123
FXUS66 KPQR 261021
AFDPQR

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

.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.

&&

.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...An upper level trough moving inland across the PNW
will support increasing southwest, onshore flow at the surface.
Marine stratus in place along the coast is trying to push inland
through the gaps in the Coast Range. MVFR/IFR CIGs are impacting
the KONP and KAST sites respectively and will remain at sub-VFR
conditions through much of the day. HREF guidance suggests the
best chance (70-90%) for stratus to reach the Willamette Valley
is around the Eugene area where MVFR CIGs reach by 12Z. Sporadic
MVFR CIGs develop through the Willamette Valley between 15-20Z,
fluctuating between 30-70%. Winds remain light and variable
through 15Z or so before increasing from the southwest at 10-15
kts. Light rain showers will increase through the day but
shouldn`t bring any major impacts to the terminals.


PDX AND APPROACHES... An 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

&&

.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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