239
FXUS66 KPQR 170925
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
225 AM PDT Sat May 17 2025

.SYNOPSIS...Periods of light rain showers expected through the
weekend and into early next week. Expect temperatures to remain
slightly below average during this period. Rain showers
along with a 10-20% chance of thunderstorms this afternoon
afternoon. Lingering showers into Sunday, though most areas
likely drier. Temperatures trending warmer, upper 60s to lower
70s, toward the end of next week.

&&

.DISCUSSION...Tonight through Friday...Shower activity is
increasing across the region as a shortwave trough is digging
into the PacNW coast. Heaviest shower activity is expected
through the morning as the deepest are of moisture comes
onshore. Shower activity will continue into the afternoon as
another disturbance approaches Vancouver Island. There is also a
slight chance (10-20%) for thunderstorms this afternoon and
evening. No strong thunderstorms are expected. Shower activity
is expected to be more persistent across the higher terrain of
the western slopes of the Cascades. Rainfall totals through
tonight across the lowlands are expected to fall between
0.10-0.40 inches, generally higher totals across the northern
portion of the forecast area. Higher totals across the Coast
Range expected with totals between 0.25-0.75 inches expected.
Highest totals across the Cascades and Cascade Foothills,
generally 0.75-1.25 inches with locally higher amounts.

Conditions trend drier on Sunday, though light showers will persist
into the afternoon as the disturbance over Vancouver Island becomes
a cut-off low east of the Cascades, centered over eastern
Washington. Weak ridging will build into the region, supporting
partly sunny skies during the afternoon, though temps will remain 5-
8 degrees below average, topping out in the low 60s inland. Model
agreement is increasing for another weak system to cross the region
on Monday with another round of light rain showers expected. Totals
of 0.10-0.20 inches expected across much of the are with totals as
high as half an inch across the higher terrain of the Cascades. Zonal
flow with another embedded disturbance passing to the north may
maintain light showers into Tuesday.

Agreement degrades middle to end of next week with cluster analysis
showing split pretty equally between ridging and troughing. NBM
guidance though continues to suggest temperatures gradually warm
closer to average toward the latter part of next week, along with
precipitation probabilities generally 15% or less Wednesday through
Friday. -Batz

&&

.AVIATION...Weak front is moving across northwest Oregon as of 09z
Sat accompanied by numerous rain showers, producing IFR
conditions at the coast and mainly MVFR with a few pockets of IFR
inland. Expect these conditions to persist through around 21z Sat,
after which time conditions will trend back towards VFR as
showers start to diminish in coverage. There remains a 15-20%
chance of thunderstorms across the Willamette Valley today. Any of
these storms will be capable of producing small hail, gusty
winds, and temporarily reduced cigs and visibilities, but
probabilities are too low for inclusion in TAFs at this time.
Winds will shift northwesterly and increase to 10-15 kt with a few
gusts to 20 kt behind the front 18-21z Sat, diminishing again
03-06z Sun.

PDX AND APPROACHES...Mainly MVFR in rain showers through 21z Sat,
improving to VFR thereafter as showers diminish in coverage. Wind
generally W-SW at or below 5 kt through 21z Sat, shifting NW and
increasing to 10-15 kt with a few gust to 20 kt through 03-06z
Sun. /CB

&&

.MARINE...Fresh northwest breezes will develop over the coastal
waters today as a weak front moves inland along the Oregon Coast
early this morning. This will produce low end Small Craft
Advisory conditions through early Sunday as winds gust to around
25 kt. Seas will generally be in the 6-8 ft range, dominated by a
mid period westerly swell on the order of 6-7 ft at 10-11 seconds.
Calmer conditions are expected during the day on Sunday as high
pressure moves overhead, bringing lighter west winds as the
westerly swell persists at 5-6 ft. Winds will shift southerly as
the next front approaches the waters Sunday night into Monday,
likely warranting another round of headlines as models depict a
80-90% probability of wind gusts to 25 kt through Monday evening.
Seas look to increase towards the middle of next week as westerly
swell builds to around 10 ft on Tuesday. /CB

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 11 AM this morning to 11 AM PDT Sunday
     for PZZ210-251>253-271>273.

&&


$$

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