Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

077
FXUS66 KSEW 280239
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
740 PM PDT Sun Sep 27 2020

.SYNOPSIS...Warm and dry conditions across Western Washington this
week with strong high pressure aloft over the region. Temperatures
warm more significantly starting Monday as offshore flow begins to
develop, with temperatures expected to be well above normal through
much of the week. A slight cooldown begins next weekend as the
next disturbance may begin approach the region.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Clear skies in place
over W WA this evening with temperatures ranging in the upper 50s to
lower 60s at the time of this writing. Upper level ridging should
keep clear skies in place...although some isolated spots more prone
to fog such as Hoquiam and Olympia might see some development late
tonight/early tomorrow morning. For forecast details...please see
the Previous Forecast Discussion section below.  18

From Previous Forecast Discussion...Warm and dry conditions will be
the general rule across the region this week as strong high pressure
amplifies over the region. Meanwhile, low level flow becomes
northerly tonight before transitioning to more of an offshore
(easterly) direction tonight into Monday. Expect to see some shallow
fog or low stratus again in the typically fog-prone river valleys
and near Puget Sound, but this is not expected to be particularly
widespread otherwise given the increasing north to northeast flow
overnight.

This sets the stage for plenty of sunshine Monday, with
temperatures warming into the 70s across much of the area - a
generally 5-7 degree increase over today`s highs. A very similar
day is expected Tuesday as compared to Monday, but few morning
clouds given the continued drying of the air mass and
temperatures will likely trend up another few degrees as the
thermal trough over the coast intensifies a bit more. Wednesday
generally looks like a copy of Tuesday across the interior, though
the coast might see a little cooling later in the afternoon as
the thermal trough begins to push inland allowing a late afternoon
sea breeze to return.

Cullen

.LONG TERM /THURSDAY THROUGH SUNDAY/...From Previous Forecast
Discussion...The long term period looks to remain generally warm and
dry, at least through most of the period. Guidance suggests the
ridge will very gradually weaken through the late stages of the weak
as the ridge axis slowly shifts eastward. Nonetheless, temperatures
will still likely remain in the 70s inland, or several degrees above
normal. Light offshore flow across the interior and some marine
influence closer to the coast will likely continue. The next
disturbance may begin to approach the area by the end of the
weekend, returning temperatures closer to seasonal normals and
perhaps a renewed chance of rain across the region.

One other note is that guidance suggests that some smoke from
fires in northern California may be transported offshore and back
around into the Pacific Northwest late by late Wednesday or
Thursday. While confidence in the precise timing and just how
concentrated the smoke may be remain quite low and depend on many
factors (including fire behavior/smoke production and winds
aloft), this wouldn`t be expected to be nearly as widespread as
the persistent smoke earlier this month. For now, just something
to be aware of and continue to monitor in the coming days.

Cullen

&&

.AVIATION...High pressure will remain in control over the area
through much of this week. Flow aloft will become westerly with
surface flow remaining light, turning offshore tonight and Monday.
VFR conditions into tonight. Fog is possible Monday morning along
the coast and into the southwest interior for brief period of IFR to
LIFR conditions. Otherwise VFR conditions will continue elsewhere
through the period with a few high clouds.

KSEA...VFR conditions through the period. A few mid to high level
clouds at times. Northerly winds 5 to 10 kts.

CEO/18

&&

.MARINE...Offshore flow will rule this week as high pressure builds
into the area. For the most part, flow will remain light and below
any headline criteria. Increasing long period swell Monday afternoon
into Tuesday with 10 to 12 feet possible. Inherited small craft
advisories for the coastal waters and for a rough bar in Grays
Harbor Bar cover this cover this well and see no need for forecast
updates with the evening package.

CEO/18

&&

.HYDROLOGY...Warm and dry conditions are expected through the next
7 days, with no significant rainfall expected across the region.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 PM Monday to 11 AM PDT Tuesday for
     Coastal Waters From Cape Flattery To James Island 10 To 60
     Nm-Coastal Waters From Cape Flattery To James Island Out 10
     Nm-Coastal Waters From James Island To Point Grenville 10
     To 60 Nm-Coastal Waters From James Island To Point
     Grenville Out 10 Nm-Coastal Waters From Point Grenville To
     Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater Out 10 Nm-Grays Harbor Bar-
     West Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

www.weather.gov/seattle



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.