221
FXUS66 KPQR 270944
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
244 AM PDT Thu Jun 27 2024

.SYNOPSIS...Scattered showers continue across NW Oregon and SW
Washington through Thursday with another day of below normal
temperatures, peaking in the upper 60s to low 70s inland.
Temperatures raise to near to above normal Friday into Saturday,
back into the 80s inland, before another weak weather system
lowers temperatures a few degrees and brings another round of
scattered showers, mainly for the coast and higher terrain late
Saturday into Monday. Rising temperatures and dry weather
returns Tuesday into at least midweek.

&&

.SHORT TERM...Thursday through Saturday...Water vapor satellite
imagery as of 2 AM Thursday shows the upper level trough axis
has pushed inland, and surface observations indicate the
surface front has done the same. Scattered showers did spread
inland ahead of the front Wednesday evening, and radar imagery
shows showers continuing currently, mainly along the coast and
higher terrain with a few showers in down to valley floors
around and north of the Portland metro area. A weak shortwave
along the back end of the upper trough will allow showers to
continue through this afternoon for the mentioned areas and the
northern Willamette Valley. Daytime temperatures will be similar
to yesterday with inland valleys only peaking in the upper 60s
to low 70s and upper 50s to 60s along the coast. Additional rain
accumulation will be limited with anywhere from a trace to 0.15
inch, up to 0.25 to 0.5 inch for localized spots in the Cascades
north of Santiam Pass that have consistent showers.

After the trough moves to the east tonight, upper level flow
becomes more zonal Friday into Saturday with a surface thermal
trough forming over southern Oregon. This will bring dry and
warmer weather to the region. Inland temperatures are expected
to rise into the upper 70s to low 80s with mid to upper 60s
along the coast. Skies will be mostly sunny Friday, but another
approaching upper trough will bring increasing cloud cover
across the region Saturday with the return of onshore flow. -HEC

.LONG TERM...Sunday through Wednesday...Ensemble guidance is in
very good agreement of a weak upper level trough moving through
the PacNW Sunday as 100% of the WPC 500mb clusters indicate this
pattern. Another round of scattered showers are expected with
this trough, though coverage looks to be less expansive than
the current trough as the surface forcing looks to be limited.
About a 15-30% of showers is forecast along the coast and
terrain as orographics will be the main forcing for showers.
Temperatures may lower a few degrees back to near normal (mid to
upper 70s).

Some ensemble members as well as deterministic models indicate
the potential for another shortwave on the back end of the
trough Monday which would allow shower chances and near normal
temperatures to continue. By Tuesday into Wednesday, 85% of the
WPC clusters indicate a ridge building over the eastern Pacific
with the other 15% indicating zonal flow. Dry weather is
expected to return with either of these patterns with
temperatures rising back into at least the low 80s. -HEC


&&

.AVIATION...Onshore flow persists through Thursday as an upper
level trough axis shifts farther east through the day. Conditions
inland will be mainly VFR with a brief period of MVFR CIGs this
morning between 15-20Z with CIGs dropping to around 1500-3000 ft.
The coast will be trickier with conditions fluctuating between
VFR with mid level clouds at 3000-6000 ft and MVFR/IFR (or lower)
with clouds below 2000 ft. Scattered light rain showers will
continue to plaque the region into Thursday afternoon before
tapering off this evening around 3Z. Winds will remain
south/southwesterly at 5-10 kts through 18-22Z before turn to the
west/northwest late this morning and into the afternoon.


PDX AND APPROACHES...VFR deck with main deck at 3000 to 5000 ft
to start before CIGS likely drop below 3000 ft Thursday morning
around 15-20z. Showers remain largely in the vicinity of the site
through the morning before increasing in coverage slightly early
Thursday afternoon before drying out by the evening. -Batz

&&

.MARINE...South/southwest flow around 10-15 kts will continue
through the morning before turning to the northeast as high
pressure offshore will return briefly through early Sat. At same
time, will see thermal low pressure over far southwest Oregon into
northwest California. As such, will get back into some northerly
winds, with gusts 20 kt in afternoons/evenings.

Yet another weak low pressure arrives later Sat, with winds
flipping back to the west or southwest. Gradients weaker, so winds
not expected above 15 kt. Seas stay in the 4 to 6 ft range.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

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