757
FXUS66 KPQR 300935
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
235 AM PDT Sun Jun 30 2024

.SYNOPSIS...Light shower chances continue across the northern
portions of the CWA today. Onshore flow will maintain near
average temperatures into early next week. There is 50-60%
chance that stronger high pressure offshore will shift over the
region towards the end of next week and bring the hottest
temperatures of the Summer so far.

&&

.SHORT TERM...Sunday through Tuesday...Upper level trough
continues moving over the PacNW today. Scattered showers
dissipated by late last night but are expected to return later
this morning into the afternoon as surface heating produces
enough localized instability. Showers will mainly be located
over the Coast Range and Cascades as orographic forcing will be
the main lifting mechanism for showers, but a few could meander
into the valley. NAM soundings show significantly less
instability for today than yesterday, so thunderstorm or heavy
shower chances are very limited with today`s scattered showers.

As the upper trough moves east Monday into Tuesday, ensemble
guidance continues to indicate strong ridging building over the
eastern Pacific with lower heights over the PacNW. This will
bring dry weather but will keep temperatures stable at right
around normal. Expect high temperatures for inland valleys in
the upper 70s to low 80s today through Tuesday with 60s along
the coast. -HEC

.LONG TERM...Wednesday through Saturday...The overall pattern
remains the same on Wednesday, according to the WPC 500 mb
cluster analysis, though the ridge axis looks to shift slightly
east over the Pacific which would allow widespread 80s for
inland valleys.

Thursday into Saturday remain a little uncertain as ensemble
members continue to struggle to handle the specifics of the
pattern. However, consensus in the WPC clusters is increasing on
either the upper ridge moving over the region or remaining close
enough to the region to warm temperatures into the 90s, though
the timing of the ridge moving inland remains uncertain. NBM and
LREF also agree with this scenario as both indicate around a
50-60% chance of temperatures reaching or exceeding 95F Friday
and Saturday for inland valleys, which would be the warmest
temperatures of the summer so far. NBM also indicates a 30-40%
chance of inland valleys reaching 100F at least one of those
days. It still needs to be mentioned that there`s a 5-15% chance
of a shortwave trough breaking through the ridge and approaching
the region Friday or Saturday, bringing stronger onshore flow
and lowering temperatures back to near normal. -HEC

&&

.AVIATION...VFR prevails inland as a weak upper level disturbances
tracks across the region. Marine stratus has begun to settle into
the coast with a mix of IFR to LIFR cigs/vis already in place a
KAST and KONP. These should see gradual improvement through the
day Sunday with MVFR to low VFR conditions prevailing come the mid
to late afternoon hours. Inland VFR conditions with CIGs around
4000-6000 ft will deteriorate as winds shift west/southwest at
low and mid levels to spread marine clouds with MVFR cigs inland
roughly after 10-13Z Sun, then gradually improving to VFR after
18-19Z Sun. The HREF projects a 60-80% chance for CIGS at or
below 3kft between 12-18z before the aforementioned improvement
finally takes place.

PDX AND APPROACHES...VFR conditions will begin to deteriorate
around 10Z with increasing chances for MVFR cigs 2000-3000 ft to
develop. Chances for MVFR peak at around ~70-80% 12-18Z Sun, then
rapidly decrease by 18Z Sun for high chances of VFR. -Batz

&&

.MARINE...Weak high pressure over the northeast Pacific with lower
surface pressure over California and the Great Basin will more or
less maintain itself into next week. A weak area of surface low
pressure will pass over the area today, supporting initially
southwest winds before turning to the west in its wake. Otherwise,
expect north to northwest winds across the waters as high pressure
strengthens toward the middle of next week, with the strongest
winds generally off the central coast of Oregon and lighter winds
farther north. Winds will generally peak in the afternoon and
evening hours each day. A thermal low develops along the northern
California/southwest Oregon coast on Tuesday and
strengthening/spreading north into Wednesday and thereafter.
This will increase the pressure gradient along the coast and over
the waters with a >90% chance that northerly wind gusts of 20-30
kt spread northward across the waters by mid week. This will in
return develop steep wind driven seas of 5-8 ft with a dominant
period of 7-8 seconds by late Tuesday or Wednesday. -Batz

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.

&&

$$

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