075
FXUS66 KPQR 261544
AFDPQR

Area Forecast Discussion UPDATED
National Weather Service Portland OR
844 AM PDT Wed Jun 26 2024

...UPDATED, for morning aviation weather.

.SYNOPSIS...A weak weather system will bring cooler temperatures
and scattered showers to NW Oregon and SW Washington today into
Thursday. Best shower chances for inland valleys will be
tonight. Dry and warmer conditions Friday and Saturday with
another weak weather system bringing lower temperatures and
scattered shower chances again late Saturday into Sunday. Mild
temperatures and limited shower chances continue early next
week.

&&



n approaching front will bring increasing mid to high level clouds
this morning with a 50-70% chance for a period of MVFR cigs around
15-19Z. Light and variable winds will increase from the southwest 5-
8 kts by 15Z. -Batz
.SHORT TERM...Wednesday through Tuesday...Satellite data early
Wednesday morning shows an upper trough approaching the
Washington and Oregon coasts. Ensemble guidance indicates this
trough will slowly move onshore today into Thursday, with the
trough axis moving onshore late tonight and the associated
surface front not long behind. Onshore flow will return today as
this system approaches, with many inland locations already
beginning to show a wind shift from northerly to southerly
winds. Cooler temperatures expected with this weather system
today and tomorrow. Coastal locations are forecast to only reach
the upper 50s to low 60s, and inland valleys are expected to
remain in the 70s (both NBM and HREF indicate less than 5%
chance of temperatures reaching 80 degrees anywhere in NW Oregon
and SW Washington). Showers are also expected today into
tomorrow. Pre- frontal showers through this afternoon will
mostly be limited to over the ocean and the coast north of
Tillamook with an occasional shower possible over the northern
Coast Range, Cascades, and NW Washington. CAMs then indicate
chances of scattered showers will increase in these areas and as
south as the Salem area this evening into early tomorrow
morning as the trough axis and surface front approach. The best
chances in the Willamette Valley remain along and north of the
Portland metro area (30-45%). Precipitation accumulation through
Thursday will be limited with these showers, anywhere from a
trace to 0.15 inch for inland valleys and a trace to 0.3 inch
for the coast and higher elevations, except for locally up to
0.5 inch in the Cascades north of Marion County.

Dry and warmer weather returns Friday into Saturday as the
trough moves to our east and upper level flow becomes more
zonal. Temperatures are forecast to rise to near to slightly
above daily normals, hovering within a couple degrees of 80F for
inland valleys. NBM indicates a 35-50% probability of
temperatures reaching 80 degrees on Friday and 50-65%
probability for the same on Saturday.

Weak troughing returns later Saturday into Sunday. This would
moderate temperatures back into the 70s for inland valleys and
60s for the coast. Ensemble members suggest the potential for
the return of scattered showers, 40-60% for the coast and higher
elevations and 15-35% for inland valleys according to the NBM.
Again, amounts look very limited at this time. Ensembles show
bit more uncertainty in the pattern early next week, though in
general the suggested patterns would bring continued mild
weather. Temperatures look to remain in the 70s for inland
valleys with mostly dry conditions, except for the potential for
lingering scattered showers Monday. -HEC
 &&

.AVIATION...Strong onshore flow across the region this am, with
widespread MVFR (CIGS 1500 to 2500 ft) as marine layer stratus
spreads inland. As of 8 am, still holes in the stratus from Portland
area to Kelso, but that will fill in by 18Z. Stratus will slowly
lift to VFR before breaking apart this afternoon.

Meanwhile, low pressure offshore will spread a few showers inland
this am. Better chance of showers later this afternoon along the
coast and inland over the Cascades, with that chance of showers for
all areas overnight. Generally, will remain VFR with broken decks
from 3500 to 6000 ft tonight into Thu am.

PDX AND APPROACHES...Onshore flow will dominate weather pattern
today, with mix of low VFR and MVFR CIGS this am into early
afternoon, then mostly VFR after 21Z. Will maintain VFR tonight, but
CIGS likely to reform at 3500 to 4000 ft. Will maintain a small
chance (25% or less) for showers today into the evening, but that
goes up a bit more tonight.                            /Rockey

&&

.MARINE...Weakening low pressure will send a cold front through
the waters today, supporting scattered rain showers. Northwest
winds will turn southwesterly this morning as the front approaches
from the west. Winds are expected to remain below 20 kt. High
pressure builds across the waters again for Thursday and Friday,
bringing a return of northerlies. Seas remain in the to 4 to 6 ft
range through most of the week as a westerly swell moves across
the waters.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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