882
FXUS66 KSEW 022103
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
203 PM PDT Tue Jul 2 2024

.SYNOPSIS...A warming trend with dry conditions is expected
through this weekend. Hot conditions with temperatures reaching
the upper 80s and 90s across much of the region by this weekend.
These warm and dry conditions will also result in elevated fire
weather concerns by the weekend. Slight cooling is possible next
week.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...A ridge of high pressure
over the eastern Pacific will strengthen and very slowly shift
east through Thursday night before stalling with its axis
along/just offshore of the Washington coast on Friday. This
synoptic progression will lead to a warming and drying trend
across the western US, including western Washington. Conditions
will seem relatively pleasant through about the 4th before things
start to get hot Friday. By Friday, high temperatures will reach
well into the 80s across the lowlands north from Seattle
northward, and into the low to mid 90s for some areas of SW
Washington. HeatRisk levels will reach widespread moderate/orange
levels by Friday.

.LONG TERM /SATURDAY THROUGH TUESDAY/...On Saturday and Sunday the
ridge axis will move overhead, likely resulting in the warmest
temperatures of the period. Temperatures will reach the upper 80s
and 90s across much of the region. At this time, the probability
of reaching 100 degrees is low across most of the region, however
the Chehalis River Valley does have probabilities ranging from
30-40% near Chehalis to 50-70% near Elma. Overnight low
temperatures will hover in the low 60s across most of the region.
These conditions will result in widespread HeatRisk levels of at
least moderate/orange with some favored areas (such as urban heat
islands and the western slopes of the Cascades and Olympics)
reaching major/red. Compared to the forecast from 12 hours ago,
there was a slight increase in the temperature forecast from
Sunday night into Monday due to some consensus that the ridge may
favor a slower eastward progression early next week. This resulted
in the highest HeatRisk across the bulk of the area on Sunday (vs
Saturday previously). For this event, we will no doubt see hot
temperatures and heat-related impacts across the region. However,
we are not in the center of this heat event (that will be further
south and east of us) and as such at this time we are not
anticipating impacts on the level of the 2021 "Heat Dome" event.
Still, this level of heat can result in multiple heat-related
illnesses for those without access to adequate cooling or
hydration.

Weak onshore flow may develop Sunday into early next week,
allowing for a gradual cooling trend. However, temperatures are
forecast to remain well above normal through much of next week.

&&

.AVIATION...N to NW flow over western WA today with strong high
pressure anchored offshore. The low level air mass remains moist
with low clouds and MVFR conditions lingering over the south sound
and coast. MVFR conditions will expand overnight with onshore
flow. Low clouds will lift/scatter Wednesday afternoon with VFR
conditions expected. 33

KSEA...SCT-BKN deck around 45000-5000ft will scatter this
afternoon and early evening. Light and variable winds with brief N
flow through 06z. Low clouds and MVFR conditions returning by 12z
Wednesday with a trend toward VFR by 18-21z. 33

&&

.MARINE...Another surge of westerly winds through the Strait of
Juan de Fuca this evening - a Small Craft Advisory is in effect.
NW winds will also be within Small Craft Advisory range over the
outer Coastal Waters. Winds will turn more N to NW on Wednesday as
strong high pressure shifts toward Vancouver Island. The flow
will turn offshore on Thursday as a thermal trough forms along the
coast. Offshore flow will continue into the weekend then flip
back onshore on Sunday. 33

&&

.FIRE WEATHER...Benign fire weather conditions are expected through
Thursday. However, a strong upper-level ridge will amplify over the
region bringing not only continued dry weather but hot temperatures
starting Friday and lasting through early next week. A thermally
induced surface trough appears to remain to our south around
southern Oregon. This should keep discourage strong offshore winds
which is a plus. However, hot, dry, and unstable conditions will be
enough to maintain elevated fire weather conditions especially with
fuels expected to dry out rapidly during this heat stretch.

McMillian

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 3 AM PDT
     Wednesday for Central U.S. Waters Strait Of Juan De Fuca-
     East Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 11 AM PDT Wednesday for Coastal
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm.

&&

$$