lend itself to the warmest temperatures of the week, with
afternoon highs reaching the upper 50s and low 60s. Changes will
be underway by Thursday afternoon as surface flow should switch to
a more south/southwesterly component ahead of the next cold front
to arrive onshore overnight into Friday. This system appears
fairly typical for the fall season and may offer more widespread,
albeit light precipitation amounts, and breezy conditions.

.LONG TERM /SATURDAY THROUGH TUESDAY/...The aforementioned front
does not seem to linger in the area for long and rapidly
progresses east into Saturday. High pressure is quick to build
back in over the area, with the core of the ridge moving inland
from its previous offshore position. Temperatures will likely
moderate back to seasonal normals through Sunday with dry

As the ridge progresses inland, the upper level flow pattern with
transition into something more consistent with that of a broad
upper level trough beginning Monday afternoon. The models are
generally picking up on what looks to be a slightly more robust
upper level trough moving through the area by late week, and may
contain more moisture than the immediately antecedent system to
move through over the weekend. Exact track, timing, QPF and
impacts cannot be speculated on at this time with certainty, but
bears watching over the next few days for more concrete details to
come in.



.AVIATION...Upper ridge offshore will gradually weaken over the next
24 hours as stalled frontal boundary well to the northwest of the
region sags southward. Northwest flow aloft continues through
Wednesday with light flow in the low levels. With the exception of
the coast, VFR expected into the evening hours. Light surface flow
will allow ceilings to redevelop and lower late tonight with
widespread low MVFR or IFR likely on Wednesday morning.

KSEA...VFR ceilings expected this evening. Ceilings lowering down to
1000-2000 feet 10Z-12z Wednesday. Conditions will likely be slow to
improve Wednesday afternoon. Surface winds light southerly. 27


.MARINE...High pressure over the waters will gradually weaken
through Thursday as a frontal boundary near Haida Gwaii gradually
sags southward toward northern Vancouver Island and stalls. A
somewhat stronger front will arrive Friday with small craft
advisory winds possible over most of the waters. Winds will ease
Friday night and Saturday as high pressure rebuilds over the
area. Light offshore flow is expected on Sunday. Felton/27


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





NWS SEW Office Area Forecast Discussion