648
FXUS66 KPQR 160343
AFDPQR

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

.EVENING UPDATE...Showers have begun to decrease this evening
with satellite and radar indicating the bulk of the lingering
activity pinned to the coast, coast range, Willapa hills, SW
Washington north of Ridgefield/Woodland, and over the Cascades.
As far as T-storms are concerned it has been a couple hours
since lightning has been detected over western OR/SW Washington
and with the loss of daytime heating chances for additional
activity appears very low(less than 5-10%) going through the
overnight hours, although Sunday afternoon likely presents
another opportunity for a rumble of thunder or two. Otherwise,
the best relative chances for lingering showers overnight will
be stay along, the north Oregon and Washington Cascades/foothills,
coast, coast range, and Willapa hills. Its worth noting most
guidance, especially CAMS like the HREF, show an extended period
of clearing over Willamette Valley into the Portland Metro area
overnight, especially along the lee side of the coast range.
With these clearer skies, light winds, and ample surface
moisture in mind, patchy fog likely develops overnight and may
locally reduce visibility  the areal extent of patchy fog was
slightly expanded to match the latest guidance and current
satellite trends. The previous discussion remains below.
-Schuldt

&&

.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...Saturday Afternoon through Monday Night...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

&&

.AVIATION...Currently VFR across the majority of the airspace with
post-frontal showers continuing to diminish over the next few
hours. CIGs look to be above FL040 through the majority of the TAF
period. However, could see some patchy MVFR conditions (30-40%
probability) to develop after 12Z Sunday.

Southwest/westerly winds around 10-15 kt with gusts up to 20 kt
through 03Z Sunday. Afterwards, winds will become light and
variable and if clouds clear, there is the potential for patchy
IFR fog to develop (25% probability) starting around 12Z Sunday.
Any fog that does develop should dissipate by 15Z Sunday as
VFR/MVFR conditions along with showers and a slight chance of
thunderstorms (25% probability) return. Any thunderstorms will
have the potential to produce small hail along with gusty and
erratic winds.

PDX AND APPROACHES...Post-frontal showers continuing to linger
over the next few hours. This will result in predominantly VFR
conditions through the TAF period. Westerly winds of 10-15 kt with
gusts up to 20 kt will decrease to light winds around 03Z Sunday.
Around 15Z Sunday VFR/MVFR conditions along with showers and a
slight chance of thunderstorms (25% probability) return. /42

&&

.MARINE...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

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

www.weather.gov/portland

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