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554
FXUS66 KPQR 152150
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
250 PM PDT Sat Jun 15 2024

.SYNOPSIS...Low pressure brings cool and showery weather with a
chance of thunderstorms today and Sunday. The best chances will
be in the afternoon across northern portions of the forecast
area. Cool and showery conditions last into Monday, then warmer
and drier weather returns Tuesday through the end of next week.

&&

.SHORT TERM...
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Saturday Afternoon through Monday Night...As of 1
PM PDT Sunday afternoon, radar imagery shows scattered showers
with isolated thunderstorms moving through NW Oregon and SW
Washington. Broad upper level troughing with a low centered over
Vancouver Island, BC remains over the region. The shortwave
along the main upper trough and associated weak cold front have
moved east of the Cascades, and the atmosphere has become
unstable behind the frontal passage. Scattered showers will
continue through the entire forecast area through tonight,
though best chances of thunderstorms are generally along and
north of the Columbia River with models indicating CAPE of
300-600 J/kg. However, can`t rule out a couple thunderstorms
south of this area as models indicate lower CAPE values of
100-300 J/kg, enough for a lightning strike or two. Thunderstorm
chances will diminish this evening as surface heating
decreases. The main impacts expected with any strong shower or
thunderstorm are brief heavy rain, lightning, gusty winds, and
small hail. The cooler air brought in behind the cold front
along with continued cloud cover will keep high temperatures in
the upper 50s to mid 60s for the lowlands with morning lows in
the 40s.

The cool and showery weather will persist over the region on
Sunday as upper level troughing remains in place, with highs
across the area similar to today. Shower activity will increase
again in the afternoon as the main upper low shifts southeast
across Washington and Oregon, bringing a renewed chance of
thunderstorms across the north through early evening. The area
will begin to dry out but remain cool on Monday as northwest
flow takes hold behind the trough departing into the Rockies,
with light shower activity mostly confined to the higher
terrain and winding down through Monday night. -CB/HEC

.LONG TERM...Tuesday through Friday...Warmer weather looks to
return Tuesday through the end of next week as WPC ensemble
clusters agree on the weakening of the trough over the western
CONUS and subsequent increasing 500 mb heights across the
Pacific Northwest. Guidance suggests temperatures will rebound
back above normal into the upper 70s to low 80s by Tuesday for
the interior lowlands as this occurs. Wednesday and Thursday
then appear to be the hottest days of the coming week as the GFS
and Euro ensembles as well as most deterministic solutions
depict a weak Rex Block developing with a low amplitude ridge
over western Canada with an open trough over northern
California. This results in rather high confidence in NBM
temperature spreads showing highs in the mid to upper 80s for
areas away from the coast both Wednesday and Thursday (70-90%
chance of temperatures above 80 degrees), with around a 25-35%
chance to reach 90 degrees from Portland to Salem and closer to
a 10% chance around Eugene. -CB/HEC
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&&

.AVIATION...
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As of 21Z Sat, post-frontal showers linger through the
region, primarily north of KSLE. A few thunderstorms have passed
through KPDX, KTTD, KSLE, and KUAO over the past few hours,
expected to continue until around 00Z Sun. Currently VFR at most
terminals, with the exception of MVFR CIGs at KSLE but should
improve back to VFR by 00Z Sun. Otherwise, expect VFR conditions
to persist through most of the TAF period, with chances of MVFR
CIGs around 10-30% for most terminals between 12-17Z Sunday.

Isolated thunderstorms remain possible until 00-03Z Sunday
(10-20% probability), primarily north of KSLE. Any thunderstorms
will have the potential to produce small hail along with gusty and
erratic winds.

Elevated westerly winds around 10-15 kt with gusts up to 20 kt
until 00-03Z Sunday. Winds will become light and variable
thereafter, persisting into tonight.

PDX AND APPROACHES...Post-frontal showers will linger until late
this evening, with predominantly VFR conditions through the TAF
period. Isolated thunderstorms remain possible (20% probability)
until 00-03Z Sunday. Westerly winds of 10-15 kt with gusts up to
20 kt will decrease to light winds by 06-07Z Sunday and remain so
until 18-19Z Sunday. -JH
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&&

.MARINE...
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Fairly innocuous conditions for the near future. Seas
remain around 5 to 7 ft at 9 to 11 seconds. Post-frontal weather
currently bringing slightly stronger west winds with gusts up to
20 kt late Saturday afternoon and decreasing into Saturday night.
Late Sunday/early Monday strong northwesterly winds will return
and may bring marginal Small Craft Winds to all waters. There is
still some uncertainty in the strength of the Monday system. -JH
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&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

www.weather.gov/portland

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