Heat in Washington, September 10, 2022

Area Forecast Discussion
National Weather Service Seattle WA
947 AM PDT Sat Sep 10 2022

.UPDATE...An upper level ridge will continue to reside across the
region today, with offshore flow persisting at the surface. Latest
satellite imagery shows smoke continuing to advect into Western
Washington this morning, especially in areas of the north-central
Sound due to the new Bolt Creek fire start overnight (near
Skykomish). This will likely continue to impact air quality
throughout the day. Further details are highlighted in the fire
weather section below. Despite all the conditions in place for a
hot day, afternoon highs today will likely trend cooler given the
smoke coverage over the region. Highs look to top out in the upper
70s to mid 80s across the interior and upper 80s for areas along
the coast under less wildfire smoke. The previous discussion
follows below, with updates made to the aviation, marine, and fire
weather sections. 14

&&

.SYNOPSIS...Upper level ridge over Western Washington today will
shift east tonight and Sunday. Low level offshore flow will weaken
this afternoon with the low level flow turning onshore tonight.
Upper level troughs moving through the area Monday through Friday
combined with low level onshore flow will result in a round of
normal temperatures. Slight chance of showers at times mainly over
the mountains.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...Satellite imagery shows
cloudy free skies over Western Washington early this morning.
Low level smoke visible up on the roof here at the office. Wide
range of temperatures at 3 am/10z with mid 60s in locations
exposed to the easterly winds while in wind sheltered areas
temperatures are as cool as near 50.

Upper level ridge over Western Washington today. Low level
offshore flow peaking this morning then easing this afternoon.
850 mb winds also light easterly this morning turning southerly
this afternoon. Still a little bit of warming aloft today. KUIL
850 mb temperature on the 00z sounding was plus 19C. 850 mb
temperatures this afternoon in the plus 20 to 22C range. These
conditions alone would give Western Washington highs in the 80s to
as warm as the mid 90s. Because of the smoke being advected in
due to the offshore flow highs will be 5 to 10 degrees less, in
the upper 70s and 80s. With the KUIL-KBLI gradient down to -4 mb
and less smoke in the area possibility the north coast will get
into the lower 90s.

Center of the upper level ridge shifting into Eastern Washington
tonight. Low level flow turning light onshore. Winds in the lower
levels light which will make it hard to scour the smoke out of the
area. Lows mostly in the 50s.

Surface low offshore will throw a wrench into the marine push
Sunday. Narrow surface ridge will give the coast a southerly surge
of marine air during the day dropping temperatures 20 degrees or
so from the highs today. For the interior the combination of light
onshore flow and cooling temperatures aloft will also a result in
cooler high temperatures but only by 5 to 10 degrees. Winds in the
lower levels turning southwesterly in the afternoon but at this
point winds do not look strong enough to scour the smoke out of
the area. In addition the southwesterly flow aloft could tap into
smoke currently offshore from the Cedar Creek fire in Oregon.

Upper level trough offshore Sunday night will approach the coast
Monday. Increasing low level onshore flow into Monday will draw
stratus along the coast into the interior Monday morning. The
increasing onshore flow will continue the cooling trend with
highs in the 60s along the coast and upper 60s to mid 70s for the
interior. The increasing onshore flow will also scour the smoke
out of Western Washington. Chance of showers over the Cascades in
the afternoon.

.LONG TERM /TUESDAY THROUGH FRIDAY/...Upper level troughiness
remaining over Western Washington through the period. Trough axis
moving through Tuesday and again late in the period. Main result
from these troughs will be a deepening of the marine layer for
possible morning drizzle and isolated showers in the mountains.
Models hinting at a stronger trough arriving late next week or
over the weekend for a better chance for showers and cooler
temperatures but a lot of uncertainty at this point so for now
will just have slight chance of showers over most of the area
Friday. Felton

&&

.AVIATION...A ridge over the area through today with light
Southwesterly flow aloft. Offshore flow at the surface. Smoke this
morning through must of today with lower vsbys at times, and
potentially lower cigs, although some uncertainty in the forecast
for the cigs today. Expect a scatter/broken smoke layer through much
of today. Stratus will increase along the coast tonight into Sunday.
East/Northeast winds through today will be breezy with increasing
south winds along the coast late tonight into Sunday morning.

KSEA...The smoke aloft will form a scatter/broken layer near 2500-
3500 feet for much of today. Confidence in lower cigs/vsbys is
lower, however, potential exists, particularly this
afternoon/evening into tonight. N/NE winds through much of today
with more southerly winds late tonight into Sunday morning. JD

&&

.MARINE...The flow is offshore for the waters today with high
pressure over the area. Small Craft Advisory winds for the central
and western Strait of Juan de Fuca as well as northern coastal
waters from the offshore flow today. SCA winds at times for the
Puget Sound. SCA winds are briefly possible at times off Grays
Harbor and over the southern outer coastal waters, but expected to
be rather limited through today. Increasing southerly winds and
stratus along the coastline late tonight into Sunday. SCA winds
possible in these areas with the increasing south winds. Increasing
southwesterly winds for most of the area on Monday. Seas mostly 4 to
6 feet through the early part of next week over the coastal waters.
A mix southerly wind wave with westerly short period swell along the
coast Sunday into Sunday night. JD

&&

.FIRE WEATHER...Red Flag Warnings remain in effect today and into
tomorrow. Critical fire weather parameters of hot, dry and windy
conditions expected with minimum RHs of 15-30 percent with gusty
N/NE/E winds of 15-30 mph for the west slopes of the Cascades,
Olympics, and much of the lowlands today. Winds easing tonight.
Local wildfires such as the Chilliwack Complex, Goat Rocks and Bolt
Creek are showing active fire behavior, with Bolt Creek showing
rapid rates of spread throughout the morning. This in particular
will have significant air quality impacts into this afternoon.  A
weak onshore push will bring slightly cooler conditions, less wind,
and higher RHs on Sunday for the lowlands. However, the Cascades,
and to some degree the Olympics, will remain dry and unstable with a
mid-level Haines of 6. As such, the Red Flag Warning will persist
for at least the Cascades throughout Sunday. Will evaluate with
latest data for any potential updates in afternoon forecast package.
The fire danger threat will lessen region wide Monday as an upper
level trough approaches the area and low level onshore flow
increases, bringing cooler and more moist conditions. 18/Felton/Bower

&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Red Flag Warning until midnight PDT tonight for Black Hills and
     Southwest Interior Lowlands-Central Coastal Lowlands-
     Central and South Puget Sound Lowlands-East Portion of the
     Olympic Mountains-North Coastal Lowlands-North and Central
     Coastal Strip-Northeast Puget Sound Lowlands Generally
     Below 1500 Feet-Southeast Puget Sound Lowlands Generally
     Below 1500 Feet-West Portion of the Olympic Mountains.

     Red Flag Warning until 7 PM PDT Sunday for West Slopes of the
     Central Cascades Generally above 1500 Feet-West Slopes of
     the North Cascades Generally above 1500 Feet.

PZ...Small Craft Advisory until 8 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca-Coastal Waters From Cape
     Flattery To James Island 10 To 60 Nm-Coastal Waters From
     Cape Flattery To James Island Out 10 Nm-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 2 PM PDT this afternoon for Puget
     Sound and Hood Canal.

&&