177
FXUS66 KPQR 180442 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
942 PM PDT Fri Jul 17 2026

Updated Aviation discussion

.SYNOPSIS...A warming and drying trend is underway across
southwest Washington and northwest Oregon as high pressure
gradually builds inland. Temperatures will climb through the
weekend and into early next week, with inland highs reaching the
upper 80s to mid 90s Monday, Tuesday and Wednesday. Hot and dry
weather is likely to persist through at least the middle of
next week.

&&

.SHORT TERM...Now through Sunday night...Broad ridging will
continue to strengthen over the Pacific Northwest through the
weekend as high pressure over The Great Basin becomes the
dominant synoptic feature through the weekend and into next
week. As the ridge develops expect conditions to slowly warm,
but with onshore flow at the surface, that will provide some
mitigation in the overall warming trend. Through the weekend
500 mb heights gradually rise and low-level thermal troughing
develops east of the Coast Range. This will result in inland
highs warming into the lower to mid 80s Saturday before climbing
into the mid to upper 80s Sunday. Coastal communities will
remain considerably cooler with highs in the mid 60s to low 70s
on Saturday and highs in the upper 60s to mid 70s, higher
elevations warm into the upper 70s to mid 80s Saturday and
Sunday. /42-12

.LONG TERM...Monday through Thursday...Ensemble guidance
remains in strong agreement that the ridge will reach its
greatest amplitude early next week, supporting the warmest
temperatures of the forecast period. However, uncertainty for
Tuesday and Wednesday have increased significantly. While
Monday remains rather unscathed as daytime highs are still
expected to be in the upper 80s to low 90s. The spread between
the models and there ensembles really start to show come Tuesday
and Wednesday. Starting at the top with the 500 mb WPC Clusters,
Tuesday the clusters are split in this manner: Cluster 1 (30%),
Cluster 2 and 3 (26%) and Cluster 4 (18%). Visually, there is
very little difference between the clusters, however the biggest
differences between the clusters is the location of an upper
level low off the coast of California and the strength of The
Great Basin High, with said clusters looking to favor The Great
Basin system rather than the Pacific Low. Wednesday, looks even
more uncertain with the Cluster percentage spread of 28%, 28%,
25% and 19%. In addition to the 500 mb spread, some ensemble
models are bringing in some monsoonal moisture into the forecast
Tuesday and Wednesday, which if that occurs, it could easily
impact daytime highs. Said monsoonal moisture will be driven by
the eastern Pacific low. The NBM is picking up on this
potential as the high temperature spread for Tuesday and
Wednesday has increased across the CWA with most areas showing
an 8-12 degree F spread.

Current probabilistic guidance indicates a 25-45% chance of
reaching 90 degrees across much of the interior lowlands on
Monday afternoon, then a 50-75% chance on Tuesday and Wednesday
afternoon. Additionally, there is a 20-40% chance of
temperatures reaching 95 degrees on Tuesday and Wednesday,
highest across the traditionally warmer valleys. While these
temperatures are typical for mid to late July, several
consecutive warm afternoons combined with limited overnight
cooling will result in pockets of Moderate HeatRisk,
particularly for those without adequate cooling or prolonged
outdoor exposure. It should be noted that on Tuesday and
Wednesday there is around a 15% chance for daytime highs around
98 degrees F. So, there is also the potential Major HeatRisk on
Tuesday (15-30%) and Wednesday (10-25%). As Thursday rolls
around, conditions looks to cool by a few degrees as a broad low
(the low mentioned on Tuesday and Wednesday) looks to push
eastward into the Pac NW. /42

&&

.AVIATION...Southwesterly flow aloft continues through Sunday as
an upper low moves into British Columbia. Expect predominately
VFR flight conditions through the TAF period. However, there is a
20-30% chance for CIGs around 2000-3000 ft over the Portland
metro and northern Willamette Valley between 12-17Z Saturday,
except around a 40% chance at KTTD. There is around a 40-50%
chance that LIFR to IFR ceilings develop at the coast between
06-10Z Saturday, otherwise MVFR stratus is expected to persist
through at least 18z Sat.

KPDX AND APPROACHES...Expect mainly VFR flight conditions
through Saturday. However, there is a 20-30% chance for a brief
period of MVFR ceilings around 2000-3000 ft between 12-17Z Sat.
Northwest winds around 4-6 kt are expected through Saturday
morning. /DH

&&

.MARINE...A typical summertime pattern will remain in place
through early next week with persistent north to northwest winds
over the coastal waters. Winds will be strongest during the
afternoon and evening hours each day, especially this weekend to
the south of Cape Falcon. Expect wind gusts up to 25 kt over the
central and southern waters this weekend, with seas becoming steep
on Sunday due to a fresh northwest swell around 6-7 ft at 7-8
seconds. Between the increasing winds and steepening seas,
conditions will become hazardous to small craft.

Steep seas early Monday are expected to become less steep through
the day as northerly winds decrease. Seas and winds decrease even
more on Tuesday, bringing benign conditions. -23

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM Saturday to 11 AM PDT Sunday for
     PZZ252-272-273.

     Small Craft Advisory from 11 AM Saturday to 11 AM PDT Sunday for
     PZZ253.

&&

$$

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