585
FXUS66 KSEW 030256
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
756 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.

&&

.UPDATE...Sky coverage remains mostly clear (with a few bands of
cumulus remaining in the Cascades and Puget Sound this evening.
Coastal stratus will push in again for Wednesday morning with some
moisture before conditions rapidly warm up and dry out by the end
of the week and this weekend. Please see discussion below for more
details (also updated aviation and marine sections).

HPR

&&

.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 aloft over western WA today with strong
high pressure anchored offshore. Conditions mostly VFR except for
along the coast where stationary low clouds have lingered throughout
the day, resulting in MVFR cigs there. More widespread MVFR
conditions expected to develop overnight with most terminals
reaching MVFR by 12-15Z Wednesday morning. A return to VFR skies is
expect by early afternoon...with locations more prone to lower cigs
holding off until mid afternoon.

KSEA...VFR conditions persisting this evening and into the overnight
period. MVFR conditions expected to develop around or a little after
12Z and persist through late morning. VFR conditions return by 20Z.
Southwest to westerly winds this evening at 4-8 kts, becoming light
and variable overnight. Westerly winds 5-10 kts expected Wednesday
afternoon.

18

&&

.MARINE...Westerly winds in the Strait and northwesterlies over the
outer coastal waters still reaching Small Craft Advisory levels and
as such will leave inherited headline in place. 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.

Seas 5 to 7 ft tonight and Wednesday before relaxing slightly to 3
to 6 ft Thursday.

33/18

&&

.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 until 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.

&&

$$