883
FXUS66 KPQR 102146
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
246 PM PDT Fri Oct 10 2025

.SYNOPSIS...An active pattern will continue through at least the
start of next week. Expect cool and showery weather with high
mountain snow. By the middle of next week, warmer and drier
conditions are on the horizon.

&&

.DISCUSSION...Tonight through Thursday...The region remains
locked in a cool and damp pattern as a broad upper-level trough
dominates the northeast Pacific. Satellite imagery early this
morning depicts a well-defined closed low centered offshore near
43.33 N/ -128.66 W, with extensive cloud cover extending inland
across the Pacific NW. Cooler overnight lows are also expected
through the weekend. Also, have issued a Frost Advisory for
Hood River County tonight. So, if you have any sensitive plants
outside, now would be a good time to start thinking about how to
protect them. There is also moderate confidence in a Freeze
Watch/Warning being issued this weekend as well, but there is
still some uncertainty at this time.

This system will remain nearly stationary before slowly
drifting eastward through tonight and Saturday. As the low
meanders eastward, it will send periodic perturbations which
will keep widespread light to moderate showers in the forecast
through Saturday morning. Rainfall totals through early Saturday
morning expected to range between 0.10 to 0.30 inches across
the interior lowlands and 0.20 to 0.35 inches for the coast,
Coast Range, and Cascade foothills. Probabilistically for 24
hour rain accumulation to exceed 0.50 inches by early Saturday
morning, there is a 25-50% chance for most of the Willamette
Valley and a 60-80% chance at the coast, Coast Range, and
Cascade foothills. As for chances to exceed 0.75 inches, there
is a 10-20% chance within the Willamette Valley and a 35-60%
chance at the coast, Coast Range, and Cascade foothills.

By Saturday, the closed low begins to deepen along the Oregon
coast, producing another round of widespread rain. Showery
conditions will then develop through Saturday night and Sunday
as the system transitions eastward. Additional rainfall amounts
for Saturday range from 0.10 to 0.25 inches are expected for
interior valleys, 0.15 to 0.50 inches for the coast, Coast Range
and Cascade. Probabilistically for 24 hour rain accumulation to
exceed 0.50 inches on Saturday, there is a 15-40% chance for
most of the Willamette Valley and a 40-80% chance at the coast,
Coast Range, and Cascades.

If we look at the probability for Saturday through Monday (72
hours) to exceed 1.00 inch, 50-75% chance within the Willamette
Valley and a 75-95% chance at the coast, Coast Range, and
Cascade foothills. For 1.50 inches 15-30% chance within the
Willamette Valley and a 50-80% chance at the coast, Coast
Range, and Cascade foothills. For 2.00 inches, there is a 05-15%
chance within the Willamette Valley and a 30-60% chance at the
coast, Coast Range, and Cascade foothills.

As the system exits the region for the start of the upcoming
week, a colder post-frontal air mass will settle across the
region. Daytime highs will fall into the mid-50s to low 60s
Sunday and Monday for most lowland areas, while higher elevations
within the Cascades will see highs in the upper 30s to upper
40s. Another low will drop southward from Canada late Sunday
into Monday. Snow levels are also expected to lower towards
4000 to 5000 feet early Sunday through Monday, resulting in
light snow accumulations along the passes. For Santiam, Bennett
and Willamette Passes along with Highway 26 near Government Camp
will most likely see a trace to 1 inch of wet snow. At the same
time, roads above 5000 ft have a 75% chance of at least 2 to 6
inches of snow. However, for elevations near pass level, there
is a 10-20% chance for 2 to 6 inches of snow. For elevations
above 5000 ft 6 to 15 inches of snow.

However, by the middle of the week, WPC 500 mb clusters have a
ridge building behind the Sunday/Monday low. This will favor a
period of relatively warmer and and drier conditions through the
middle of next week, with PoPs generally around 10-20%.

By Thursday into Friday, some ensemble members rebuild the
offshore low and nudge it back toward the coast. If this occurs,
weak onshore flow and increasing cloud cover could return, with
PoPs rising into the 30% range. Confidence remains low for this
late-week scenario, as models continue to define the positioning
and strength of the returning trough.
/42~12

&&

.AVIATION...An upper level low pressure offshore will continue
to spin bands of showers into the area from the south and
southwest. This weather pattern will result in predominantly VFR
conditions for terminals across northwest Oregon and southwest
Washington through 12z Saturday. The probability of conditions
dropping into MVFR or lower thresholds at any given hour and TAF
site will generally be 10% or less for the remainder of this
afternoon and evening and will primarily be tied to the strongest
showers. In addition, there is a 10% chance of a thunderstorm at
any given terminal through 06z Saturday.

More persistent showers on Saturday will lead to more widespread
deteriorating flight conditions. Most locations appear to have a
40-50% chance of experiencing flight conditions in MVFR thresholds
and a 10-20% chance of IFR conditions at any given hour between
15z Saturday and 21z Saturday. Finally, there is a 10% chance of a
thunderstorm at any given terminal through 06z Saturday.


KPDX AND APPROACHES...An upper level low pressure offshore will
continue to spin bands of showers into the area with predominantly
VFR conditions through 12z Saturday. The probability of
conditions dropping into MVFR thresholds through 12z Saturday is
generally 10% or less at any given hour. In addition, there is a
10% chance of a brief thunderstorm impacting the site through 06z
Saturday. Finally, more persistent showers on Saturday will
produce increasing chances (40-50% chance) for flight conditions
to settle into MVFR thresholds between 12-18z Saturday that appear
more likely than not to persist through at least 21z Saturday.
There is a 10-20% chance that IFR conditions at least temporarily
dip into high end IFR thresholds between 15-18z Saturday.

&&

.MARINE...A low pressure system continues to spin off the
Oregon coast. The low pressure system will weaken further
tonight as it moves onshore Saturday. Southwesterly winds
Saturday morning turn northwest later in the day. These northwest
winds are expected to increase to 15-25 kt with gusts up to 30
kt. There is a 40% chance of Gale Force wind gusts across the
northerly outer waters late Saturday. Either way, seas there is an
80% chance that seas peak in the 10-13 ft range with dominant
periods around 10 seconds late Saturday into early Sunday bringing
a period of particularly hazardous seas.

A weak low pressure will drop southward along the West Coast late
Sunday into Monday. This will usher in another round of northerly
winds in its wake. High pressure builds back across the northeast
Pacific during the middle half of next week bringing a return to
tamer seas. There is a fair amount of uncertainty in the overall
weather pattern towards next weekend. This is reflected in the
wide significant wave height probabilities depicted in our wave
statistical guidance, which suggests there is an 80% chance that
wave heights end up somewhere between 7 and 17 ft across the
waters next Friday.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Frost Advisory from midnight tonight to 8 AM PDT Saturday for
     ORZ121.

WA...None.

PZ...Small Craft Advisory from 5 PM this afternoon to 11 PM PDT this
     evening for PZZ210.

     Small Craft Advisory from 5 PM to 11 PM PDT Saturday for PZZ210.

     Small Craft Advisory from 3 PM to 11 PM PDT Saturday for
     PZZ251>253-272-273.

     Hazardous Seas Watch from Saturday evening through Sunday
     afternoon for PZZ251>253-272-273.

     Small Craft Advisory from noon to 5 PM PDT Saturday for PZZ271.

     Hazardous Seas Watch from Saturday afternoon through Sunday
     afternoon for PZZ271.

&&

$$

www.weather.gov/portland

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