731
FXUS66 KPQR 010932
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
232 AM PDT Fri Aug 1 2025

.SYNOPSIS...Near average temperatures expected through Saturday,
turning slightly cooler Sunday into early next week. Chances for
showers and thunderstorms continue along the Cascades through this
evening. Mostly sunny conditions for Friday and Saturday, followed by
increasing clouds on Sunday with chances for showers and
thunderstorms over the Cascades late Sunday. General troughing and
onshore flow moderate temperatures Monday through Wednesday with
slight chances for more widespread rain late Wednesday into
Thursday, followed by upper level ridging with potential for warmer
temperatures into the weekend, however uncertainty is high that far
out in time.

&&

.SHORT TERM...Today through Sunday night...The low pressure system
in the Gulf of Alaska will maintain southerly flow over the region
today. A shortwave trough lifting northward this morning is expected
to promote clearing skies through this afternoon. With sunnier skies
expected, temperatures warm into the 80s. Another weak disturbance,
along with residual moisture and instability over the Lane County
Cascades will bring a 20% chance of thunderstorms near the crest
this afternoon, with most of the convection staying east of the
crest.

Onshore flow increases on Saturday as southerly flow aloft
transitions to dry southwesterly flow. Expect near average
temperatures along with another mostly sunny day, aside from morning
clouds along the coast and lower Columbia. Cloud cover will increase
on Sunday as weak shortwave troughing approaches the region.
Temperatures are expected to be a few degrees cooler on Sunday due
to the increase in cloud cover and cooler temperatures aloft; most
locations will see high temperatures in the 70s, except 60s at the
coast and near 80 degrees over the Willamette Valley. This trough
will also bring increasing chances (20-40%) for showers over the
Cascades and foothills late Sunday afternoon through Sunday night.
Cannot completely rule out isolated thunderstorms as well, depending
on the timing of this trough and the degree of instability.
NBM thunder probabilities currently range between 10-20%. DH/TK

.LONG TERM...Monday through Thursday...The long term forecast is
highlighted by onshore flow, near to slightly below average
temperatures for early August, and a mix of sun and clouds each day
with clouds being most prevalent during the morning hours. This mild
weather pattern is in response to a series of two or three shortwave
troughs that move over the area during the early to middle part of
next week, each one helping to deepen the marine layer. There is
also a 15-30% chance of light rain or drizzle with low marine
stratus along/near the coast Tuesday and Wednesday, mainly to the
north of Newport. Inland areas are more likely to stay dry.

Chances for more widespread rain increase late Wednesday night into
next Thursday, albeit to around 10-20%. However this is also when
model spread increases significantly and the forecast becomes much
more uncertain. As of right now, it appears two scenarios are
possible heading into late next week. The first scenario would be
continued upper level troughing over the area, which would support
cooler temperatures and potential widespread rain. The second
scenario would be the gradual development of upper level ridging,
bringing dry weather with warmer temperatures in the mid 80s to low
90s. As of right now, the WPC`s cluster analysis suggests there is
around a 40-50% chance scenario one verifies with troughing, and a
50-60% chance scenario two verifies with ridging. If the first
scenario verifies, widespread wetting rains will be possible. But,
the NBM is showing only a 10-20% chance for at least 0.25" of rain
over a 48 hour period, except around 5% across Lane County. There is
increasing confidence of upper level ridging building on Friday and
into next weekend. DH/TK

&&

.AVIATION...High confidence (80%-95% probability) that predominately
IFR/LIFR conditions will persist along the coast through around 19Z
Friday. Marine flight levels are expect to improve towards VFR
around 18Z-21Z Friday as daytime heating will help to break up the
marine stratus. For inland locations, widespread VFR conditions
expected to persist through the TAF period with SCT/BKN high clouds.
North/northwesterly winds around 5-10 kt across the airspace through
the TAF period.

PDX AND APPROACHES...VFR with SCT/BKN high clouds. Northwesterly
winds less than 10 kt. /42

&&

.MARINE...Minimal changes in the overall weather pattern through
the weekend as high pressure across the waters will maintain
north/northwest winds through early next week with gusts up to 20
kt. Seas remain around 2-4 feet at 7-9 seconds.

Guidance is suggesting that a broad trough, approaching the
region will result in a pattern change towards the start of next
week. This system would bring about a southerly wind shift across
all waters with conditions remaining below small craft conditions.
However, some guidance is suggesting around a 25% probability of
Small Craft Advisory gusts around 25 kt.

Satellite and surface observations are supporting dense fog across
all waters. As a result will maintain the current dense fog
advisory as visibilities of 1 NM or less could occur through
around noon on Friday. Given the minimal changes in the overall
pattern, expect a return of dense fog across all waters Friday
night. /42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Dense Fog Advisory until noon PDT today for PZZ210-251>253-
     271>273.
&&

$$

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